Fiber
The few studies that have examined the association between
fiber and sleep duration collectively suggest that higher fiber
intake is associated with normal (as opposed to long or short)
sleep duration.
In NHANES 2007–2008, normal sleepers had the highest fiber
intake, whereas short and long sleepers (those who slept five to
six hours or more than nine hours) both had lower fiber intake,
and very short sleepers (those who slept less than five hours per
night) had the lowest fiber intake.^12
Cross-sectional studies of other populations have produced
similar findings.15,25 Experimental evidence is scant, but the afore-
mentioned trial conducted at Columbia University found that
higher fiber intake resulted in deeper, more restorative sleep,
as indicated by increased slow-wave sleep.^13
Sugar
Data on the association of sugar with sleep duration are lim-
ited and conflicting. In NHANES 2005–2010, higher total sugar
intake was associated with short sleep (equal to or less than
six hours per night).^14 Consistent with this finding, the NHANES
2007–2008 analysis found that short sleepers (five to six hours
per night) had higher sugar intake than normal sleepers, but
counterintuitively, very short sleepers (less than five hours per
night) had lower sugar intake than normal sleepers.^12 Therefore,
it’s unclear what impact, if any, sugar may have on sleep duration.
With respect to the relationship between sugar and sleep qual-
ity, the Columbia University trial found that higher sugar intake
negatively impacted sleep quality, in that it was associated with
more sleep arousals during the night.^13
Fruits and Vegetables
One recent prospective analysis of nearly 14,000 women in the
United Kingdom (UK) Women’s Cohort Study found, contrary to
the authors’ expectations, that every additional portion of total
fruit and vegetable consumption was associated with shorter
sleep, albeit with a small effect size.^26
However, other cross-sectional and prospective studies
of nationally representative samples of UK adults have found
that sleep duration is nonlinearly
associated with fruit and vegetable
consumption and that participants
sleeping the recommended seven to
nine hours per night have the high-
est intake compared with both short
and long sleepers.2 7, 2 8 Several cross-
sectional studies of other popula-
tions likewise have found that short
sleep duration is associated with
lower consumption of fruits and/or
vegetables.15,2 9,3 0
Several small, short-term experi-
mental studies have focused on the
beneficial effects of certain specific
fruits, such as tart cherries. In healthy
young adults, a supplement of tart cherry juice increased urinary
melatonin concentration, total sleep time, and sleep efficiency
compared with placebo.^31 In adults with chronic insomnia, a simi-
lar supplement significantly reduced insomnia severity and wake
time after sleep onset.^32
A separate intervention tested the effects of seven different
cultivars of Jerte Valley cherries. All seven cultivars produced
an increase in urinary melatonin and total sleep time for both
middle-aged and elderly participants. Certain cultivars also
produced other sleep benefits, including decreased nighttime
awakenings and reduced sleep onset latency, but these benefits
varied depending on the age group (middle-aged vs elderly).^33
The positive impact of cherries, if confirmed, is likely related
to their relatively high concentration of melatonin and their high
antioxidant capacity.^4 Tart cherry juice is known to reduce cir-
culating inflammatory markers and increase antioxidant capac-
ity in athletes.34,35 Because patients with sleep disorders tend
to demonstrate high levels of oxidative stress, the antioxidant
properties of cherries may help promote sleep by minimizing
oxidative damage.^36
In addition, kiwifruit has been suspected of having a positive
impact on sleep duration and quality. In one four-week trial of
adults with sleep problems, consumption of two kiwifruits per day
one hour before bedtime significantly increased total sleep time
and sleep efficiency, while also decreasing sleep onset latency
and wake time after sleep onset.^37
The benefits of kiwifruit have been attributed to its high anti-
oxidant capacity and its unusually high content of serotonin, which
may promote sleep.^4
Kiwifruit also is a good source of folate. Whereas folate defi-
ciency has been linked to insomnia and restless leg syndrome,
folate supplementation has been shown to alleviate these symp-
toms.38,39 Again, however, larger trials are needed to confirm
kiwifruit’s sleep benefits.Mediterranean Diet
Repeated studies have shown a correlation between the Medi-
terranean diet and healthy sleep. For example, in the Multi-Ethnic
Study of Atherosclerosis ancillary sleep study, individuals with34 today’s dietitian august 2019