Thiamin Requirements and Reference Intakes

It is apparent from the central role of thiamin in carhohydrate metaholism that the requirement will depend on carhohydrate intake to a considerable extent. In practice, requirements are calculated on the basis of total energy intake, assuming that the average diet provides 40% of energy from fat. For diets that are lower in fat, and hence higher in carbohydrate and protein, thiamin requirements will be somewhat higher. 

On the basis of depletion/repletion studies, an intake ofO.2 mgper 1,000kcal is required to maintain normal urinary excretion, but an intake of 0.3 mg per 1,000 kcal is required for a normal transketolase activation coefficient. At low levels of energy intake, there will be a requirement for metabolism of endogenous substrates and to maintain nervous system thiamin triphosphate. 

Reference intakes (see Table 6.2) are based on 0.5 mgper 1,000 kcal (0.12 mg per MJ) for adults consuming more than 2,000 kcal per day, with the proviso that even in fasting there is a requirement for 0.8 mg of thiamin per day to permit the metabolism of endogenous energy-yielding substrates. 

On the basis of depletion/ repletion studies, an intcike of 0.2 mg per 1,000 kcal is required to mainttdn normal urinary excretion, but cm intake of 0.3 mg per 

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Because thiamin has a central role in energy-yielding, and especially carbohydrate, metabolism, requirements depend mainly on carbohydrate intake, and have been related to non-fat energy. In practice, requirements and reference intakes are calculated... 

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