Melatonin found in grapes
Research conducted by scientists in Milan, Italy, published in the Journal of the Science of Food and Agriculture and summarized in the June 5, 2006 issue of Chemistry & Industry has uncovered another beneficial compound in grapes: the hormone melatonin. Melatonin is made in humans and other mammals by the pineal gland in the brain, and in the gastrointestinal tract and retina, and has only recently been found in plants. Human blood levels range from 20 picograms per milliliter in the morning to 55 pg/mL at night (a picogram is one-trillionth of a gram). The hormone’s antioxidant and anticancer properties add even more benefits to those already discovered for grapes, such as those attributed to polyphenolic compounds known as anthocyanins and proanthocyanidins. Another polyphenol, resveratrol, has been associated with an increase in lifespan when given to roundworms, yeast and mice.
Marcello Iriti and Mara Rossoni of the University of Milan, along with Franco Faoro of the Instituto di Virologia Vegetale, also in Milan, tested eight grape varieties and found the highest levels of melatonin in the skin of Nebbiolo, Merlot, Cabernet Savignon, Sangiovesse and Croatina grapes, which are used to make some of the most popular red wines. The grape variety with the highest melatonin content was Nebbiolo. The amounts were determined using high-performance liquid chromatography (HPLC) and confirmed by enzyme-linked immunosorbent assay (ELISA) tests.
The discovery could explain why some individuals find that a glass or two of wine in the evening helps them unwind, although drinking large quantities of alcohol has been associated with poor sleep quality. Dr Iriti stated, “The melatonin content in wine could help regulate the circadian rhythm [sleep-wake patterns], just like the melatonin produced by the pineal gland in mammals.”
Further studies are in progress to determine whether melatonin is also detectable in wines made from the grape varieties in which the hormone is found. “This would be particularly interesting,” they conclude, “not only for a possible synergistic effect with the other numerous antioxidant compounds present in wine, but also because absorption of melatonin seems notably effective when it is dissolved in ethanol.”
Hoping to better understand the connection between insomnia and diseases, researchers have conducted studies examining the levels of various chemical signals (called cytokines) in sleep and insomnia. They have discovered that nighttime secretion of the cytokine interleukin-6 is significantly increased in patients with primary insomnia ( Burgos I et al 2005). Interleukin-6 is a pro-inflammatory cytokine that is linked to cardiovascular and other diseases. Researchers have found that lack of sleep correlates with interleukin-6 production both day and night, which might also explain why so many insomniacs experience daytime sleepiness: interleukin-6 is involved in regulating sleep (Vgontzas AN et al 2005). Additional studies have found that tumor necrosis factor, another pro-inflammatory cytokine, is increased in insomniacs during the daytime and that levels of these two cytokines are closely related to the level of fatigue experienced (Vgontzas AN et al 2002). These findings mean that insomnia may promote a constant state of low-grade inflammation that may accelerate many diseases of aging.
Melatonin is a hormone released by the pineal gland in response to the absence of light. Its release into the bloodstream triggers a chain of events that promotes sleep. It is well known for this role and may be used effectively as an oral supplement to help reentrain the sleep cycle in situations such as jet lag, in which the normal circadian rhythm of sleeping and waking gets out of sync with the local environment (Burgess HJ et al 2003; Eastman CI et al 2005; Erren TC et al 2004).
In light of the recent research demonstrating melatonin’s many roles in the body, it seems that low levels of this hormone may actually be dangerous. For instance, there appears to be a relationship between the age-related decline in melatonin production and the decline in immune function that also accompanies old age. Known as immunosenescence, this phenomenon is associated with an increased incidence of cancer and infectious disease. As a result, some scientists have proposed that melatonin may be useful to enhance immunity and reduce the incidence and severity of these age-related maladies (Srinivasan V et al 2005). One researcher stated, “Chronic sleep loss could contribute to acceleration of the aging process” (Copinschi G 2005).
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