Women with higher blood concentrations of carotenoids -- a phytochemical found in carrots, collard greens and other fruits and vegetables -- are at decreased risk of certain breast cancers compared to women with lower levels, suggests a new study.
The breast cancers linked to carotenoid levels are estrogen receptor (ER) negative. These tumorsdo not have receptors for the hormone estrogen. These tumors are less common and often more difficult to treat than the more common ER-positive tumors that typically respond to estrogen. Previous research has linked carotenoids to decreased breast cancer risk but the research is still emerging.
The new study published in the American Journal of Clinical Nutrition included 1,502 women with breast cancer and the same number of healthy controls from the European Prospective Investigation into Cancer and Nutrition (EPIC) group. Researchers chose to focus primarily on pre-menopausal and ER-negative cancers because their review of the literature suggested that dietary carotenoids and fruit/ vegetable intake are more strongly related to these types of tumors. They used plasma levels in place of
Researchers compared prediagnostic blood levels of six carotenoids, including beta-carotene and alpha-carotene, along with vitamin C. They took into account weight as well as other known risk factors for breast cancer.
Risk of ER-negative breast cancer was 59 percent and 39 percent lower in women who had the highest blood concentrations of beta-carotene and alpha-carotene, respectively, compared to those who had the lowest levels. ER-positive breast cancer risk was not associated with carotenoids or other nutrients.
Carotenoids are a large group of phytochemicals found in fruits and vegetables. They are often recognizable by the orange, red, and yellow colors they give foods. Many green leafy vegetables are also high in carotenoids. Previous research has found that high blood levels of carotenoids signify high fruit and vegetable consumption in general, meaning the decreased link could be related to other plant foods.
But supplements are not associated with decreased risk. And beta-carotene in high-dose supplements, especially in smokers, seems to increase lung cancer risk and mortality. The authors note that other factors including genetics and lifestyle can affect plasma carotenoid levels and may have affected the study results. This study, and others, will be included in AICR/WCRF’s upcoming continuous update project report on breast cancerprevention.
This study was supported by: Wereld Kanker Onderzoek Fond; Europe Against Cancer Program of the European Commission; Deutsche Krebshilfe, Deutsches Krebsforschungszentrum; German Federal Ministry of Education and Research; Danish Cancer Society; Health Research Fund of the Spanish Ministry of Health, Spanish Regional Governments of Andalucia, Asturia, Basque Country, Murcia (No. 6236), and Navarra; Catalan Institute of Oncology, Red de Centros RCESP, C03/09, Spain; Cancer Research UK; Medical Research Council, United Kingdom; Stroke Association, United Kingdom; British Heart Foundation; Department of Health, United Kingdom; Food Standards Agency, United Kingdom; Wellcome Trust, United Kingdom; Helenic Health Foundation; Italian Association for Research on Cancer; Italian National Research Council, Fondazione-Istituto Banco, Napoli, Italy; Dutch Ministry of Public Health, Welfare and Sports; Dutch Prev ention Funds; LK Research Funds; Dutch ZON (Zorg Onderzoek Nederland); World Cancer Research Fund; Swedish Cancer Society; Swedish Scientific Council; Regional Government of Skane, Sweden; European Research Council; French League against Cancer; National Institute for Health and Medical Research, France; Mutuelle Généralede; Education Nationale, France; 3M Co, France; Gustave Roussy Institute, France; and General Councils of France.
Source: Marije F Bakker et al. Plasma carotenoids, vitamin C, tocopherols, and retinol and the risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition cohort. Am J Clin Nutr ajcn101659; First published online January 20, 2016.
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Published on February 12, 2016