New Research Expands our Understanding of How Cruciferous Vegetables Help Prevent Cancer

New research has greatly advanced scientists' understanding of just how cruciferous vegetables such as cabbage, cauliflower, broccoli, kale and Brussels sprouts help prevent cancer. When these vegetables are cut, chewed or digested, a sulfur-containing compound called sinigrin is brought into contact with the enzyme myrosinase, resulting in the release of glucose and breakdown products, including highly reactive compounds called isothiocyanates. Isothiocyanates are not only potent inducers of the liver's Phase II enzymes, which detoxify carcinogens, but research recently conducted at the Institute for Food Research in the U.K. shows one of these compounds, allyl isothicyanate, also inhibits mitosis (cell division) and stimulates apoptosis (programmed cell death) in human tumor cells.

Sulforaphane, a compound formed when cruciferous vegetables are chopped or chewed, is already known to trigger the liver to produce enzymes that detoxify cancer-causing chemicals, inhibit chemically-induced breast cancers in animal studies, and induce colon cancer cells to commit suicide.

An in vitro study published in the Journal of Nutrition suggests that sulforaphane can also help stop the proliferation of breast cancer cells, even in the later stages of their growth.

Sulforaphane may also offer special protection to those with colon cancer-susceptible genes, suggests a study conducted at Rutgers University and published online on May 4, 2006, in the journal Carcinogenesis.

In this study, researchers sought to learn whether sulforaphane could inhibit cancers arising from one's genetic makeup. Rutgers researchers Ernest Mario, Ah-Ng Tony Kong and colleagues used mice bred with a genetic mutation that switches off the tumor suppressor gene known as APC, the same gene that is inactivated in the majority of human colon cancers. Animals with this mutation spontaneously develop intestinal polyps, the precursors to colon cancer. The study found that animals who were fed sulforaphane had tumors that were smaller, grew more slowly and had higher apoptotic (cell suicide) indices. Additionally, those fed a higher dose of sulforaphane had less risk of developing polyps than those fed a lower dose.

The researchers found that sulforaphane suppressed certain kinase enzymes. These cell signaling enzymes are expressed not only in laboratory animals, but also in humans, and the ones supppressed by sulforaphane are involved in activities that promote colon cancer.

According to lead researcher, Dr. Kong, "Our study corroborates the notion that sulforaphane has chemopreventive activity…Our research has substantiated the connection between diet and cancer prevention, and it is now clear that the expression of cancer-related genes can be influenced by chemopreventive compounds in the things we eat."

Human population as well as animal studies consistently show that diets high in cruciferous vegetables, such as cauliflower, are associated with lower incidence of certain cancers, including lung, colon, breast and ovarian cancer. Now, research published in the International Journal of Cancer (Zhao H, Lin J) suggests that bladder cancer can join the list.

University of Texas researchers analyzed the diets of 697 newly diagnosed bladder cancer cases and 708 healthy controls matched by age, gender and ethnicity. Average daily intake of cruciferous vegetables was significantly lower in those with bladder cancer than in healthy controls.

Those eating the most cruciferous vegetables were found to have a 29% lower risk of bladder cancer compared to participants eating the least of this family of vegetables.

Crucifers' protective benefits were even more pronounced in three groups typically at higher risk for bladder cancer: men, smokers, and older individuals (aged at least 64).

Diagnosed in about 336,000 people every year worldwide, bladder cancer is three times more likely to affect men than women, according to the European School of Oncology.

Crucifers' well known cancer-fighting properties are thought to result from their high levels of active phytochemicals called glucosinolates, which our bodies metabolize into powerful anti-carcinogens called isothiocyanates.

Isothiocyanates offer the bladder, in particular, significant protection, most likely because the majority of compounds produced by isothiocyanate metabolism travel through the bladder en route to excretion in the urine, suggested the researchers.

Optimize Your Cells' Detoxification / Cleansing Ability

For about 20 years, we've known that many phytonutrients work as antioxidants to disarm free radicals before they can damage DNA, cell membranes and fat-containing molecules such as cholesterol. Now, new research is revealing that phytonutrients in crucifers, such as cauliflower, work at a much deeper level. These compounds actually signal our genes to increase production of enzymes involved in detoxification, the cleansing process through which our bodies eliminate harmful compounds.

The phytonutrients in cruciferous vegetables initiate an intricate dance inside our cells in which gene response elements direct and balance the steps among dozens of detoxification enzyme partners, each performing its own protective role in perfect balance with the other dancers. The natural synergy that results optimizes our cells' ability to disarm and clear free radicals and toxins, including potential carcinogens, which may be why crucifers appear to lower our risk of cancer more effectively than any other vegetables or fruits.

Recent studies show that those eating the most cruciferous vegetables have a much lower risk of prostate, colorectal and lung cancer-even whencompared to those who regularly eat other vegetables:

In a study of over 1,200 men, conducted at the Fred Hutchinson Cancer Research Center in Seattle, WA, those eating 28 servings of vegetables a week had a 35% lower risk of prostate cancer, but those consuming just 3 or more servings of cruciferous vegetables each week had a 44% lower prostate cancer risk.

In the Netherlands Cohort Study on Diet and Cancer, in which data was collected on over 100,000 people for more than 6 years, those eating the most vegetables benefited with a 25% lower risk of colorectal cancers, but those eating the most cruciferous vegetables did almost twice as well with a 49% drop in their colorectal cancer risk.

A study of Chinese women in Singapore, a city in which air pollution levels are often high putting stress on the detoxification capacity of residents' lungs, found that in non-smokers, eating cruciferous vegetables lowered risk of lung cancer by 30%. In smokers, regular cruciferous vegetable consumption reduced lung cancer risk an amazing 69%!

How many weekly servings of cruciferous vegetables do you need to lower your risk of cancer? Just 3 to 5 servings-less than one serving a day! (1 serving = 1 cup)

To get the most benefit from your cruciferous vegetables like cauliflower, be sure to choose organically grown varieties (their phytonutrient levels are higher than conventionally grown), and steam lightly (this method of cooking has been shown to not only retain the most phytonutrients but to maximize their availability).

For a brief overview of the process through which cruciferous vegetables boost our ability to detoxify or cleanse harmful compounds and examples of how specific phytonutrients in crucifers work together to protect us against cancer, see our FAQ: Optimizing Your Cells' Detoxification/Cleansing Ability by Eating Cruciferous Vegetables.

A Weekly Serving of Cruciferous Vegetables Halves Advanced Prostate Cancer Risk

A study of 29,361 men, enrolled on the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial found that men who ate more than a serving of either broccoli or cauliflower each week almost halved their risk of developing advanced-stage prostate cancer (cancer that had spread beyond the prostate gland), compared with their peers who ate these vegetables less than once a month.

Specifically, compared to men eating broccoli just once a month, those eating a weekly serving lowered their risk of advanced prostate cancer by 45%. Cauliflower was even a bit more protective. Compared to men eating one serving of cauliflower per month, those enjoying a weekly serving lowered their risk of advanced prostate cancer by 52%. (Kirsch VA, Peters U. et al., J Natl Cancer Inst.)

Spicing Your Cauliflower with Turmeric Could Help Promote Men's Health

Prostate cancer-the second leading cause of cancer death in American men with 500,000 new cases appearing each year-is a rare occurrence among men in India, whose low risk is attributed to a diet rich in Brassica family vegetables and the curry spice, turmeric.

Scientists tested turmeric, a concentrated source of the phytonutrient curcumin, along with phenethyl isothiocyanates, a phytonutrient abundant in cruciferous vegetables including cauliflower, cabbage, broccoli, Brussels sprouts, kale, kohlrabi and turnips.

When tested singly, both phenethyl isothiocyanate and curcumin greatly retarded the growth of human prostate cancer cells implanted in immune-deficient laboratory animals. In animals with well-established prostate cancer tumors, neither phenethyl isothiocyanate nor curcumin by itself had a protective effect, but when combined, they significantly reduced both tumor growth and the ability of the prostate cancer cells to spread (metastasize) in the test animals.

The researchers believe the combination of cruciferous vegetables and curcumin could be an effective therapy not only to prevent prostate cancer, but to inhibit the spread of established prostate cancers.

Best of all, this combination-cauliflower spiced with turmeric-is absolutely delicious! The best way to prepare it is to cut cauliflower florets in quarters and let them sit for 5-10 minutes; this allows time for the production of phenethyl isothiocyanates, which form when cruciferous vegetables are cut, but stops when they are heated. Then sprinkle with turmeric, and healthy sauté on medium heat in a few tablespoons of vegetable or chicken broth for 5 minutes. Remove from the heat and top with olive oil, sea salt and pepper to taste.

Protection against Rheumatoid Arthritis

While one study suggests that high doses of supplemental vitamin C makes osteoarthritis, a type of degenerative arthritis that occurs with aging, worse in laboratory animals, another indicates that vitamin C-rich foods, such as cauliflower, provide humans with protection against inflammatory polyarthritis, a form of rheumatoid arthritis involving two or more joints.

The findings, presented in the Annals of the Rheumatic Diseases were drawn from a study of more than 20,000 subjects who kept diet diaries and were arthritis-free when the study began, and focused on subjects who developed inflammatory polyarthritis and similar subjects who remained arthritis-free during the follow-up period.

Subjects who consumed the lowest amounts of vitamin C-rich foods were more than three times more likely to develop arthritis than those who consumed the highest amounts.

Cardiovascular Benefits

Consumption of cruciferous vegetables, such as cauliflower, is known to reduce the risk of a number of cancers, especially lung, colon, breast, ovarian and bladder cancer. Now, research reveals that crucifers provide significant cardiovascular benefits as well.

Researchers from the University of Hawaii have shown that, at the tiny concentration of just 100 micromoles per liter, a phytonutrient found in cruciferous vegetables, indole-3-carbinol, lowers liver cells' secretion of the cholesterol transporter, apolipoproteinB-100 by 56%! Apolipoprotein B-100 (apoB) is the main carrier of LDL cholesterol to tissues, and high levels have been linked to plaque formation in the blood vessels.

When liver cells were treated with I-3-C, not only was apoB-100 secretion cut by more than half, but significant decreases also occurred in the synthesis of lipids (fats), including triglycerides and cholesterol esters. (Maiyoh GK, Kuh JE, et al., J Nutr.)