A recent 12-year prospective longitudinal study of 59,000 African American women has shown that those who consumed more vegetables per day and per week are less likely to develop estrogen receptor-negative breast cancer than women with low vegetable intake. The incidence of ER-negative/PR-negative breast cancer was 43 percent lower among those women who were consuming at least two (of any kind) vegetables per day compared with women who ate fewer than four vegetables per week. These results are important because African American women are more likely than white women to be diagnosed with estrogen receptor-negative tumors, which have a poorer prognosis than estrogen receptor-positive tumors.
However, what caught my eye was the following information. While looking for some more detailed information within the food frequency data, researchers also found that higher intake of cruciferous vegetables (Brassicas) in particular showed a reduced risk of breast cancer overall in this group of women (all types of breast cancer - some good news!). Cruciferous vegetables, which include kale, mustard, and collard greens, broccoli, along with cabbage, cauliflower and the rest of the vegetables on the list found on the right side of this blog, are sources of the group of phytochemicals called glucosinolates, which may play a role in preventing the development of breast cancer through their effects on both estrogen metabolism and detoxification enzymes.
Very simply, estrogen (estradiol) is converted to two metabolites: 16-alpha-hydroxyestrone, which acts as a breast tumor promoter or the alternative product of estrogen metabolism, 2-hydroxyestrone, which does not exhibit estrogenic properties in breast tissue. Very simply you can use the analogy of these two estrogen metabolite levels in your blood as 16-alpha-hydroxyestrone = LDL or bad cholesterol and 2-hydroxyestrone = HDL or good cholesterol.
Again, very simply, our body has two sets of liver enzymes involved in detoxification. Brassica vegetables have been shown to decrease some Phase 1 enzymes, which can actually create a carcinogen, and have also been shown to increase Phase ll enzymes, which work to convert toxic or carcinogenic molecules into less potent molecules that can be less toxic and also excreted quickly into urine.
These are just two ways that eating Brassica vegetables can potentially decrease the risk of developing breast cancer. The amount to eat of these vegetables to consume on a daily or weekly basis is not clearly defined, but clearly this study shows that consuming even modest amounts of vegetables of any kind (two servings per day) can significantly reduce risk of a type of breast cancer that has a poor prognosis when diagnosed in African American women, and other researchers have shown that 3-5 servings per week of Brassica vegetables can reduce cancer risk.
We're lucky that locally-grown Brassica vegetables are available nearly year round, especially since many farmers in northern areas are erecting hoop houses (passive green houses) in which greens like kale can be grown even when it is cold and snowy outside. In addition, kale and many other Brassica vegetables survive and even love that first frost, turning just a tad bit sweeter. Head down to your local farmers' markets to purchase kale and Brussels sprouts as just two examples of breast-cancer fighting Brassicas!
Where kale is more than decoration on my plate (a minimum of 3-5 days per week)!
Diana Dyer, MS, RD