Broccoli (Sprouts or Extract)

Can Halt the Growth of Breast Cancer Cells

There are several very important substances in the sprouts of broccoli, one of them being indole-3-carbinol. This component of broccoli and other members of the Brassica genus, halts the growth of breast cancer cells and likely prostate cancer. Other vegetables in the Brassica genus include brussels sprouts, bok choy, kale, chard and turnips and they are also likely to be helpful.  It appears to be helpful for treating and preventing breast and prostate cancer and indole-3-carbinol may also help treat the disease.

Indole-3-carbinol works by halting the cell cycle in breast cancer cells without actually killing the cells. The cell cycle is a rigidly prescribed series of steps a cell must go through before it can divide in two, involving the duplication of the cell's contents and a final split.

If you can alter specific components of the cell cycle, you can stop the growth of cancer cells without killing normal cells. Indole-3-carbinol interferes with the cell cycle in a way that hints at a totally new signaling pathway in the cell. The chemical seems to be working by a very unusual mechanism. It turns off a gene for an enzyme important in the cell's growth cycle. The compound also works independently of the hormone estrogen, which makes it a good candidate for use in combination therapy with drugs that interfere with estrogen, such as tamoxifen.

What's exciting about this is that indole-3-carbinol has low toxicity but is a very effective agent against breast cancer -- it's one of the most effective agents at blocking tumorigenesis in rats. Given in the diet, indole-3-carbinol can block 95 percent of all breast cancers in rats.

It appears that indole-3-carbinol does not act on estrogen at all, but rather works through a different mechanism to halt the cell cycle. The chemicals produced when indole-3-carbinol reacts with stomach acid are the ones responsible for the anti-estrogen and certain toxic effects of the broccoli compounds. Indole-3-carbinol specifically causes a sudden drop in the production of the enzyme CDK6, or cyclin-dependent kinase 6. CDK6 is one of several protein complexes targeted by hormones that regulate the progression of the cell cycle, and was identified only three years ago.

Indole 3 carbinol as contained in sprouted vegetables seems a better idea than drugs to treat breast cancer. As it is likely also to be very beneficial in the treatment of prostate cancer, and the two diseases have very similar contributing factors, it may be a good idea to get the entire family of beneficial nutrients. The best way to do this would not be to eat broccoli but to consume broccoli sprouts which are hundreds of times more potent than regular broccoli.

Researchers attempted to calculate how much broccoli one would have to eat in order to produce a significant degree of protection against cancer, based on epidemiologic evidence. They found that one would have to eat about two pounds of an average broccoli a week in order to reduce, say, one's risk of colon cancer by about 50%.  It is impossible to determine by the looks of this cruciferous vegetable alone or even with knowledge of how and where it was grown whether you are buying the 'high-inducer' or 'low-inducer' broccoli. The enzyme-inducing abilities of samples taken from 22 varieties of fresh and 7 brands of frozen mature broccoli varied greatly. Only sophisticated scientific measurements can determine the concentrations.

But fresh broccoli sprouts offer an alternative. One can get away with eating 10 to 100 times lower quantities. Three day old sprouts have the additional advantage that they're far more uniform in their potency. Broccoli sprouts look and taste something like alfalfa sprouts. The report also notes that small quantities of broccoli sprout extracts markedly reduced the size of rat mammary tumors that were induced by chemical carcinogens.

The researchers refer to the concept of "chemoprotection" -- "deliberate efforts to increase the body's own defense mechanisms to reduce susceptibility to carcinogens by administration of substances that can be precisely identified, and ideally, delivered in the diet. The interesting aspect of chemoprotection strategies is that they're almost never organ-specific. Chemoprotection produces a general cancer protective effect which blocks multiple steps -- a cascade of steps -- that are common to cancer formation.

Nutrition and Cancer 2004;48(1):84-94