Effect of a multivitamin and mineral supplement on infection and quality of life. A randomized, double-blind, placebo-controlled trial.

BACKGROUND Use of multivitamin and mineral supplements is common among U.S. adults, yet few well-designed trials have assessed the reputed benefits. OBJECTIVE To determine the effect of a daily multivitamin and mineral supplement on infection and well-being. DESIGN Randomized, double-blind, placebo-controlled trial. SETTING Primary care clinics at two medical centers in North Carolina. PARTICIPANTS 130 community-dwelling adults stratified by age (45 to 64 years or >or=65 years) and presence of type 2 diabetes mellitus. INTERVENTION Multivitamin and mineral supplement or placebo taken daily for 1 year. MEASUREMENTS Incidence of participant-reported symptoms of infection, incidence of infection-associated absenteeism, and scores on the physical and mental health subscales of the Medical Outcomes Study 12-Item Short Form. RESULTS More participants receiving placebo reported an infectious illness over the study year than did participants receiving multivitamin and mineral supplements (73% vs. 43%; P < 0.001). Infection-related absenteeism was also higher in the placebo group than in the treatment group (57% vs. 21%; P < 0.001). Participants with type 2 diabetes mellitus (n = 51) accounted for this finding. Among diabetic participants receiving placebo, 93% reported an infection compared with 17% of those receiving supplements (P < 0.001). Medical Outcomes Study 12-Item Short Form scores did not differ between the treatment and placebo groups. CONCLUSIONS A multivitamin and mineral supplement reduced the incidence of participant-reported infection and related absenteeism in a sample of participants with type 2 diabetes mellitus and a high prevalence of subclinical micronutrient deficiency. A larger clinical trial is needed to determine whether these findings can be replicated not only in diabetic persons but also in any population with a high rate of suboptimal nutrition or potential underlying disease impairment.