Women who have higher levels of pigments found in fruits and vegetables called carotenoids may have a lower risk of breast cancer. This inverse relationship was found to be particularly strong for more lean women, those with ER-negative tumors, and current smokers. Women who smoke or consume alcohol(Drug information on alcohol) may gain more benefit from consumption of carotenoids, according to the authors. These results of a pooled analysis of prospective trials published in the Journal of the National Cancer Institute.
“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,” state the authors. For ER-positive breast cancers, hormone-level effects may mask the beneficial effects of carotenoids.
A. Heather Eliassen, ScD, of the department of medicine at Brigham & Women's Hospital and Harvard Medical School, and colleagues included more than 3,000 subjects and almost 4,000 control subjects among worldwide publications on serum and plasma carotenoid levels and breast cancer. The analysis includes 80% of the published prospective data.
Circulating levels of carotenoids are seen as a better way to understand the effect of dietary carotenoids without the high inaccuracies of subject-reported diet, the spectrum of carotenoid levels from different food sources, and varying levels of nutrient absorption among individuals. On their own, the studies showed statistically significant or a suggested inverse relationship between breast cancer risk and levels of at least one carotenoid.
The reported carotenoid levels of trial participants were recalibrated to a common benchmark in order to compare levels between different trials. The levels of α-carotene, β-carotene, lycopene, β-cryptoxanthin, lutein, and zeaxanthin, the most common carotenoids, accounting for the vast majority of circulating carotenoids in our body from the foods we eat.
Unadjusted analysis showed a significant inverse association between lycopene levels and breast cancer risk (P = .05). Factors that appeared to contribute to this association included body mass index (BMS), smoking, and menopausal status. When incorporating these factors, levels of each individual carotenoid, except β-cryptoxanthin, was inversely associated with breast cancer risk.
ER-negative breast tumors had the strongest, and statistically significant correlation with carotenoid levels. An association of both α-carotene and β-carotene, and ER-negative tumors was statistically significant (P = .04 and P = .001, respectively). Neither tumor size nor involvement of nodes correlated with breast cancer risk and carotenoid levels. The recent Dietary Approaches to Stop Hypertension study also recently showed a reciprocal relationship of fruit and vegetable consumption and ER-negative status but not ER-positive status.
The authors assessed whether the role of lifestyle factors including alcohol consumption, BMI menopausal status, postmenopausal hormone use, smoking status, and diagnosis affected whether carotenoids could influence breast cancer risk. Two associates appeared to be important. A statistically significant inverse interaction between total carotenoids and breast cancer risk was found for current smokers, regardless of the ER status of the breast tumor. The association also varied by BMI. Stronger inverse associations with breast cancer risk were seen for more lean women with a BMI of 25 or lower.
Carotenoids are organic pigments found in fruits and vegetables that range in color from yellow to red. α-carotene, β-carotene, lycopene, β-cryptoxanthin are converted by the body to vitamin A. The color of a carotenoid is related to their structure and type. Orange and yellow fruits and vegetables such as carrots and apricots tend to have high vitamin A activity because they contain β-carotene, the most well-known carotenoid, while lycopene is orange-red and found in tomatoes and watermelon.
Both epidemiological and laboratory studies have hinted that carotenoids have anticancer properties, including anti-oxidation properties. Meta-analyses of dietary intake have shown a lower risk of breast cancer for those who consume higher levels of fruit and vegetables. In vitro studies have demonstrated that carotenoids can decrease proliferation of breast cancer cells. Several epidemiological studies have also shown that men who consume a diet high in lycopene have a lower probability of developing prostate cancer compared to men who consume less lycopene.
“A diet high in carotenoid-rich fruits and vegetables offers many health benefits, including a possible reduced risk of breast cancer,” conclude the authors.