Articles for Our Patients ~ Vanessa Wada, M.S., R.D.

A Bitter Sweet Vegetable

Author: Vanessa Wada, M.S., R.D. • Language: ENG

What do broccoli, cauliflower, cabbage, Brussels sprouts, collard greens, bok choy, and mustard greens all have in common? They are all considered cruciferous vegetables. Kale, kohlrabi, turnip, rutabaga, arugula, horseradish, radish, wasabi and watercress also fall under this category but are less common. So what are cruciferous vegetables and why are they generating attention? These amazing vegetables are from the Brassica genus and they contain 1000s of phytochemicals along with vitamins, minerals, and fiber. But cruciferous vegetables are a special kind of vegetable. And that’s because they contain a UNIQUE set of highly concentrated phytochemicals which have been shown to be very protective against ALL stages of cancer. These phytochemicals are called glucosinolates, and there are more than 100 glucosinolates known to man! These sulfur-containing compounds are responsible for their pungent aroma and sometimes bitter taste. When chewed, enzymes are released to break down the glucosinolates into isothiocyanates and indoles which display therapeutic effect on the body.1 Epidemiological studies have shown evidence for a reduction in prostate, lung, breast, and colon cancer in people who consume cruciferous vegetables.2 In general, overall cancer risk is reduced.
One type of isothiocyanate is a phytochemical called sulforaphane. It’s highly concentrated in broccoli and broccoli sprouts. Sulforaphane was identified as a chemopreventive agent over a decade ago to induce detoxification enzymes and inhibit carcinogen activity. But research since then has shown that sulforaphane has therapeutic action against cancer cells at ALL stages by acting as a blocking agent against early initiation events, inhibiting enzymes that are involved in carcinogenic activity, modifying cancer pathways, inducing the destruction of cancer cells, and activating detoxifying enzymes. There is even evidence for its ability to protect against viral or bacterial pathogens.2
Evidence points to strong statistical significance for an inverse relationship between raw cruciferous vegetable intake and bladder cancer. So with increasing raw cruciferous vegetable intake, the lower the risk one has for developing bladder cancer. And there is an even stronger inverse relationship with regards to smokers as smoking is the leading cause of bladder cancer. Smokers who consume raw cruciferous vegetables have been observed to have a lower risk of developing bladder cancer than those who don’t. It appears that isothiocyanates are protective against bladder cancer because they are metabolized and almost exclusively excreted through the urine. Storage of urine also increases the bladder epithelium exposure to isothiocyanates where 90-95% of bladder cancer occurs in the United States. Furthermore, if consumed raw, cruciferous vegetables provide 2-9 times more isothiocyanates in humans as compared to their cooked counterparts.3         

Some research suggests that consumption of broccoli and cauliflower have a significant inverse effect on extraprostatic prostate cancer (a late stage of prostate cancer where the cancer has spread beyond the prostate gland). Additionally, high cruciferous vegetable intake may be associated with reduced risk of aggressive prostate cancer.4
And for women, there is some evidence that sulforaphane inhibits breast cancer cell growth, activates apoptosis (destruction of cancer cells), and decreases the expression of key proteins that promote human breast cancer cell growth.5
Now before you go running home to that kale in the corner of your vegetable bin, it is worth mentioning that cooking of cruciferous vegetables may destroy these important phytochemicals including important enzymes responsible for catalyzing important reactions. Studies have shown that cooking can reduce isothiocyanate exposure by60-90%!3 Therefore, to reap the benefits, consume them raw or minimally cooked when they are most nutrient dense.
So while we may not like Brussels sprouts or that bitter taste often associated with cruciferous vegetables, once they get into the body, they are doing some amazing things! We may not feel any changes or see their effects unravel before our eyes in a matter of days, but cruciferous vegetables are working as a functional food and naturally designed by Mother Nature to help us prevent some undesired cancers. Prevention is the key and cruciferous vegetable consumption is a way of practicing prevention! So eat up!
References:1) Higdon, J., Delage, B., Williams, D. et. al. (2007). Cruciferous Vegetables and Human Cancer Risk: Epidemiologic Evidence and Mechanistic. Basis Pharmacol Res. 55(3): 224–2362) Myzak, M. & Dashwooda, R. (2006). Chemoprotection by sulforaphane: Keep one eye beyond Keap1. Cancer Lett. 233(2): 208–2183) Tang, L., Zirpoli, G., Guru, K. et. al. (2008). Consumption of Raw Cruciferous Vegetables is Inversely Associated with Bladder Cancer Risk. Cancer Epidemiol Biomarkers Prev. 17(4): 938-9444) Victoria A. Kirsh , Peters, U., Mayne, S. et al. (2007). Prospective Study of Fruit and Vegetable Intake and Risk of Prostate Cancer. J Natl Cancer Inst. 99(15): 1200-95) Pledgie-Tracy, A., Sobolewski, M., Davidson, N. (2007). Sulforaphane induces cell type–specific apoptosis in human breast cancer cell lines. Mol Cancer Ther. 6(3): 1013-1021

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