Looking For Another Reason to Eat More Fruit and Vegetables?
Recently, Wang and colleagues found that higher intakes of certain carotenoids was associated with a reduced risk of breast cancer. This research is welcome news for those of us who may have just made it over the one-month milestone of a New Year’s Resolution to eat more fruit and vegetables, particularly the green and leafy kind, in 2014 and may need a stimulus to keep going.
For this piece of research, the authors conducted a case-control study. They identified 561 women who had been recently given a breast cancer diagnosis and were attending hospitals in Guangdong province in China, and matched them to 561 controls who were attending hospitals in the same area. The authors used a validated food frequency questionnaire that was designed for use in the population to estimate nutrient intakes. Specifically, the researchers were interested in intakes of the carotenoids alpha-carotene, beta-carotene, lycopene, beta-cryptoxanthin and lutein+zeaxanthin, and how they related to breast cancer diagnosis.
The authors found some demographic differences between the case and control groups: the cases tended to belong to lower income categories, were more likely to be exposed to passive smoke, and were more likely to have a close relative with a cancer diagnosis. Overall carotenoid intake was quite high compared to intakes found in similar populations in other parts of the world, particularly lutein+zeaxanthin (see Koushik et al. for an overview of carotenoid intakes in various countries in older women), including the USA. There were significant differences found in the intake of all the carotenoids, which appears to be driven by a reduced intake of both fruit and vegetables in the cases. Compared to the 25% of women with the lowest intake of alpha-carotene, beta-carotene, beta-cryptoxanthin and lutein+zeaxanthin, the 25% of women with the highest intake of these carotenoids had a reduced risk of breast cancer, varying from 30 to 60% lower. It appeared that breast cancer type (presence of the estrogen or progesterone receptors) did not affect the relationship.
These results are similar to other studies conducted over the past few decades. Back in 1996, Freudenheim and co-workers found that carotenoids beta-carotene and lutein+zeaxanthin were associated with reduced breast cancer risk. A decade later, Gaudet and colleagues also found that women with higher carotenoid intakes had a reduced risk of breast cancer. Riboli and colleagues conducted a review of epidemiological evidence of whether fruit and vegetables could affect cancer risk, and also found a protective effect.
These results are from observational research, therefore one cannot conclude that consuming carotenoids will reduce risk of breast cancer. However, this is unimportant for people who are teetering on the brink of breaking their New Year’s Resolution to eat more fruits and vegetables. A balanced diet that includes recommended amounts of fruit and vegetables helps people to obtain all the nutrients that they need, particularly fiber, vitamins C, K and the antioxidant carotenoids like beta-carotene, lutein and zeaxanthin. Many people do not get enough fruit and vegetables (for example, see study by Murphy and associates). So read the hot-off-the-press study by Wang, become motivated again, search the internet for a new and tasty way to consume your kale, yellow bell peppers and goji berries (wait, is that a new smoothie combination…?), and hold on to your healthy diet for a bit longer!
Wang L, Li B, Pan MX, Mo XF, Chen YM, Zhang CX. Specific carotenoid intake is inversely associated with the risk of breast cancer among Chinese women. Br J Nutr. 2014 Feb 6:1-10. [Epub ahead of print] http://www.ncbi.nlm.nih.gov/pubmed/24502868
Freudenheim JL, Marshall JR, Vena JE, Laughlin R, Brasure JR, Swanson MK, Nemoto T, Graham S. Premenopausal breast cancer risk and intake of vegetables, fruits, and related nutrients. J Natl Cancer Inst. 1996 Mar 20;88(6):340-8. http://www.ncbi.nlm.nih.gov/pubmed/8609642
Gaudet MM, Britton JA, Kabat GC, Steck-Scott S, Eng SM, Teitelbaum SL, Terry MB, Neugut AI, Gammon MD. Fruits, vegetables, and micronutrients in relation to breast cancer modified by menopause and hormone receptor status. Cancer Epidemiol Biomarkers Prev. 2004 Sep;13(9):1485-94. http://www.ncbi.nlm.nih.gov/pubmed/15342450
Koushik A, Hunter DJ, Spiegelman D, Anderson KE, Buring JE, Freudenheim JL, Goldbohm RA, Hankinson SE, Larsson SC, Leitzmann M, Marshall JR, McCullough ML, Miller AB, Rodriguez C, Rohan TE, Ross JA, Schatzkin A, Schouten LJ, Willett WC, Wolk A, Zhang SM, Smith-Warner SA. Intake of the major carotenoids and the risk of epithelial ovarian cancer in a pooled analysis of 10 cohort studies. Int J Cancer. 2006 Nov 1;119(9):2148-54. http://www.ncbi.nlm.nih.gov/pubmed/16823847
Murphy MM, Barraj LM, Herman D, Bi X, Cheatham R, Randolph RK. Phytonutrient intake by adults in the United States in relation to fruit and vegetable consumption. J Acad Nutr Diet. 2012 Feb;112(2):222-9. http://www.ncbi.nlm.nih.gov/pubmed/22741166
Riboli E, Norat T. Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. Am J Clin Nutr. 2003 Sep;78(3 Suppl):559S-569S. http://www.ncbi.nlm.nih.gov/pubmed/12936950
Zhang CX, Ho SC, Chen YM, Fu JH, Cheng SZ, Lin FY. Greater vegetable and fruit intake is associated with a lower risk of breast cancer among Chinese women. Int J Cancer. 2009 Jul 1;125(1):181-8. doi: 10.1002/ijc.24358. http://www.ncbi.nlm.nih.gov/pubmed/19358284