Do you enjoy a glass of wine before bedtime? There may be something to that. It turns out that several types of fine-wine grapes contain significant amounts of a hormone that helps the body get to sleep, according to Italian scientists.
In a study published online in the Journal of the Science of Food and Agriculture, several wine grapes traditionally used in France and Italy were found to be rich in melatonin, a hormone that not only tells the body it's time to turn in for the night, but also acts as a powerful antioxidant and detoxifies cells.
However, study coauthor Franco Faoro warned against chugging back Chianti as a way to battle insomnia. "At present we do not know if melatonin is also present in wine," said Faoro, a researcher at the Instituto di Virologia Vegetale in Milan. While he believes the hormone is likely retained after fermentation, he noted that melatonin levels varied widely among the eight varieties tested and therefore could vary widely in different varietal wines or blends.
Melatonin was originally believed to be found only in vertebrates, produced mainly by the pea-sized pineal gland in the center of the brain. Typically, the gland uses the amino acid tryptophan, found in abundance in foods such as milk and turkey, to produce the hormone. Humans can't create tryptophan, so they must consume it from other sources in order to produce melatonin.
Recent findings show that some plants, fungi and invertebrates contain melatonin and that humans can consume the hormone directly, without tryptophan being required for its production. (Herbal melatonin pills are now sold as sleep remedies.) These discoveries have prompted new research into which species contain melatonin.
For their current study, the Italian scientists selected eight different vinifera varieties, sourced from their controlled vineyards at the Experimental Institute for Viticulture in Treviso, in northeastern Italy. The team used the local grapes Croatina and Marzemino; Piedmont's leading varieties, Nebbiolo and Barbera; Tuscany's traditional Sangiovese; and three Bordeaux varieties, Cabernet Franc, Cabernet Sauvignon and Merlot.
For each variety, the scientists used 5 grams of crushed grape skins infused with methanol and suspended in water. In this state, melatonin takes on a specific ultraviolet wavelength, allowing its presence to be detected and measured with a chromatograph, the study explained. Each test was performed three times, and the results were averaged.
Nebbiolo contained the most melatonin, with 0.965 nanograms per gram of grape skin, followed by Croatina (0.87 ng/g) and Barbera (0.63 ng/g). After that, the amounts began to taper off, with 0.42 ng/g in Cabernet Sauvignon, 0.33 ng/g in Sangiovese and 0.26 ng/g in Merlot.
Both Marzemino and Cabernet Franc contained only trace amounts of melatonin, with 0.03 ng/g and 0.005 ng/g, respectively.
In a side experiment, the scientists also tinkered with an additional Merlot sample, treating it with benzothiadiazole (BTH), a hormone known to elicit plant defenses. That nearly tripled the melatonin levels in the Merlot, to 0.726 ng/g. But the researchers left it at that, saying the addition of BTH to wine grapes may be important in the clinical application of melatonin.
Despite the findings, Faoro has another explanation for why red wine may help bring on the Sandman: "The effect of the alcohol in red wine would certainly be much more of a determinant."