Sulforaphane Usage

Numerous observational studies have found that a high consumption of vegetables in the cabbage family is associated with a reduced risk of cancer, especially breast, prostate, lung, stomach, colon, and rectal cancer. ¹ On this basis, scientists have looked for anticancer substances in these foods. Sulforaphane is one such candidate substance ( indole-3-carbinol , I3C, is another). In test-tube and animal studies , sulforaphane exhibits properties that suggest it could indeed help prevent many forms of cancer. ^{2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22} However, it is a long way from such studies to reliable evidence of benefit. Observational studies are notoriously poor guides to treatment, sometimes leading to conclusions that are the reverse of what is ultimately found to be correct. ²³ The problem is that they can’t show cause-and-effect—they only show association. It is possible, for example, that people who consume more cabbage-family vegetables share other traits that are responsible for reduced cancer rates. Consider the history of hormone replacement therapy. In the 1990s, scientists had concluded that estrogen prevents heart disease, based largely on observational studies that showed menopausal women who use hormone replacement have lower heart disease rates. When double-blind , placebo-controlled studies were performed, however, they showed that hormone replacement therapy actually increases heart disease risk. For all we know, we could be making a similar mistake with cabbage-family vegetables.

Certainly, it is too great a leap to jump to one constituent of such vegetables and advocate that substance for preventing cancer. Thousands of substances show anticancer properties in the test tube and fail to pan out in real life. The beta-carotene story is another instructive example. Not only did observational studies show that people who consume foods high in beta-carotene have less lung cancer, test-tube studies found that beta-carotene has anti-cancer properties. However, subsequent large double-blind studies found that beta-carotene supplements do not help prevent lung cancer, and might even increase risk.

The bottom line: At present, we cannot recommend sulforaphane for preventing cancer.