Chlorella is a single-celled, freshwater, green algae typically sold as a powder or compressed into tablets. Researchers in Japan were the first to show that mothers given chlorella saw increased concentrations in their breast milk of protective antibodies called immunoglobulin, type A (IgA). Approximately 95 percent of all infections start in the mucosal (moist) surfaces, including the eyes, nostrils, and mouth, and IgA provides an immunological barrier by neutralizing and preventing viruses from penetrating into the body. The IgA in saliva, for instance, is considered the first line of defense against such respiratory-tract infections as pneumonia and influenza.

Although it appears chlorella extract supplements failed to boost overall immune function, there is evidence that whole algae may be effective. In one study, researchers rounded up athletes ripe for infection during the middle of training camp. Among the control group, who received no supplements, IgA levels dropped significantly during intense exercise. But among those who were given chlorella, IgA levels remained steady.

Chlorella also looks promising for the treatment of hepatitis C. A randomized, double-blind, placebo-controlled study found that about two teaspoons a day of chlorella appeared to boost the activity of natural killer cells in participants’ bodies, which can naturally help kill hepatitis C-infected cells. A clinical study of hepatitis-C patients found that chlorella supplementation may lower the level of liver inflammation, but the study was small and uncontrolled.

One note of caution: A disturbing case report from Omaha, Nebraska, was published, entitled “Chlorella-Induced Psychosis.” A 48-year-old woman suffered a psychotic break two months after starting to take chlorella. Her physicians told her to stop it and put her on an antipsychotic drug. One week later, she was reportedly fine. Chlorella had never before been linked to psychosis, so they initially presumed it was just a fluke. In other words, the psychosis may have just coincidentally begun after the woman started taking chlorella, and the reason she felt better after stopping it may have just been due to the drug kicking in. But seven weeks later, she was still on the drug and had restarted taking chlorella—and she became psychotic again. The chlorella was stopped, and her psychosis resolved again. Perhaps it wasn’t the chlorella itself that triggered the episode but some toxic impurity or adulteration? We don’t know. Given the ill-regulated supplement market, it may be hard to know what you’re getting when you try to buy “food” in supplement bottles.

The information on this page has been compiled from Dr. Greger’s research. Sources for each video listed can be found by going to the video’s page and clicking on the Sources Cited tab. References may also be found at the back of his books.

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