Headlines in major newspapers around the country have reported
apparently discouraging results from the Women's Health
Initiative (WHI), a major study that found that 8 years
on a low-fat diet program did not reduce women's overall
risks of heart attacks, strokes, breast cancer, or colon
cancer. Even so, there is no doubt that diet can have a
significant impact on women's health, so how do we get to
the bottom of the problem of finding the right combination
of fats, carbohydrates, proteins, and other nutrients to
eat?
Studying and understanding the impact of dietary modifications
is always complicated. Consider the following:
Any time we limit our intake of one type or category
of food, we tend to fill the gap by eating more of another
type of food. In the WHI, women were not encouraged to
cut calories or lose weight.
Our bodies have an astonishingly efficient "thermostat"
that works hard all our lives to return us to whatever
body weight and body composition it has been set at, based
on what has been normal for us over the long-term. That
is why keeping weight off after just about any kind of
crash diet is so hard to do.
More About the Women's Health Initiative
Reduced-Fat Diet Study
The Women's Health Initiative is a massive, ongoing research
effort that began in 1992, and has involved over 160,000 women
in several studies. Its goals were to determine, among other
things, how to lower the incidence of breast cancer, colon
cancer, stroke, and cardiovascular disease. They investigated
whether low-fat diets could reduce the risk of developing
these diseases.
The women participating in the low-fat diet study were divided
into two groups: one group was encouraged to continue eating
as they always had, while the other group was encouraged (through
participation in a series of training sessions) to modify
their diets to reduce fat and increase their consumption of
fruits, vegetables, and grains. By comparing the rates at
which women in the two groups later developed health problems
including breast and colon cancer and cardiovascular disease,
scientists hoped to see whether the training sessions would
work and whether the low-fat diet would improve women's health.
The reported results were not encouraging, since few differences
emerged in the health status of the women in the two groups.
However, there were a number of weaknesses in the study that
made the results difficult to interpret.
All dietary fat is not alike. For example, we know
that saturated fats and trans-fats can have particularly
negative health effects and that certain fats - like those
found in walnuts or some fish oils - can actually be beneficial.
Nevertheless, the study did not attempt to influence which
types of fats any of the women were eating.
The diets that women in the two groups reported eating
were not as different as scientists had hoped they would
be. The low-fat group averaged 29% calories from fat instead
of the targeted 20%. Their reported consumption of fruits
and vegetables was only slightly raised, and their consumption
of grains did not change. We can't be sure whether or
not the incidence of cancer, stroke, and cardiovascular
disease in the two groups would have been different if
the diets had been less similar.
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Women in the diet modification group whose total fat
intake was reduced the most did significantly
lower their risk for invasive breast cancer. And those
who consumed less saturated fat and ate more fruits and
vegetables reduced their blood pressure, cholesterol and
other problems that may eventually reduce their risk of
heart attack, stroke, and heart disease.
There was no attempt to modify overall calorie intake
or to lose weight in either group. Research clearly shows
that being overweight increases the risk of breast cancer,
heart disease, arthritis, and many other diseases, so
more targeted dietary modifications that include emphasis
on achieving and maintaining healthy body weight might
be more effective.
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Over the 8 years of the study, women in the group
that had not been asked to modify their diets also
reported reducing fats and increasing fruits and vegetables
in their diets. Is that because they were in a study
asking questions about the food they eat? We don't
know, but it suggests that women are willing to change
their diets to improve their health, even if they
aren't told to do so in a study.
The study did not last long enough to tell for
sure whether the two groups will differ in incidence
or deaths from cancer or cardiovascular disease. While
the 8 years that these women have been followed represents
a big investment of time and money, we know that many
cancers and other health conditions take 15-20 years
to develop, showing up for the first time among older
women. It is impossible to say whether even the modest
dietary modification that was accomplished in this
study will result in health benefits for these women
over the next 10 or 20 years.
There is no way to know whether the dietary intervention
in this study would have been more effective if it
had been started earlier in the women's lives - when
the women were in their 20's or 30's, rather that
at 50-79 years of age.
What We Have Learned from the Study
Don't let the negative headlines fool you. Although the
results of this study are not as clear cut nor as positive
as scientists would have hoped, they still provide important
information.
Women whose fat intake was lowered the most
had better health outcomes.
One of the most important messages is that dietary
changes are easier to talk about than to do something
about. The 19,541 participants in the low-fat group
probably started out with very good intentions about
following the recommended diet, but that turned
out to be impossible for many of them. Whether this
is because of pressure to join the family for dessert,
the endless temptation created by advertisements
for foods that were not compatible with the diet,
or other causes, it is important for us to take
such real-world obstacles into account.
Maintaining Moderation and Balance
So what's a woman to eat? Most people, under
most circumstances, will benefit from a well-balanced
diet that is low in saturated- and trans-fats, includes
plenty of fresh fruits, vegetables, and whole grains,
and moderate amounts of dairy products and meat protein.
Helpful nutritional guidelines are available at: http://www.usda.gov/news/usdakids/food_pyr.html.
General guidelines for healthy eating may need to be modified
to accommodate specific health problems or disease risks.
For example, someone with high cholesterol might need
to reduce their total fat intake more than someone with
normal cholesterol.
Don't forget to watch calories. The way to lose weight
is to use up more calories than you consume. Because excess
weight can cause or complicate so many health problems,
reaching and maintaining a healthy body weight is important.
Remember that serving size and portion size are not the
same thing. Serving size is a standardized quantity
of food that we use to measure nutrients. Portion
size is the amount we pile on our plates. Keep in
mind that one serving of cooked vegetables is usually
about one-half cup (about a hand-full!) and a serving
of meat is about the size of a deck of cards. This means
that most people can fit in all those recommended servings
every day while still reducing their total calorie intake
and losing weight. But it also means that the portions
you serve yourself may be much higher in calories than
the standard serving size would be.
In summary, the best nutritional science available to
us today confirms that in spite of recent newspaper headlines
that may have suggested otherwise, reducing saturated
fats and increasing fresh fruits, vegetables, and whole
grains as part of a lower calorie diet is almost always
a good thing to do, and never a dangerous one.
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