WASHINGTON - Cutting dietary fat may also cut the risk of ovarian cancer,
says a study of almost 40,000 older women that found the first hard evidence
that menu changes protect against this particularly lethal cancer.
But don't wait too long to get started: The protection didn't kick in until the
women had eaten less fat for four years and counting.
Until now, the only known prescription against ovarian cancer - aside from
surgically removing the ovaries - was to use birth control pills. Use for five
years can lower the cancer risk by up to 60 per cent, protection that lingers
years after pill use ends.
The new findings now offer an option for postmenopausal women to try as well.
Those who followed a low-fat diet for eight years cut their chances of ovarian
cancer by 40 per cent, researchers reported Tuesday in the Journal of the
National Cancer Institute.
"This is really good news," said Dr. Jacques Rossouw of the National Institutes
of Health, which funded the work. "But you have to stick with the diet."
It's arguably the most promising finding of the mammoth Women's Health
Initiative dietary study, which enrolled tens of thousands of healthy women ages
50 to 79 to track the role of fat in several leading killers. Some women were
assigned to cut the total fat in their diets to 20 per cent of calories - from
an average of 35 per cent - while others continued their usual diets for
comparison.
Yet the study so far has found the diet made little impact on rates of breast
cancer, colorectal cancer and heart disease. There are a number of theories:
Maybe the women started healthier eating too late; most were overweight, a major
risk factor, and the diet wasn't designed to shed pounds. Nor did most women
actually cut enough fat.
But despite all those hurdles, a low-fat diet did appear protective against
ovarian cancer - and the women who started with the worst diets and cut fat the
most got the most benefit.
Ovarian cancer is fairly rare, affecting one in 60 women compared with the one
in nine who will get breast cancer. But it is among the grimmest of diagnoses,
because ovarian cancer usually is detected only after it has spread throughout
the abdomen, making it much harder to treat. Only 45 per cent of patients
survive five years.
The American Cancer Society estimates that 22,430 U.S. women will be diagnosed
with ovarian cancer this year; 15,280 women will die of it. In Canada, there
will be an estimated 2,400 new cases this year, and 1,700 women will die from
the disease, according to the Canadian Cancer Society.
Ovarian cancer can strike anytime in adulthood, but risk increases with age.
Mutations in the so-called breast cancer genes BRCA1 and BRCA2 also increase the
risk of ovarian cancer - and women in the new study have not yet been tested for
those genes, to see if the low-fat diet proves more or less beneficial for them.
Why would diet affect ovaries? The theory is that fat intake increases the
amount of estrogen circulating in the blood, which may in turn overstimulate
sensitive ovaries.
Indeed, blood tests showed study participants on the low-fat diet experienced a
15 per cent reduction in estradiol, a key form of estrogen, while non-dieters
experienced no change, said study co-author Dr. Ross Prentice of Seattle's Fred
Hutchinson Cancer Research Center.
"It's quite noteworthy," Prentice said of the ovarian protection. "We're really
pleased to have something positive to say to American women - that undertaking a
low-fat diet likely reduces your risk of ovarian cancer and perhaps other
cancers as well."
Estrogen plays a role in breast cancer, too. Yet when researchers last year
checked women in this same study, they found only a nine per cent drop in breast
cancer risk, not quite large enough to be sure it wasn't due to chance. But even
then, the women who cut the most fat fared better - just like with the new
ovarian cancer data.
Most of the dieters cut their fat intake to 24 per cent of calories, not quite
as much as recommended. And over time, the fat crept back: Eight years later,
they were up to 29 per cent - still lower than the average American diet, noted
Rossouw, of NIH's National Heart, Lung and Blood Institute.
"It's feasible," he said of the diet. And, "once there is news that this does
work, it may be easier to motivate people to do."
