Written by Marcia J. Egles, MD. Study shows that higher total carotenoids were associated with 18-28% statistically lower risk of breast cancer.
As recently reported in a large American study with twenty years of follow-up, women with high plasma carotenoids were at reduced breast cancer risk, particularly for the more aggressive and ultimately more fatal varieties of the disease (1).
Carotenoids are a “micronutrient” in foods. The carotenoid family includes not only carotenes which are the bright orange pigments of carrots, but also lutein, lycopene, and others. Fruits and vegetables provide most of the carotenoids found in the diet.
The Nurses’ Health Study (2) of Harvard University, has provided high quality data for more than 600 studies, including this current study. In 1989-1990 as part of the Nurses’ Health Study, 32,826 women donated blood samples which were archived in liquid nitrogen for future research. These women were registered nurses, age 43-69, who completed extensive health questionnaires every 2 years with a follow-up rate of 97%. In 2000 to 2002, a second blood sample was contributed by 18,743 of these women, and also archived. Between the first blood collection and June 2010, two thousand one hundred and eighty-eight breast cancer cases were diagnosed in these participants. These cases were then matched with control participants and the blood samples were analyzed for carotenoids (1).
The study found that higher total carotenoids, as well as higher concentrations of specific carotenoids such as alpha-carotene, beta-carotene, and lycopene in the blood, were associated with 18 to 28% statistically lower risks of breast cancer. For example, women in the top quintile (top fifth) of beta-carotene levels (data includes both the 10 year and the 20 year sets of blood samples) when compared with those in the lowest quintile, had a relative risk of breast cancer of 0.72 (95%confidence interval 0.59-0.88, p-trend less than 0.001). Carotenoid concentrations were also strongly inversely associated with breast cancer recurrence and death. For beta-carotene, the top quintile compared to the bottom quintile, the relative risk of cancer recurrence was 0.32 (95% C.I. 0.21 to 0.51, p-trend less than 0.001).
These beneficial associations were observed predominantly in lean women (body mass indices less than 25). In women with body mass indices greater than 30, no associations were seen. The association of alpha-carotene with breast cancer was significantly strong in non-smokers but insignificant in current smokers (relative risk 0.74, 95% C.I. 0.60-0.92, p trend= 0.01 for non-smokers. Not significant for smokers- relative risk 1.23, 95% C.I. 0.54-2.80, p-trend=0.22.)
Since the study had data from both ten and twenty years ago, with breast cancer cases occurring throughout the twenty years, it sought to examine the timing of carotenoid exposure to its possible effects on breast cancer. Similar associations of reductions in breast cancer risk were seen for both sets of blood samples across the time- that is with both the ten year and the twenty year old samples when the two sets of samples were considered separately. Higher carotenoid levels at both less than ten years and at more than 10 years prior to diagnosis appeared to be protective, and may be particularly important for preventing tumor initiation.
The results of this large, prospective analysis suggest that normal–weight women with higher circulating carotenoid concentrations are at reduced risk for breast cancer. These results concur with a previous study reported by the same main author involving a review of pooled data from eight other studies (3). The researchers concluded that their results might appropriately encourage women to increase their consumption of carotenoid-rich fruits and vegetables, to not smoke, and to maintain a healthy weight.
Source: Eliassen, A. Heather, et al. “Plasma carotenoids and risk of breast cancer over 20 y of follow-up.” The American journal of clinical nutrition (2015): ajcn105080. (C) 2015 by the American Society for Nutrition
© 2015 by the American Society for Nutrition
Posted September 3, 2015.
Marcia Egles, MD, graduated from Vanderbilt University School of Medicine in 1986. She completed her residency in Internal Medicine at St. Louis University Hospital. Dr. Egles is certified in Internal Medicine and is a member of the American College of Physicians. She resides in Avon, IN with her husband and two sons.
References:
- Eliassen AH, Liao X, Rosner B, Tamimi RM, Tworoger SS, Hankinson SE. Plasma carotenoids and risk of breast cancer over 20 y of follow-up. Am J Clin Nutr. 2015;101(6):1197-1205.
- Colditz GA, Hankinson SE. The Nurses’ Health Study: lifestyle and health among women. Nat Rev CANCER, 2005 May;5(5):388-96.
- A. Heather Eliassen, Sara J. Hendrickson, Louise A. Brinton et al. Circulating Carotenoids and Risk of Breast Cancer: Pooled Analysis of Eight Prospective Studies J Natl Cancer Inst. 2012 Dec 19; 104(24): 1905–1916. Published online 2012 Dec 18. doi: 10.1093/jnci/djs461
