Q & A Library

Chlorella is a microscopic, green freshwater organism (an alga) that is aggressively promoted on the Internet for its supposed health benefits. You may have read that it boosts energy, absorbs pesticides from the foods in your diet, fights cancer, eliminates infections, lowers blood pressure and cholesterol levels, cleanses the blood and the digestive system, regulates blood sugar and benefits health in many other ways. This sounds impressive, but there is very little scientific evidence to back up these extravagant claims.

After World War II, chlorella was investigated as a possible commercial food source, and some research suggested that it prevented liver disease in mice, might reduce the side effects of chemotherapy, and might slow the growth of some cancer cells. According to the American Cancer Society, early lab and animal research suggested that extracts of chlorella might have anticancer properties but we have no evidence that they can effectively prevent or treat cancer. Results of a 2003 study published in the Canadian Medical Association Journal showed that chlorella failed to boost immune response to flu shots.

Chlorella will probably not hurt you (unless you're allergic to it), but we have no studies on the effects of long-term use. More importantly, we have no strong evidence to show that it will do you any good.

For the record, I don't approve of the use of two other types of algae, blue green algae (aphanizomenon) and spirulina. Both are in a different group from chlorella. Some species of blue green algae produce toxins, including neurotoxins that can increase long-term risks of degenerative diseases of the central nervous system. I see no reason to include any blue-green algae in the diet.

If you must have your algae, chlorella is a much better choice.

Andrew Weil, M.D.