Question

Which source is least credible

Answer 1

The least credible source from this list is "a blog post from a celebrity athlete".
A trusted health professional is a person appropriately trained and experienced who is able to provide credible, safe and up-to-date medical information. The American Cancer Society is a voluntary health organisation focused on eliminating cancer. It publishes scientific journals of high impact and has its emphasis on medical and scientific matters. The U.S. Food and Drug Administration is a federal agency of the U.S. Department of Health and Human Services. Its purpose is to protect and promote the public health through the monitoring of food, drugs, vaccines, cosmetics, veterinary products, medical devices and dietary supplements.