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Grapes May Help With
Sleep
Fruit May Contain Sleep Hormone
Melatonin
By Miranda Hitti
WebMD Medical News
 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 edition.
Researchers included Marcello Iriti, Ph.D., 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
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 colleagues.
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
M.D., 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, Ph.D., who worked on Iriti's
study, for a response.
Faoro's e-mail 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.
© WebMD Inc. All rights reserved.
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