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Fortify Your Knowledge About Vitamins

How Vitamins are Regulated

Vitamin products are regulated by FDA as "Dietary Supplements." The law defines dietary supplements, in part, as products taken by mouth that contain a "dietary ingredient" intended to supplement the diet.

Listed in the "dietary ingredient" category are not only vitamins, but minerals, botanicals products, amino acids, and substances such as enzymes, microbial probiotics, and metabolites. Dietary supplements can also be extracts or concentrates, and may be found in many forms. The Dietary Supplement Health and Education Act of 1994 requires that all such products be labeled as dietary supplements.

In June 2007, FDA established dietary supplement "current Good Manufacturing Practice" (cGMP) regulations requiring that manufacturers evaluate their products through testing identity, purity, strength, and composition.

Risks of Overdoing It

As is the case with all dietary supplements, the decision to use supplemental vitamins should not be taken lightly, says Vasilios Frankos, Ph.D., Director of FDA's Division of Dietary Supplement Programs.

"Vitamins are not dangerous unless you get too much of them," he says. "More is not necessarily better with supplements, especially if you take fat-soluble vitamins.” For some vitamins and minerals, the National Academy of Sciences has established upper limits of intake (ULs) that it recommends not be exceeded during any given day. (For more information, visit www.nap.edu/catalog.php?record_id=6432#toc).

Also, the AAFP lists the following side effects that are sometimes associated with taking too much of a vitamin.

Fat-soluble Vitamins

  • A (retinol, retinal, retinoic acid): Nausea, vomiting, headache, dizziness, blurred vision, clumsiness, birth defects, liver problems, possible risk of osteoporosis. You may be at greater risk of these effects if you drink high amounts of alcohol or you have liver problems, high cholesterol levels or don't get enough protein.
  • D (calciferol): Nausea, vomiting, poor appetite, constipation, weakness, weight loss, confusion, heart rhythm problems, deposits of calcium and phosphate in soft tissues.

If you take blood thinners, talk to your doctor before taking vitamin E or vitamin K pills.

Water-soluble Vitamins

  • B-3 (niacin): flushing, redness of the skin, upset stomach.
  • B-6 (pyridoxine, pyridoxal, and pyridoxamine): Nerve damage to the limbs, which may cause numbness, trouble walking, and pain.
  • C (ascorbic acid): Upset stomach, kidney stones, increased iron absorption.
  • Folic Acid (folate): High levels may, especially in older adults, hide signs of B-12 deficiency, a condition that can cause nerve damage.

Taking too much of a vitamin can also cause problems with some medical tests or interfere with how some drugs work.

Report Problems

If you believe that you are experiencing an adverse response to taking a vitamin or a dietary supplement, Frankos advises reporting it to your health care provider, as well as to the manufacturer whose name or phone number appears on the label. You can also report directly to FDA through its MedWatch program at 1-800-FDA-1088 or online at www.fda.gov/medwatch

Starting December 22, 2007, any serious adverse events reported to a dietary supplement manufacturer must be reported to FDA within 15 days of the manufacturer receiving the adverse event report.

For more information about topics for your health, visit the FDA Consumer Information Center (www.fda.gov/consumer). 

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