The use of vitamins, like the use of all dietary supplements, has risen in recent years—even though schools of thought on their relative value differ greatly.
Some claim that taking vitamins is beneficial, both in making up for patients’ diet deficiencies and in reducing their risk of serious disease.
Others maintain that the benefits are marginal at best and that vitamins may actually increase the risk of disease.
Patients and their physicians stand to benefit from a better understanding of vitamins and a strategy for optimizing their use. Fortify your knowledge of the pros and cons with this baker’s dozen of facts and figures:
1. The CDC offers these statistics:
• More than half of the U S adult population used dietary supplements in 2003-2006, up from more than 40% in 1988-1994.
• Multivitamin/mineral (MVM) supplements were used most frequently.
• The use of supplemental calcium increased to 61% of women aged 60 years and older, up from 28%.
• About one-third of women aged 20 to 39 years used a dietary supplement containing folic acid.
• The use of supplements containing vitamin D increased for men and women in most age groups in 1999-2002.
2. The United States leads the world in dietary supplement intake. About two-thirds of adults, or 186 million persons, took some sort of supplement in 2012. Sales of dietary supplements have grown 5.5% a year since 1997; 34% of sales comes from vitamins.
3. More than one-third of Americans take MVM supplements. Use increases with age—about 1 in 4 young children takes an MVM, and by age 71 years, more than 40% of adults take one.
4. In a study of lung cancer in the Women’s Health Initiative, vitamin D intake was associated with a lower lung cancer risk in never-smoking, postmenopausal women. Lower vitamin A intake may be important for a beneficial association of 1 g Ca + 400 IU vitamin D3 supplementation with lung cancer.
5. Results from the Physicians’ Health Study II showed a modest but statistically significant cancer reduction benefit associated with long-term daily multivitamin use by middle-aged and older men.
6. European researchers found that vitamins C and E as well as selenium may reduce the risk of pancreatic cancer by two-thirds. They noted that experiments using antioxidant dietary supplements have not produced significant results.
7. The U S Preventive Services Task Force Recommendation states that appropriate intake of vitamin D and calcium is essential to overall health but that there is inadequate evidence to determine the effect of combined vitamin D and calcium supplementation on the incidence of fractures in men or premenopausal women.
8. In a 22-year study, vitamin B6, folic acid, iron, magnesium, and zinc were associated with an increased mortality risk for older women. In a clinical trial of 35,000 men aged 50 years and older, vitamin E increased the risk of prostate cancer by 17%.
9. Megadoses of certain vitamins may increase a person’s risk of heart disease and cancer. Megadoses were described as vitamins that provide anywhere from 5 to 20 times more than the recommended daily intake of certain nutrients.
10. The 2005 Dietary Guidelines for Americans advised that nutrient needs be met primarily through consuming foods, with supplementation suggested for certain sensitive populations, emphasizing that it is not a substitute for a healthful diet.
11. An Endocrine Society Clinical Practice Guideline recommended vitamin D supplementation at suggested daily intake and tolerable upper limit levels, depending on age and clinical circumstances, suggesting the measurement of serum 25-hydroxyvitamin D level by a reliable assay as the initial diagnostic test for patients at risk for deficiency and treatment for deficient patients with vitamin D2 or vitamin D3.
12. Problems with regularly measuring serum vitamin D levels to assess for deficiency include a lack of standardization in the screening process, ambiguity about the level of 25-hydroxy-vitamin D that should be considered normal and the treatment implications, and a lack of cost-effectiveness.
13. The NIH’s Dietary Supplement Label Database provides a look at the ingredients listed on the labels of about 17,000 dietary supplements.