Women might want to make sure they don’t skimp on the salads. The natural plant pigments that give carrots their signature orange hue and make leafy vegetables green also might help ward off breast cancer, especially in women who smoke, according to a recent study in the International Journal of Cancer.
Previous studies have suggested that eating foods high in carotenoids might protect against cancer. Researchers at the Harvard School of Public Health wanted to look specifically at what kind of impact eating carotenoid-rich foods might have on breast cancer risk. This was one of the largest studies on the subject, including more than 5,700 women with breast cancer, and nearly 6,400 women with no history of breast cancer. “Our large study population provided us with greater power to observe smaller associations,” says lead author Laura Mignone, ScD, Postdoctoral Fellow at the Harvard School of Public Health.
The study participants were interviewed about their diet, and specifically about how many carotenoid-rich foods (including oranges, broccoli, carrots, romaine lettuce, and spinach) they ate each day or week.
Eating several servings of different fruits and vegetables each day didn’t appear to lower breast cancer risk, but eating carotenoid-rich fruits and vegetables did seem to have an impact—at least on younger women. Premenopausal women who ate two or more servings of carotenoid-rich fruits and vegetables a day (especially foods high in the carotenoids alpha-carotene, beta-carotene, lutein/zeaxanthin, and vitamin A) had a 17 percent lower risk of breast cancer than women who ate fewer than four servings a week.
The benefits of a diet high in carotenoids were especially pronounced in smokers. Smokers with the highest vitamin A intake had a 25 percent lower breast cancer risk compared to those with the lowest vitamin A in their diet. Smoking leads to the formation of free radicals—harmful molecules that can trigger the cell damage that leads to cancer. Carotenoids, which are antioxidants, can protect against this damage. They also may prevent cancer cells from multiplying (proliferating).
The researchers aren’t sure why only premenopausal women were protected, but they say the carotenoids might affect the estrogen exposure that can fuel the growth of breast cancer and other hormone-dependent cancers (estrogen production stops after menopause).
Surprisingly, the researchers found that eating foods high in one carotenoid—beta-cryptoxanthin—actually appeared to increase breast cancer risk in postmenopausal women who ate the greatest amounts. However, Dr. Mignone says this finding may be due to chance, because previous studies did not observe any increased breast cancer risk with beta-cryptoxanthin.
The discovery of a connection between carotenoids and reduced breast cancer risk gives women yet another reason to eat their fruits and vegetables daily. “This study contributes to the body of evidence that supports a protective association between dietary carotenoid intake and breast cancer risk,” Dr. Mignone says. “Based on the results of this and previous studies, premenopausal women may want to increase their intake of carotenoid-rich fruits and vegetables.” However, she cautions women against taking dietary supplements for this purpose, because high doses of beta-carotene from supplements have been linked to an increased risk of lung cancer.
Mignone LI, et al., Dietary carotenoids and the risk of invasive breast cancer. Int J Cancer. 2009;124:2929-2937.