Our resident Sleep Expert, Christabel Majendie explores the relationship between food and sleep.

There is an obvious link between sleeping and eating; when you have eaten you are more likely to feel sleepy. People are maybe less aware that it is harder to nod off on an empty stomach. Hunger promotes wakefulness, in a sense our brain is telling us to go out foraging.

However, it is generally not a good idea to have a huge feast just before sleeping so leave a couple of hours to digest a heavy meal before bedtime. This is particularly important if you are prone to reflux as the digestive juices produced on eating are more likely to escape the stomach and cause discomfort if you are lying flat. But a snack before bed might be a good idea if you have eaten early and your stomach is rumbling. Which leads to the question of what to eat if you are hungry before bed?

Tryptophan is an amino acid involved in the production of the neurotransmitter serotonin and the hormone melatonin, both important for sleep regulation. Tryptophan is found in some proteins such as chicken, turkey, milk and dairy products. It is also present in some nuts and seeds, beans and bananas. So it seems logical to include these in any bedtime snacks you choose to have. Nutritionists suggest combining these with a complex carbohydrate to boast melatonin levels. So you could try some peanut butter on wholemeal toast, some natural yogurt with banana and seeds, a bowl of low-sugar cereal and milk or simply some warm milk to drink. Having said all that, scientific research has yet to show that these foods can make a difference to your sleep.

What about the old wives’ tale about cheese before bed giving you nightmares? Again there is no good evidence to suggest this is true. In fact, since cheese contains tryptophan, in theory it may actually help you sleep. However, the advice is to avoid large quantities of high-fat foods before bed as these take longer to digest and can disrupt sleep. So eating a cheese fondue before bed may not be beneficial. The key is moderation; keep it snack-size.

Tart cherry juice has been advocated as a promoter of sleep due to its naturally high concentration of melatonin. One scientific study (although funded by a cherry juice manufacturer) found that elderly adults with chronic insomnia showed a slight reduction in their symptoms and less wake time after sleep onset compared to placebo after drinking the juice twice a day, once in the morning and once a few hours before bed. However, this was a small study that did not explore long term effects and participants still showed significant sleep disturbance despite the small effect.

So although the theory makes sense, there is little scientific evidence to suggest these foods can improve your sleep in practice. It might be that the level of tryptophan or melatonin found in these foods is too low to have a detectable effect on sleep. Or it might be that the time you eat these foods is the crucial factor. Studies show that a melatonin supplement (only available in the UK on prescription) has less of an effect on sleep if taken just before bedtime. The maximum effect occurs if taken in the afternoon or early evening but this depends on the individual’s internal circadian rhythm or biological clock which can vary widely from person to person.

There are some obvious foods to avoid before bed: chocolate contains caffeine so it’s best to not have this as your bedtime snack. This also applies to drinks such as hot chocolate, coca cola, tea, coffee and energy drinks. Switch to decaffeinated drinks, milk or water. Also be aware of some medications that may contain caffeine such as pain killers, cold relief and weight loss pills.

Alcohol will have an effect on your sleep so if you have a few drinks it’s best to leave a couple of hours before heading to bed. People often find they are drawn to alcohol in the evening as it helps with relaxation, a prerequisite for sleep. It also helps you to fall asleep more quickly but it will then lead to more night awakenings, dehydration, and early morning waking leaving you feeling more tired the next day. It also suppresses rapid eye movement (REM) sleep which is important for memory, learning and other cognitive skills.

Nutritionists suggest lack of magnesium may be linked to sleep problems. Foods rich in magnesium include green leafy vegetables, pumpkin seeds, almonds and wheatgerm. A deficiency in B vitamins has also been suggested to cause sleep problems. Magnesium and B-complex vitamin supplements are available over the counter but check with your doctor before taking these.

What about sleep’s effect on what we eat? This is an interesting area of research indicating that poor sleep leads us to seek out more unhealthy food the following day. The link appears to be due to sleep’s effect on some of the hormones that control our appetite. Studies have shown that after sleep deprivation, ghrelin increases, the hormone that makes us feel hungry, while leptin decreases, the hormone that makes us feel satiated. So poor sleep may actually influence the foods you eat and subsequently your weight. In fact, there is some evidence to suggest that under sleeping puts you at risk of being overweight and obese. While this may be partly explained by sleep’s role in the regulation of metabolic hormones, it may also be due to the internal biological clock being out of sync with the social clock. It is now well established that every cell in the body contains an internal clock that dictates cellular and biological processes. This includes liver and pancreatic cells and other organs involved in digestion. So put more simply some people may be eating at a time when their bodies are not geared up for food intake.

It comes down to a simple message: prioritise a healthy diet and a healthy sleep routine; listen to your natural internal clock to tell you when to eat, when to relax and when to sleep. And stick to a regular routine so your body knows what to expect.