Q.What is beta-glucan? I have seen advertisements calling it an activator of the immune system.

A. Beta-1,3-glucan is a sugar derived from the cell wall of baker's yeast. Numerous experimental studies in test tubes and animals have shown this substance to activate white blood cells. In fact, there have been over 1,600 research papers on beta-1,3-glucan since the 1960s. What the research indicates is that beta-1,3-glucan is very effective at activating a type of white blood cell known as a macrophage. These cells compose the immune system's first line of defense against foreign invaders. A macrophage can recognize and kill tumor cells, remove cellular debris resulting from oxidative damage, speed up recovery of damaged tissue, and further activate other components of the immune system.

Although the research in test tube and animal studies is positive, many questions still remain about the effectiveness of beta-1,3-glucan as an oral supplement in humans. In short, most of the claims used to market beta-1,3-glucan are currently not substantiated by human research. Nonetheless, it does appear to be very safe. It is usually recommended in amounts ranging from 50 to 100 mg daily although some products contain as much as 500 mg per capsule.