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 Most plants contain different flavonoids in varying concentrations.
Some scientists believe these naturally occurring compounds have
antioxidant and anti-inflammatory properties that could help explain
some of the health benefits associated with diets rich in fruits and
vegetables.
"We found that increased intake of fruits like apples, berries and
grapes was associated with less weight gain and these are high
sources of some types of flavonoids," said lead study author Monica
Bertoia of Harvard T.H. Chan School of Public Health in Boston.
Not all types of flavonoids, however, were linked to reduced weight
gain once researchers accounted for how much fiber people ate,
Bertoia added by email.
"The goal of this research is to determine which fruits and
vegetables may be best for weight maintenance in order to refine
dietary guidelines that currently recommend eating more fruits and
vegetables but don't clearly specify which fruits and vegetables are
better than others for the prevention of obesity," Bertoia said.
To examine the connection between flavonoids and weight, Bertoia and
colleagues analyzed survey data on about 124,000 U.S. health
professionals collected between 1986 and 2011.
They excluded people with chronic diseases and individuals who were
obese at the start of the surveys, and also temporarily dropped data
on women when they were pregnant.
Participants reported their weight every two years and completed
dietary questionnaires every four years.
Based on what people said they ate, researchers used U.S. Department
of Agriculture data on flavonoid content in specific foods to
determine how much of these compounds participants consumed.
Across all the studies, half of the participants consumed at least
224 milligrams to 247 milligrams of flavonoids a day.
Over each four year period, people gained an average of 2.2 to 4.4
pounds.
But people with higher than average flavonoid consumption tended to
gain slightly less weight, researchers report in The BMJ.
The difference amounted to about one-tenth to three-fifths of a
pound over four years for each standard deviation above the average
amount of flavonoid consumption.
For example, consuming 7 milligrams more flavonols - a subtype of
flavonoids found in tea and onions - than average each day was
associated with gaining roughly one-sixth of a pound less weight
over four years.
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To measure the impact of all flavonoids, researchers adjusted for a
wide variety of factors that can influence weight including age,
gender, exercise, smoking, alcohol, caffeine, sleep and sedentary
television time. They also accounted for other things people
consumed, such as juices, fried foods, whole versus refined grains,
full-fat versus low-fat dairy, sodas, processed versus non-processed
meats, trans fats and seafood.
After adjusting for fiber consumption, which may influence weight
gain by decreasing how much fat people absorb, only three types of
flavonoids were associated with reduced weight gain in the study –
anthocyanins, which came mainly from blueberries and strawberries in
participants’ daily diets; flavonols and flavonoid polymers, which
came mostly from tea and apples.
Other limitations of the study include its reliance on survey
participants to accurately report what they ate and how much they
weighed, the researchers note. Food questionnaires used in the
surveys also may not have captured every dietary source of
flavonoids.
Still, the findings suggest that choosing high flavonoid fruits and
vegetables such as apples, pears, berries and peppers may help with
weight control, the authors conclude.
It's also possible, however, that people who eat more fruits and
vegetables may have an easier time with weight management because
they consume a healthier diet and eat fewer calories, noted Samantha
Heller, a registered dietician and exercise physiologist affiliated
with New York University Langone Medical Center in New York City.
"When we frontload our diet with plant based foods such as berries
and peppers, we crowd out less healthy options like French fries and
burgers," Heller, who wasn't involved in the study, said by email.
"It could also be that these people are more health conscious than
others."
SOURCE: http://bit.ly/1ORjhga The BMJ, online January 28, 2016.
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