Carotenoids - micronutrients in fruits and vegetables - have been found to reduce the risk of breast cancer in women, according to a study published in the Journal of the National Cancer Institute last week.
High levels of carotenoids were linked to a lower risk of breast cancer, particularly estrogen receptor-negative breast cancer types, according to researchers from Brigham & Women's Hospital and Harvard Medical School, who reviewed eight prospective studies.
The reduction in breast cancer risk was linked to high levels of alpha-carotene, beta-carotene, lycopene, lutein and zeaxanthin and overall levels of total carotenoids circulating in the women's bloodstream.
According to the researchers, the metabolisation of alpha-carotene, beta-carotene and beta-cryptoxanthin into retinol, which is a naturally occurring form of vitamin A in the blood, could be related to the compounds' anti-cancer effects. Vitamin A regulates the growth, development and death of cells by affecting gene expression, the study explained.
"Carotenoids also may be directly anticarcinogenic by several other mechanisms, including improved gap junction communication, enhanced immune system functioning, or antioxidant scavenging of reactive oxygen species; this may inhibit cellular dysregulation or DNA damage," the study said.
Foods that are particularly high in carotenoids include carrots, spinach and kale.
The eight cohort studies analysed by the researchers included over 80% of the prospective data on plasma or serum carotenoids and breast cancer published around the world. They covered over 3,000 case subjects and almost 4,000 matched control subjects. Most of the studies found an inverse relation between carotenoids and breast cancer, including various carotenoids.