Oral zinc augmentation with vitamins A and D increases plasma zinc concentration: implications for burden of disease.
A study evaluating zinc supplementation in patients with Alzheimer's disease yielded variable zinc plasma levels in spite of positive cognitive and physiological results. In an attempt to raise and sustain plasma zinc levels, a single patient was given 15 mg zinc/day with various combinations of vitamins. A sustained raise in plasma zinc concentration (and therefore its potential bioavailability) was obtained only when the zinc was augmented with both vitamins A and D (in RDA concentrations). In order to verify these results, a follow-up study was conducted in 70 volunteers. Seven groups of 10 healthy subjects received various combinations of zinc and the two vitamins A and D, namely: zinc, vitamin A, vitamin D, zinc plus vitamin A, zinc plus vitamin D, vitamins A and D, and zinc plus vitamins A and D. Plasma zinc levels were determined at baseline, 3 weeks and 6 weeks. Plasma zinc levels increased significantly (p < 0.02) from 11.82 (+/-2.60) to 13.32 (+/-3.04) mum/L only in the group receiving the combination of zinc and vitamins A and D. This novel method of increasing plasma zinc levels by the augmentation of vitamins A and D may have implications for the reduction of burden of disease.