http://www.nytimes.com/2006/02/07/he...gewanted=print

February 7, 2006
Study Finds Low-Fat Diet Won't Stop Cancer or Heart Disease
By GINA KOLATA
The largest study ever to ask whether a low-fat diet keeps women from
getting cancer or heart disease has found that the diet had no effect.

The $415 million federal study involved nearly 49,000 women aged 50 to
79 who were followed for eight years. In the end, those assigned to a
low-fat diet had the same rates of breast cancer, colon cancer heart
attack and stroke as those who ate whatever they pleased, researchers
are reporting today.

"These are three totally negative studies," said Dr. David Freedman, a
statistician at the University of California at Berkeley, who is not
connected with the study but has written books on clinical trial design
and analysis. And, he said, the results should be taken seriously for
what they are - a rigorous attempt that failed to confirm a popular
hypothesis that a low-fat diet can prevent three major diseases in
women.

And the studies were so large and so expensive that they are "the Rolls
Royce of studies," said Dr. Michael Thun, who directs epidemiological
research for the American Cancer Society. As such, he said, they are
likely to be the final word.

"We usually have only one shot at a very large scale trial on a
particular issue," Dr. Thun said.

The studies were part of the Women's Health Initiative of the National
Institutes of Health, the same program that showed that hormone therapy
after menopause can have more risks than benefits. In this case, the
diet studies addressed a tricky problem. For decades, many scientists
have been saying, and many members of the public have been believing,
that what you eat - the composition of the diet - determines how
likely you are to get a chronic disease. But it has been hard to prove.
Studies of dietary fiber and colon cancer failed to find that fiber was
protective. Studies of vitamins thought to protect against cancer
failed to show an effect.

Gradually, many cancer researchers began questioning the dietary
fat-cancer hypothesis, but it has retained a hold on the public
imagination.

"Nothing fascinates the American public so much as the notion that what
you eat rather than how much you eat affects your health," said Dr.
Peter Libby, a cardiologist and professor at Harvard Medical School.

But the new studies, reported in the Feb. 8 issue of the Journal of the
American Medical Association, found that women who were randomly
assigned to follow a low-fat diet ate significantly less fat over the
next eight years. But they had just as much breast and colon cancer and
just as much heart disease.

And, confounding many popular notions about fat in the diet, the
different diets did not make much difference in anyone's weight. The
common belief that carbohydrates in the diet lead to higher insulin
levels, higher blood glucose levels and more diabetes was also not
confirmed. There was no such effect among the women eating low-fat
diets.

As for heart disease risk factors, the only one affected was LDL
cholesterol, which increases heart disease risk. The levels were
slightly higher in women eating the higher fat diet, but not enough to
make a noticeable difference in their risk of heart disease.

The studies follow a smaller one, reported last year, on low-fat diets
for women who had breast cancer. That study hinted that eating less fat
might help prevent a recurrence. But the current study, asking if a
low-fat diet could protect women from breast cancer in the first place,
had findings that fell short of statistical significance, meaning they
could have occurred by chance. In essence, there was no solid evidence
that a low-fat diet helped in prevention.

"These studies are revolutionary," said Dr. Jules Hirsch, physician in
chief emeritus at Rockefeller University, who has spent a lifetime
studying the effects of diets on weight and health. "They should put a
stop to this era of thinking that we have all the information we need
to change the whole national diet and make everybody healthy."

Although all the study participants were women, the colon cancer and
heart disease results also should apply to men, said Dr. Jacques
Rossouw, the project officer for the Women's Health Initiative. He
explained that the observational studies that led to the colon
cancer-dietary fat hypothesis included both men and women. As for heart
disease, he said, researchers have consistently found that women and
men respond in the same way to dietary fat.

The results, the study investigators agreed, do not justify
recommending low-fat diets to the public to reduce their heart disease
and cancer risk.

As for the cancer society, Dr. Thun said, with these results that he
describes as "completely null over the eight-year follow-up for both
cancers and heart disease," his group has no plans to suggest that
low-fat diets are going to protect against cancer.

Dr. Rossouw, however, said he was still intrigued by the breast cancer
data, even though it was not statistically significant. The women on
low-fat diets had a 9 percent lower rate of breast cancer - the
incidence was 42 per 1,000 per year in women in the low-fat diet group,
as compared with 45 per 1,000 per year in women consuming their regular
diet. That might mean that fat in the diet might have a small effect,
Dr. Rossouw said, perhaps in some subgroups of women or over a longer
period of time. He added that the study investigators would continue to
follow the women to see if the effect became more pronounced.

Another of the study's investigators, Dr. Rowan Chlebowski, a medical
oncologist at Harbor-U.C.L.A. Medical Center, shared Dr. Rossouw's
hopes for a low-fat diet. "There will be different interpretations, but
there's a reason for optimism," Dr. Chlebowski said.

While cancer researchers say they were disappointed by the results,
heart disease researchers say they are not surprised that simply
reducing total fat made had no effect.

"The problem is that this study was designed two decades ago when the
fad was low fat," Dr. Libby said. Now, he said, he and others are
persuaded that a so-called Mediterranean diet is best - not
necessarily low in fat but low in saturated fats, like butter and cream
cheese. That, with exercise, should help prevent heart disease, he
says.

But, of course, that advice has never been tested in a large randomized
clinical trial, Dr. Libby admits. And he says, "if they did a study
like that and it was negative, then I'd have to give up my cherished
hypotheses for data."

The low-fat diet was not easy, Dr. Chlebowski notes. Women were told to
aim for a diet that had just 20 percent of its calories as fat. Most
substantially cut their dietary fat, but most fell short of that 20
percent goal. The diet they were told to follow "is different than the
way most people eat," Dr. Chlebowski said. It meant, for example, no
butter on bread, no cream cheese on bagels, no oil in salad dressings.

"If a physician told a patient to eat less fat, that will do nothing,"
he said. "If you send someone to a dietician one time, that will do
next to nothing." The women in the study had 18 sessions of meeting in
small groups with a trained nutritionist in the first year and four
sessions a year after that.

In the first year, the women on the low-fat diets reduced the
percentage of fat in their diet to 24 percent of daily calories and by
the end of the study their diets contained 29 percent of their calories
as fat. In the first year, the women in the control group were eating
35 percent of their calories as fat and by the end of the study their
dietary fat content was 37 percent.

Some medical specialists stressed that the study did not mean people
should abandon low-fat diets.

"What we are saying is that a modest reduction of fat and a
substitution with fruits and vegetables did not do anything for heart
disease and stroke or breast cancer or colorectal cancer," said Dr.
Nanette Wenger, a cardiologist and professor of medicine at Emory
University Medical School. "It doesn't say that this diet is not
beneficial," she added.

But the overall lesson, said Dr. Freedman, is clear.

"A lot of observational data show diet matters, but those studies have
big flaws and that's why we have to do experiments," he said "We, the
scientific community, tend to go off the deep end giving dietary advice
based on pretty flimsy evidence."