High-Carb Diet May Increase
Breast Cancer Risk
August 10, 2004
A diet high in carbohydrates may be linked to an increased risk of breast
cancer, researchers report. In a study of Mexican women, those who consumed
the highest percentage of carbohydrates - particularly sugars - were most
likely to develop breast cancer.
But it is probably premature to use the findings in the debate over
low-carbohydrate diets.
"The most important point is that this should be regarded as preliminary
data," study co-author Dr. Walter Willett of Harvard Medical School in
Boston told Reuters Health. "A prospective study of this relation should be
conducted in Latin America because the results could be extremely
important."
Willett noted that most of the elevated cancer risk was related to
consumption of sugar and refined starches. "There is already good reason to
keep intakes of these low for the prevention of heart disease and type 2
diabetes," he noted.
Willett's group compared 475 Mexico City women who had breast cancer with
1,391 female residents who had not been diagnosed with cancer. On average,
participants got 57 percent of their total calories from carbohydrates, 28
percent from fat and 15 percent from protein.
Carbohydrate intake was directly related to the risk of breast cancer, the
researchers report in the medical journal Cancer Epidemiology, Biomarkers
and Prevention. Women whose diet contained the highest percentage of
carbohydrates were more than twice as likely to have breast cancer as women
who consumed the least carbohydrates.
The risk was increased even though the team accounted for other factors that
can influence the risk of breast cancer, including age, total calorie
intake, socioeconomic status, family history of breast cancer and the number
of times a woman has giving birth.
Sucrose -- table sugar -- was the carbohydrate most strongly associated with
an increased risk of breast cancer. The association between sugar and breast
cancer was stronger among women who had gone through menopause.
Carbohydrates may influence the risk of breast cancer by their effect on the
body's insulin pathway, according to the researchers, who were led by Dr.
Isabelle Romieu at the Instituto Nacional de Salud Publica in Cuernavaca,
Mexico.
After a person eats starchy or sugary carbohydrates, blood sugar rises. This
spike in glucose triggers the secretion of the sugar-processing hormone
insulin. Elevated levels of insulin may in turn lead to increased levels of
a protein called IGF-I, and recent research has shown that IGF-I may be
related to an increased risk of breast cancer, particularly in premenopausal
women, according to the report.
Although some studies have suggested a link between fat and breast cancer
risk, the study found that consumption of polyunsaturated fat -- found in
fish and vegetable oils -- was associated with a reduced risk of breast
cancer, particularly among postmenopausal women.
In addition, although body weight has been associated with the risk of
breast cancer in some studies, body mass index, or BMI -- a measure of
weight in relation to height, was not related to breast cancer risk in this
study.
The researchers point out that carbohydrates make up a high proportion of
the Mexican diet. A recent survey found that urban Mexican women obtained an
average of 64 percent of total calories from carbohydrates.
SOURCE: Cancer Epidemiology, Biomarkers and Prevention, August 2004.