chapter 11: the significance of sleep and your immune system

For over 2,000 years, the relationship between immunity and sleep has been a hot topic, and even Hippocrates confirmed the role of ‘sleepiness’ during an acute infection¹⁰².

Along with the circadian rhythm, sleep is known to regulate immune function. Ensuring you get sufficient sleep is crucial for gut health and immunity, since numerous studies have shown a significant decrease in immunity, after either a night without sleep or after a lengthy continual period of sleep deprivation¹⁰³. The studies’ findings confirm that both lymphocytes and NK cells are reduced when we are sleep-deprived and immune function is altered. In fact, one study showed that just a single night with a lack of sleep can decrease NK cell activity by as much as 30 per cent. A second study also reported a reduction of 30 per cent in NK cell activity in healthy participants who slept less than seven hours compared with participants who slept seven to nine hours¹⁰⁴.

Chronic disturbance of our circadian rhythm and sleep deprivation, which impacts our gut bacteria and promotes alterations in their composition, is also associated with dysbiosis. These harmful changes may then lead to inflammation, metabolic disorders and weakened immunity. This process may also alter the metabolism of neurotransmitters and result in nervous system dysfunction. The individual then experiences sleep problems and this, ultimately, initiates a vicious cycle. However, research shows that individuals who get morning sunlight exposure reportedly have a better quality of sleep. Further studies have also highlighted that vitamin D impacts sleep quality, and low serum levels of vitamin D have been linked to a greater risk of sleep disorders and inferior sleep quality¹⁰⁵. Ensuring we get enough natural sunlight is key for a good night’s sleep.

Sleep deprivation may also increase inflammation and stress hormones in your body, and this may explain why not getting enough sleep is linked with worse gut symptoms. Therefore, ensuring sufficient good-quality sleep is key for our immunity, gut health and overall health.

Let’s explore some of the most effective strategies for ensuring sufficient shut-eye.

How to sleep well

Sleep requirements differ from person to person; however, the NHS states that most healthy adults need between seven and nine hours of sleep each night to allow our bodies to recover and function at their best, while children and teens need even more¹⁰⁶. It is commonly believed that our sleep requirements reduce as we get older; however, elderly individuals still need at least seven hours of sleep. Unfortunately, many of us aren’t sleeping as much as we should. Of the 5,000 individuals who participated in a British Sleep Council survey, 74 per cent said they had less than seven hours sleep a night, while 12 per cent confessed they had less than five hours, which is more than the 7 per cent who said the same in 2013.

If you are struggling with your sleep, consider the following tips:

During the day

• Try to wake up at the same time each day.
• Aim to go for a walk before breakfast, as morning light turns off your brain’s production of melatonin, the hormone that encourages sleep.
• Try to get outside in the sunshine at some point during the day, as this will help keep your vitamin D levels topped up (studies have shown that low vitamin D levels are associated with inferior quality and decreased duration of sleep). It also helps to maintain your body’s circadian rhythms, which impacts your sleep-wake cycle.
• Exercise regularly, but try to exercise at least a few hours before you go to bed. Exercising too close to bedtime can make it harder to fall asleep and also lead to disrupted sleep.
• Limit caffeine from midday. Caffeine increases the stress hormone, cortisol, which can not only impact sleep, but increased levels may also reduce your immune system’s ability to fight infection.
• Avoid lengthy afternoon naps.
• Stress is an important cause of insomnia, so adopt the most appropriate stress-management for you.

Before bed

• Refrain from eating late at night. If your gut is having to do a lot of substantial digestion work, this will impact the quality of your sleep and make it harder to fall asleep.
• Limit alcohol and nicotine in the evening, as they can interrupt your sleep.
• Adopt a relaxing routine before bedtime, such as listening to soothing music or having a warm scented-oil bath. Try an Epsom salt (magnesium salt) bath, which has been shown to promote sleep.
• Write down three positive things that occurred that day. This is part of my bedtime routine. In fact, this has been shown to be one of the most effective strategies to boost mood.
• At least 30 minutes before bed, turn off your electronic devices – light from these devices can stimulate brain activity, making it more difficult to fall asleep.
• Dim the lights before bedtime, as this will encourage your brain to realize that it’s time for bed.
• Create a relaxing environment in your bedroom – studies have indicated that there is a strong association in people’s minds between sleep and the bedroom.
• Make sure your bedroom isn’t too hot or cold – 18.3°C (65°F) has been suggested as an ideal sleeping temperature.

In bed

• Avoid using your phone or laptop; instead read a book to help you relax.
• Focus on steady breathing to help you relax.
• If you are unable to fall asleep, read a book or listen to music until you are ready to go to sleep.

Glycine

Glycine is an amino acid that has been shown to help regulate the body’s immune response, limit inflammation, and promote healing and repair. It also helps the body make serotonin, which is a neurotransmitter that has a profound impact on sleep and also mood. Glycine affects sleep in different ways, and several studies indicate that supplementation of 3g of glycine before bedtime can improve sleep quality, and reduce sleepiness and fatigue during the day in sleep deprived individuals107. Glycine supplementation before bedtime has also been reported to help you fall asleep quicker, reduce insomnia symptoms and promote sleep efficiency.

Do note that there are commonly used medications that may interact with glycine. If you take any medication or supplements, please do seek advice from your doctor before beginning to use glycine as a supplement. Clozapine is one drug that is used in the treatment of schizophrenia, and supplementing with glycine whilst taking clozapine may decrease the effectiveness of clozapine. Thus, it is recommended that people who are taking clozapine do not use glycine. Also, women who are pregnant or breastfeeding should not supplement with glycine, since we don’t know if it’s safe to use during pregnancy or lactation.

Key points

• Keep to a consistent bedtime routine in a dark environment.
• Avoid screen time before bedtime.
• Aim for 7–9 hours sleep time.
• Keep to a consistent waking time.
• Aim for a walk in the morning.
• Ensure you get some sunshine during the day.
• Avoid caffeine-containing drinks or foods after 12pm.
• Limit alcohol as it is known to disturb sleep.
• Supplement with 3g of glycine, if advised.