BOSTON, Feb. 21 (UPI) -- Eating eggs during adolescence could protect women against breast cancer while butter might increase the risk for the disease, a new study released Friday suggests.
Harvard University researchers analyzed data from the Nurses' Health Study -- an ongoing study involving more than 121,000 women -- and found women who ate more eggs during their teen years had a reduced risk of breast cancer, while butter appeared to increase the risk in this group of women.
"Women who had, during adolescence, a higher consumption of eggs ... had a lower risk of breast cancer, whereas risk of breast cancer was increased among women who consumed more butter," said Dr. Lindsay Frazier, the study's lead author and a pediatrician at Harvard.
Women who had higher intakes of vegetable fat and dietary fiber also had a lowered risk of developing the disease, Lindsay added.
As reported in the Feb. 21 issue of the journal Breast Cancer Research, Frazier's team found that eggs might reduce the risk of breast cancer because they "are rich sources of essential amino acids, minerals and vitamins."
Indeed, "fiber might affect the risk of breast cancer by decreasing estrogen levels," the team reported. Estrogen has been shown to play a role in causing breast cancer.
It is unclear why vegetable fat would reduce risk. The researchers also were not certain why butter would be associated with an increased risk when neither total fat nor animal fat intake appeared to increase the risk of the cancer.
Frazier and colleagues cautioned this was only an exploratory study and "the findings require confirmation" by additional studies.
Heather Feigelson, a senior epidemiologist with the American Cancer Society, agreed with the assessment.
"I don't give any stock to the findings of the egg and the butter," Feigelson told United Press International. "I think the egg is a fluke," she said. It may just simply be due to a recall bias, she said, noting the questionnaires asked the women to recall their diets some 20 to 50 years after the fact.
"Eating eggs may be something that's easier to recall for people than how many times a week did they have rice or some other food," she said.
Feigelson said there has been some speculation among the medical community that diet during the teen years can be critical because this is when the breasts are developing and the tissue could be especially susceptible to damage that could induce cancer later. However, there is scant science to support that hypothesis, she cautioned.
Women should not change their dietary habits based on this study, Feigelson said.
"I'm more of an advocate of making sure that adolescents are physically active and maintain a healthy weight than eat eggs or don't eat butter or any one specific thing," she said. "A healthy diet and physical activity may be one of the most important things that women of all ages, including adolescent girls, can do to reduce their risk of breast cancer."
In 1986, when the study participants were 40 to 65 years of age, they completed a questionnaire about their food intake between the ages of 12 to 18 years. Nearly 850 of the women developed breast cancer between 1976 and 1986.
After controlling for other factors that could increase breast cancer risk -- such as family history and use of hormone replacement therapy -- the researchers found those with the highest egg consumption had an 18 percent decrease in their risk for the cancer.
Higher intakes of vegetable fat and dietary fiber were associated with a 15 percent and 22 percent reduction in risk, respectively.
Those with the most butter intake had a 6 percent increase in risk.
(Reported by Steve Mitchell, UPI Medical Correspondent, in Washington)