Recently I returned home after travelling for three months in Southeast Asia. As is common with International travel, I had a fairly difficult time trying to readjust my sleep patterns to the time change. However, melatonin supplements were very helpful for me and contributed to the inspiration to do a bit more research on this essential hormone. What I found was that melatonin is not only critical for falling asleep, it also plays a key role in digestive health and is a powerful antioxidant for the prevention and treatment of Alzheimer's disease, cancer, high cholesterol, obesity and fertility issues.
You body produces melatonin in the pineal gland, located near the middle of the brain. Melatonin levels begin to rise around 9pm, inducing the desire to sleep, and stay elevated until about 9am. Whether your body produces melatonin is completely dependent on light. Even having a TV or computer on in the bedroom will decrease melatonin production and affect the circadian rhythm. In addition to the pineal gland, the enteroendocrine cells in the gastrointestinal tract or gut, often referred to as the "second" brain, also produce melatonin. Studies with mice have shown that even when the pineal gland is removed, melatonin levels in the GI tract remain unaffected. It's easy to see the connection when you think of the similar circadian rhythms of bowel movements (going at the same time every day) and how sleep patterns are disrupted after eating a heavy meal at night. Melatonin is therefore essential for good intestinal bacteria and digestive function, shown to also be helpful for those with IBS, spastic colon and colitis.
Melatonin also has many healing and antioxidant properties. It has been shown to stimulate the immune system, reduce/regulate inflammation, and destroy free radicals, which prevents cell damage. For this reason, melatonin can inhibit cancer growth by destroying cancer cells, halting/shrinking tumor growth and preventing the stimulation of estrogen, which plays a role in hormonally influenced types of cancer. Melatonin has also been touted as an anti-aging hormone. Mice studies have shown that is reduces oxidative stress and neurodegeneration. Specifically for Alzheimer's disease, it's been shown to reduce amyloid plaque build-up, a key marker for this degenerative disorder. It also seems to halt cognitive impairment in mild cases of dementia.
Studies have also shown that melatonin can reduce cholesterol absorption and total cholesterol. It also can help control weight gain (regardless of food intake) and cases of obesity related to high blood pressure. Studies show that melatonin improves blood lipid profile and reduces triglycerides (a fat found in the blood), which too much of can contribute to heart disease and metabolic syndrome. One final benefit worth mentioning, although studies continue to prove its ever-expanding role in our overall health, is its ability to improve fertility for women with poor egg quality, almost doubling the effect of IVF success.
Since melatonin levels appear to decrease with age, it's important to do everything you can to increase or maintain the highest levels possible. The best way to increase your melatonin production is to make sure that you sleep during the night in absolute darkness. Even a small trace of ambient light can impact the amount of melatonin your body produces and disrupt sleep cycles. To prepare for this, it's also important to get into the habit of dimming the lights a few hours before bed. If you are finding it difficult to sleep due to jetlag or stress, you can also try a melatonin supplement. However, make sure that it's a natural and high quality form if you go this route. Finally, although minimal, you can find small amounts of melatonin in some foods such as mustard, goji berries, walnuts, almonds, sunflowers, cardamom, fennel, coriander, olive oil, tomato, grape skins, and cherries. 
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