The melatonin content in certain plant foods such as almonds, raspberries and goji berries may explain the improvement in sleep quality associated with tart cherry consumption.
Images thanks to joka2000 and Donovan & Meggin Eastman via Flickr; Aadx, Rumun999, User:FoeNyx, Nataraja, J. Dncsn, Softeis, Sanjay Acharya, and www.bluewaikiki.com via Wikimedia Commons; and Dr Frank Gaillard.
We know that not sleeping enough is associated with changes in diet—people tend to eat worse, but what about the opposite question-- can food affect sleep? We saw from the kiwifruit study that this seemed possible, but the mechanism they suggested for the effect—the serotonin levels in kiwifruit, doesn't make any sense, since serotonin can't cross the blood-brain barrier. So you can eat all the serotonin you want and it shouldn't affect your brain chemistry. A different brain chemical, though, melatonin, can get from our gut to our brain.
Melatonin is a hormone secreted at night to help regulate our circadian rhythms by the pineal gland in the center of our brain. 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. Melatonin is not only produced in the pineal gland, though, but is also naturally present in edible plants.
That might explain the results of this study, the Effects of a Tart Cherry Juice Beverage on the Sleep of Older Adults with Insomnia. This research group had been doing an earlier study on tart cherry juice as a sports recovery drink. See, there's a phytonutrient in cherries with anti-inflammatory effects on par with drugs like aspirin and ibuprofen, so they were trying to see they could help reduce muscle soreness after exercise and some of the participants in the study just anecdotally said they were sleeping better on the cherries. That was unexpected, but the researchers realized that cherries are a plant food 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 rate in 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. Now they couldn't use whole cherries for the study, because how could you fool people with a placebo cherry? So they used cherry juice versus "cherry Koolaid," and found significant but modest improvements in sleep. Some, for example, fell to sleep a few minutes faster and had 17 fewer minutes of waking after sleep onset, meaning waking up in the middle of the night. So 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 koolaid. Similar results were found in people eating the actual cherries—7 different varieties, boosting 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, an ounce of walnuts. A tablespoon of flaxseeds has about as much as a tomato, all less than the tart cherries, but people may eat a lot more tomatoes than cherries, especially tart cherries. Sweet cherries have 50 times less melatonin than tart. Dried cherries appear to have none.
In fact the melatonin content of tomatoes was suggested as one of the reasons traditional Mediterranean diets were so healthy.
A few spices are pretty potent, just a teaspoon of fenugreek seeds, or mustard seeds has as much as a few tomatoes, but the bronze, silver, and gold go to almonds, raspberries, and goji berries off the chart.
Now even gojis just have 15 micrograms an ounce, but melatonin is potent stuff. You inject 10 into people you can boost their blood levels 50 fold in 5 minutes.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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The mention of kiwifruit is in reference to Friday's video of the day Kiwifruit for Insomnia.
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.
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?
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