Does Eating Vegetables Make a Difference in Breast Cancer?

In the Journal of the National Cancer Institute it is reported that there is no overall effect of fruit and vegetable intake on breast cancer risk.
(Jung S, Spiegelman D, Baglietto L, et al. Fruit and vegetable intake and risk of breast cancer by hormone receptor status. J Natl Cancer Inst. 2013 Jan 24).

The authors did however show evidence that there is a protective effect of fruit and vegetable consumption for ER negative breast cancer. This is consistent across 20 pooled studies.
The role of fruits and vegetables as dietary modifiers of breast cancer risk has been studied for 40 years. The results have been inconsistent and in the past, suggested protection for premenopausal disease.

In the study by Jung et al a variety of individual plant foods were found to be protective against ER negative disease. Included in this group are strawberries rich in ellagic acid, apples which contain quercetin, peaches, nectarines, apricots, carrots, leafy lettuces and greens which are high in carotenoids.

It has been reported that total circulating carotenoids were associated with a 19% decrease in breast cancer (Eliassen AH, Hendrickson SJ, Brinton LA, et al). A word of caution: A few studies have shown that carotenoid supplementation however is not beneficial and may increase the risk for lung cancer and premature death in smokers.

Another important observation is that ER negative disease, especially triple negative disease is higher amongst younger women of black and Hispanic background in areas of lower socioeconomic status. It has been postulated that increased ER negative disesase in these groups is partly due to different reproductive patterns as opposed to poverty, race or ethnicity.

A study in Scotland has shown that a higher frequency of ER negative breast cancers is found in women living at lower income levels and in areas associated with high stress, more exposure to environmental toxins, higher levels of DNA damaging oxygen radicals and poor nutrition (Thomson CS, Hole DJ, Twelves CJ, Brewster DH, Black RJ. Prognostic factors in women with breast cancer: distribution by socioeconomic status and effect on differences in survival. J Epidemiol Community Health. 2001;55(5): 308–315).

It has been pointed out that other health behaviors are also important to consider including, physical activity, non-smoking and cancer screening. These additional influences make it difficult to separate individual factors that act independently to reduce ER negative breast cancer.

While this study supports the public message for increased vegetable and fruit intake as a potential benefit for ER-negative breast cancer, more research needs to be done to verify the findings across different ethnic groups within the population (the Pooling Project includes predominantly non-Hispanic whites) and to consider additional disease subgroups, particularly since a large percentage of studies were missing information on hormone receptor status.