We know that inadequate sleeping is associated with changes in diet—people tend to eat worse—but what about the opposite question: Can food affect sleep? In a study on kiwifruit, this seemed possible (see Kiwifruit For Insomnia), but the mechanism the researchers suggested for the effect—the serotonin levels in kiwifruit—doesn’t make any sense, since serotonin can’t cross the blood-brain barrier. We can eat all the serotonin we want and it shouldn’t affect our brain chemistry. A different brain chemical, though, melatonin, can get from our gut to our brain.
Melatonin is a hormone secreted at night by the pineal gland in the center of our brain to help regulate our circadian rhythm. Supplements of the stuff are used to prevent and reduce jet lag, and about 20 years ago MIT got the patent to use melatonin to help people sleep. But melatonin “is not only produced in the pineal gland—it is also naturally present in edible plants.”
That might explain the results of a study, “Effects of a Tart Cherry Juice Beverage on the Sleep of Older Adults with Insomnia” (See Tart Cherries for Insomnia). The research group had been doing an earlier study on tart cherry juice as a sports recovery drink. There’s a phytonutrient in cherries with anti-inflammatory effects on par with drugs like aspirin and ibuprofen, so the researchers were trying to see whether tart cherry juice could reduce muscle soreness after exercise. During the study, some of the participants anecdotally noted that they were sleeping better on the cherries. That was unexpected, but the researchers realized that cherries were a source of melatonin so they put them to the test.
The reason they chose older subjects is that melatonin production tends to drop as we age, which may be one reason why there’s a higher insomnia rates among the elderly. So, they took a group of older men and women suffering from chronic insomnia and put half on cherries and half on placebo. They couldn’t use whole cherries for the study—how could you fool people with a placebo cherry? So they used cherry juice versus cherry Kool-Aid.
They found that participants did in fact sleep a little better on the cherry juice. The effect was modest, but significant. Some, for example, fell to sleep a few minutes faster and had 17 fewer minutes of waking after sleep onset (waking up in the middle of the night). It was no insomnia cure, but it helped—without side effects.
How do we know it was the melatonin, though? They repeated the study, this time measuring the melatonin levels, and indeed saw a boost in circulating melatonin levels after the cherry juice, but not after the Kool-Aid. Similar results were found in people eating the actual cherries—seven different varieties boosted melatonin levels and actual sleep times. The effects of all the other phytonutrients in cherries can’t be precluded—maybe they helped too—but if it is the melatonin, there are more potent sources than cherries.
Orange bell peppers have a lot, as do walnuts—and a tablespoon of flaxseeds has about as much as a tomato. See the chart in my video Tart Cherries for Insomnia. The melatonin content of tomatoes was suggested as one of the reasons traditional Mediterranean diets were so healthy. They have less melatonin than the tart cherries, but people may eat a lot more tomatoes than cherries. Sweet cherries have 50 times less melatonin than tart ones; dried cherries appear to have none.
A few spices are pretty potent: just a teaspoon of fenugreek or mustard seeds has as much as a few tomatoes. The bronze and silver go to almonds and raspberries, though. And the gold goes to gojis. Goji berries were just off the charts.
Aren’t goji berries really expensive, though? Not if you buy them as lycium berries. Check out my video Are Goji Berries Good for You?
I’ve previously explored Human Neurotransmitters in Plants in the context of boosting serotonin levels in the brain to improve mood. See:
Melatonin may also play a role in cancer prevention. See Melatonin & Breast Cancer.
-Michael Greger, M.D.
Image thanks to: Elizabeth / Flickr
The number one question in sleep research is “Why do we sleep?” followed by the question,“How much sleep do we need?” After literally hundreds of studies, we still don’t know the best answer to either question. A few years ago, I featured a large, 100,000-person study which suggested that both short and long sleep duration were associated with increased mortality, with people getting around seven hours of sleep living longest (See Optimal Sleep Duration). Since then, a meta-analysis that included over a million people was published, and found the same thing.
We still don’t know, however, whether “sleep duration is a cause or simply a marker of ill health.” Maybe sleeping too little or too long does make us unhealthy—or maybe we see the associated shortened lifespan because being unhealthy causes us to sleep shorter or longer.
Similar work has now been published on cognitive function. After controlling for a long list of factors, men and women in their 50s and 60s getting seven or eight hours appeared to have the best short-term memory compared to those that got much more or much less. The same thing was just demonstrated with immune function where “both reduced and prolonged habitual sleep durations were associated with an increased risk of pneumonia.”
It’s easy to not get too much sleep—just set an alarm. But what if we’re having problems getting enough? What if we’re one of the one in three adults that suffer symptoms of insomnia? There are sleeping pills like Valium that we can take in the short term, but they have a number of adverse side effects. Non-pharmacological approaches such as cognitive behavioral therapy are often difficult, time-consuming, and not always effective. Wouldn’t it be great to have “natural treatments that can improve both sleep onset and help patients improve the quality of sleep while improving next-day symptoms over the long term?”
What about a study on kiwifruit, featured in my video, Kiwifruit for Insomnia? Participants were given two kiwifruit an hour before bed every night for four weeks. Why kiwifruits? Well, people with sleep disorders tend to have high levels of oxidative stress, so maybe antioxidant rich foods might help? But all fruits and vegetables have antioxidants. Kiwifruits contain twice the serotonin of tomatoes—but it shouldn’t cross the blood-brain barrier. Kiwifruit has folate, and a deficiency might cause insomnia—but there’s a lot more folate in some other plant foods.
The reason they studied kiwifruits is because they got grant money from a kiwifruit company. And I’m glad they did because they found some really remarkable results: significantly improved sleep onset, duration, and efficiency using both subjective and objective measurements. Participants went from sleeping an average of six hours a night to seven—by just eating a few kiwifruits.
Videos on other natural remedies for various conditions include:
- Flax Seeds For Breast Pain
- Dietary Osteoarthritis Treatment
- Saffron for the Treatment of PMS
- Lavender for Migraine Headaches
- Prunes vs. Metamucil vs. Vegan Diet
- Black Raspberries versus Oral Cancer
- Strawberries versus Esophageal Cancer
-Michael Greger, M.D.
Image credit: Peter Miller / Flickr