Scientists debunk the myth that you lose most heat through your head | Medical research

When it comes to wrapping up on a cold winter’s day, a cosy hat is obligatory. After all, most of our body heat is lost through our heads – or so we are led to believe.

Closer inspection of heat loss in the hatless, however, reveals the claim to be nonsense, say scientists who have dispelled this and five other modern myths.

They traced the origins of the hat-wearing advice back to a US army survival manual from 1970 which strongly recommended covering the head when it is cold, since “40 to 45 percent of body heat” is lost from the head.

Rachel Vreeman and Aaron Carroll, at the centre for health policy at Indiana University in Indianapolis, rubbish the claim in the British Medical Journal this week. If this were true, they say, humans would be just as cold if they went without a hat as if they went without trousers. “Patently, this is just not the case,” they write.

The myth is thought to have arisen through a flawed interpretation of a vaguely scientific experiment by the US military in the 1950s. In those studies, volunteers were dressed in Arctic survival suits and exposed to bitterly cold conditions. Because it was the only part of their bodies left uncovered, most of their heat was lost through their heads.

The face, head and chest are more sensitive to changes in temperature than the rest of the body, making it feel as if covering them up does more to prevent heat loss. In fact, covering one part of the body has as much effect as covering any other. If the experiment had been performed with people wearing only swimming trunks, they would have lost no more than 10% of their body heat through their heads, the scientists add.

The researchers then decided to look at several other widely held beliefs to see if there was any published scientific evidence to support them. In many cases, they found several studies that completely undermined them. “Examining common medical myths reminds us to be aware of when evidence supports our advice, and when we operate based on unexamined beliefs,” they write.

Another myth exposed by the study was that sugar makes children hyperactive. At least a dozen high-quality studies have investigated the possibility of a link between children’s behaviour and sugar intake, but none has found any difference between children who consumed a lot and those who did not. The belief appears mostly to be a figment of parents’ imaginations. “When parents think their children have been given a drink containing sugar, even if it is really sugar-free, they rate their children’s behaviour as more hyperactive,” the researchers write.

The warning that snacking at night makes you fat is on similarly thin ice, Vreeman and Carroll discovered. At first glance, some research suggests there may be a link, with one study showing that obese women tended to eat later in the day than slimmer women. But according to the BMJ article, “The obese women were not just night eaters, they were also eating more meals, and taking in more calories makes you gain weight regardless of when calories are consumed. “

The researchers also have some unwelcome news for those hoping to survive the festive excesses by turning to hangover cures. After an extensive review of evidence for the curative benefits of bananas, aspirin, vegemite, fructose, glucose, artichoke, prickly pear and the drugs tropisetron and tolfenamic acid, they conclude that none has been proven to cure hangovers. “No scientific evidence … supports any cure or effective prevention for alcohol hangovers,” they state. “The most effective way to avoid a hangover is to consume alcohol only in moderation or not at all.”

The team went on to show that contrary to popular belief, the Christmas plant poinsettia with it blood-red leaves is not toxic, and that suicides do not rise over the holiday period

Do you lose most heat from your head?

We were told we must not capsize at all costs. If we did, we would have only seconds to get out of the water before the cold took hold. Here in Torres del Paine National Park, in Patagonia, the toothpaste-turquoise icebergs come in every imaginable shape, from grand pianos to rockets. Occasionally, as we paddle the kayak, we hear pistol-shots of ice chunks breaking off them.

Before this trip I’d never spent much time thinking about how the body loses heat. Now everything I do factors in the extreme cold. The nights are bone-chilling, even inside the tent. I sleep in my middle-of-the-range sleeping bag, wearing all of my clothes – four pairs of trousers, three fleeces, two hats and waterproofs. But it’s still not enough. Mariano, our guide, sleeps outside the tent, with nothing but his super-thick sleeping bag to shelter him from the wind. He insists he prefers it that way, and doesn’t even bother wearing a hat. I worry about him: what about the popular myth that you lose most of your body heat through your head?

Over the years, physiologists have tested theories about how people get cold with the help of various crews of human guinea pigs, from hardy students to members of the armed forces. Experiments in this field tend to require people who are prepared to endure a certain amount of discomfort.

Thea Pretorius from the University of Manitoba in Canada uses Scuba equipment to help assess how much heat humans lose from their heads. The volunteers in Pretorius’s studies are not only hardy, but also hairy – at least on top of their heads. Baldness would add unnecessary complication to this line of enquiry.

In one of Pretorius’s studies, volunteers were given drugs to stop them shivering, which the body does involuntarily to stem heat loss. Then they were lowered with a hoist into cold water. In some trials they were entirely submerged. In others they were not lowered as far: their heads were left exposed above the water’s surface. The second variable in this experiment was their clothing. Sometimes they just wore swimming costumes. At other times they were insulated by a rubber dry suit, two pairs of socks and wool gloves. Everyone spent 45 minutes in 17C (62F) water.

As expected, all the volunteers lost heat quickest when they initially entered the water. But the rest of the results debunk popular expectation. The volunteers whose heat loss came almost entirely from their heads (those who were fully submerged whilst wearing insulating clothing) lost only half as much heat as those whose heat loss came almost entirely from their bodies (the volunteers in swimming costumes with their heads poking out of the water). In other words, we don’t lose most heat from our heads. The results show that having your head immersed in cold water only adds 10% to your overall heat loss in a cold pool. And given that the head accounts for 7% to 9% of the body’s surface, that doesn’t seem excessive.

But before you throw your collection of woolly hats in the bin, there’s another finding to bear in mind: when the head is allowed to get cold and the body is effectively insulated, the body’s core temperature drops a lot more rapidly than most people would expect. 

One reason seems to be that the scalp contains lots of blood vessels that sit particularly close to the surface of the skin – as evidenced by the copious bleeding that happens when you cut your head. If you are dressed in warm clothes without a hat on a freezing day, the environment cools the hot blood flowing from your warm body as it passes through the scalp. And this blood then travels back down to the warm body, cooling it as it goes. The second reason involves shivering. It is a curious physiological fact that people do not shiver when only their head is exposed to the elements. Because shivering slows your rate of cooling, not shivering makes you cool quicker than you otherwise would.

What matters in an extreme environment like Patagonia, is not so much your rate of cooling as much as the final temperature that your body drops to. Mariano seems to have figured this out. He absolutely needs to keep his body insulated to maintain his core temperature, but not so much his head. Experience had taught him that all he needed was an amazing sleeping bag. Next time I’m getting one.

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You can hear more Medical Myths on Health Check on the BBC World Service.

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I Am A Man Who’s Head Is Always Hot (Often With Headaches) For Several Years. Can Anyone Help?

Question

Asked by RKS HOT

I Am A Man Who’s Head Is Always Hot (Often With Headaches) For Several Years. Can Anyone Help?

I’m a male who just turned 66. For the past 4-5+ years I’ve suffered something similar to menopause. Most of the day, but slightly more as I am waking or laying down to sleep, my head becomes very hot. My temp. is always normal. Sometimes I become flush (when I’m up) usually when stress is higher, but not all the time.

The only temporary relief I get is if I immerse my head deep in a bucket of cool water for at least 1-2 minutes, which is refreshing. I hand squeegee most of the water from my hair – (I have a full head of hair). I leave my hair as wet as I can without dripping. Within a half an hour, the heat from my scull has dried most of the water. If I go out in the cold just before it dries, you can see water vapor steaming from my head.

I’ve mentioned this to several physicians (MD – I.M.’s, specialists), but none had an answer. One suggested male menopause, but the hot head is the only symptom I have (and continuously for years). I’m on several meds., but the prescribing doctors I talked to knew of no drug link to this problem.

Have you heard of such a case before? What am I suffering from? Is there help?

Thank you

Answer

Two things come to mind:

• There could be a hormone imbalance. This can be determined by a simple blood test for testosterone and thyroid hormones. When it comes to thyroid testing, many doctors only test TSH (thyroid stiumlating hormone) levels, but it’s also important to check the Free T4 level as well. For more information on that, read: The Power of Hormones

• If you always have head pain when your head is hot, you may be dealing with Migraines. We have an excellent Migraine site where you can learn more and ask questions if you think that’s a possibility: MyMigraineConnection.com

You should know: The answer above provides general health information that is not intended to replace medical advice or treatment recommendations from a qualified healthcare professional.

Heat Headache: What You Need to Know About Hot Weather and Headaches

A heat headache is a dull, throbbing pain that is exacerbated by heat. Millions of Americans suffer from headache disorders like migraines and cluster headaches. According to the National Headache Foundation, more than 37 million Americans suffer from migraines, and heat can make symptoms worse.

These headaches often worsen in the summer months thanks to the heat and other factors like dehydration. If you experience a heat headache, dehydration might be part of the problem.

With dehydration, blood vessels in the brain shrink, slowly pulling the brain away from the skull. This causes a pain response that produces a headache.

Causes of Heat-Induced Headaches

A heat headache can be caused by a variety of factors or present itself as a side effect of a more serious heat-related illness. In most cases, heat — whether it’s the ambient outdoor temperature or the result of a hot work environment like being on the front lines as a firefighter — is the main cause of these headaches.

Here are some of the other contributing factors that lead to heat headaches:

• Dehydration
• Bright lights, including the sun’s glare
• Dramatic changes in barometric pressure
• Excessive heat
• Heat-related illness such as heat exhaustion and heat stroke
• High humidity or a high heat index

As temperatures increase, your body needs more fluids to function properly because, when your body sweats in an attempt to cool down, you lose vital electrolytes, like sodium, and water. If you don’t drink enough hydrating fluids during high temperatures, you can develop dehydration. Dehydration can trigger headaches or even migraines.

The weather can also affect hormone levels in the brain, which may increase susceptibility to migraine headaches and other severe headaches. Many people know that sunlight helps produce vitamin D, resulting in a mood boost. However, research shows that increases in the temperatures outside may also increase the amount of serotonin in your brain — the hormone responsible for stress. As stress increases, so does the likelihood of developing a headache.

One study examined the impacts of heat on cognitive function in soldiers operating in desert areas. The study found that when it came to attention, motor function, and memory, intense heat and humidity resulted in poor performance compared to normal weather conditions.

Excessive exposure to high levels of heat and humidity can also lead to heat-related illness, including heat exhaustion and heatstroke. Heat headaches are one of the main symptoms of heat exhaustion and heatstroke. The conditions can occur simultaneously or you may get a headache before developing other heat-illness symptoms.

Heat exhaustion occurs when the body becomes dehydrated. Heatstroke is a dangerous medical condition where the body’s core temperature rises above 104 degrees Fahrenheit. It is potentially life-threatening and one of the first signs is a heat headache along with lethargy and confusion.

Elderly individuals and young children are more likely to suffer from dehydration. Young children are still developing and may not be able to cool down as easily as adults. And Elderly people may suffer from other illnesses that increase the risk of dehydration. Plus, as we get older, our bodies lose water more quickly, and it’s harder to remedy dehydration.

Symptoms of Heat Headache

Heat headaches cause more symptoms than just throbbing head pain. Since most heat headaches are the result of dehydration, the condition can affect your muscles and central nervous system.

Here are some of the main symptoms of heat headaches:

• Throbbing or pounding head pain
• Muscle cramps
• Heat cramps
• Dizziness and feeling faint
• Nausea
• Extreme thirst
• Low blood pressure
• Fatigue and lethargy
• Light sensitivity
• Dehydration

If you experience the symptoms of a heat headache, the main course of action is to remedy dehydration. While you could drink water or a sports drink, these fluids are less effective and take longer to work than a precisely balanced rehydration solution. Oral rehydration solutions can help give your body what it needs to ease the signs of dehydration.

Relieve Dehydration With ORS

Drink DripDrop ORS before heading out into hot temperatures and keep drinking it throughout the day to ward off dehydration.

If you suffer from heat headaches or are at higher risk for heat exhaustion, try to limit strenuous physical activity on hot days and during heat waves. If your job requires you to work outdoors regardless of the weather, try wearing a hat, sunglasses, and loose-fitting clothing to help your body stay cool.

Wear sunscreen to prevent sunburn, as sunburn may also increase the risk of heat headaches. Whenever possible, take breaks in the shade or a cool environment like an office break room with air conditioning.

If you already have a heat headache, you can take an over-the-counter painkiller like Tylenol or ibuprofen to reduce the pain. Place ice packs on your head and neck or underneath your armpits to cool your body down faster. You can also pack a cooling towel in your work bag that you can use to stay cool when the temperatures skyrocket.

When To Seek Medical Attention

Know when to get help. If your heat headache is accompanied by a body temperature higher than 104 degrees Fahrenheit, seek medical attention immediately, as you may be suffering from heatstroke. Visit a medical professional if your heat headache is accompanied by vomiting, confusion, or slurred speech. These are indicators of a more serious problem.

If you suffer from chronic headache pain, visit a doctor who can help you identify headache and migraine triggers. They may ask you to keep a headache diary to figure out what’s causing your headache. A doctor can also give you tips to manage pain caused by higher temperatures.

Dehydration Relief Fast

If you’re suffering from dehydration — with signs like headache and muscle cramps — addressing fluid and electrolyte loss is the best course of action. Drinking an oral rehydration solution like DripDrop ORS is a doctor-recommended way to address mild to moderate dehydration.

If you’re thinking about trying DripDrop ORS but aren’t ready to commit to a whole box, sign up for a two-stick trial so you can see what the buzz is all about. Once you decide you love it, you can join our flexible Subscribe & Save program to receive as many sticks as you want at the best value.

The Claim: You Lose Most of Your Body Heat Through Your Head

THE CLAIM: You lose most of your body heat through your head.

THE FACTS: Put on a hat, parents tell their children before sending them outside on bitter winter days. While that might be sound advice, the popular belief behind it — that most of the body’s heat escapes through the head — is misguided.

The amount of heat released by any part of the body depends largely on its surface area, and on a cold day you would lose more heat through an exposed leg or arm than a bare head.

Dr. Daniel I. Sessler, an anesthesiologist and expert on hypothermia at the University of Louisville medical school, said the popular myth stemmed from military experiments conducted five decades ago. In those studies, he said, researchers dressed subjects in Arctic survival suits and exposed them to frigid conditions. But the suits only covered the subjects from the neck down, he said, so naturally most of their body heat escaped through their heads.

That isn’t a fair comparison, Dr. Sessler said. If you did the same experiment with someone wearing a swimsuit, only about 10 percent of the heat loss would come from the head.

The body responds to cold temperatures in at least two ways. One is the constriction of blood vessels in the arms and legs, reducing blood flow to the extremities. This protects the brain and vital organs in the trunk but leaves the fingers and toes susceptible to frostbite, in effect sacrificing them. Another response to cold is shivering, which generates heat.

The face, head and upper chest are up to five times as sensitive to changes in temperature as other areas, Dr. Sessler said. This creates the illusion that covering up those areas traps in more heat, but clothing another part of the body does just as much to reduce overall heat loss.

THE BOTTOM LINE: The body does not lose most of its heat through the head.

ANAHAD O’CONNOR

Really? [email protected]

How to keep a cool head in oppressing heat

Come summer and it is quite natural to get affected by the sun. Headaches, usually triggered by hormones (particularly with women) or stress, are often set off by the sun as well. Tips on tackling headaches.

Hindustan Times | By Shikha Sharma

UPDATED ON JUN 21, 2014 08:17 PM IST

It is natural to be affected by the sun. It is, after all, the biggest thing in our solar system and as the Earth inches closer to the hot ball of fire in the summer, it’s impossible to not feel its effects. Headaches, usually triggered by hormones (particularly with women) or stress, are often set off by the sun as well.

Read: Light up your life this summer!

Sun headaches
Limit exposure: Wear a hat or carry an umbrella. Our dark hair has a higher propensity to absorb and trap heat, and cause headaches.
Lather up: Switch to a milder shampoo and wash your hair more often to keep the sebaceous glands healthy.
Drink up: Dehydration brings on headaches faster, so carry a bottle of water if you step out. Drink at least 10 glasses of water daily.
Pack it in: A weekly henna hair pack will keep the scalp cool.
Take a deep breath: Often, headaches are just a response to lack of oxygenation. Practise pranayam daily to balance the air flow in the body and to increase oxygen intake.
Cool down: After coming in from the heat, place a wet band on your head and eyes.

Read: Gadgets not responsible for headaches

Hormonal headaches
Ditch dairy: Cut out milk, cheese, other dairy products and coffee before the week of the menstrual cycle.
Balance it out: Drink coconut water and nimbu pani regularly.
Go green: Cucumber and other vegetable juices help. Also gorge on summer fruits like watermelon and muskmelon.
Say no to salt: Lower your intake because it causes water retention.
Trust your nose: Aromatherapy is often effective at controlling headaches. Try oil of neroli or peppermint.
Hit the sack: At least eight hours nightly is mandatory during the menstrual cycle.

Read: How to deal with headaches

(All Photos: Getty)

Tension on your mind. ..
Calm down: A daily session of anulom-vilom pranayam is one of the best natural therapies.
Clear it out: Avoid wearing sunshades indoors. Don’t wear your sunglasses or a tight headband for long periods.
Eat right, eat often: Small meals at frequent intervals are best, as skipping meals can trigger headaches.

If your headaches persist even after the summer or if they follow an unusual pattern, see your doctor. You shouldn’t ignore them or suffer through life with them.

From HT Brunch, May 11
Follow us on twitter.com/HTBrunch
Connect with us on facebook.com/hindustantimesbrunch

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Most of your body heat is lost through the head

Losing body heat. Which part of the body loses heat most quickly? Is it true that you lose most of your body heat through your head? Which organ produces the most heat in the body? Is a hat the most effective means of keeping warm in cold weather?

MYTH: You lost most of the heat from your head.

FACT: The head doesn’t lose more heat than other parts of the body. The lost heat from the body is actually proportional to the skin area that is exposed to the cold air.

A common statement is “It’s easier to keep the heat in, rather than to keep cold out”. Many assume that bodyheat disappears upwards and especially through that big brain of yours.

Origins of the Myth

This medical myth can be traced back to the 70s and the US military handbook for survival in harsh conditions. According to this survival guide, 40-50% of the body heat evaporates through the head and the book advices the soldiers to wear a hat to keep warm.

As a more modern version of the manual (2002) states, the cold itself may not be the biggest threat but rather the effects it has on the human ability to function properly: “Cold is a far greater threat to survival than it appears. It decreases your ability to think and weakens your will to do anything except to get warm. Cold is an insidious enemy; as it numbs the mind and body, it subdues the will to survive”.

Even in the modern version from 2002 the myth prevails:

“For example, always keep your head covered. You can lose 40 to 45 percent of body heat from an unprotected head and even more from the unprotected neck, wrist, and ankles. These areas of the body are good radiators of heat and have very little insulating fat. The brain is very susceptible to cold and can stand the least amount of cooling. Because there is much blood circulation in the head, most of which is on the surface, you can lose heat quickly if you do not cover your head.”

It sounds resonable and logical but it’s actually a myth.

Your head contains a lot of blood veins and arteries. It is reasonable to assume that when this part of the body is exposed to cold, it can cool down the whole system quickly. But as it turns out what is important is how much the overall body temperature drops. If the rest of the body is well insulated and warm, your body will keep a constant hot temperature even if your face is exposed to cold temperatures. A sleeping bag is consequently a very effective method of staying warm in a safe and secure manner. In harsh conditions, your ears could still get cold damage, but you will survive as long as the rest of the body doesn’t drop to dangerously low temperature levels.

Debunking of heat loss myth

One reason people believe more heat is lost through the head is simply because we are more sensitive to changes in temperature in the face and the area around the nose. This leads to the sensory feeling that cold is actually more cold than it is, because we have a “temp radar” (thermoreceptors) in our face, which tracks even small changes in temperature.

Humans feel that heat is evaporating from the face more quickly than the rest of the body. This in conjunction with the “dive reflex” of many mammals, including humans, triggers a reaction in the body which switches the blood supply to focus on the most vital parts, the brain, the hart and the lungs. Bloodflow is effectively shut down for arms, legs and other less critical organs. The extremities of the human body are also designed to cope with oxygen deprivation and more extreme temperatures without being damaged.

This myth was also proved wrong in this BBC article:

“In other words, we don’t lose most heat from our heads. The results show that having your head immersed in cold water only adds 10% to your overall heat loss in a cold pool. And given that the head accounts for 7% to 9% of the body’s surface, that doesn’t seem excessive.”

What research is the myth based on?

The Guardian explains this in an article about this myth here. It most likely stems from a poor scientific study by the US army during the 1950s. People were dressed in arctic survival clothes and exposed to freezing weather. The only part of their bodies left uncovered was the head. Consequently, most of the heat was lost through their heads. But as long as the rest of the body keeps a healthy heat level, it does not really matter which part of the body is exposed to cold, or through which part of the skin the heat sips out.

90,000 5 common myths and their refutation | by Eggheado | Eggheado: Health

We all remember one well-known mother’s wisdom: “Don’t go for a walk without a hat. All the heat goes through the head. ” In principle, it is clear where the “legs grow” from, because heat always rises up.

In fact, each person perceives this belief in his own way, some even believe that more than 80 percent of body heat goes through the head.

In reality, the heat from one part of the body is equal to the amount of heat from any other part of the body.This myth has its roots in the 1950s. It all started with an extremely ill-conceived experiment by the US Army.

The military decided to “keep” several volunteers in the cold, and later to measure the temperature of each part of the body. An important detail: the military leaders provided the subjects with everything they needed to survive in the harsh Arctic conditions, but forgot to give the volunteers hats.

Therefore, despite the fact that people gradually lost heat through the whole body, it is natural that most of it left through the head.This is to be expected.

After this experiment, “sensational” conclusions were published: the head must be covered, because about half of the heat loss occurs through the head.

Later, after analyzing this phenomenon by more sane scientists, it turned out that all parts of the body in this case are the same, and through the head a person loses no more than 10 percent of the heat.

When going out into the cold, one should not forget about the hat.Although this advice applies to the whole body – all parts of it should be warm.

Some people attribute this statement to the genius of the last century – Albert Einstein , although in fairness it should be noted that not a single work of the great scientist or his associates ever said that a person uses no more than 10 percent of his own brain.

The results of the work of American specialists show that references to this myth are contained in a 1907 source, and this hypothesis is “falling apart” under the influence of numerous studies of patients with brain damage. The authors of these studies have convincingly proved that people use significantly more than a tenth of their brain, since specialists have never been able to identify at least one completely inactive part of this organ. It is quite clear that there can be no question of “non-functioning” 90%.

In conclusion, let us add that most often the “10%” myth is repeated by people actively promoting human self-improvement.

Those who constantly use mineral water, believing that they quench their thirst for the benefit of their health, are in the captivity of delusion.This is confirmed by a number of factors.

First, the human body needs ordinary drinking water. Although it can sometimes be replaced with mineral water, it is not the best idea to completely replace plain water with mineral water.

Secondly, you need to understand that mineral water is different. It is divided into medical and dining rooms. Quenching thirst with medicinal mineral water is just as harmful as quenching hunger with analgin tablets. The thing is that in such water the concentration of salts is 5-7 times higher than the norms permissible for drinking water.It follows from this that only people suffering from certain diseases will be able to experience the benefits of drinking such water. As for healthy people, the constant use of medicinal mineral water is a direct path to kidney stone disease. However, many choose to follow this path.

Based on the above, we recommend that you understand the following rule for yourself: from time to time it is permissible to quench your thirst with table mineral water, and to be treated with medicinal mineral water.

At first, nutritionists told us that eggs are good in the morning before work, then they began to talk about harm to the heart. But still, the first statement is probably more correct.

Yes, eggs contain cholesterol, but our body converts it and reduces its amount during digestion. The study found that eating 2 eggs per day over a 12-week follow-up did not alter cholesterol levels in the body.

And besides the fact that eggs are low in calories (75 kcal per egg), they also contain vitamin D, vitamin B-12 and other useful nutrients.

A study by the University of Florida University of Florida showed that caffeine is still present in decaf coffee, and in fairly large quantities.

People with certain medical conditions (for example, hypertension), as well as representatives of some religious denominations, refuse to use caffeine. However, 10 cups of instant coffee that says “caffeine-free” on the can contains the same amount of caffeine as two cups of regular coffee. This conclusion was drawn from an analysis of 10 decaffeinated coffees sold in the United States.

The average serving of instant “decaffeinated coffee” contains between 8. 6 and 13.9 milligrams of caffeine. A serving of “decaffeinated ground coffee” contains 12-13.4 milligrams. US and Western European standards require a single serving of “decaf” to contain no more than 3 milligrams of caffeine. For comparison, a cup of regular instant coffee contains 85 milligrams of caffeine, and a glass of Coca-Cola has 31 milligrams.Even small doses of caffeine affect the heart rate, blood pressure and psyche. This information was published by the Journal of Analytical Toxicology.

According to the US Food and Drug Administration, the amount of caffeine in a cup of coffee depends on many factors: the type of coffee (for example, Robusta has almost twice as much caffeine as Arabica), where the coffee beans are produced, how preparation (“boiled” coffee contains more caffeine than instant coffee), etc.e. It is considered normal to consume 300 milligrams of caffeine per day.

Keeping your head warm? Is it necessary?

• Claudia Hammond
• BBC Future

October 27, 2015

Photo by Getty

To wear or not to wear is the question. Should I wear a hat when it gets cold? The answer to this question correspondent

BBC Future looked into the results of immersing people in icy water and observing how the inhabitants of Patagonia were insulated.

We were told that we must not turn over in our boat at any cost. Otherwise, we would have only a few seconds to get out of the water before the cold would freeze us.

Here in the Torres del Paine National Park in Patagonia, toothpaste-turquoise icebergs come in all shapes and sizes, from grand pianos to rockets.

From time to time, while we are kayaking, there are the sounds of gunshots and chunks of ice breaking.

Before this trip, I had never thought about how our body loses heat.Now everything I do is multiplied by the hellish cold.

At night, even in a tent, it gets to the bone. I sleep in a medium-sized sleeping bag with all my clothes on (four pairs of pants, three fleeced jackets, two hats, and another layer of waterproof layer).

But this is still not enough for me.

Mariano, our guide, sleeps outside with only a very thick sleeping bag to protect him from the wind.

He assures that he likes it better, and is not going to wear a hat at all.

I’m worried about him – but what about the well-known myth that the body loses most of its heat from an uncovered head?

What Thea Pretorius’ harsh experiments have shown

For many years, physiologists have tried to figure out exactly how people freeze. In this they were assisted by various groups of “guinea pigs” – from hardy students to military personnel.

Experiments in this area usually require people who are able to withstand a certain level of discomfort.

Thea Pretorius of the University of Manitoba in Canada uses scuba gear to estimate how much heat is removed from the surface of the head.

Author of the photo, Thinkstock

Caption,

Due to the effect of cold on the head, we do not lose so much heat. And what is the conclusion from this?

All volunteers participating in the experiment are distinguished not only by their endurance, but also by their hairiness (at least, their heads).

Bald head would add unnecessary complications at this stage of the study.

In one of Thea Pretorius’s experiments, volunteers were given a special substance to stop trembling (with its help the body stops the loss of heat).

Then the subjects were lowered into cold water on a winch. Sometimes they were immersed entirely in water, sometimes their heads were left above the surface of the water.

The second variable in the experiment was the participants’ clothing: the volunteers were dressed in either a bathing suit or an insulated rubberized dry suit, two pairs of socks and wool gloves.Everyone spent 45 minutes in 17-degree water.

As expected, the volunteers lost the most heat immediately after immersion in the water. However, other experimental results have debunked popular myths.

Volunteers who plunged into the water with their heads, but in waterproof suits, lost half as much heat as those who were in simple bathing suits and kept their heads above the surface of the water.

In other words, we do not lose so much heat due to the effect of cold on the head.

According to the results of the experiment, immersion of the head in water increases heat loss by only 10%.

This is not so much, considering that the surface of the head is 7-9% of the entire surface of the body.

So you don’t need a hat?

However, before you go out and throw your entire collection of wool hats in the bin, consider another lesson from this experiment.

If the head is exposed to cold and the body is warm, the overall body temperature drops much faster than most people would imagine.

One of the reasons for this phenomenon is that there are a lot of blood vessels in the scalp, and all of them are especially close to the surface of the skin (which is why, by the way, any cut on the head leads to such profuse bleeding).

Author of the photo, Thinkstock

Caption to the photo,

When the head is cold, people do not tremble. And this is very bad

If on a cold day you put on warm clothes, but forgot to pull on a hat, the air will cool the hot blood as it flows through the vessels of the scalp.The cooled blood then returns to the torso and spreads the cold.

Another reason is trembling. It is curious that people do not shiver when only their head is exposed to the cold.

And since shivering slows down the cooling process of the body, its absence ensures that you will freeze much faster than with a covered head.

In extreme conditions, such as in Patagonia, the final temperature to which your body cools down plays a much larger role than how quickly it happens.

Mariano seems to have grasped this principle. He really needs to take care of his body temperature and keep him warm, and the hat is not so necessary. He knows from experience that all he really needs is a very warm sleeping bag.

Next time I’ll take one too.

Are we losing most of our body heat through our heads?

_{Apperently …}

You can lose 40 to 45 percent of body heat from an unprotected head and even more from an unprotected neck, wrist and ankles.These areas of the body are good heat sources and have very little insulating fat. The brain is very susceptible to cold and can withstand the least amount of cooling. Since there is a lot of blood in the head, most of which is on the surface, you can quickly lose heat if you don’t cover your head. – FM 21-76 US ARMY SURVIVAL MANUAL BASIC PRINCIPLES OF COLD WEATHER SURVIVAL, PG 148.

_{Could this be correct? Does more heat come from our heads than from other parts of the body?}

Short answer: No.

In general, heat loss is necessary to promote thermoregulation and prevent excessive heat build-up in the body to avoid the effects of heatstroke. However, heat loss in the head is the same as for any exposed part of the body. Exposed body surface area, along with relative humidity and temperature, determines heat loss primarily through evaporation, and our head accounts for only 10 percent of our body surface area. Thus, at rest heat loss through the head is only 7-10 percent of the total heat release.- source

See below: Total heat loss through the head.

When you start exercising , cerebral blood flow increases due to increased cardiac output, and the percentage of heat lost through the head is about 50 percent of total body heat loss. As you continue to exercise, more oxygen is directed to the muscles and blood flow to this tissue increases. The core temperature needs to be maintained, and as the body temperature rises, the arterioles of the skin dilate or dilate, redirecting blood flow to the skin, which cools the blood.Consequently, total blood flow to the brain is reduced and the percentage of body heat lost through the head is reduced to about 10 percent. The percentage of lost scalp returns to 7% after the start of sweating. – source

Shivering is an exercise …

But this is important, if they are shivering, the percentage of heat loss through the scalp can increase to 55% , so protecting the head is a very important part of treating a hypothermic patient.And, as you can imagine, the primary defense against cold and hypothermia is peripheral vasoconstriction, this shunts blood to the nucleus, reduces blood circulation in the skin, and increases the percentage of heat loss through the scalp. – source

Total heat loss through the head

Source: Thermal effect of immersion in the head in cold water in shivering people.

One hypothesis predicts significant heat loss through the head due to the large amount of superficial blood flow in the scalp and because scalp blood vessels do not constrict in response to cold as superficial vessels in other areas of the body (8). An alternative hypothesis predicts minimal heat loss from the head, because head and neck immersion will only occupy 7-9% more body surface area (20). In addition, mathematical modeling predicts minimal conductive heat loss directly through the scalp and skull (27).

These results are consistent with previous data (9) in that the assumption of proportionally greater heat loss from the head was not supported.

_{Whole body skin heat loss (n = 8) for base (20 minutes) and dive (30 minutes) periods. * More than insulation, P <0.001. † More than forehead under the same conditions, P <0.05.}

The measured heat loss from the head under both penetration conditions was only 100 kJ (compared to 17 kJ under the two insertion conditions). In contrast, the total heat loss in body-exposed configurations was 914 and 988 kJ, respectively, in frontal impact and frontal impact conditions. In the latter case, the head only accounted for 10% of the total body heat loss when the head and body were immersed in water.The surface area of ​​the submerged head is 7% of the total body surface area.

_{Energy production and loss within 30 min. 17 ° C water immersion (n = 8). Total loss includes cutaneous and respiratory loss of the whole body. Body loss includes trunk, legs and arms. * More than insulation, P <0.001. † More than head under the same conditions, P <0.005. ‡ Conditions higher than slope, p <0.001.}

Thus, these results indicate that heat loss from the head does not increase out of proportion to what would be expected from the contribution of the head to total body surface area.

Nonetheless …

Due to the body being exposed to cold water and intact tremors, additional immersion of the dorsal head increased core cooling from 3. 8 to 9.4 ° C / h ( 250%) in water with a temperature of 1-2 ° C.

Oliver_S is right: “No, Mom, Science says I don’t need to wear a hat! … “

” … Okay, Mom, I’ll take it with me in case I get cold! ”

^{Quoted and worth reading …
(8) Froese G and Burton AC. Heat loses a person’s head. J Appl Physiol 10: 235-241, 1957
(9) Gisbrecht G., Lockhart T., Bristow J. & Steinman A. Thermal effects of immersion of the spinal head in cold water on non-trembling people. J Appl Physiol 99: 1958-1964 2005.
(20) Leighton R., Mintz W.J., Annis J., Rack M. and Webb P. Calorimetry with heat flux converters: comparison with suit calorimeter. J Appl Physiol 54: 1361-1367, 1983.
(27) Xu X, Tikuisis P, Giesbrecht G. Mathematical model of human brain cooling during drowning in cold water. J Appl Physiol 86: 265-272, 1999.}

Which place in the body loses the most heat?

It doesn’t have to be a bare head, as your mother warned you.

The amount of heat given off by any part of the body depends to a large extent on how much that part is exposed. On a cold day, you can easily overcool through your hand without a mitten or bare foot.

The myth about the head is not only stable, but also official. The current military field manual of the US Army recommends to wear a headdress (hat) in the cold.”40-45% of the heat,” says the charter, “the body loses through the head.” This idea seems to have been rooted in the 1950s, when military scientists put subjects in Arctic life suits (without covering their heads) and measured heat loss at extremely low temperatures.

According to Gordon Gisbrecht, a professor at the University of Manitoba and the world’s leading expert on survival in cold conditions, the head and neck are only 10% of the body surface area, and in terms of heat loss, they are no different from the rest of the skin.

If our heads seem to get colder in the cold, it is only because the concentration of nerve cells in the neck and head, compared to other parts of the body, makes them more sensitive to temperature changes. But information from our nervous system (feeling cold) is not a direct sign of heat loss. Everything depends on blood circulation – there is no corresponding increase in the number of blood vessels in the head and neck.

The body responds to cold by closing off blood vessels in unprotected skin and reducing blood flow to the extremities.This is why the ears, nose, and fingers and toes are susceptible to frostbite, while the brain and vital organs remain unaffected under the same conditions. The second reaction to cold is chills : muscles produce involuntary small contractions, thus generating heat . Both of these reactions are automatic; they are controlled by the pineal region of the brain, the so-called hypothalamus , which also controls other instinctive states – hunger, thirst, fatigue.

Professor Gisbrecht is by no means an armchair theorist. To study the effects of cold on the human body, since 1991, he entered himself into a state of hypothermia thirty-nine times. Hypothermia (from the Greek hypo, “under”, and therme, “heat”) is the point at which the internal body temperature drops below 35 ° C, and the key processes (metabolism, etc.) slow down in it … To test all this for himself, the fearless Dr. Gisbrecht plunged into an ice-hole with icy water more than once and drove his thundering snowmobile across the ice of frozen seas in the pitch darkness of the night.Thanks to this, Gisbrecht earned the nickname “Professor Popsicle” – by analogy with the popular North American popsicles on a stick.

If by the will of fate you suddenly find yourself in the icy lake water, the main thing, as Dr. Gisbrecht advises, is to control your breathing in the first minute. When you begin to breathe calmly and evenly, remember that you have ten minutes before the cold begins to affect the muscles, and about an hour before hypothermia sets in. And one more thing: hot drinks do not help in defeating the cold (although sweet ones do, since they provide the body with fuel to generate heat).And do not breathe on your hands trying to warm them. The moisture in your breath will make fingers even colder and increase your risk of frostbite.

90,000 Which part of the body loses maximum heat?

Without a hat, a person will freeze instantly and fall ill – this opinion is very common. Therefore, many believe that it is through the head that the bulk of the body’s heat leaves. Is it really?

The amount of heat that any part of the body gives off depends mainly on the extent to which that part is exposed.On a cold day, you can simply overcool through your hand without a mitten or bare foot. The myth about the head is not only staunch, but also official. The current military field manual of the American ground forces advises to put on a hat in the cold. “40-45% of the heat,” says the charter, “the body loses through the head.”

This idea has been so ingrained since 1950 that military scientists put subjects in various experiments in Arctic life suits (without head cover) and measured the heat loss at extremely low temperatures…

However, in reality, the head and neck occupy only 10% of the body surface area, and in terms of heat loss, they are no different from all other skin. If the head, as it might seem, gets colder in the cold, it is only because the concentration of neurons in the neck and head, unlike other parts of the body, makes them more sensitive to temperature changes.

However, information from the nervous system (namely the feeling of coldness) is not a direct sign of heat loss. It all depends on blood circulation – there is no such increase in the number of blood vessels in the head and neck.The body reacts to cold by closing vessels in unprotected skin and decreasing blood flow to the limbs. This is why the ears, nose, and fingers and toes are susceptible to frostbite, while the brain and vital organs remain unaffected under the same conditions.

Another reaction to cold is chills: the muscles involuntarily produce mini-contractions, thus creating warmth. These 2 reactions are automatic.

Therefore, the head, as well as other parts of the body, must be protected from the cold in the same way.

90,000 5 misconceptions we learned from childhood

Source translation for mixstuff – molten

When we grow up to two years old, we begin to ask questions about our body. As we grow up, our questions become more and more complex and numerous so that any reasonable person can answer them. And it is no coincidence that around this time our parents take us to a school that can provide these answers.

Unfortunately, many of the answers you get are lies that seem to be deliberately designed to make the world around you more boring. How else can you get you to stop asking this bunch of questions? For example, you may continue to believe that

5. We have a total of 5 senses

Sight, smell, touch, taste, hearing. These are your five senses. Since kindergarten, it has become a tradition that if someone thinks that he has six senses, he is either a psychic or Night Shyamalan (director of the famous “Sixth Sense; approx.mixstuff.ru). The original classification of feelings is most often attributed to Aristotle, so if you are trying to argue that there are more than five senses, you may be arguing with the person who invented the intellect.

Scientists are still not entirely sure how many feelings we have, and what exactly these feelings are. Depending on how you count them, there are from 14 to 20 senses. You have known five of them since childhood, but the rest are much more interesting.

The Harvard School of Medicine has six additional senses that are difficult to argue against. Close your eyes, then touch your nose with your index finger. How do you know where which finger is without seeing them? How do you know where your nose is? This is proprioception, understanding by the body where what is in the body and in relation to what.

Perhaps one of the most interesting “unaccounted for” feelings is your sense of time. Leading neurologist David Eagleman believes that this is the most important of all feelings, as it is the thread that ties the rest of the senses together.A set of sensations from, say, an apple, without a sense of time, will tell you that they are all happening at the same time.

It’s also worth noting that feelings that your kindergarten teacher forgot to mention can also work as superpowers. For example, if you are walking through a forest and you hear a bear growling in the bushes to your left, the sound of the roar will reach your left ear one millionth of a second faster than your right. Your sense of time will allow you to catch this difference, and determine the location of the bear in space.

4. Tastes in the tongue

Many people from an early age are sure that each zone on the tongue is responsible for the sensation of a certain taste.

True:

This delusion has been passed down from generation to generation for decades, but it is completely untrue. As often happens, it all started with a mistranslation of a century-old German study. In 1901, the German scientist D.P. Hanig experimented with taste, and found that some volunteers perceive certain tastes more vividly in certain areas of the tongue.Forty years later, a Harvard researcher with a suitable surname, Dr. Boring (here: bleak; approx. Mixstuff.ru), has incorrectly translated the results of the German study.

Researchers have long known that all areas of the tongue are equally good at detecting different tastes. One can hardly speak of a sudden onset of democracy and equality within a single language, since each language has individual characteristics. Your tongue is like a fingerprint. Each of our “language cards” will taste different tastes, sometimes from the same meal.

The taste map of the language was officially debunked thirty years later, although smart books continue to place colorful illustrations of the map of the language, and bourgeois wine producers convince you to buy special glasses that would allow you to direct the drink exactly to the language that is optimal for the “disclosure of this wonderful bouquet” zone.

3. Your personality is determined by the “left” or “right” of the brain

Surely you have heard the widespread opinion that if you are left-handed, then you have some features that help you to better express yourself in creativity, and “rightness” is better suited for logical or intellectual work.This is because the right side of your brain (which controls the left side of your body) is entirely responsible for creativity, while the left side is responsible for logic.

True:

As it turns out, the whole concept of a creative genius occupying the right side of the brain is one big myth. Although this myth has spread so widely that teachers often talk about the need for balanced development of the activity of the right and left hemispheres, or the child’s brain will develop disproportionately, like these armwrestlers, with one frail and the other incredibly developed arms.

Certain parts of the brain are indeed responsible for certain functions, but the idea that they are located in different hemispheres is simply ridiculous. For example, although grammar and vocabulary are located on the left side of the brain, the divisions for intonation and accent are on the right. So you cannot master the language without turning on both hemispheres.

This is how most of the brain functions. Along with language, emotions (for which the right hemisphere seems to be responsible) and arithmetic (where the cold and calculating left side supposedly dominates) receive support from both sides of the brain.Scientists will tell you that in order to be truly creative or strong in logic, you need the resources of both hemispheres.

2. You lose most of your body temperature through your head

One of my mother’s wisdoms, probably, still echoes in your head: “Don’t go for a walk without a hat. Most of the heat goes through the head. ” After all, that might make sense, as heat rises upward.

True:

In general, the belief in the percentage of heat loss through the head varies for everyone; some even believe that up to 80 percent of body heat is lost through the head.

In fact, covering one part of the body has the same effect as covering any other part of the body. The origin of this myth dates back to the 1950s. In one of the least elaborate studies of all time, the US Army decided to put several test subjects in the cold, and then measure the temperature of each part of the body. A small detail: the army provided the subjects with a survival kit for the Arctic, but forgot to give them hats.

So, although the subjects lost heat through all parts of their body, of course, the greatest heat loss occurred through the head.What else did they expect? After that, the army scientists proudly printed out their survival manual with brilliant advice on how best to cover your head, because 40-45 percent of the body’s heat loss occurs through the head.

Later, sane scientists found out that all parts of the body are the same, and that through the head you lose no more than 10 percent of the heat.

But when you go out into the cold, do not forget to wear a hat anyway. Although the same applies to all your limbs, and indeed all parts of your body.

1. Your metabolism makes you fat or thin

From a young age, we learn that even if you watch what you eat and exercise regularly, in the end you will still get fat because of something called metabolism. Metabolism is how much energy your body uses in order to breathe, for the heart to beat, and the rest necessary for normal function to exist.

True:

If you want to know why you are fat or thin, take the number of calories you put into your body and subtract the calories used by the body.The further you go from zero, the thicker you will get. Slow metabolic theory suggests that calorie intake is a dark horse that cannot be controlled.

And there is no particular time of day for eating that will magically make your figure slimmer. In fact, scientists who are not working on new miracle breakfasts for weight loss believe that if you are trying to lose weight, then the best option would be to skip breakfast.

They say that there is no particular difference between the metabolism of overweight and thin people. Researchers at the Mayo Clinic found that the metabolism of overweight and underweight people is the opposite of what we usually hear: lean people actually have a slower metabolism than their heavier counterparts.

What about those who swear they eat no more than a hummingbird per day, but still continue to gain weight? Research shows that they are not necessarily misguided, they just fall prey to misperceptions and misconceptions.It’s just that overweight people eat large portions, and underestimating how much they eat, they believe that they are forced to suffer from some unfair advantage in the form of “improper metabolism.”

.

90,000 Keep your head warm? Is it necessary? | The world | Inosmi

To wear or not to wear – that is the question. Should I wear a hat when it gets cold? The BBC Future correspondent looked for the answer to this question in the results of immersing people in icy water and observing how the inhabitants of Patagonia warm themselves.

We were told that we must not turn over in our boat at any cost. Otherwise, we would have only a few seconds to get out of the water before the cold would freeze us.

Here in the Torres del Paine National Park in Patagonia, toothpaste-turquoise icebergs come in every shape imaginable, from grand pianos to rockets.

From time to time, while we are kayaking, the sounds of pistol shots and chunks of ice breaking are heard.

Before this trip, I had never thought about how exactly our body loses heat. Now everything I do is multiplied by the hellish cold.

At night, even in a tent, it gets to the bone. I sleep in a medium-sized sleeping bag with all my clothes on (four pairs of pants, three fleeced jackets, two hats and another layer of waterproof layer).

Shivering slows down the cooling process of the body

But this is still not enough for me.

Mariano, our guide, sleeps outside with only one very thick sleeping bag to protect him from the wind.

He assures that he likes it better, and is not going to put on a hat at all.

I’m worried about him – but what about the famous myth that the body loses most of the heat due to the bare head?

What Thea Pretorius’ harsh experiments have shown

For many years, physiologists have tried to figure out exactly how people freeze. In this they were assisted by various groups of “guinea pigs” – from hardy students to military personnel.

Experiments in this area generally require people who are able to withstand a certain level of discomfort.

Thea Pretorius of the University of Manitoba in Canada uses scuba gear to estimate how much heat is removed from the surface of the head.

Due to the effect of cold on the head, we do not lose so much heat. And what is the conclusion from this?

All volunteers participating in the experiment are distinguished not only by their endurance, but also by their hairiness (at least, their heads).

Bald head would add unnecessary complications at this stage of the study.

In one of Thea Pretorius’s experiments, volunteers were given a special substance to stop tremors (with its help the body stops the loss of heat).

Then the subjects were lowered into cold water on a winch. Sometimes they were immersed entirely in water, sometimes their heads were left above the surface of the water.

The second variable in the experiment was the participants’ clothing: the volunteers were dressed in either a bathing suit or an insulated rubberized dry suit, two pairs of socks and wool gloves.Everyone spent 45 minutes in 17-degree water.

Submerging the head in water increases heat loss by only 10%.

As expected, the volunteers lost the most heat immediately after submersion. However, other experimental results have debunked popular myths.

Volunteers who plunged into the water with their heads, but in waterproof suits, lost half as much heat as those who were in simple bathing suits and kept their heads above the surface of the water.

In other words, we do not lose so much heat due to the effect of cold on the head.

According to the results of the experiment, immersion of the head in water increases heat loss by only 10%.

This is not so much, considering that the surface of the head is 7-9% of the entire surface of the body.

So you don’t need a hat?

However, before you go out and throw your entire collection of wool hats in the trash can, consider another lesson from this experiment.

If the head is cold and the body is warm, the overall body temperature drops much faster than most people would imagine.

One of the reasons for this phenomenon is that there are a lot of blood vessels in the scalp, and all of them are especially close to the surface of the skin (which is why, by the way, any cut on the head leads to such profuse bleeding).

When the head is cold, people do not tremble. And this is very bad

If on a cold day you put on warm clothes, but forgot to pull on a hat, the air will cool the hot blood as it flows through the vessels of the scalp.