(Canadian Medical Association Journal) -- Scott Halperin and colleagues report on a randomized, double-blind, placebo-controlled trial in which they measured the antibody response to influenza vaccine in health adults who had been taking the supplement Chlorella for 28 days and in those who had been taking an inactive placebo.

Although claims for health benefits of the supplement include an improvement in immune function, and some experiments have shown some immunomodulating potential, the authors found the Chlorella-derived supplement did not increase antibody response to the flu vaccine overall, although some increase was seen in participants aged 50 to 55.

The authors state: "It is clear from this study and others that some dietary supplements may have therapeutic utility." It says further studies should be undertaken to clarify the actual clinical benefits.