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Low-fat diet 'fails to lower health risks'
No change found in women's diseases
But more research needed, experts say
Feb. 8, 2006. 01:00 AM
ELAINE CAREY
HEALTH REPORTER
Staying on a low-fat diet does not appear to reduce the risk of breast and colorectal cancer or heart disease in older women, a large American study says.
The latest bombshell from the landmark Women's Health Initiative study, released in three papers in the Journal of the American Medical Association yesterday, left health experts scrambling to try and explain the confounding results.
The new study followed almost 50,000 American women aged 50 to 79 for eight years to test the impact of a diet low in fat and high in fruits, vegetables and grains. In the end, those assigned to the low-fat diet had the same rates of breast cancer, colon cancer and heart attack and stroke as those who ate whatever they pleased, the study found.
The findings "are a bit surprising and a bit more disappointing," said Dr. Andrea Eisen, head of preventive oncology at Sunnybrook & Women's Health Sciences Centre. "Generally, people have been given advice to cut back on fat and there's a big campaign to eat more fruit and vegetables and I'm not sure it is totally justified," she said.
"These studies are revolutionary," Dr. Jules Hirsch, who has spent a lifetime studying the effects of diets on weight and health, told The New York Times. "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."
However, Ross Prentice, a co-author of the study, qualified the findings, saying that the 20,000 women in the low-fat diet group had a 9 per cent lower rate of breast cancer compared with women in the control group who continued to eat what they wanted, but that was not enough to be statistically significant.
"The bottom line is that changing to a low-fat diet may reduce breast cancer risk, especially among women who have a relatively high-fat diet to begin with," Prentice said, "but we don't view our data as strong enough at this time to make a broad recommendation that all women initiate a low-fat diet for that purpose."
In women who cut the most fat there were signs of less breast cancer, and in women who ate small amounts of the worst kind of fats, signs of less heart disease, the researchers said, adding longer follow-up may lead to more definitive results. The women also didn't reduce their fat intake as much as the diet demanded and most remained overweight, a major risk factor.
A low-fat diet had no significant impact on the incidence of stroke, heart attack, cardiovascular disease or coronary artery disease, indicating people have to do more than eat more healthfully for a number of years to avoid disease, said an accompanying editorial.
"To reduce the risk of cardiovascular disease, individuals should maintain a desirable body weight, be physically active, avoid tobacco exposure and eat a diet consistent with national guidelines," it said.
The low-fat group reduced their fat intake by an average of only 2.9 per cent and didn't distinguish between so-called "good" and "bad" fats.
"I think you can safely say that very small changes are going to lead to very small changes in cardiovascular disease," said Dr. Grant Pierce, chair of the scientific research group of the Heart & Stroke Foundation of Canada.
"We may be knocking the icing off the cake but we've still got a very big cake."
Women in the low-fat group aimed to reduce their fat intake to 20 per cent of their diet and to increase their consumption of fruits and vegetables to at least five servings a day and grains to six servings a day.
While they did increase their fruit and vegetable consumption by one serving a day and grains by about a half serving, "that's not a whole lot, is it?" Pierce asked. "I think you have to take that into consideration."
The study showed a trend toward higher rates of cardiovascular disease in subjects who ate higher amounts of trans fats, and a trend toward lower rates of disease in those with a higher vegetable intake, he said.
"The trends are there as we would expect, but maybe it's just a matter that you can't tinker with the diet, you need to make some real changes," Pierce said.
In interviews with more than 50 specialists conducted by ABC News, questions were raised about the study's shortcomings. The experts said:
The study was too short to detect a reduction in breast and colon cancer from dietary fat.
The amount of fat reduction was too small and was unlikely to produce meaningful benefits.
The researchers simply looked at fat intake in general and did not distinguish between healthy fats like olive oil and unhealthy fats like trans fats.
The study also suggests that dietary intervention has to take place at an early age to avoid disease developing, Pierce said.
"We know cardiovascular disease is already starting in children as young as 10 years old," he said. "If we modify their diet then, I would suspect it would have a major impact on cardiovascular disease but we really haven't done the studies yet."
With files from Star Wire Services