U.S. health regulators are issuing a warning against false claims about the ability of some products to battle the flu. The FDA has sent letters to nine internet distributors of dietary supplements. The letter also appears on the FDA's website. It's intended to make customers aware of a variety of herbal products that the distributors claim reduce the duration or severity of the flu. The FDA's Gary Coody says there are no over-the-counter products that can accomplish such claims.