Can low-dose vitamin and mineral supplements improve antioxidant defenses in older hospitalized adults?

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Researchers recruited 81 hospitalized adults older than 65 years for a randomized, double-blind, placebo-controlled study examining how low-dose antioxidant vitamin and mineral supplements affected biological and functional measures of free radical metabolism.

Participants were randomly assigned to four groups receiving daily treatment for 2 years: placebo; minerals alone, with 20 mg zinc and 100 micrograms selenium; vitamins alone, with 120 mg vitamin C, 6 mg beta-carotene and 15 mg vitamin E; or minerals plus vitamins, with 20 mg zinc, 100 micrograms selenium, 120 mg vitamin C, 6 mg beta-carotene and 15 mg vitamin E.

Fifty-seven participants completed the study. Vitamin C, zinc and selenium deficiencies were common at baseline. By as early as 6 months of treatment, serum vitamin and mineral levels had increased significantly in the corresponding supplementation groups. The increases ranged from 1.1- to 4.0-fold, depending on the nutrient.

Antioxidant defense was assessed in vitro using red blood cells exposed to a compound named in the abstract as “2,2'-azo-bis (2-amidinopropane) by hydrochloride.” Cell resistance increased in participants receiving vitamins (p = 0.002). Resistance was positively correlated with serum vitamin C (p < 0.0001), the alpha-tocopherol/cholesterol ratio (p = 0.06), beta-carotene (p = 0.0014), and serum copper and selenium (p < 0.05).

Red blood cell antioxidant defense was lower in older subjects than in young control subjects: the time to 50% hemolysis was 69 ± 14 minutes and 109 ± 12 minutes, respectively.

Erythrocyte glutathione peroxidase activity increased in the groups receiving minerals. However, no significant change was observed in the other indicators of oxidative stress: erythrocyte superoxide dismutase activity, thiobarbituric acid-reactive substances, and glutathione measured as total, reduced and oxidized forms.

The researchers concluded that low-dose vitamin and mineral supplementation could normalize biological nutrient status as early as 6 months into treatment. They also concluded that low doses of vitamin C, vitamin E and beta-carotene improved antioxidant defense in older subjects, as measured by a functional test exposing red blood cells to free radicals in vitro.