Vitamins: More Good Than Bad or Ugly?

Does the evidence still support vitamin and mineral supplementation?

Vitamins have taken a beating recently. Men (n 5 35,553) who received vitamin E supplements in a large 4-arm trial (selenium was given alone or in combination with vitamin E) had a slightly increased risk of prostate cancer (1.17 times greater).1 Even though results in the selenium limb did not reach statistical significance, the study demonstrated that vitamin E—an antioxidant— and other commonly used supplements do not prevent prostate cancer.

Responses to the data were interesting. Tim Byers, MD, MPH, a cancer prevention specialist, said, “Although I have been among those critical of hazards of high-dose supplementation, I view this finding as contributing to an overall pattern showing little or no association rather than to an overall conclusion of proven harm.”² Then came data that showed supplements—including multivita- mins, vitamin B6, folic acid, iron, magnesium, zinc, and copper—were associated with greater all-cause mortality after 19 years’ follow-up (1.06 to 1.45 times).^3,4

A FRESH LOOK AT FOLIC ACID

For a balanced perspective, let us examine the results of a recent study that took a fresh look at folic acid supplementation in pregnancy—from 4 weeks’ gestation through 8 weeks after delivery.⁵ The study was performed in Norway, where the diet is not routinely supplemented with folate. Previous outcome measures for the benefits of folic acid during pregnancy focused on spina bifida. This study focused instead on language delay in children at 3 years of age. Children of mothers who received folic acid supplementation were 45% less likely to experience a severe language delay.

BEST WAY TO DIAGNOSE B12 DEFICIENCY

Another recent study looked at the effects of vitamin B12 status in older adults. The outcome measure was cognition consequent to white matter volume, cerebral infarcts, total brain volume (assessed by MRI), and selected cognitive domain performances (5 over 4.6 years).⁶ The cohort comprised 121 persons who made up the Chicago Health and Aging Project (65 years of age and older). Vitamin B12–related markers—methyl- malonic acid (MMA), cystathionine, 2-methylcitrate, and homocysteine—but not vitamin B12 itself, affected overall memory, perceptual speed, episodic and semantic memory, and brain volume. The authors’ conclusion: “Vitamin B12 status may affect the brain through multiple mechanisms.” Low B12 status, as inferred by its “markers” (remember, with B12 deficiency MMA goes up not down), predisposed the elderly to cognitive decline and other forms of brain injury.

The authors also reiterate a truism that impacts the diagnosis of B12 deficiency. Tolerate this paradox: B12 levels are not the best way to diagnose B12 deficiency in the elderly. MMA levels are more sensitive and specific. With the consequent brain injury, low-normal B12 levels and a high index of suspicion should prompt measurement of MMA levels in this population.

Although questions remain about selected vitamin and mineral supplementation, interpretation of recent data requires wisdom. Vitamin E may not prevent prostate cancer. General use of vitamin and mineral supplements, especially in excessive doses, can be harmful. But, in selected situations—pregnancy and aging— patients still benefit from the judicious use of vitamins.