A. Heather Eliassen of the Channing Division of Network Medicine, the Department of Medicine at Brigham & Women's Hospital and Harvard Medical School, and colleagues, conducted an analysis of eight studies involving 80 percent of the world's published prospective data on plasma or serum carotenoids and breast cancer.
The analysis included 3,055 case subjects and 3,956 matched control subjects.
The study, published in the Journal of the National Cancer Institute, found in more than 3,000 case subjects, there were statistically significantly inverse associations between circulating levels of individual and total carotenoids and breast cancer risk, with a stronger finding in estrogen receptor-breast cancers -- breast cancers that grow in response to the hormone estrogen.
"The inverse associations we observed among ER-negative tumors highlight carotenoids as one of the first modifiable risk factors for this poor prognosis tumor type," the study authors wrote in the study.
Some evidence has shown that carotenoids inhibit the growth of ER-positive breast cancers as well, it's possible that its effect is hidden by hormone related associations which overpower other risk factors. Still, the researchers said: "A diet high in carotenoid-rich fruits and vegetables offers many health benefits, including a possible reduced risk of breast cancer."
The website the World's Healthiest Foods said foods that contain carotenoids include:
-- The orange-colored fruits and vegetables such as carrots, apricots, mangoes, squash, papaya, and sweet potatoes contain significant amounts of beta-carotene, alpha-carotene and beta-cryptoxanthin.
-- Green vegetables, especially spinach, kale and collard greens, also contain beta-carotene, and are the best sources of lutein.
-- Lycopene is found in tomatoes, guava, and pink grapefruit.
-- Salmon, shellfish, milk and egg yolks also provide carotenoids.