Low-fat, low-cal, low-carb. Atkins, South Beach, The
Zone. Food fads may be distracting attention from
something more insidiously piling on pounds: beverages.
One of every five calories in the American diet is
liquid. The nation's single biggest "food" is soda, and
nutrition experts have long demonized it.
Now they are escalating the fight.
In reports to be published in science journals this
week, two groups of researchers hope to add evidence to
the theory that soda and other sugar-sweetened drinks
don't just go hand-in-hand with obesity, but actually
cause it. Not that these drinks are the only cause -
genetics, exercise and other factors are involved - but
that they are one cause, perhaps the leading cause.
A small point? In reality, proving this would be a
scientific leap that could help make the case for higher
taxes on soda, restrictions on how and where it is sold
- maybe even a surgeon general's warning on labels.
"We've done it with cigarettes," said one scientist
advocating this, Barry Popkin at the University of North
Carolina in Chapel Hill.
Comparing soda and obesity to tobacco and lung cancer is
a baseless crusade, industry spokesmen say.
"I think that's laughable," said Richard Adamson, a
senior science consultant to the American Beverage
Association. Lack of exercise and poor eating habits are
far bigger contributors to America's weight woes, he
said.
"The science is being stretched," said Adam Drewnowski,
director of nutritional sciences at the University of
Washington in Seattle. He owns stock in beverage
companies and has done extensive research in the field,
much of it financed by industry but also some by
government.
However, those making the case against soda include some
of the nation's top obesity researchers at prestigious
institutions like Harvard and Yale.
"There are many different lines of evidence, just like
smoking," said Dr. David Ludwig, a Harvard pediatrician
who wants a "fat tax" on fast food and drinks.
Beverage companies seem worried. Some are making sodas
"healthier" by adding calcium and vitamins, and pushing
fortified but sugary sports drinks in schools that ban
soda. This could help them duck any regulations aimed at
"empty calorie" drinks, said Jennifer Follett, a USDA
nutritionist at the University of California in Davis.
"Even defining 'milk' is getting tough these days," with
so many flavored varieties and sweetened liquid yogurts,
she complained. "It tastes like you're sucking on ice
cream."
Proving that something causes disease is not easy. It
took decades with tobacco, asbestos and other substances
now known to cause cancer, and met strong industry
opposition. It would be especially tough for a disease
as complex as obesity.
Diet is hard to study. Most people drink at least some
sweetened beverages and also get calories from other
drinks like milk and orange juice, diluting the strength
of any observations about excess weight from soda alone.
Children are growing and gaining weight naturally, "so
we have this added complication" of trying to determine
how much extra gain is due to sweet-drink consumption,
said Alison Field, a nutrition expert at
Harvard-affiliated Children's Hospital in Boston.
"Given these caveats, it's amazing the association we do
see," she said.
She was among hundreds of scientists who packed a "mock
trial" of such drinks at a conference of the Obesity
Society last year in Vancouver, British Columbia.
Here is the "food police" indictment of soda and its
sugar-sweetened co-conspirators. You be the judge:
Count One: Guilt by association.
Soft drink consumption rose more than 60 percent among
adults and more than doubled in kids from 1977-97. The
prevalence of obesity roughly doubled in that time.
Scientists say these parallel trends are one criterion
for proving cause-and-effect.
Numerous studies link sugary drink consumption with
weight gain or obesity. One by Ludwig of 548
Massachusetts schoolchildren found that for each
additional sweet drink consumed per day, the odds of
obesity increased 60 percent.
Another at Harvard of 51,603 nurses compared two
periods, 1991-95 and 1995-99, and found that women whose
soda drinking increased had bigger rises in body-mass
index than those who drank less or the same.
Count Two: Physical evidence.
Biologically, the calories from sugar-sweetened
beverages are fundamentally different in the body than
those from food.
The main sweetener in soda - high-fructose corn syrup -
can increase fats in the blood called triglycerides,
which raises the risk of heart problems, diabetes and
other health woes.
This sweetener also doesn't spur production of insulin
to make the body "process" calories, nor does it spur
leptin, a substance that tamps down appetite, as other
carbohydrates do, explained Dr. George Bray of the
Pennington Biomedical Research Center in Baton Rouge,
La.
"There's a lack of fullness or satiety. The brain just
seems to add it on," said Dr. Louis Aronne, a Weill-Cornell
Medical College doctor who is president of the Obesity
Society.
Two studies by Penn State nutritionist Barbara Rolls
illustrate this. One gave 14 men lemonade, diet
lemonade, water or no drink and then allowed them to eat
as much as they wanted at lunch. Food intake didn't
vary, no matter what they drank.
The second study gave 44 women water, diet soda, regular
soda, orange juice, milk or no drink before lunch. Total
intake was 104 calories greater for those given caloric
beverages than those given diet soda, water or no
beverage. Caloric drinks didn't help women feel any
fuller either.
Then there is the "jelly bean study." Purdue University
researchers gave 15 men and women 450 calories a day of
either soda or jelly beans for a month, then switched
them for the next month and kept track of total
consumption. Candy eaters ate less food to compensate
for the extra calories. Soda drinkers did not.
Count Three: Bad influence on others.
Sugar-sweetened beverages affect the intake of other
foods, such as lowering milk consumption. Popkin
contends they also may be psychological triggers of poor
eating habits and cravings for fast food.
He examined dietary patterns of 9,500 American adults in
a federal study from 1999-2002. Those who drank
healthier beverages - water, low-fat milk, unsweetened
coffee or tea - were more likely to eat vegetables and
less likely to eat fast food.
Conversely, "fast-food consumption was doubled if they
were high soda consumers and vegetable consumption was
halved," he said.
Harvard epidemiologist Eric Rimm saw a similar effect in
a different federally funded study of more than 5,000
young adults. With high soda consumption, "you see this
pattern of less healthy intake across the board," he
said at the obesity meeting.
Count Four: Consistency of evidence.
Many studies of different types link sugary drinks and
weight gain or obesity. Some even show a "dose-response"
relationship - as consumption rises, so does weight.
Collectively, they meet many criteria for proving cause
and effect, Dr. William Dietz, director of nutrition at
the federal Centers for Disease Control and Prevention
wrote in an editorial accompanying a study in February's
Journal of Pediatrics.
In rebuttal, Adamson, the beverage industry spokesman,
sees no such consistency. He cites a 2004 Harvard study
of more than 10,000 children and teens. Consumption of
sugar-added beverages was tied to body-mass index gain
in boys but not girls, a gender difference that warrants
a "jaundiced eye" to claims that soda is at fault, he
said.
He also points to a Harvard study finding no link
between weight changes and soda consumption among 1,345
North Dakota children ages 2 to 5 - a group that
arguably drinks far less soda than teens and adults.
"Whatever association there is doesn't seem to be
large," said Richard Forshee, deputy director of the
Center for Food, Nutrition and Agriculture Policy at the
University of Maryland who has received research funding
from the beverage industry and global sugar producers.
As for soda being linked to poor eating patterns, "you
don't know which is cause and which is effect,"
Drewnowski said.
People who consume lots of fresh-squeezed juice,
vegetables and fruits are fundamentally not the same as
those who subsist on colas and bologna sandwiches, he
contends.
"There is a difference: The first group is rich,"
Drewnowski said. He thinks government subsidies of
fruits and vegetables would be better public policy than
taxing a cheap source of calories.
He also disputes the claim that soda calories are not
satisfying. He did a study in which 32 men and women
were given either colas or fat-free Raspberry Newtons
before lunch on four separate occasions.
"There was absolutely no difference in satiety" as
measured by how much they ate or how hungry they said
they were, he said.
That research was paid for by industry, a factor that
can affect study outcomes, said Kelly Brownell, a
psychologist and food policy researcher at Yale
University and a vocal advocate for curbs on soda and
fast food.
When you look at studies according to who footed the
bill, "the literature parts like Moses parting the
ocean," he said, referring to the biblical parting of
the Red Sea.
Does the evidence add up to a conviction of soda?
One of the nation's leading epidemiologists who has no
firm stake in the debate, the American Cancer Society's
Dr. Michael Thun, thinks it does.
"Caloric imbalance causes obesity, so in the sense that
any one part of the diet is contributing excess
calories, it's contributing causally to the obesity,"
Thun said. "It doesn't mean that something is the only
cause. It means that in the absence of that factor there
would be less of that condition."
Does it merit a warning on soda cans?
"I think it would be a good candidate for a warning,"
Thun said. "It's something that should be seriously
considered."
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References:
worldhealth.net
Marilynn Marchione, AP Medical Writer
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