It is well established that diet can have a pronounced effect on sleep. Both caffeine and alcohol can for example disrupt sleep. Also, it is known that the macronutrient (fat, protein and carbohydrate) content of the diet can affect sleep. It is known for example that carbohydrate meals can cause a significant release of insulin and this can create a situation whereby tryptophan is more likely to enter the brain, via the blood brain barrier, and this in turn can increase the synthesis of serotonin, which in turn can act as a substrate for melatonin, an important hormone in the induction of sleep. By this mechanism, it is known that high carbohydrate diets can induce a better quality of sleep through increased serotonin production. Sleep is highly important as it is a primary defence against stress, although ironically stress prevents a good quality sleep and this can exacerbate the detrimental effects of the stress. Nutritional strategies that can break this cycle are therefore of interests.
It is known that high carbohydrate diets can induce sleep through activation of the serotonin synthesis pathway in the brain. The increase in serotonin, then causes an increase in melatonin, which subsequently induces sleep. It is known that increasing the carbohydrate and protein content of the diet of infants significantly increases sleep duration. However, investigation of the mechanisms by which this occurs suggests that it is not the tryptophan content of the protein that is associated with this sleep duration. In addition, the use of animal versus plant protein appears not to be important. Of course this does not mean that neurotransmitter effects in the brain are not evident. It is highly likely that neurotransmitter chemistry is influenced by macronutrient changes. However, it does suggest that increasing the tryptophan content of the diet is not as important as the actual macronutrient content. As carbohydrate can increase serotonin synthesis without the need for additional dietary tryptophan, this appears to be the most likely explanation for the association between higher protein and carbohydrate diets and longer sleep duration.
Short sleep duration is associated with an increased energy intake and obesity, and this may have a stress connection. This association between weight gain and sleep quality is present in young children, and so improving the quality of sleep in infants may have long term health advantages that go beyond the benefits of a better night’s sleep for the caring parents. Studies for example have shown that modifying the macronutrient intake of infants can increase sleep duration. In one study, isocaloric substitution of fat for protein and carbohydrate was associated with a longer sleep duration at age 2, but not age 3 years. For each 5 % increase in in energy from either protein or carbohydrate, at the expense of fat, there was a 6 min increase in sleep duration at age 2 years. The researchers investigated if the type of fat removed from the diet was associated with sleep duration, and found that at age 3 years, replacing saturated with unsaturated fat was associated with a 7 min shorter sleep duration.
Eat Well, Stay Healthy, Protect Yourself
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