The researchers write about their findings in a paper that is available to read online, ahead of the May print issue of the journal Appetite.
First author Michael A. Grandner, Instructor in Psychiatry and member of the Center for Sleep and Circadian Neurobiology at Penn, says in a statement:
"Although many of us inherently recognize that there is a relationship between what we eat and how we sleep, there have been very few scientific studies that have explored this connection, especially in a real-world situation."
He says we already know from previous studies that in general, people who report sleeping between 7 and 8 hours of sleep a night are also the ones most likely to be in better health and feeling well, so he and his colleagues just wanted to know:
"Are there differences in the diet of those who report shorter sleep, longer sleep, or standard sleep patterns?"
The team looked for an answer by analyzing data from NHANES (short for National Health and Nutrition Examination Survey), an annual national survey that is sponsored by the Centers for Disease Control and Prevention (CDC).
The survey selects a representative sample of the US population, by age and demographics. The survey questions gather data about respondents' demographics, socioeconomic cicumstances, diet, and health.
Grandner describes what they found:
"Overall, people who sleep 7 - 8 hours each night differ in terms of their diet, compared to people who sleep less or more. We also found that short and long sleep are associated with lower food variety."
The StudyFor their analysis, the team used data from the 2007-2008 NHANES, and focused on responses to questions about sleep and diet. They put the respondents into groups, depending on how much sleep they said they were getting each night.
The groups were: very short sleep (less than 5 hours a night), short sleep (5 to 6 hours a night) standard or normal sleep (7 to 8 hours a night), and long sleep (9 hours or more a night).
The NHANES data contains detailed information about respondents' daily diet, gathered in interviews with specially trained staff. This includes, for example, details about occasional glasses of water to comprehensive accounts of every part of each meal, allowing the researchers to calculate the nutrient and calorie intake of each of the sleep duration groups.
Diet Variations Linked to Sleep PatternsGrandner and colleagues found that calorie intake varied across the groups, with short sleepers consuming the most calories, followed by normal sleepers, followed by very short sleepers, followed by long sleepers.
When they looked at food variety, they found this was highest in the normal sleep group and lowest in the very short sleep group.
There were differences among the groups in intake of proteins, carbohydrates, vitamins and minerals, but when the researchers analyzed these with statistical tools they found the differences were largely driven by a handful of key nutrients.
This analysis showed that, compared to the diet of the normal sleep group:
- Very short sleep was linked to less intake of tap water, lycopene (present in foods that are red and orange in colour, for instance tomatoes), and total carbohydrates.
- Short sleep was linked to lower intake of vitamin C, tap water, selenium (found in nuts, shellfish and meat), and higher intake of lutein/zeaxanthin (found in green, leafy vegetables).
- Long sleep was tied to lower intake of choline (found in eggs and fatty meats), theobromine (present in chocolate and tea), dodecanoic acid (a saturated fat) , and total carbohydrates, and a higher intake of alcohol.
ImplicationsGrandner points out that the study does not tell us, if people were to change their diet, would it affect their sleep pattern?
"This will be an important area to explore going forward as we know that short sleep duration is associated with weight gain and obesity, diabetes, and cardiovascular disease."
He says people who sleep too long also have health problems.
"If we can pinpoint the ideal mix of nutrients and calories to promote healthy sleep, the healthcare community has the potential to make a major dent in obesity and other cardiometabolic risk factors," he urges.
Grants from the National Institutes of Health supported the study.
If you are someone who struggles to get a good night's sleep, you may wish to try restricting rather than extending the amount of time you spend in bed: this is the latest suggestion from the new Good-Night Guide from The Sleep Council, which says sleep restriction can help people who only manage limited sleep, to fall asleep faster and wake up less often.
Written by Catharine Paddock PhD