 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 that serotonin levels in kiwifruit doesn't make any sense, and 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. 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 also is 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. The 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, ibuprofen, because they were trying to see if they could help reduce muscle soreness after exercise. And some of the participants in the study just anecdotally said that 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 it 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 higher insomnia rates 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 this study, because how could you fool people with a fake placebo cherry? So they used cherry juice versus cherry Kool-Aid, and found significant, but modest, improvements in sleep. So 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? Well, 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, boosting melatonin levels, and actual sleep times. The effects of all the other phytonutrients in cherries can't be precluded. Maybe they help too. But if it is the melatonin, there are more potent sources than cherries. Orange bell peppers have a bit, an ounce of walnuts, a tablespoon of flax seeds has about as much as a tomato, all less than the tart cherries that were tested. But people may eat a lot more tomatoes than cherries, especially tart cherries. Sweet cherries have 50 times less melatonin than tart, and 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 about as much as a few tomatoes. But the bronze, silver, and gold go to almonds, raspberries, and goji berries off the charts. Now even gojis just have 15 micrograms an ounce, but melatonin is potent stuff. You inject just 10 into people, and you can boost their blood levels 50-fold in 5 minutes.