Melatonin is a naturally occurring hormone that plays a significant role in the body’s internal processes. It regulates the sleep-wake cycle, helping the body prepare for rest. Understanding its origins clarifies its roles and impact on daily rhythms. This article explores where melatonin comes from: its natural synthesis within the body, its presence in food, and its production for dietary supplements.
How the Body Produces Melatonin
The primary source of melatonin in the human body is the pineal gland, a small endocrine gland located in the brain. This gland synthesizes and secretes melatonin mainly during periods of darkness. The process begins with the amino acid tryptophan, which is obtained through diet. Tryptophan is first converted into 5-hydroxytryptophan (5-HTP) by the enzyme tryptophan hydroxylase.
Subsequently, 5-HTP is decarboxylated to form serotonin, a neurotransmitter. Serotonin then undergoes two more enzymatic steps to become melatonin. The activity of an enzyme called N-acetyltransferase (NAT) is particularly important, as it often limits the rate of melatonin production, with higher activity at night.
Light and darkness are powerful regulators of this synthesis, influencing the body’s circadian rhythm. When light enters the eyes, it signals the brain to suppress melatonin production, promoting wakefulness. Conversely, as darkness falls, melatonin synthesis increases, signaling to the body that it is time to wind down and prepare for sleep. This rhythmic production helps to synchronize the body’s internal clock with the external environment.
Melatonin from Food Sources
Melatonin is present in various natural food sources, though typically in smaller concentrations compared to what the body produces or what is found in supplements. Tart cherries, particularly Montmorency varieties, are known to contain melatonin, and studies show consuming their juice can elevate levels.
Nuts like pistachios and almonds also contain melatonin, with pistachios having high levels. Grains such as oats and rice also contain melatonin. Fruits and vegetables, including strawberries, grapes, mushrooms, and tomatoes, are natural sources. While these foods can provide some melatonin, the amounts are generally not significant enough to have a major physiological impact on sleep compared to the body’s own production.
Understanding Melatonin Supplements
The melatonin found in over-the-counter supplements is primarily produced synthetically in laboratories. This manufacturing process allows for consistent production and specific dosing. While older methods sometimes involved extracting melatonin from animal pineal glands, this practice is less common today due to concerns about purity and potential contaminants.
Synthetic melatonin is chemically identical to the melatonin produced naturally by the human body. These external, or exogenous, sources of melatonin are used by individuals to support sleep or to help adjust sleep cycles, such as when experiencing jet lag. Synthetic supplements provide a way to introduce melatonin into the body beyond natural production or dietary intake.