Many claims circle around shark cartilage

Shark cartilage is just what it sounds like: cartilage from sharks. The cartilage, which is ground up and stuffed into capsules or pressed into tablets, is composed of collagen, water, phosphate, calcium and chondroitin sulfate. It may not sound like a magic elixir, but some extravagant claims about the power of shark cartilage have been made over the last decade.

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Uses: Typically used to ease the discomfort associated with arthritis, shark cartilage also is thought to inhibit the growth of new blood vessels, leading to its possible ability to limit the growth of cancerous tumors -- or even cure cancer.

Dose: Recommendations vary widely, from 500 milligrams to 5,000 milligrams, one to six times a day.

Precautions: It’s probably not dangerous, although high doses can cause a bad taste in the mouth, nausea, constipation, low blood pressure and fatigue. There are no known interactions with drugs or food.

Research: Most studies have been done in the lab or on animals, not on humans, but some show shark cartilage may have anti-inflammatory effects. Also, the federal government has launched a large randomized, controlled trial to study whether shark cartilage improves the survival of people with advanced colorectal or breast cancer.

Dietary supplements makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your health-care provider for advice on selecting a brand.

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-- Shari Roan