A number of dietary and nutritional factors have been studied in relation to breast cancer risk, with observational and interventional research suggesting associations between certain nutrients and disease incidence.
Vitamin D status has been examined in several studies. A retrospective study published in Breast Cancer Research and Treatment (e-published March 8, 2011) evaluated vitamin D status in 224 women with breast cancer, ranging from stage 0 to stage III. Participants were divided into three groups: one received no vitamin D supplementation, one received 1,000 IU per day, and a third received a high dose of 50,000 IU per day. Only the high-dose group experienced a significant increase in serum 25-hydroxyvitamin D [25(OH)D] levels.
Additional evidence comes from a nested case–control study published in Cancer Epidemiology, Biomarkers & Prevention (September 2010; 19(9):2341–2350), which compared vitamin D levels in 636 women with breast cancer and 1,272 healthy controls. Higher vitamin D levels were inversely associated with breast cancer incidence, with the association being more pronounced in women under 53 years of age. In postmenopausal women, the risk reduction was smaller.
Carotenoids have also been studied in relation to breast cancer. Research published in Cancer Research (2009; 69(24):9323–9329) compared 602 breast cancer patients with 626 controls. The study found that circulating carotenoid levels were inversely related to breast cancer risk. Among women with high mammographic density, those with higher carotenoid levels experienced up to a 50% reduction in breast cancer risk, whereas this relationship was not observed in women with low mammographic density.
Carotenoids are fat-soluble plant pigments responsible for the bright colors of many fruits and vegetables. Some carotenoids can be converted to vitamin A in the body. The most well-known carotenoid is beta-carotene, which has the highest vitamin A activity. Other carotenoids include alpha-carotene, lycopene, lutein, astaxanthin, beta-cryptoxanthin, and zeaxanthin.
Flavonoids, another class of plant pigments, have antioxidant properties that protect plants from oxidative stress during photosynthesis and may provide similar antioxidant effects in humans. A study published in the American Journal of Epidemiology (2007; 165(5):514–523) compared 1,434 women with breast cancer to 1,440 healthy controls. The researchers reported that higher dietary intake of flavonoids was associated with a lower risk of breast cancer.
Lignans, which are phytoestrogens with antioxidant activity, are found in the cell walls of plants and occur in foods such as flaxseed, soybeans, whole grains, rye, broccoli, pumpkin seeds, and certain berries. A prospective study published in the Journal of the National Cancer Institute (2007; 99(6):475–486) analyzed lignan intake in 58,049 postmenopausal French women. Dietary intake was assessed using a self-administered food questionnaire in women who were not taking soy isoflavone supplements. Women in the highest quartile of lignan intake had a 17% lower risk of developing breast cancer compared with those in the lowest quartile.
Diet earlier in life has also been examined. A population-based case–control study published in Cancer Causes & Control (2006; 17(10):1253–1261) compared 3,024 breast cancer patients aged 25 to 74 years with 3,420 matched controls. Using food-frequency questionnaires, the researchers found that dietary patterns during adolescence were associated with later breast cancer risk. Higher intake of lignans and isoflavones during the teenage years was associated with a reduced risk of developing breast cancer in adulthood.
Animal research has also explored nutrient effects. A study published in Carcinogenesis (2009; 30(7)) investigated the effect of vitamin C on estrogen-induced breast tumors in rats genetically prone to tumor development. Among animals given estradiol alone, 82% developed breast tumors. Rats receiving both estradiol and vitamin C developed 29% fewer tumors over the 240-day study period.
Taken together, these studies suggest associations between nutrient intake, dietary patterns, and breast cancer risk across different populations and study designs. The findings are observational or experimental in nature and do not establish causation, but they contribute to a broader understanding of how nutrition may relate to breast cancer risk.
Educational note:
This article is for informational purposes only and is not intended as medical advice
