by Dr. Leo Galland
The benefits of various vitamins, or nutritional supplements, are mentioned almost every day in the news. But with all the reports it can be confusing to know what vitamins do what. So here is a quick look at some of the major vitamins and minerals.
Studies indicate potential benefits and adverse effects of vitamins and minerals:
- Vitamin D may help prevent winter illnesses like colds and flu (this benefit was shown for post-menopausal women). Some people with low vitamin D levels might experience improvement in joint or muscle pain, depression or immunity when taking vitamin D. Vitamin D could help reduce the risk of falls and fractures in elderly people and improve dental health. Vitamin D may also help reduce the risk of breast cancer in post-menopausal women and of colon cancer in men and women. But too much Vitamin D can increase the risk of kidney stones.
- Vitamin C supplements might decrease the risk of cataracts and the severity of colds and protect the stomach from the irritant effects of aspirin. High doses of vitamin C may cause stomach pain or diarrhea, however.
- Vitamin A supplements (in the form of retinol) may boost immune responses and decrease the severity of acne, but too much vitamin A can cause liver disease, bone loss, dry skin and headaches.
- Beta-carotene supplements (a precursor of vitamin A) may help decrease the risk of colon cancer and improve immune function in the elderly, but they were shown to increase the risk of lung cancer in smokers and to interfere with the benefits of statin drugs, which are used to reduce cholesterol. One problem with beta-carotene supplements is that there are many related nutrients called carotenoids, which have more powerful effects than beta-carotene. Taking beta-carotene may reduce the blood level of these other carotenoids (lutein, lycopene, astaxanthin, cryptoxanthin, alpha-carotene).
- Vitamin E supplements may either improve or hinder strong immune responses in the elderly. Vitamin E can interfere with the benefits of statin drugs, which are used for reducing cholesterol levels. One problem with vitamin E supplements is that there are many related molecules, called tocopherols, which make up the vitamin E family. Most studies use a synthetic form of vitamin E called d, l-alphatocopherol. The natural form of alphatocopherol is d-alphatocopherol and giving d, l-alphatocopherol may be the wrong way to test the effects of vitamin E. In addition, there are other tocopherols (beta, gamma and delta tocopherols) that may have important effects in the body. Taking any form of alphatocopherol can reduce the blood levels of these other tocopherols. Gamma tocopherol is a more potent antioxidant than alphatocopherol and is the major tocopherol in the U.S. diet.
- Supplements of zinc, along with vitamin B6, selenium and lutein may reduce the risk or severity of macular degeneration, the leading cause of blindiness in the US. Zinc may also improve immunity and healing, reduce severity of acne and help antidepressants work better, especially for people with low levels of zinc in plasma. High doses of zinc have been used to treat tinnitus and to prevent sickle crises in people with sick cell anemia. Too much zinc can create a deficiency of copper, which may adversely affect neurological function, thyroid function and bone health.
- Boron is a trace mineral with positive effects on bone health and estrogen function. Boron supplements may help prevent or reverse bone loss and may help to prevent prostate cancer.
- Vitamin K is essential for blood clotting. Vitamin K also has beneficial effects on bone strength. Vitamin K comes in two natural forms called vitamin K1 (derived from plants and bacteria) and vitamin K2 (made by animals from vitamin K1). Vitamin K supplements have been shown in studies to reduce the risk of osteoporosis and certain kinds of cancer.
- Calcium supplements may decrease the risk of osteoporosis and fractures and may reduce blood pressure. Calcium supplements may either decrease or increase the risk of kidney stones, depending upon dietary and genetic risk factors for stones. Some studies but not others have suggested that high calcium may increase a man’s risk of prostate cancer. Chewable, powdered or liquid calcium can help prevent or relieve GERD, or heartburn. Calcium supplements can be constipating.
- Selenium supplements in the form of selenomethionine may help reduce the incidence of asthma, breast cancer and prostate cancer. Selenium may help statin drugs (used to reduce cholesterol) work better. One study found that selenium supplements were associated with an increased risk of skin cancer.
With so many people interested in nutritional supplements, it is more important than ever to learn more about what vitamins and minerals can do.
For more information on what vitamins do what, here are a few resources:
National Institutes of Health (NIH) Office of Dietary Supplements
United States Department of Agriculture (USDA) Food and Nutrition Information Center