Another Benefit of a Mediterranean Diet for Older Adults May Be Better Sleep, Study Says
The evidence, though, does come with a lot of caveats.
You’ve probably heard about the myriad of health benefits that have been associated with following a Mediterranean diet, including reduced risk of heart disease and certain cancers. Now a new study, published September 5, 2018, in the journal Geriatrics & Gerontology, has suggested eating a Mediterranean diet may also help improve the quality of sleep in older adults.
While previous research has shown some indication that there is a link between good sleep and what we eat, research has not yet revealed exactly how the two influence one another. “There is not much information on sleep and specific nutrients in food,” says Eirini Mamalaki, lead author of the study and a PhD candidate at Harokopio University in Athens, Greece.
Mamalaki and colleagues assessed the diets and sleep patterns of 1,639 adults ages 65 and over from a suburb of Athens and an urban area in Greece, via questionnaires that participants completed. Anyone diagnosed with dementia and anyone undergoing treatment for sleep problems were excluded from the study.
The participants answered questions about how many times they woke up during the night, how long it took them to fall asleep, and whether or not they felt refreshed upon waking; as well as about how often they ate dairy products, cereals, fruits, vegetables, meat, fish, legumes, added fats, alcoholic beverages, and sweets.
The results showed that those who followed a diet closest to the Mediterranean model were found to have better sleep quality than those whose diets were less similar to that ideal, meaning they reported that they tended to take less time to fall asleep, slept more soundly throughout the night, felt rested upon waking in the morning and throughout the following day, and felt they were able to get the sleep they needed.
Notably, the diet didn’t seem to have an effect on how long individuals slept — researchers didn’t find any difference in sleep quantity among those who ate a diet more or less aligned with a Mediterranean one. Interestingly, this positive effect on sleep in those following a Mediterranean diet was only seen in those under age 75.
The Mediterranean Diet Is Linked to a Lot of Other Health Benefits, Which Led Researchers to Ask if It Might Be Good for Sleep, Too
The Mediterranean diet is rich in fruits, vegetables, nuts, legumes, whole grains, and seeds; it includes healthy fats, such as olive oil and omega-3 fatty acids from fish; it limits (but doesn’t eliminate) red meat and unhealthy fats like butter; and it relies on spices and herbs rather than salt to add flavor to meals.
The diet is modeled after the way of cooking and eating in countries that surround the Mediterranean Sea (hence the name), but it typically includes the lifestyle of those people, too. The diet allows wine in moderation (one glass per day for women and two glasses for men). And meals are most often shared in a social setting, in the company of friends and family.
This healthy diet has been linked to a reduced risk of developing certain chronic conditions, including heart disease, breast cancer, Parkinson’s disease, and Alzheimer’s disease. It’s been shown to reduce levels of low-density lipoprotein (LDL) cholesterol, which is also known as the "bad" cholesterol.
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And because of these known positive health effects of following a Mediterranean diet, the researchers were interested in whether such eating patterns benefit sleep, too, they noted in the paper.
The research is still somewhat preliminary in that it only suggests there is a link between diet and sleep; it does not explain why that link might exist or whether that relationship is causal. “Poor sleep quality has been linked to inflammation,” says Mamalaki. (High-fat, high-sugar, high-salt, and processed foods — ones found very sparingly in a Mediterranean diet — are known to cause inflammation.) “This may be one mechanism.”
Another possible explanation may be that eating a Mediterranean diet has been shown to have a protective effect against metabolic syndrome, Mamalaki says. (Some of that research is summarized in a review published in January 2017 in the journal Oncotarget.) “And poor sleep is associated with metabolic disturbances,” Mamalaki says. “So the Mediterranean diet may have a protective effect.”
Researchers Caution That This Data Shows a Link Between Diet and Sleep, Not Necessarily a Causal Relationship
Another important caveat, the researchers caution, is that this study is observational in design and identifies a link between following a Mediterranean diet and sleep quality, but the investigation wasn’t designed to show a causal relationship — that eating a Mediterranean diet definitively causes people to have good-quality sleep.
Still, the results do suggest that future research should explore the question further, says Mamalaki.
Future research should also explore the question of whether poor sleep may cause people to eat unhealthy foods or whether an unhealthy diet leads to poor sleep.
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The study researchers also note that participants self-reported information such as sleep duration and sleep quality, which means that “the possibility of misreporting cannot be ruled out,” says Mary Yannakoulia, PhD, one of the principle investigators and an associate professor of nutrition and eating behavior in the School of Health Sciences and Education at Harokopio University. “Objective sleep measurements (such as polysomnography tests) are typically invasive methods and it is difficult to use them in a large-scale study,” says Dr. Yannakoulia.
The Bottom Line: There May Be Sleep Benefits to a Mediterranean Diet, but the Evidence Is Far From Conclusive
The takeaway message, according to the researchers, is that there are lots of benefits and no known downside to following a healthy diet. “Adherence to a Mediterranean-type dietary pattern has been repeatedly shown to have multiple beneficial effects for older people, including preventing cognitive decline,” says Yannakoulia. “Thus, starting to follow such a diet would be good for several health aspects of the older adults, including sleep.”
Still, others caution the benefits shouldn’t be overstated given that the evidence is far from conclusive.
While the data may be interpreted to mean that diet can play a role in sleep quality, they also might be a result of people who have good sleep habits being more interested in eating a healthy diet to begin with, says Kelly Baron, PhD, a clinical psychologist and associate professor focusing on obesity and sleep medicine in the department of family and preventive medicine at the University of Utah in Salt Lake City, who was not involved in the research. “The study doesn’t have great detail and it’s hard to tell cause and effect.”
Dr. Baron also notes that the strongest association between a healthy Mediterranean diet and good sleep was seen in adults between 65 and 75. “In older age groups, poor sleep is linked to chronic conditions associated with age, such as pain or overactive bladder.” She also notes that diet is just one part of a bigger picture when it comes to good sleep; factors such as good sleep habits and cognitive behavioral therapy can also play a role.
The bottom line is that the study points to some possible benefits for quality of sleep in those who are eating a healthy Mediterranean diet, but more research needs to be done to flesh out exactly what and how the two might be associated, Baron says.