Previous studies have shown an interesting but complicated relationship between sleep and diet. The link between sleep apnea and obesity is certainly real, as those with excess weight are at a much, much higher risk for developing obstructive sleep apnea. But what about sleep in general? Are there certain foods that affect how we sleep? Anecdotal evidence suggests eating foods with melatonin may help with sleep, but these studies remain controversial. Additionally, given that Vitamin D (usually acquired from the sun, but also can be obtained from food) is thought to have an effect on sleep, a study was developed to test consumption of a Vitamin D on sleep in a group compared with a group not consuming large amounts of Vitamin D. So, what type of food was used that contained so much Vitamin D? Fatty fish, of course!
In this study, 95 subjects were used to test how a diet containing Atlantic salmon affects sleep. Subjects were assigned to two groups. They were either assigned to eat fish 3 times per week for about 6 months, or they were assigned to eat another type of meat (chicken, beef, or pork) for 6 months. Before and after this 6-month period, sleep was tested using a motion detector watch, which is standard for calculating the amount and quality of sleep obtained. Sleep was studied for one week before and one week after the fish or meat intervention. In addition, Vitamin D levels and quality of life were tested using blood samples and questionnaires at both time points.
Sleep statistics were compared for before and after the diet change in each group. Interestingly, results showed that those in the non-fish group (i.e., those eating other types of meat) took longer to fall asleep after the diet change, whereas those in the fish-eating group did not. There was a decrease in sleep quality (time spent asleep divided by time spent in bed) in both the fish- and the meat-eating group. Finally, the meat-eating group showed an increased amount of total wake time when compared to before diet change. After the diet change, the fish-eating group showed an increased quality of life, as reported in questionnaires. Finally, when Vitamin D levels were tested, the fish-eating group had higher levels when compared with the meat-eating group. Sleep and Vitamin D may be related in this population, as there was a correlation between sleep quality and Vitamin D status1.
Although this study suggests that eating Atlantic salmon will improve your sleep, it is probably not that simple. It may be that the increased Vitamin D levels obtained from eating fish did improve sleep, or it may be that those who were eating other types of meat were taking in sleep-harming nutrients. This study is interesting, however, but since each individual is different, it is important to pay attention to how different foods affect your sleep. If you eat something that gives you a disrupted night in bed, avoid it next time! Your body knows best!
1. Pre-publication online release: Journal of Clinical Sleep Medicine -- Fish consumption, sleep, daily functioning and heart rate variability