How sleep affects your body

Written by: 
Simon Crompton, medical writer & author

Research has suggested that a lack of sleep is associated with increased risk of some cancers, heart disease and diabetes. There’s also an increasing consensus that lack of sleep can contribute to weight gain. The reason is that our vital hormonal systems regulate and reset the body at night. Our nocturnal functions are vital to our daytime wellbeing.

Sleeplessness and your weight

Kidney filtration and bowel activity reduce at night. There is little evidence that eating shortly before sleeping, leaving food in an inactive gut, has any ill effect apart from leaving you feeling a bit full in the morning. Though some diet gurus say that eating carbohydratesA group of compounds that are an important energy source, including sugars and starch. before bedtime makes you put on weight, it shouldn’t make a difference because your metabolismThe chemical reactions necessary to sustain life. is working more slowly.

But the hormones that regulate your metabolismThe chemical reactions necessary to sustain life. and hunger levels do change with sleep. Studies by the National Sleep Foundation in America have revealed that sleep keeps down the levels of an appetite-driving hormoneA substance produced by a gland in one part of the body and carried by the blood to the organs or tissues where it has an effect. called ghrelin. It also keeps up levels of the hormoneA substance produced by a gland in one part of the body and carried by the blood to the organs or tissues where it has an effect. leptin, which prevents the body from thinking that it needs more food. In other words, sleep helps you to keep slim, while lack of sleep can contribute to obesityExcess accumulation of fat in the body.. Experiments indicate that restricting sleep can mean that your body thinks it is short of up to 900 calories a day.

Brain and senses 

Our brains career on a rollercoaster of changing activity as we go through the phases of sleep — non-rapid eye movement sleep, which includes light sleep, true sleep and deep sleep, and rapid eye movement (REM) sleep, which is when we dream. As sleep deepens, most brain cells fire off less rapidly, but in a far more co-ordinated pattern than during waking hours. With sleep, our eye movements change, darting around wildly during REM sleep. Our mouths become dry but our ears remain alert to noise.

Increased immunity 

The immune systemThe organs specialised to fight infection. is more active at night. Experiments have shown that during sleep it releases more proteins called cytokines, which mean that the system can launch co-ordinated attacks on invaders. Research from Stanford University indicates that the immune systemThe organs specialised to fight infection. fights invading bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. hardest at night, and least during the day. In fact, there are studies showing that if we don’t sleep, we become more susceptible to infectionInvasion by organisms that may be harmful, for example bacteria or parasites. from colds. Malcolm von Schantz, associate dean at the Surrey Sleep Research Centre, says that this is why asthma attacks — which can be caused by an overreaction of the immune systemThe organs specialised to fight infection. — are more common at night.

Skin renewal 

Our skin changes at night as it receives extra supplies of bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.. Research by cosmetics companies suggests that after shearing off layers of surface dead cells in the day, our skin increases the rate of production of new cells in deep sleep. There is some objective evidence too that the skin is improved at night. A study presented to the European Sleep Research Society suggested that people who were sleep-deprived were consistently rated as looking less healthy and attractive, partly because of their skin tone.

Repair and regeneration 

The levels of stressRelating to injury or concern. hormones such as cortisolA steroid hormone important for helping to regulate carbohydrate metabolism and the stress response., which keep us active during the day, drop in the evening. Instead, the body secretes growth hormones in large amounts, making us grow up until early adulthood. As we get older, growth hormones are responsible for promoting the repair of damaged tissue. The body also produces more melatonin, which helps us to sleep and may also help to protect us against certain types of cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body.. Temperature drop our in-built body clock lowers our temperature by about 1C at night because our body is far more likely to descend into sleep if it is cool. That’s why we tend to feel chilly if we nod off on the sofa. Temperatures fall to their lowest level during the 10 to 30-minute periods of REM when we need to be under a duvet. As morning comes, body temperature rises, which helps us to wake up.

Limb transformation 

Several scientists have noticed that limbs, hands and feet tend to become enlarged during sleep. This is possibly because they have become engorged with bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.. Our limbs become paralysed during REM sleep, preventing us from acting out our dreams.

Heart and blood 

According to the Division of Sleep Medicine at Harvard Medical School, one function of sleep may be to give the heart a chance to rest from the constant demands of waking life. For most of the night, the heart rate decreases and blood pressure drops as bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. is pushed around the body with less and less force. During REM sleep, however, the heart rate increases again.

Top tips for sleeping: diet

Cold remedies and painkillers

To perk you up, caffeine is added — up to 60mg per dose, equal to half a cup of coffee.

Cheese

There is ittle evidence to support its sleep-depriving properties, although its high fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. content means it stays in the stomach, possibly causing restlessness.

Malted drinks and hot chocolate 

These bedtime drinks can contain about 4tsp of sugar, which raises bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. glucoseA simple sugar that is an important source of energy in the body. levels and keeps you alert.

Ginger 

A “stimulating” herb, according to herbalists. Avoid ginger-tea infusions before bed.

Luxury ice creams 

The good-quality coffee flavours can contain significant amounts of caffeine per serving.

Ginseng 

High doses of the herb have been associated with nervousness and insomnia.

Hot milk 

The amino acidAn organic compound that is the basic building block of all proteins. tryptophan, present in milk, is said to enhance sleep, but one cup is unlikely to contain enough to have a sedative effect.

Rice and pasta 

A carbohydrate-rich dinner may help you to relax. Carbohydrates help in the production of the feelgood brain chemical serotonin.

Turkey

It contains tryptophan. Combined with bread in a late-night sandwich, it may have a soporific effect.

Camomile tea 

An old remedy, but an effective one. Camomile contains plant compounds that have similar effects to anti-anxiety drugs.

Valerian

This herbal remedy has had mixed success as a sedative in trials, but some people swear by it.

And finally . . .

Eat regularly. Experts tell us that people who eat at regular times throughout the day usually have better sleep habits.

(c) Simon Crompton   www.simoncrompton.com