Shark cartilage is not proven cure.(Knight Ridder Newspapers)

Q. First I hear that shark cartilage can prevent or treat cancer, then I hear it can't. Which view is correct?

A. Shark cartilage typically comes from sharks caught in the Pacific Ocean. The quick answer to your question is that some research suggests shark cartilage shows promise as a cancer fighter. But the complete story is far from in, and the current evidence does not support the heavy marketing of this supplement as a cure for cancer.

First, let's lay to rest one myth of epic proportions: Contrary to widespread belief, sharks do get cancer. Several forms of cancer have been identified in sharks.

Laboratory research indicates that shark cartilage might help prevent angiogenesis (the growth of new blood vessels). Since many cancers need to grow new blood vessels to channel in blood and nourishment, this effect has value in cancer treatment.

Shark cartilage apparently offers no benefit in people with advanced, previously treated cancer, including breast, colorectal, lung, prostate, non-Hodgkin's lymphoma, and brain cancer.

One the plus side, preliminary evidence suggests that a particular water-soluble shark cartilage extract, AE-941 (Neovastat), might increase survival time in some patients with kidney cell cancer. There also is anecdotal evidence that shark cartilage might be beneficial for Kaposi sarcoma lesions.

Several preclinical and clinical trials are now evaluating the possible anti-cancer effects of numerous shark cartilage derivatives and extracts.