Dietary supplements: Sorting out the science - Harvard Health

• Pharmaceuticals undergo extensive testing to prove they're effective and safe before they can be sold, but dietary supplements can be sold without proof of claims, effectiveness or safety.
• Daily multivitamin consumption does not lower heart disease risk.
• The FDA has found more than 500 supplements adulterated with pharmaceuticals or closely related compounds. Those can cause unwanted side effects and may be especially risky when taken with heart drugs or other prescription medications.

Because of the potential risks and unclear benefits of supplements, most doctors advise against them. However, doctors often recommend specific vitamin and mineral supplements to their patients, such as calcium and vitamin D to prevent osteoporosis and iron for people with iron deficiency.