Fiber and Saturated Fat Are Associated with Sleep Arousals and Slow Wave Sleep, Journal of Clinical Sleep Medicine, January 2016
Conclusions: Low fiber and high saturated fat and sugar intake is associated with lighter, less restorative sleep with more arousals.
Here’s the press release:
Study Suggests That What You Eat Can Influence How You Sleep, American Academy of Sleep Medicine, 14 January 2016
A new study found that eating less fiber, more saturated fat and more sugar is associated with lighter, less restorative, and more disrupted sleep.
“Our main finding was that diet quality influenced sleep quality,” said principal investigator Marie-Pierre St-Onge, PhD. “It was most surprising that a single day of greater fat intake and lower fiber could influence sleep parameters.”
Participants were fed a “healthy” diet for 4 days. On the 5th day, they were given $25 to purchase any food they wanted for the day. The 5th day’s self-selected food was analyzed in their lab.
Now, on the 5th day, they slept just as long as the other days, an average of 7 hours, 35 minutes. (These were relatively young, normal weight, healthy volunteers who didn’t have sleep problems.) But the 5th day’s sleep was more disrupted than the sleep on the 4 days prior.
I was confused by their comparisons. Maybe you can help me out. Were they saying that the 5th days’ sleep was worse because the food on the fifth day was different than the food on the other 4 days? Or were they just looking at people’s food on one day, the fifth day? If it was the former, I can imagine several factors that could disrupt sleep other than diet composition: The 5th day was an unusual day. They had to find food, and it was restricted in cost. There may have been more food preparation. The time that they ate the food, and who they ate it with, could have been different. And, of course, diet composition other than the items highlighted (fiber, saturated fat, sugar) could be playing a role, e.g. they did eat more calories, on average, on the 5th day.
If they were just looking at one day, the 5th day, to determine how nutrients affect sleep, that might make more sense. But it was only one day.
My criticisms and confusions aside, I think that nutrients can and do affect sleep. Dietary fat is digested slower, leaves the stomach more slowly, and may slow digestion of a whole meal. That effort could delay sleep. Fiber – all types: soluble, insoluble, resistant starch – affects gut flora which in turn affects all sorts of nerve-related functions including mood and sleep. I think there’s something to this study. It would be nice to see something larger and more controlled.