We know that 7-8 hours of sleep per night tends to lead to better health overall, at least at a population level. We also know that the way you sleep (and how much) is linked to overeating, but is it possible that healthy diets can keep you up at night? Does a causal link exist in both directions?
A recently published research study looking at the USA National Health and Nutrition Examination Survey (NHANES) in 2007-2008 involving 4,548 people looked at how much sleep the participants reported getting each night, as well as a very detailed report of their daily diet. For the purposes of this study, very short sleep patterns were defined as less than five hours a night, short sleep was five to six hours a night, standard sleep was 7 to 8 hours, and long sleep was nine or more hours a night. Their analyses revealed that people in the different sleep categories also had different diet patterns. Short sleepers (5-6 hours) seemed to take in the most calories, followed by normal sleepers (7-8 hours), and then very short sleepers (<5 hours). Long sleepers (9+ hours) tended to consume least calories of all. However, normal sleepers seemed to report the greatest variety in their diets, with very short sleepers reporting the least variation in what they ate. This is important because a varied diet tends to be a marker for good health since it includes multiple sources of nutrients.
In more detailed analyses looking and both macro and micro nutrients, very short sleepers reported drinking less tap water and consumed fewer total carbohydrates and lycopene than people with other sleep patterns. Lycopene is found in red and orange-colored fruits and vegetables and is high in cancer-fighting antioxidants. Short sleepers tended to take in less vitamin C, tap water and had lower selenium consumption, but more lutein or zeaxanthin, (which are found in green, leafy vegetables). Long sleep was associated with consuming less theobromine, which is found in chocolate and tea, the saturated fat dodecanoic acid, choline found in eggs and fatty meats and total carbohydrates. Long sleepers also drank more booze.
What do all the correlations mean? The first thing to note is that they are not proof of a causal link. In fact, the study probably raises more questions than it answers – which is a good thing, in my view. Previous research has suggested that sleep deprivation interferes with hunger and satiety hormones crucial to regulating appetite. But the study authors raise the possibility that the relationship works both ways, and that diet can alter possibly sleep as well. Some of the interactions are well-known already, such as how drinking too much water and interrupt sleep by waking you up to use the bathroom, or how consuming heavy and spicy foods can keep you up, but there may be less apparent effects as well. Slightly odd that more alcohol is associated with longer sleep though. I wonder what the quality of that sleep was like?