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Carb-Linked Dip in 'Good' Cholesterol OK
In the pre-Atkins era, high-carbohydrate,
low-fat diets were all the rage. However, proponents of low-carb,
high-fat diets have pointed out that high consumption of carbohydrates
can lower blood levels of high-density lipoprotein (HDL) -- the
"good" cholesterol -- over time.
Now a new study suggests that carbohydrate-based
dips in HDL pose no real threat to health, because blood levels
of low-density lipoprotein (LDL), the "bad" cholesterol, tend
to fall in equal proportion at the same time.
"If that ratio doesn't change when
HDL goes down, then there's no real reason for concern," said
Dr. Alice H. Lichtenstein, director of the cardiovascular nutrition
laboratory at Tufts University and a spokeswoman for the American
Heart Association (AHA).
Through the 1990s, food products
with labels proclaiming them "nonfat" or "low-fat" were ubiquitous
in American supermarkets, as consumers sought to trim waistlines
and improve cardiovascular health by avoiding fat in favor of
carbs.
At the same time, studies began
show that these types of diets could produce a decline in blood
levels of HDL, a form of cholesterol that actually helps arteries
stay healthy.
The issue caused "a fair amount
of concern" for dietary experts, Lichtenstein said.
The latest research, presented
Friday at the AHA's annual conference on Arteriosclerosis, Thrombosis,
and Vascular Biology in San Francisco, may allay those concerns.
A research team led by Sophie Desroches,
a doctoral student in nutrition at Laval University in Quebec
City, Canada, had 65 adult men consume the AHA's recommended diet
for six weeks. The AHA regimen advises that people consume 58
percent of their total daily calories from carbohydrates, 26 percent
from fat (less than 7 percent from saturated fat), and 16 percent
from protein.
According to the researchers, blood
levels of HDL cholesterol fell by an average of 10 percent in
men placed on this diet over the six-week study period. However,
levels of LDL fell in equal proportion, so that the all-important
ratio of good-to-bad cholesterol remained stable.
In a statement, Desroches said
the findings suggest that carbohydrate-linked reductions in HDL
"should not raise concerns about cardiovascular health."
Lichtenstein agreed. "When you
institute any kind of dietary modification, you want to make sure
you don't decrease HDL without also decreasing LDL," she explained.
"You want to make sure that that ratio doesn't go up."
She said advocates of the dietary
craze of the moment, the Atkins diet, have long pointed to lowered
HDL levels as a reason to abandon carbohydrates. But Lichtenstein
said high-calorie intakes -- not carbs -- are most responsible
for extreme dips in HDL, whatever the diet.
In the 1990s, "there was a proliferation
of low-fat and nonfat products," she pointed out, "so many people
started gorging on low-fat ice cream, cookies, and chips in the
mistaken notion that they wouldn't gain weight."
Waistlines expanded, she added,
and "when your body weight increases, that does have an adverse
effect on blood lipids."
"That's when people said, 'Aha!
See? This high-carbohydrate diet causes weight gain; it's really
bad for you,'" she said.
What's needed, she believes, is
a change in attitude among the American public towards eating
in general.
Whether it's a high-carb or low-carb
diet, "there's this feeling that 'Oh, if I choose this side or
that side, I can eat what I want and still lose weight,'" she
said. "The bottom line is that that never turns out to be the
case."
Experts at the AHA continue to
reject the Atkins regimen because of its reliance on artery-clogging
fats. As to Atkins' effects on HDL cholesterol, Lichtenstein says
there's not enough long-term data to show an effect one way or
another.
"We really don't know," she said.
When it comes to the AHA's recommended
diet -- which emphasizes carbohydrates sourced from whole grains,
vegetables and fruits -- "everyone is simply recommending moderation,"
Lichtenstein said. "In all diets, it's all about calories -- that's
the bottom line."
More information
Learn more about fat in your diet
from the National
Heart, Lung and Blood Institute, and get tips on eating well
from the American
Dietetic Association.
Reference
Source 101
For more information on how to prevent other diseases, use
PreventDisease.com's "Quick
Prevention Resources".
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