Your body needs small quantities of many vitamins to function properly, but it can't produce vitamins from scratch. Rather, you ingest vitamins from sources such as food and dietary supplements. However, you might increase your risk of health problems if you haphazardly choose your vitamin sources and dosages.
Supplementation
Dietary supplements aren't intended to substitute your intake of nutritious foods such as fruits, whole grains, vegetables and lean proteins. However, you might benefit from supplementing your diet with a vitamin supplement if you have trouble eating the right foods, if you eat a restrictive diet or if you have certain conditions. Your doctor might request that you take a vitamin supplement if you have a disease of the intestines, pancreas, liver or gallbladder. He might also recommend vitamin supplementation if you have a digestive problem, or if you are trying to conceive, are pregnant, breastfeeding or postmenopausal. Under these circumstances, your doctor or a registered dietitian should be the one to recommend a specific supplement.
Overdose Risks
You increase your health risks by taking more than the recommended dosage of many vitamins. Water-soluble vitamins such as vitamin C tend to be less risky in high quantities than fat-soluble vitamins because excess amounts of water-soluble vitamins leave your body through urine. However, they too might cause some health problems. For instance, overdosing on vitamin C can cause cramping, bloating, diarrhea and increased likelihood of developing kidney stones, according to the Colorado State University Extension. Taking high levels of vitamin B can cause nausea, cramping, irritability and abnormal liver function, and taking large amounts of folic acid might mask a deficiency in vitamin B-12. Overdoses of fat-soluble vitamins can cause further health problems because those vitamins linger in the body. A vitamin A overdose can cause growth retardation, hair loss, and an enlarged spleen and liver. A vitamin D overdose can cause kidney damage, mental retardation and physical growth retardation. A vitamin E overdose might cause digestive tract problems.
Dietary Supplement Risks
Because multivitamins and other vitamin supplements fall under the "dietary supplement" category, they aren't as rigorously regulated as medications are. A manufacturer or distributor of a vitamin supplement is responsible for testing its products, but the U.S. Food and Drug Administration, or FDA, isn't in charge of finding proof of supplements' efficacy or safety. However, the FDA might ban or recall a product that is already on the market if it has received reports of dangers and has enough evidence to back up these claims. Though vitamin product recalls aren't common, they do occur.
Choosing Multivitamin
You can reduce your risk of taking a harmful vitamin product or ingesting too much of a certain vitamin if you do your homework before you start supplementing your diet. Stick with multivitamins that only offer 100 percent or less of your recommended daily intake for most vitamins and steer clear of varieties that offer "mega doses" of 200 to 1,000 percent unless your doctor suggests otherwise. Additionally, carefully read the label on your supplement to pinpoint its active ingredients, the vitamins it contains and the serving sizes. Other important precautions to take: Look for "USP" on the product label -- for "U.S. Pharmacopeia," an official public standards-setting authority -- to ensure it meets basic safety standards, make sure the supplement hasn't expired and keep up with advisories and alerts on the FDA's website to ensure that the product hasn't been linked to adverse health effects.
References
- University of Iowa Health Care; "Vitamins -- Too Much of a Good Thing"; Phil Kissack; January 2003
- Colorado State University Extension; "Water-Soluble Vitamins"; J. Anderson et al
- Colorado State University Extension; "Fat-Soluble Vitamins"; J. Anderson et al
- Harvard School of Public Health: Vitamins
- MayoClinic.com: Dietary Supplements -- Nutrition in a Pill?
- U.S. Food and Drug Administration: Dietary Supplements
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