Alcohol is one of the most firmly established risk factors for breast cancer, with increased risk incurred even at low levels of consumption, including red wine. The increased risk may be greater among postmenopausal women and for estrogen receptor positive (ER+) tumors. Consuming alcohol also negatively affects breast cancer prognosis.
Latest research finds that alcohol plus some polyphenols raise breast cancer risk
Large prospective study
The prospective study referenced at the beginning of this news article was designed to investigate the associations between breast cancer risk and a wide range of dietary polyphenols, as well as assessing how alcohol consumption influences these relationships. Polyphenols are plant-based antioxidant micronutrients that often contribute to the color, smell or taste of foods. The study included 4,141 French women enrolled in the Supplementation with Antioxidant Vitamins and Minerals (SU.VI.MAX) cohort. Dietary intakes were assessed upon enrollment by repeated 24-hour food logs. Polyphenol intake was divided into quartiles (women in the lowest 25% of consumption were placed in the lowest quartile). The analyses divided the women into two groups based on median alcohol intake: (1) non to light drinkers consuming less than 6.5 g/day (or approximately half a drink per day); and (2) women consuming at least 6.5 g/day. The women were followed between 1994 and 2007, with a median follow up period of 12.6 years. A total of 152 of the 4,141 participants were diagnosed with breast cancer during follow up.
Polyphenol intake linked to reduced breast cancer risk in non or light drinkers
When analyzing the results for non to light alcohol drinkers, it was found that intakes of some classes of polyphenols were associated with significantly reduced risk of breast cancer. The analyses compared the breast cancer risk associated with the highest quartile compared to the lowest quartile of intake. Women in this group with high consumption of flavonoids had a 65% lower risk of breast cancer than women with low intake. The comparable reduction in risk was 64% for flavonols, 62% for hydroxybenzoic acids, 61% for proanthocyanidins, 58% for theaflavins and 52% for catechins.
Flavonoids are pigments found in a wide variety of plants (e.g., apigenin, luteolin and tangeretin). Flavonols (e.g., quercetin, kaempferol and fisetin) are a type of flavonoid. Hydroxybenzoic acids are found in many types of plant foods, including lentils, honey, buckwheat, and plums. Proanthocyanidins are founds in most berries, as well as in cinnamon, apples, red grapes, black currants, certain nuts, persimmons, and purple rice. Anthocyanins are dark red/purple pigments found in cherries, blackberries, pomegranates, black currants and purple sweet potatoes. Theaflavins are found primarily in black tea. Catechins such as (-)-epigallocatechin gallate (EGCG) are found in green tea, as well as in red grapes, lentils, buckwheat, red beans, peaches, and avocados. Overall, the polyphenols linked to lower breast cancer risk in the study are found in an very wide variety of plant foods.
Polyphenol intake linked to increased breast cancer risk in moderate to heavy drinkers
When analyzing the results for moderate to heavy alcohol drinkers, it was found that the some of the same polyphenols were associated with significantly increased risk of breast cancer. Women in this group with high consumption of flavonoids had 2.46 times the risk of breast cancer as women with low intake. The comparable increase in risk was 2.28 for hydroxybenzoic acids, 2.98 for proanthocyanidins, and 2.28 for catechins. Intake of flavonols and theaflavins did not increase breast cancer risk among moderate to heavy alcohol drinkers. High anthocyanin intake was associated with 2.94 times the risk of breast cancer in this group. The authors conclude that several classes of polyphenols could potentially contribute to breast cancer prevention among non-drinkers and light alcohol drinkers, but some may actually heighten the risk of breast cancer among women with greater alcohol intake.