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Megadose Effects of Vitamin C on Vitamin B-12 Status in the Rat¹

Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108

Effects of ascorbic acid ingestion on the severity of vitamin B-12 deficiency were investigated by feeding weanling rats experimental diets containing 0–100 µg of vitamin B-12 activity per kg of diet, with or without 6.0 mg of ascorbic acid per ml supplied in drinking water for 15 wk. This daily consumption of up to 150 mg of ascorbic acid did not impair growth, but did result in significantly higher concentrations of ascorbic acid in plasma, liver, adrenal glands and feces. When rats were fed diets deficient or marginally deficient in vitamin B-12, liver concentrations of vitamin B-12 were markedly lower than in liver of rats fed adequate vitamin B-12. Ascorbic acid ingestion raised values significantly in the vitamin B-12-deficient diet group. Urinary methylmalonic acid was significantly elevated in the deficient rats. However, it was significantly reduced to more normal values by ascorbic acid in rats with both low and marginal vitamin B-12 status, as defined by dietary and liver concentrations of vitamin B-12 activity. Although coprophagy was not prevented, rats showed no increased consumption of feces with the higher ascorbic acid content. Thus, the results of this research indicate that vitamin C ingestion partially protects rats from vitamin B-12 deficiency.

KEY WORDS: • ascorbic acid • cobalamins • corrinoids • methylmalonic acid • vitamin B-12 analogues • vitamin C

¹ Published as paper No. 16,644 of the contribution series of the Minnesota Agricultural Experiment Station based on research of Project 18-067 and also supported in part by the Research Service, U.S. Veterans Administration and by National Institutes of Health Grants AM 19041 and AM 20526.

Manuscript received 4 January 1989. Revision accepted 12 April 1989.