higher adherence to a Mediterranean diet were at lower risk of
insomnia symptoms and of insomnia symptoms in combination
with short sleep duration.^40
Analyses of French, Spanish, and Greek adults likewise found
that adherence to a Mediterranean-style diet was associated with
reduced insomnia symptoms or overall improved sleep qual-
ity.41-4 3 As for the connection between the Mediterranean diet and
sleep duration, the trend appears to be that higher adherence to
a Mediterranean diet is associated with a greater likelihood of
normal sleep duration.40,42
Current research on the Mediterranean diet and sleep can
demonstrate only associations, not causality. However, there’s
some evidence to suggest that the high fiber and low saturated
fat content of the Mediterranean diet may be responsible for the
observed links. In the Columbia University randomized crossover
trial, each 10 g increase in fiber consumption was associated with
a 2.6% increase in time spent in slow-wave sleep, whereas each
10% increase in energy from saturated fat was associated with a
7.1% reduction in time spent in slow-wave sleep.^13
Esther Lopez-Garcia, PhD, MPH, MhPharm, a professor of
preventive medicine and public health in the School of Medicine
at Spain’s Universidad Autónoma de Madrid, suggests that other
biological mechanisms also may be at work. “For example, the
anti-inflammatory and antioxidant effect of the [Mediterranean
diet] may favor healthy sleep, or the consumption of olives and
grapes linked to this diet, which are rich in melatonin, a compound
that favors the circadian cycle [may do the same],” she says.
Finally, Lopez-Garcia notes that “adherence to healthful diets
also implies cooking raw products instead of processed, devot-
ing time to eating and planning eating, which is associated with
a more organized and less stressful life,” and this, in turn, “may
have an important impact on sleep patterns.”
Future Directions
According to Dashti, the next step is to move from cross-
sectional research toward more longitudinal and experimental
study designs, which will give researchers a better idea of how
particular dietary habits affect sleep patterns over time. In addition,
there’s a need for more objective assessment of both diet and
sleep to increase the reliability of research findings.
“Previously we have relied on self-reported data on sleep
habits and food intake, and even though people have some idea
of what they’re eating and how much they’re sleeping, it’s not that
accurate,” Dashti says, adding that technological advancements—
such as wearable sleep monitors—are making it easier to gather
accurate data. “We’re better able to assess sleep duration, and
also other dimensions of sleep such as quality.”
Another important step for researchers will be to examine how
the timing of consumption affects the impact of specific foods.
“What food, at what quantity, at what time?” asks Marie Pierre
St-Onge, PhD, an associate professor of nutritional medicine at
New York’s Columbia University Irving Medical Center. “Should
you eat the food in the morning or before going to bed?”
As the research unfolds, St-Onge envisions that dietitians could
have an expanded role in treating individuals who suffer from
inadequate sleep. “Those patients with insomnia or obstructive
sleep apnea—we could have dietitians be involved in their treat-
ment showing that diet can influence their sleep at night,” she says.Takeaways for Dietitians
Because research surrounding dietary impacts on sleep is
still in the early stages, there are few specific recommenda-
tions dietitians can make to clients regarding what foods to eat
for better sleep. For now, a key message to convey is that there’s
indeed a connection between diet and sleep.
“Overall, what the studies seem to suggest is that to improve
your sleep, you need a better overall diet,” Dashti says.
Some of the most consistent findings so far relate to the Medi-
terranean diet pattern. “The more ‘Mediterranean’ your dietary
habits are, the better your sleep quality is,” says Mary Yannakou-
lia, PhD, an associate professor of nutrition and eating behavior
at Harokopio University in Athens, Greece.
Although the mechanisms are unclear, Yannakoulia encourages
this dietary pattern for anyone looking to improve sleep. She
asserts, however, that the benefits of a Mediterranean diet may
not come from food alone. “The Mediterranean diet is part of the
Mediterranean lifestyle that includes, apart from the diet per se,
adequate rest, regular physical activity, and conviviality,” she says.
While also a proponent of the Mediterranean diet, Lopez-Garcia
encourages dietitians to recommend other healthful dietary pat-
terns as well, such as the Dietary Approaches to Stop Hyperten-
sion, the Healthy Eating Index, and plant-based diets in general.
“They all advocate for using minimally processed foods and
high-quality fats, with low amounts of added sugars and salt,”
she says. “In addition to the important nutrients they provide,
these diets are digested slowly, which leads to a gentle rise in
blood sugar and insulin. This produces fewer peaks of hunger,
less deprivation, and less production of stress hormones. All of
this also has a beneficial impact on sleep.”
Finally, dietitians should make sure to discuss the impact of
stimulants with clients. “The circadian system is intertwined with
sleep, and thus nutritional compounds that affect the circadian
system influence sleep,” Noorwali says, adding that the most
robust effects are seen with caffeine and alcohol.^44
A wide array of study populations have found that daily
caffeine intake is strongly associated with sleep problems—
even a small amount of regular caffeine consumption is
associated with altered sleep duration, onset, and perceived
quality.^45 Similarly, while alcohol consumption before sleep
makes it easier to fall asleep quickly, alcohol alters sleep
architecture and is associated with disrupted, poor-quality
sleep.^46 “Advice on moderation and timing of these compounds
will be beneficial,” Noorwali adds.— Jamie Santa Cruz is a freelance writer of health and
medical topics based in Parker, Colorado.For references, view this article on
our website at http://www.TodaysDietitian.com.august 2019 http://www.todaysdietitian.com 35