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Evidence Suggests Breast Cancer Prevention from Carotenoids

Carotenoids: Pepper Peaches TomatoesEarly studies on breast cancer prevention by carotenoids in plant foods showed uncertain findings. But a better research method may offer new hope.

The AICR/WCRF expert report and its updates show that eating plenty of sweet potatoes, carrots and other carotenoid-rich produce protects against cancers of the mouth, pharynx, larynx and lung. Now, researchers are finding new evidence that carotenoids may also reduce risk of breast cancer.

Better Research Methods

Study data from dietary questionnaires where subjects are asked to recall what and how much they ate may not have been as accurate as taking blood samples to measure levels of carotenoids.

Dagfinn Aune, an epidemiologist at Imperial College in London, published a study that assessed carotenoid intake while comparing the two research methods. The study was funded by AICR's umbrella organization, the World Cancer Research Fund, as part of the Continuous Update Project.

Cancer-preventing phytochemicals called carotenoids are abundant in orange foods like carrots, although they're also found in many dark green vegetables, including broccoli, kale and spinach.

Some individual carotenoids are:

  • beta-carotene, alpha-carotene and beta-cryptoxanthin which the body uses to form vitamin A
  • lycopene, a possible shield against prostate cancer
  • zeaxanthin and lutein, which also may promote eye health.

Aune and his colleagues reviewed 24 publications on breast cancer risk and carotenoids. In the studies where people reported how much they ate based on memory, no link was found between five of the dietary carotenoids and breast cancer risk. However, the studies measuring blood concentration showed a strong link between carotenoids and reduced breast cancer risk.

Using blood samples seems to be more accurate than relying on study participants' memories, Aune says: We saw a 20-30 percent decreased risk of breast cancer when comparing the highest blood concentration of carotenoids to the lowest."

Second Analysis Agrees

A separate analysis by researchers at Harvard University Medical School pooled data from eight population studies. These studies represented 80 percent of the available research using blood levels of carotenoids. The researchers collected blood samples from women who were initially healthy, then tracked their health over time. Most of the women were postmenopausal.

The studies included approximately 3,000 women who were diagnosed with breast cancer and 4,000 women who were not. The cancer-free women were matched in age and other risk factors to those who were diagnosed with the disease.

Women who had the highest blood levels of total carotenoids were linked to almost 20 percent lower breast cancer risk.

We need bigger studies on the subject with [blood level] biomarkers, says Aune. It could be specific benefits of carotenoids but it could also be the whole package of antioxidants and other beneficial things you find in plant foods.

AICR Newsletter Winter 2014; Issue 122

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