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close this bookScurvy and its Prevention and Control in Major Emergencies (WHO; 1999; 70 pages)
View the documentAcknowledgements
View the documentScurvy: definition
open this folder and view contentsIntroduction
open this folder and view contentsScurvy
open this folder and view contentsVitamin C
close this folderRecommended Daily Allowance (RDA)
View the documentProblem of calculating RDA for vitamin C
View the documentMinimum or optimum requirements
View the documentFactors affecting vitamin C reserves
View the documentMegadoses
View the documentHypervitaminosis/vitamin C toxicity
View the documentSupplementation frequency
open this folder and view contentsSources of vitamin C
open this folder and view contentsStrategies to prevent scurvy in large refugee populations
View the documentCosts
open this folder and view contentsConclusions and recommendations
View the documentReferences
View the documentAnnex 1
View the documentAnnex 2
View the documentAnnex 3
View the documentBack Cover

Supplementation frequency

RDAs are based on the assumption that people obtain the required nutrients daily. In reality, many people consume at least some nutrients only sporadically. Reliance on vitamin C supplements, e.g. tablets or highly fortified blended cereal-legume foods, may not be justified, especially if they are not consumed regularly. Data obtained from animal studies indicate that the frequency of nutrient supplementation is a factor that should be considered in establishing dietary recommendations (Snook et al., 1983). Human studies show that after single-dose administration, plasma levels return to their normal values in about 12 to 13 hours, no matter how much vitamin C has been consumed. This suggests that in order to maintain equilibrium in serum C levels, the vitamin should be ingested several times a day.

Snook et al. (1983) carried out a study to determine if subjects given a relatively large nutrient supplement (4 times the RDA) every 4 days maintained blood and urinary levels of the nutrient comparable to those of subjects given small doses (1/3 the RDA) with every meal. Results suggest that subjects adjust to receiving supplements of vitamin C on a periodic basis, which is contrary to the observation that serum levels maintain an equilibrium.

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