Antioxidant vitamins are among the dietary supplements that are most used by people with MS. Antioxidants act on free radicals, which are chemicals known to damage cells.
Antioxidants can affect both the immune and nervous systems. By decreasing the impact of harmful free radicals, cell damage may be reduced. Free radicals play a key role in the immune system’s attack on the nervous system, helping to damage both nerve cells and the cells that insulate them. By studying EAE, an animal model of MS, researchers have found that free radicals are likely involved in the disease process and that antioxidants may help. However, as many antioxidants have been shown to stimulate the immune system, they pose a theoretical risk for people with MS.
No large-scale, rigorous clinical trials have been conducted to definitively determine the safety or effectiveness of antioxidants in MS. Some small-scale, short-term studies have been cited to prove the safety of antioxidants in MS; however, this work does not definitively prove safety. The beneficial results documented in EAE are also sometimes cited, but EAE is far from a perfect model of MS and results from this work are often not directly applicable to MS. Many research projects are currently underway to further our understanding of antioxidants and MS.
As the research does not provide clear answers at this time, those with MS should approach antioxidants cautiously. It may be reasonable to avoid these supplements altogether and rely on dietary intake of antioxidants. Antioxidants are found in fruits and vegetables. Dietary intake of modest levels of antioxidant-rich foods is likely to result in adequate levels, while avoiding the excess that is possible with supplementation. More information is available at www.mypyramid.gov.
Vitamins A, C, and E
Vitamins A, C, and E are antioxidant vitamins, as is beta-carotene, a compound that is converted to vitamin A. Antioxidants are discussed at length in the above section. If people choose to take antioxidant vitamin supplements, relatively low daily doses may be most appropriate: vitamin A, 5,000 IU or less; vitamin C, 90 to 120mg or less; vitamin E, 100 IU or less.
High doses of these compounds may be associated with toxic effects. Consuming more than 10,000 IU of vitamin A daily may cause nausea, headache, blurred vision, and liver damage. This dose may produce birth defects in pregnant women. Daily doses of 2,500mg or more of vitamin C may produce bloating, diarrhea, and kidney stones. High doses of vitamin E (1,500IU or 1,000 mg daily) may cause bleeding problems, stomach upset and other problems.
There are other reasons to be cautious about antioxidant vitamins. Smokers should be aware that vitamin A and beta-carotene supplements have been associated with an increased risk of lung cancer and death in people who smoke. Since it may inhibit blood clotting, vitamin E should be avoided by people taking blood-thinning medications or undergoing surgery and by those who suffer from bleeding disorders. Those taking blood-thinning medications should also be aware that vitamin C has been shown to decrease the effectiveness of those drugs.
People with MS should approach vitamin C with caution. Claims exist that vitamin C can prevent or treat the common cold and urinary tract infections (UTIs). The common cold is a viral infection that has the potential to trigger MS attacks. UTIs can occur frequently in women with MS. Little evidence exists to support either of these claims about vitamin C. Cranberry juice may be more effective than vitamin C in UTI prevention, and antibiotics should be used for treatment of known UTIs to avoid possible serious complications (See Herbs page for more information on cranberry). Furthermore, vitamin C is known to stimulate the immune system, especially in high doses. This poses a theoretical risk for people with MS. If vitamin C is used, low doses (90-120mg or less daily) may be most reasonable. This is roughly equivalent to amount found in one cup of orange juice.
References and Additional Reading
Bowling AC. Complementary and Alternative Medicine and Multiple Sclerosis. New York: Demos Medical Publishing, 2007.
Bowling AC, Stewart TS. Dietary Supplements and Multiple Sclerosis: A Health Professional’s Guide. New York: Demos Medical Publishing, 2004.
Jellin JM, Batz F, Hitchens K, et al. Natural Medicines Comprehensive Database. Stockton, CA: Therapeutic Research Faculty, 2009.
Ulbricht CE, Basch EM, eds. Natural Standard Herb and Supplement Reference: Evidence-Based Clinical Reviews. St. Louis: Elsevier-Mosby, 2005.