Do you notice inconsistency?

Do reliable references support the  claims?

Beware of: 

Testimonials about personal experiences.

Disreputable publications.

Lack of evidence or supporting studies made by other scientists.

Examine the background philosophy of of the individual organizations or publications making the claims.

Usually a reputable author is one who educational background or affiliation  is with a reputable  national university or medical center that offer courses in the field of nutrition, medicine or closely allied specialty.

Avoid practitioners that  prescribe vitamins supplement for everyone or who sell them in connection with they practice.

Examine, product label carefully, and be skeptical of any product promotions  not clearly stated on the label.

Scientist normally  report they studies in reputable scientific journals.