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Laura Mignone and colleagues from the Harvard School of Public Health, US, looking at the correlation between dietary consumption of certain classes of vitamins and nutrients in fruits and vegetables, suggest that a high consumption of carotenoids may reduce the risk of premenopausal breast cancer, particularly in smokers. A recent article in the International Journal of Cancer details their study examining the association of carotenoid consumption and breast cancers.
A series of review articles have indicated that carotenoids have a protective influence on certain cancers in animals, and therefore may also have the same effect in humans. Carotenoids are plant pigments that can be found in yellow and orange vegetables and fruits and in dark green leafy vegetables. In an interview with Reuters Health Mignone points out that carotenoids are strong antioxidants and may play a role in protecting the body from the various carcinogens to which people are exposed. Indeed, hypothesised mechanisms for the protective properties of carotenoids against cancer include their potential antiproliferative and antioxidant properties. Specific carotenoids such as â-carotene, á-carotene and â-cryptoxanthin possess retinoic acid activity and are able to influence cell differentiation. Others, such as lutein and zeaxanthin are able to reduce cell proliferation despite not having any retinoic acid activity. The other proposed mechanism involves the inhibition of estrogen signalling by 17â-estradiol that may alleviate the effects of hormone-dependent malignancies.
The study by Mignone and colleagues involved examining the association between consumption of carotenoids and breast cancer in a large population-based case-control study of women (pre and postmenopausal). An inverse association was observed among premenopausal women for high levels of vitamin A, â-carotene, á-carotene and lutein/zeaxanthin. The results indicated that the risk of premenopausal breast cancer was reduced with the consumption of carotenoid rich vegetables such as carrots, kales and green leafy vegetables. Higher intake of the above mentioned carotenoids and vitamin A from food was associated with statistically lower risk among premenopausal women. Contrastingly, this was not observed in postmenopausal women.
The authors state that it is unclear why the association between carotenoids and breast cancer is limited to premenopausal women, although it may be related to the increasing cell turnover in breast epithelium under the influence of cyclic ovarian estrogen exposure. Other risk factors considered by the study include smoking and the known oxidative stress induced by tobacco smoke. Considering this, it is suggested that premenopausal women, particularly smokers, might benefit from increasing their dietary intake of carotenoid-rich vegetables to at least two servings each day, which might reduce the risk of breast cancer by 17%.
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