Grapes May Help With Sleep
The Purple Fruit May Contain the Sleep Hormone, Melatonin
June 19, 2006 -- Scientists in Italy have uncorked a new finding about
grapes: The juicy fruit might be packing melatonin, a sleep hormone.
In humans, the brain's pineal gland makes melatonin to help regulate cycles
of sleep and wakefulness. Melatonin levels rise in the evening as a cue for
sleep, and ebb as dawn approaches.
News about a possible link between grapes and the sleep hormone appears in
the Journal of the Science of Food and Agriculture's early online
Researchers included Marcello Iriti, PhD, of Milan's Istituto di Virologia
Vegetale (Institute of Vegetable Virology).
They tested extracts from eight types of grapes -- Nebbiolo, Croatina,
Sangiovese, Merlot, Marzemino, Cabernet Franc, Cabernet Sauvignon, and Barbera
-- for melatonin and found evidence of the hormone.
Most to Least Melatonin
The grapes all came from the same vineyards in northeastern Italy and were
at the same stage of maturity. Some came from plants treated with
benzothiadiazole, a synthetic chemical that helps plants ward off disease.
Iriti's team used two different tests to check for melatonin and found
varying amounts among the varieties. On both tests, Nebbiolo grapes showed the
most melatonin, followed by Croatina grapes. Merlot from plants treated with
benzothiadiazole ranked third.
Treating grapevines with benzothiadiazole might increase melatonin in
grapes, Iriti and colleagues note.
As for the other grape varieties, they all showed some amount of melatonin
on both tests, but their rankings varied.
The researchers didn't check melatonin levels in wine, but they point out
that melatonin might get a boost from the antioxidants and alcohol in wine.
Maybe Not Melatonin?
Plants don't sleep. So why would they need melatonin?
Melatonin might help defend against plant diseases, write Iriti and
But not all experts are convinced grapes in fact contain the substance.
The journal's sister publication, Chemistry & Industry, also
has a news story about Iriti's study (both publications come from the
London-based Society of Chemical Industry).
In the Chemistry & Industry article, Richard Wurtman, MD, of
the Massachusetts Institute of Technology, is quoted questioning whether
Iriti's team might have actually found a close chemical cousin of melatonin --
not melatonin itself -- in the grapes.
WebMD contacted University of Milan plant pathology professor Franco Faoro,
PhD, who worked on Iriti's study, for a response.
Faoro's email to WebMD doesn't directly address the possibility that the
grapes didn't contain melatonin: "I would like to stress, as reported in the paper, that melatonin
content in grape berry is very variable, depending on the varieties, and,
possibly on the growing conditions," Faoro writes.