 Multiple studies published over the last two decades suggest that exercise can mitigate the deleterious effects of age on immune function, thus increasing anti-cancer immunity, in part by stimulating natural killer cell activity. Natural killer cells, part of our immune system, were to eliminate both tumor cells and virus-infected cells, and we can boost their activity with physical activity. Here's the difference in natural killer cell activity between women involved in athletic competitions compared to their sedentary counterparts. There is a growing consensus that natural killers appear to be the immune system component that is most responsive to the effects of both acute and chronic exercise across the board, from older women to younger men. Significantly higher NK activity in racing cyclists in their 20s. Even just moderate exercise, though, like daily walking, appears to significantly improve NK activity within six weeks. This may be why exercise helps protect against cancer. But sustained vigorous exercise may actually impair natural killer cell immunity, which may be one reason endurance athletes like marathon runners may appear to be more likely to get upper respiratory tract infections. In an upcoming video on preserving athletic immunity with chlorella, I feature a study that showed consuming chlorella appear to prevent the loss in immune function as measured by antibody production. But what effect might the green algae have on natural killer cell activity? Petri dish and animal studies suggest that the algae chlorella could affect natural killer cell activity, but there was no direct evidence for the effect of chlorella supplementation on such a response in humans until this randomized double-blind placebo-controlled trial gave people about two teaspoons of chlorella a day for six weeks, and compared to placebo, they got a significant increase in natural killer cell activities. Does this actually translate, though, into clinical benefits? We didn't know until now. The efficacy of chlorella supplementation in adults with chronic hepatitis C infection. It's estimated that up to 4 million people in the US have chronic hepatitis C virus infection, the leading cause of liver transplants, and estimated to kill a quarter million Americans this decade. The current treatment is costly and brutal, costing up to about $85,000, and nearly half can't even complete the course of drugs, some part of the many complications associated with the treatment. So that's why there's such a need for novel treatment options. After three months of chlorella, there were reported improvements in quality of life, but that could have just been a placebo effect since the control group wasn't given green sugar pills. This however is harder to explain, a significant improvement in ALT, which is a marker of liver inflammation, which could be explained by beneficial immunostimulatory effect of chlorella supplementation. No serious adverse effects were reported, so why not give it a try? Well, the brand they used was tied to a disturbing case report recently, chlorella-induced psychosis. A 48-year-old woman in Omaha suffers a psychotic break out of the blue two months after starting chlorella. They stopped it and started her on an anti-psychotic drug, and a week later, she was fine. Now, chlorella has never been linked to psychosis before, so presumably it was just a coincidence that the psychosis started after she started taking chlorella, and the reason she felt better after stopping it was because the drug was kicking in. But seven weeks later, still on the drug, she became psychotic again after starting back on the chlorella. They stopped the chlorella again, this time that's all they did, and the psychosis resolved. Now, maybe it wasn't the chlorella itself, but some toxic impurity or adulteration. We don't know. While chlorella is marketed to promote mental health, this case underscores the importance of educating the public about the potential adverse effects and the need for more research in herbal products being marketed here in the United States.