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Study: Vegetarians May be at Lower Risk of Developing Breast Cancer (dateline September 29, 2002)

A new study finds that vegetarian women may be less likely to develop breast cancer. However, the researchers are uncertain whether the lack of meat in the diet plays as large of a role in preventing breast cancer as the significant consumption of vegetables. In the study of lifelong vegetarians, the women who did not eat meat consumed far more vegetables than the non-vegetarians, suggesting the vegetables may offer a protective benefit against the disease. The data are preliminary but add insight into the controversial link between diet and breast cancer risk.

To study the effect of lifelong vegetarianism on the risk of developing breast cancer, Isabel dos Santos Silva and colleagues from Department of Epidemiology and Population Health at the London School of Hygiene and Tropical Medicine followed women who came to England from India, Pakistan, and Bangladesh. The researchers compared the Hindu women, who tended to be lifelong vegetarians to the Muslim women, who were likely to consume meat.

The researchers identified several risk factors among the women in the study who developed breast cancer, including a family history of breast cancer, older age at the birth of the first child, and those less likely to breastfeed their children (this latter factor is not well-established, although some studies suggest that breastfeeding may lower the risk of developing breast cancer).

After accounting for these factors, the study shows that the lifelong vegetarians were less likely to develop breast cancer, compared to the women who consumed meat. The findings suggest that vegetarianism lowers the risk of breast cancer. However, dos Santos Silva and her colleagues are not certain whether the lack of meat in the diet plays as significant a role in preventing breast cancer as the large consumption of vegetables. The lifelong vegetarians consume many more vegetables than the women who ate meat.

Further research is needed to determine whether nutrients found in vegetables help prevent breast cancer. Preliminary studies have shown that certain vitamins, particularly vitamin A, may play key roles in protecting against breast cancer. Other research suggests that a diet rich in soy may also help counteract breast cancer development.

Physicians believe that the link between diet and breast cancer will continue to be controversial. There is a much higher incidence of breast cancer in areas with high fat diets (such as the United States) than areas with low-fat diets (such as Asia). However, researchers have identified other factors that seem to play a larger role in determining breast cancer risk (although 80% of women diagnosed with breast cancer have no known risk factors).

Risk factors for breast cancer include:

  • Advancing age
  • Family history of breast cancer
  • Personal history of biopsy revealing pre-cancerous conditions, such as lobular carcinoma in situ (LCIS)
  • Genetic mutations of the BRCA1 or BRCA2 genes
  • Early onset of menstruation (before age 12)
  • Late menopause (after age 50)
  • Not having children, or having children after age 30

While it is unclear whether a diet rich in vegetables can lower breast cancer risk, a healthy diet low in saturated fat and high in fruits and vegetables offers several benefits, including protection against heart disease and colon cancer.

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