Verifying vitamin C supplements

Vitamin C (ascorbic acid or dehydroascorbic acid) is an essential water-soluble vitamin that the human body can't manufacture. It must, therefore, come from foods or supplements. Fruits and vegetables are the richest food sources of vitamin C. Dietary supplements are typically sold as ascorbic acid, calcium ascorbate (Ester-C®), sodium ascorbate, or a combination of these forms. Supplements also commonly contain natural sources of vitamin C such as rose hips (the pear-shaped fruit of the rose, without the flower's petals) and/or acerola (a cherry-like fruit).

Vitamin C helps the body produce collagen, a basic component of connective tissue. Collagen is an important structural element in blood vessel walls, gums, and bones, making it particularly important to anyone recovering from wounds or surgery. Vitamin C also acts as an antioxidant, scavenging potentially harmful molecules called free radicals. Although not firmly established by clinical trials, this antioxidant activity may help boost immune function and protect against cancer, cataracts, age-related macular degeneration of the retina, and other chronic diseases. Vitamin C intake may be particularly helpful to smokers, who may suffer from oxidative stress and cell damage, which can deplete the body's store of vitamin C. Vitamin C also enhances iron absorption from supplements and plant foods. However, be aware that vitamin C can also affect other drugs you may be taking.

Good sources of vitamin C include many vegetables, such as broccoli and brussel sprouts, as well citrus and other fruits. A healthful diet should provide the Recommended Dietary Allowance (RDA) of the vitamin.

Regulations from the U.S. Food and Drug Administration (FDA) require that any vitamin C sold as a dietary supplement in the United States contain at least 100% of its labeled amount. The United States Pharmacopeia (USP) requires that products contain 90% to 110% of the claimed amount and that they meet certain specifications for disintegration and purity. Unfortunately, the FDA doesn't test for quality before sales, and products stating that they meet the USP standards don't always do so. Therefore, ConsumerLab.com tested several leading vitamin C dietary supplements to determine whether they contained 100% of the labeled amounts of vitamin C and whether tablets could disintegrate properly.

ConsumerLab.com purchased 15 brands of vitamin C products, including 4 products for children. All were tested for their levels of vitamin C. In addition, tablets were tested for their ability to disintegrate in simulated gastric fluid, as needed for absorption.

All of the 15 products tested met their claims for vitamin C and could disintegrate properly for absorption. Results were better than seen in ConsumerLab.com's last Product Review of Vitamin C in 2000 in which several products were found to contain somewhat less than claimed and one product would not disintegrate properly.

Products that passed the test:
The list below provides examples of some of vitamin C products that passed CL's testing:

Nature Made® Recommended By Pharmacists C Vitamin 500 mg (500 mg ascorbic acid / tablet)
Nature's Bounty® C&E Vitamin C 500 mg, Vitamin E 400 I.U., USP (500 mg ascorbic acid and rose hips / softgel)
Nature's Bounty® Vitamin C-500 mg, USP (500 mg ascorbic acid / tablet)
Nutrilite® Bio C Plus (250 mg from ascorbic acid and acerola concentrate)
Puritan's Pride® Ester-C® 500 mg (500 mg from calcium ascorbate / tablet)
Puritan's Pride® Inspired by Nature™ Vitamin C-1000 mg with Rose Hips USP (1000 mg from ascorbic acid and rose hips / tablet)
Puritan's Pride® Inspired by Nature™ Vitamin C-500 mg with Rose Hips USP (500 mg from ascorbic acid and rose hips / tablet)
Spring Valley® C&E Vitamin C 500 mg, Vitamin E 400 I.U., USP (500 mg from ascorbic acid and rose hips / softgel)
Spring Valley® Ester-C® 500 mg (500 mg from calcium ascorbate / tablet)
Vitamin World® Naturally Inspired™ C&E Vitamin C 500 mg, Vitamin E 400 I.U., USP (500 mg ascorbic acid and rose hips / softgel)
Vitamin World® Naturally Inspired™ Delicious Chewable Vitamin C-500 mg with Rose Hips, Natural Orange Flavor, Color Free, USP (500 mg from sodium ascorbate, ascorbic acid, rose hips / chewable tablet)
Vitamin World® Naturally Inspired™ Ester C® 1000 mg with Bioflavonoids (1000 mg from calcium ascorbate / tablet)
Vitamin World® Naturally Inspired™ Ester C® 500 mg, Vitamin C Activity with Bioflavonoid Complex (500 mg from calcium ascorbate / tablet)
Vitamin World® Naturally Inspired™ Vitamin C-1000 mg with Rose Hips, USP (1000 mg from ascorbic acid and rose hips / tablet)
Vitamin World® Naturally Inspired™ Vitamin C-500 mg with Rose Hips, USP (500 mg from ascorbic acid and rose hips / tablet)