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In multiple studies, cancer researchers have determined that a plant-based diet and less alcohol consumption significantly reduce the risk of breast cancer.
In the most recent study, researchers from Columbia University, Stanford University and UCLA followed 91,779 women for 14 years as part of the California Teachers study. The women were followed between 1995 and 2009.
The researchers tracked the number of breast cancers and tumors among the women during the women and matched these results with the respective diet patterns of the women. The researchers grouped the women into five basic diet patterns:
1) plant-based diet - high in fruits and vegetables
2) high-protein, high-fat diet - high in meats, eggs, fried foods, and fats
3) diet high in carbohydrates, processed and convenient foods, pasta, and bread products
4) ethnic diet - high in legumes, soy foods, rice, and dark-green leafy vegetables
5) salad and wine diet - high in lettuce, fish, wine, low-fat salad dressing, coffee and tea
Of these patterns, those who ate the most (highest quartile) plant-based diet pattern (1) had 15% less incidence of breast cancer and 34% less incidence of breast cancers that were estrogen receptor-negative and progesterone receptor-negative (ER-/PR-).
While the non-plant-based diets scored the lowest, the researchers also found that the "salad and wine diet" pattern produced a 29% higher incidence of estrogen receptor-positive progesterone receptor-positive (ER+/PR+) tumors.
With regard to the alcohol consumption, the researchers noted that alcohol was a contributing factor, but not the only contributing factor.
The researchers concluded that:
"The finding that greater consumption of a plant-based dietary pattern is associated with a reduced breast cancer risk, particularly for ER-/PR- tumors, offers a potential avenue for prevention."
Other studies have shown that a plant-based diet reduces the risk of breast and other cancers
Specific to breast cancer, a study from France's INSERM scientists conducted a large study that followed 65,374 women for nearly 10 years (9.7 to be exact). Here the researchers divided the women into two primary eating patterns:
The Western diet plan resulted in a 20% greater incidence of breast cancer among those eating the most (highest quartile) of this diet, and 33% greater risk for ER+/PR+ tumors. Meanwhile, those eating the most of the Mediterranean diet plan had 15% incidence of all breast cancers.
This study also captured a difference of 6% greater breast cancer risk among those with greater alcohol consumption. This appears to be consistent with the new study as well.
Alcohol a greater factor in some breast cancers
Specific to alcohol, another study - this from Sweden's Karolinska Institute - followed 51,847 women for more than eight years. This study found that those women who drank more than 10 grams of alcohol per day had a 35% greater incidence of ER+/PR+ breast cancers. This was increased among women who were taking hormones.
The researchers noted that the ER+ relationship was important, as they stated in their conclusion:
"The observed association between risk of developing postmenopausal ER+ breast cancer and alcohol drinking, especially among those women who use postmenopausal hormones, may be important, because the majority of breast tumors among postmenopausal women overexpress ER."
Fiber content in diet critical in breast cancer
The relationship between diet and breast cancer becomes more evident as we examine a 2008 study of 51,823 Swedish women who were also followed for more than eight years. Here the researchers found that those women who had the highest quartile of total fiber intake had a 34% decreased incidence of breast cancer and a 38% reduced incidence of ER+/PR+ tumors.
This study also found that among those taking hormones, the reduction of breast cancer incidence was a whopping 50%.
The researchers also found that those eating more cereal-based fiber (grains) had an even greater reduction in breast cancer incidence. A plant-based diet is naturally higher in fiber because whole fruits, vegetables and grains contain various plant fibers.
So it seems that fiber is a critical issue, and plant-based foods maintain higher fiber content, while the Western diet maintains lower fiber content.
Certainly this is compounded by the increased content of numerous anti-cancer phytochemicals.
Link LB, Canchola AJ, Bernstein L, Clarke CA, Stram DO, Ursin G, Horn-Ross PL. Dietary patterns and breast cancer risk in the California Teachers Study cohort. Am J Clin Nutr. 2013 Oct 9.
Cottet V, Touvier M, Fournier A, Touillaud MS, Lafay L, Clavel-Chapelon F, Boutron-Ruault MC. Postmenopausal breast cancer risk and dietary patterns in the E3N-EPIC prospective cohort study. Am J Epidemiol. 2009 Nov 15;170(10):1257-67. doi: 10.1093/aje/kwp257.
Suzuki R, Ye W, Rylander-Rudqvist T, Saji S, Colditz GA, Wolk A. Alcohol and postmenopausal breast cancer risk defined by estrogen and progesterone receptor status: a prospective cohort study. J Natl Cancer Inst. 2005 Nov 2;97(21):1601-8.
Suzuki R, Rylander-Rudqvist T, Ye W, Saji S, Adlercreutz H, Wolk A. Dietary fiber intake and risk of postmenopausal breast cancer defined by estrogen and progesterone receptor status--a prospective cohort study among Swedish women. Int J Cancer. 2008 Jan 15;122(2):403-12.