Studies on the absorption of L-xyloascorbic acid (vitamin C) in young and elderly subjects.

Absorption of ascorbic acid was assessed by measuring its urinary excretion following the administration of a standard dose under pre-determined conditions. The absorption mechanism appeared to be a saturable one and with intakes of up to 1 g over 90 per cent of the subsequent urinary excretion occurred during the first 8 h. Significantly less ascorbic acid was absorbed by elderly persons than by young ones; after a 500 mg dose the mean urinary excretion by nine elderly females (mean age 82.6) was 25 mg and by six young females (mean age 21.8) 245 mg. It is suggested that impaired gastrointestinal absorption is an important factor in the aetiology of low blood concentrations of ascorbic acid in the elderly.