Can herbal supplements boost immunity?

Many herbal preparations and other supplements claim to "support immunity" or otherwise boost the health of your immune system. Although a few preparations have been found to alter some components of immune function, thus far there is no evidence that they actually bolster immunity to the point where they protect against infection and disease. Demonstrating whether an herb -- or any substance -- can enhance immunity is, as yet, a highly complicated matter. Scientists don't know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for overall immunity.

But everyone's immune system is unique. Each person's physiology responds to active substances differently. So if your grandmother says she's been using an herbal preparation for years that protects her from illness, who's to say that it doesn't? The problem arises when scientists try to study such a preparation among large numbers of people. The fact that it works for one person won't show up in the research data if it's not doing the same for a larger group. But without evidence from a scientific study that shows the preparation has some benefit for a larger group, you are likely to be making a poor investment by using it.