This study investigated how the previously reported association between carotenoid consumption and risk of breast cancer is related to breast density. Women with dense breasts have been reported to be at increased risk of breast cancer. The study included 604 women with breast cancer and 626 cancer-free controls in the Nurses' Health Study for whom circulating carotenoid (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin) levels had been measured and mammograms obtained prospectively.

Total circulating carotenoid levels were found to be inversely associated with overall risk of breast cancer, but not with mammographic breast density. However, high carotenoid levels were associated with decreased risk of breast cancer for women with dense breasts. Among women in the highest third of mammographic density, total circulating carotenoids were associated with a 50% lower risk of breast cancer. Similarly, among these women, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were associated with 40% to 50% reductions in breast cancer risk. No such inverse associations were observed among study participants with low mammographic density. The authors conclude that carotenoids may play a role in reducing breast cancer risk, especially among women with high breast density.

Food sources of carotenoids

The association of carotenoid consumption with reduced risk of breast cancer has been reported in numerous studies. This study makes a significant contribution with the finding that carotenoids may be especially effective in reducing breast cancer risk among women with high breast density. The following foods are good dietary sources of carotenoids while also having been found to be associated with reduced risk of breast cancer in other studies:

Arugula
Bell peppers
Carrots
Collard greens
Hot peppers
Kale
Lettuce, romaine
Mustard greens

Pumpkins
Saffron
Squash
Tomatoes
Watercress
Watermelon
Zucchini

Olive oil and black pepper have both been found to increase the bioavailabilty of beta-carotene from other foods. Supplementation with beta-carotene or with vitamin A will not provide the same beneficial effects as consuming high-carotenoid foods. In fact, these supplements have been associated with increased risk of certain cancers (e.g., lung cancer).