Carotenoids May Lower Breast Cancer Risk: It’s in the BloodEating lots of carrots, broccoli and other carotenoid-rich fruits and vegetables provide many cancer-protective benefits such as weight control but population studies suggest the foods do not, by themselves, protect against breast cancer. Most of the studies estimate carotenoid intake by asking participants to recall their diet, a technique subject to forgetfulness and other measurement errors.
It’s possible these measurement errors may be obscuring the link to reduced breast cancer risk, finds a new analysis of the literature that looked at carotenoid intake assessed by both dietary recall and blood concentrations. The study was published in the online July issue of the American Journal of Clinical Nutrition.
The study was funded by the World Cancer Research Fund as part of AICR/WCRF's Continuous Update Project (CUP).
For the analysis, researchers reviewed the 24 relevant publications on breast cancer risk and six carotenoids. Some used dietary recall to estimate the carotenoid intake and others measured carotenoid blood levels. The carotenoids studied include beta-carotene, alpha carotene, lycopene and lutein.
For the dietary studies, no link was found between five of the dietary carotenoids and breast cancer risk. Estimates of high beta-carotene intake showed a slight reduced risk.
Yet the studies measuring blood concentration showed a strong link between carotenoids and reduced breast cancer risk. The reduced risk was seen for total carotenoids and the individual phytochemicals. The analysis suggests that dietary studies add blood measures when possible to better determine carotenoid intake.
It’s possible the risk reduction may be due to factors linked to higher blood concentrations of carotenoids. These people may exercise more and be less overweight, for example. Many, but not all, of the studies adjusted for these factors. More studies that take these factors into account are needed, note the authors.
Source: Aune D, et al. Dietary compared with blood concentrations of carotenoids and breast cancer risk: a systematic review and meta-analysis of prospective studies. Am J Clin Nutr. 2012 Jul 3.