By greens, we mean leafy cruciferous vegetables, including collard greens, mustard greens turnip greens, and arugula (Eruca sativa). Cruciferous vegetables have been shown to inhibit the growth of human pancreatic cancer cells and to reduce the risk of lung, gallbladder, bladder, prostate, ovarian and colorectal cancer.
Greens are a good dietary source of vitamin C, vitamin A, vitamin K, folate, manganese, and various other minerals. Greens have been shown to have antioxidant and anti-inflammatory properties, and to improve glucose metabolism and be cardioprotective. Greens contain beta-carotene, lutein and other carotenoids, kaempferol, indole-3-carbinol (I3C), 3,3'-diindolylmethane (DIM) and several other isothiocyanates, most of which have been reported to have anti-cancer properties.
Breast cancer-related effects of eating greens
Components of greens have been found to down-regulate hormone receptor expression, promote apoptosis, suppress cell cycle progression and inhibit angiogenesis of human breast cancer cells. Consumption of brassica vegetables has been shown to reduce the estrogen metabolite 16alpha-hydroxyestrone, which is a breast cancer promoter, and to be marginally inversely associated with breast cancer risk in population studies.
Lutein consumption and circulating lutein levels have been found to be associated with reduced risk of breast cancer in several epidemiological studies. Lutein has been shown to inhibit the progression of both ER+ and ER+ breast cancer cells under hypoxia, a low-oxygen condition in which solid breast tumors can thrive. Lutein has also been shown to potentiate the effect of taxane chemotherapy drugs (Taxol and Taxotere) in breast cancer cells.
In addition, quercetin and I3C have both been shown increase the anti-cancer effects of Taxol (paclitaxel).
Collard greens and mustard greens are healthiest when prepared by steaming and not by stir-frying. Non-organic greens must be washed very thoroughly to remove pesticide residue.
Some cruciferous vegetables, including collard greens but not turnip greens, contain thioglucoside compounds in sufficient amounts to potentially interfere with the formation of thyroid hormone in women with iodine deficiency.
Below are links to recent studies concerning this food. For a more complete list, including less recent studies, please click on greens.