Heart experts say a study
which shows a lack of health benefits from a low-fat diet
failed to take into account other risk factors.
A US study of over 19,500 women found
cutting back on fat for almost a decade failed to offer
significant protection against some cancers and heart
disease.
But British experts say salt levels were
not cut, and many of the women were overweight or obese.
The study is published in the Journal
of the American Medical Association.
Researchers running the Women's Health
Initiative study of post-menopausal health asked more
than 19,500 women aged 50 to 79 to reduce their total
fat consumption and eat more fruit and vegetables.
The women were then monitored over eight
years during the 1990s, and compared with another group
of 29,300 women whose diet was unchanged.
Rates of breast and bowel cancer and
heart disease were measured.
Although some improvements were seen
in the study group, most were insignificant.
A 9% reduction in breast cancer incidence
meant that out of 10,000 women, 42 in the low-fat group
and 45 in the control group developed the disease each
year.
And overall rates of bowel cancer were
not lowered by the healthier diet - although reducing
fat consumption did produce a 9% decrease in colon polyps
which can lead to colon cancer.
In addition, no reduction was seen in
heart disease risk among the women eating less fat.
Their rates of heart disease fell by
just 3%, while blood levels of "bad" cholesterol, low
density lipoprotein (LDL), dropped by only 2.4%.
The American researchers say that they
are not disheartened by the results.
They said the difference between "good"
and "bad" fats was not recognised when the study started,
so women were only told to reduce fat consumption - rather
than to reduce levels of trans-fats, which are classed
as bad, while fats in nuts, fish and vegetable oils are
said to have health benefits.
Heart benefits
Dr Ross Prentice, one of the study authors,
from the Fred Hutchinson Cancer Research Centre in Seattle,
Washington, said: "While the study didn't give us the
results that some people were hoping for, it suggests
that we're on the right track.
"Women can be confident that cutting
back on fat and following the recommended dietary guidelines...
certainly won't hurt when it comes to maintaining a healthy
lifestyle and preventing chronic disease."
But Judy O'Sullivan, a cardiac nurse
at the British Heart Foundation, said: "Numerous studies
have confirmed there are huge heart benefits from maintaining
a healthy lifestyle which involves a balanced diet and
regular physical activity.
"It is easy to identify a number of important
reasons why this study did not agree with previous research.
"It didn't reflect current advice for
good heart health, such as salt reduction, increasing
intake of good fats such as those in oily fish, and increasing
exercise.
"Additionally, most of the women in the
study were overweight or obese, which increases your risk
of developing diabetes - another risk factor for heart
disease."
Dr Emma Knight, science information manager
at Cancer Research UK, said: "People should continue to
eat a healthy balanced diet, with lots of fruit and veg.
"At present, the only diet-related factors
that definitely increase breast cancer risk are obesity
and alcohol.
"Bowel cancer risk can be increased by
a diet high in red and processed meat, but is lowered
by eating a high-fibre diet."
