In general, high intakes of vitamin C are considered to be of low toxicity. Chronic toxicity studies generally indicate that ascorbic acid is well tolerated in animals. Oral ascorbic acid may be administered to most laboratory animals at doses of several grams per kilogram of body weight without appearance of any obvious general effect on health (NRC, 1987). Male guinea pigs fed 8.7% ascorbic acid for 6 weeks had decreased bone density and decreased urinary hydroxyproline compared to controls (Bray and Briggs, 1984). Helgebostad (1984) reports that high doses of 100 to 200 mg per kg (45.5 to 91 mg per lb) body weight daily were harmful to mink, with pronounced anemia in pregnant females and reduced number and size of kits.
Data are unavailable on tolerance and toxicity of ascorbic acid for dogs and particularly for cats. Intakes of 0.5 and 0.3 g ascorbic acid per day in cats and dogs, respectively, do not appear to affect these animals adversely in short-term studies (Belfield, 1967; Leveque, 1969; Vaananen and Wekman, 1979). In studies conducted on dogs, Leveque (1969) reported allergic types of reaction in the mouth. These signs disappeared when the level of ascorbic acid intake by the dogs was reduced. However, this observation was incidental, and the study was not controlled.