Healthnotes Newswire (August 31, 2000)—Chinese men who eat more cruciferous vegetables, such as broccoli, cabbage, Brussels sprouts, cauliflower, and bok choy, are at a lower risk of developing lung cancer, according to a new study in this week’s edition of The Lancet.¹

In this study, researchers measured the urinary excretion of compounds called isothiocyanates in people who had been diagnosed with lung cancer and in a group of healthy individuals. Since isothiocyanates are formed from chemicals found almost exclusively in cruciferous vegetables, the amount of these compounds in the urine was considered to be a good indicator of cruciferous vegetable intake. Blood samples were also taken to measure the activity of two enzymes that are important for detoxification and elimination of tobacco smoke.

The researchers found that men with measurable amounts of urinary isothiocyanates had a 35% lower risk of lung cancer than did men whose levels were undetectable. Among men with low activity of detoxification enzymes, excretion of isothiocyanates was associated with a 70% reduction in lung cancer risk.

These findings suggest that consumption of cruciferous vegetables may reduce the risk of lung cancer, particularly in people whose natural detoxification mechanisms are impaired. The results of this study are consistent with those of other studies that have found the intake of the cruciferous vegetables to correlate with reduced risk of colon cancer,² prostate cancer,³ and non-Hodgkin’s lymphoma.⁴ These studies showed protective effects with as little as three servings per week. However, these types of epidemiological (population) studies do not indicate cause-and-effect; therefore, the potential anticancer effect of cruciferous vegetables in humans remains unproven.

If eating cruciferous vegetables does help prevent cancer, it is still unclear which chemical compounds in these vegetables are responsible for the protective effect. While the authors of this new study credit the isothiocyanates, which are thought to aid in the detoxification of toxic chemicals in the liver, others disagree. Another compound in cruciferous vegetables that has been implicated in cancer prevention is indole-3-carbinol, a chemical shown to increase liver detoxification as well as to favorably alter the activity of certain genes involved in cancer growth.^{5 6} In a recent trial, indole-3-carbinol was shown to induce complete regression of early-stage cervical cancers.⁷

Although additional research is needed, people interested in preventing cancer should consider putting broccoli, cauliflower, cabbage, or Brussels sprouts on their plates several times a week.