Vitamins –Over half of adults in the United States take a multivitamin, an annual $20 billion dollar industry in this country. We’ve heard a lot of stories about them recently, some contradictory.
Who would have thought a multivitamin would be bad for you? But the recently published Iowa Women’s Health Study indicates a higher risk of dying in women 50-65 years old who take vitamins, especially if they contain iron.
Vitamin E used to be touted as preventing heart disease and cancer. Several years ago the HOPE-TOO trial found that vitamin E not only didn’t protect against heart disease, but participants taking vitamin E were 13% more likely to experience heart failure. The SELECT trial showed 17% higher risk of prostate cancer in those who take Vitamin E. Vitamin E has also been shown to increase the risk of hemorrhagic stroke (bleeding in the brain.) However, it does appear to slow macular degeneration in the eyes.
What does it all mean? And what are vitamins anyway?
Vitamins are essential organic compounds that the human body needs for life, but cannot synthesize by itself. Therefore humans must consume these compounds in the diet.
Important vitamins include the following:
- Vitamin A: Carotenes, the yellow pigment found in vegetables like carrots, are pro-vitamins, which are converted into vitamin A, which is important in vision.
- Vitamin B: There are eight important B vitamins that help the body convert carbohydrates into glucose (sugar) for energy. B vitamins are involved in many of the body’s enzymatic reactions for metabolism, and are needed for good brain development. They also help red blood cell health and prevent anemia.
- Vitamin C: It aids in absorption of iron, and is needed to form collagen in bones, cartilage muscle and blood vessels. It is found in citrus fruits such as oranges and limes. Limes were carried on board British Naval ships to prevent scurvy (vitamin C deficiency) in the sailor of the 18th and 19th centuries, thus the British sailor’s nickname of “limeys”.
- Vitamin D: Otherwise known as the sunshine vitamin. As little as 10 minutes of sun exposure daily can prevent deficiency. D vitamins aid in absorption of calcium, helping to form and maintain strong bones and prevent osteoporosis. Vitamin D is found in milk and dairy products.
- Vitamin E: Vitamin E is an antioxidant which protects cells from free radicals which may cause cell damage. It is also involved in immune function.
Unlike medications, vitamins as dietary supplements that you can buy in pill or liquid form do not have to be evaluated or approved by the Food and Drug Administration (FDA). It is the responsibility of the manufacturer to ensure the product is safe and that label claims are accurate and truthful. Vitamins have been evaluated in deficiencies, but have not been well studied in healthy subjects until recently. Many of the studies are not well designed and are contradictory, without proof of the claims made (like no proof that vitamin C prevents colds.)
So what are we fairly certain about with vitamins? Too much and too little can both be harmful. There is a healthful range. Vitamins A, D, E, and K are fat soluble vitamins and have known toxic levels. We used to think water soluble vitamins like B and C were not harmful in large amounts, and that the excess would just come out in the urine if not needed by the body. We now know that vitamin C in amounts greater than 2000mg/day increases the risk for kidney stones, causes excess iron absorption (with its own risks to the liver), and causes diarrhea. Excess vitamin B6 at 100mg/day can cause numbness in the fingers and toes.
Many foods in the United States, especially cereals, breads and flour are supplemented with extra vitamins. Also, there are mineral supplements added to food and drinks. These minerals are fraught with the same problems as the vitamins.
We know that vitamins naturally within foods are absorbed and used better in the body than those placed as supplements or those we take as pills. And there have been no cases of toxicity of vitamins from eating too much food, but people have certainly have overdosed on vitamins with tablets, powders, and vitamin drinks. People who eat the right foods and don’t have medical problems like difficulty with absorption, gastric bypass or genetic disorders are unlikely to have vitamin deficiencies.
What’s the bottom line? Grandma was right. Eat your vegetables!
Some useful references:
Fact sheets at NIH Office of Dietary Supplements. http://ods.od.nih.gov/
National Center for Complementary and Alternative Medicine. http://nccam.nih.gov/
U.S. Pharmacopeia http://www.usp.org/USPVerified/dietarySupplements/
Eat Right American Dietetic Association http://www.eatright.org/Media/content.aspx?id=6442452592
Mayo Clinic http://www.mayoclinic.com/health/