Vitamins May Not Be All That Helpful

It is not unusual to view an advertisement for a vitamin that suggests it helps people with cardiovascular problems, cancer, diabetes, or other chronic diseases. Judging the validity of these advertisements is often difficult due to what often appears to be conflicting data, and the use of personal anecdotes.
What is the evidence? A study was conducted by the U.S. Agency for Healthcare Research and Quality and published in 2006. (The complete report, Multivitamin/Mineral Supplements and Prevention of Chronic Disease can be viewed here)
The study examined the use of vitamins for the prevention of the following:
• breast cancer, colorectal cancer, lung cancer, prostate cancer, gastric cancer, or any other malignancy (including colorectal polyps)
• myocardial infarction, stroke
• type 2 diabetes mellitus
• Parkinson’s disease, cognitive decline, memory loss, dementia
• cataracts, macular degeneration, hearing loss
• osteoporosis, osteopenia, rheumatoid arthritis, osteoarthritis
• hepatitis, non-alcoholic fatty-liver disease
• chronic renal insufficiency, chronic nephrolithiasis
• HIV infection, hepatitis C, tuberculosis
• chronic obstructive pulmonary disease

The results of the study
The authors concluded there is limited evidence to date suggesting potential benefits of multivitamin/mineral supplements in the primary prevention of cancer in individuals with poor nutritional status or suboptimal antioxidant intake.
The evidence also indicates that multivitamin/mineral supplement use does not have significant effects in the primary prevention of cardiovascular disease and cataracts.
Regular supplementation of a single nutrient or a mixture of nutrients for years has no significant benefits in the primary prevention of cancer, cardiovascular disease, cataract, age-related macular degeneration or cognitive decline.
A few exceptions, that were reported in a single reviewed study included a decreased incidence of prostate cancer with use of synthetic α-tocopherol (50 mg per day) in smokers, a decreased progression of age-related macular degeneration with high doses of zinc alone or zinc in combination with antioxidants in persons at high risk for developing advanced stages of the disease, and a decreased incidence of cancer with use of selenium (200 mcg per day).
Supplementation with calcium has short-term (particularly within one year) benefit on retaining bone mineral density in postmenopausal women, and a possible effect in preventing vertebral fractures. Combined vitamin D3 (700–800 IU/day) and calcium (1000 mg/day) may reduce the risk of hip and other non-vertebral fractures in individuals with low levels of intake. Supplementation with β-carotene increased lung cancer risk in persons with asbestos exposure or cigarette smoking.
Users of Vitamins Beware
The overall quality and quantity of the literature on the safety of multivitamin/mineral supplements is limited. Among the adverse effects reported were vitamin A supplementation may moderately increase serum triglyceride levels. Calcium supplementation may increase the risk of kidney stones. Vitamin E supplementation was associated with an increased incidence of nosebleeds but was not associated with an increased risk of more serious bleeding events.

Bottom Line: Vitamins may be helpful for a few conditions. Nothing beats a good diet with fresh fruits and vegetables, plenty of exercise, and adequate sleep. Vitamins and supplements are not the cure all for many diseases or the major source of disease prevention.

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