Sound out those claims on the net
Internet myths abound: antiperspirants cause breast cancer; the MMR (measles, mumps and rubella) vaccination for children leads to autism; and ingesting powdered shark cartilage inhibits cancer are just a few. Medical opinion is that there's no scientific evidence for these claims.
A good rule of thumb is to look at sites that aren't trying to sell you a specific product, that aren't sponsored by a particular drug or equipment manufacturer, and that carry research done on a scientific basis rather than individual testimonials or opinions.
The following sites offer a more balanced approach and a chance to check on claims made elsewhere:
www.quackwatch.org A non-profit group that aims to spike health myths and frauds through a team of volunteers and independent health experts.
www.consumer.org.hk The Hong Kong Consumer Council's site isn't health-specific, but it does include health and medicine alerts and recalls.
www.consumerlab.com This US site conducts independent tests on dietary and health supplements.