Thiamin has a pyrimidine ring and a thiazole ring joined by a methylene bridge. It dissolves readily in water, and is rapidly destroyed by heat in neutral or alkaline solution. Thiamin is absorbed from the upper part of the small intestine, maximal absorption from a single dose being about 5 mg. Bacteria in the lower gut can synthesize thiamin but this not available for absorption.
Sources
To produce 4.184 MJ of energy from food, 0.4 mg thiamin have to be provided. Therefore, if a food is being a source of thiamin, it must provide more of the vitamin than is required for obtaining the energy it is supplying. Thiamine is found in a wide variety of foods at low concentrations. Yeast and pork meat are the most highly concentrated sources of thiamine. Cereal grains, however, are the most important dietary sources of thiamine in the diet as these foods are consumed readily in most diets. Of the cereal grains, whole grains contain more thiamine than refined grains, as thiamine is found mostly in the outer layers of the grain and in the germ.
Requirement of thiamin
The requirement for thiamin is expressed per 4.184 MJ (1000kcal) ingested. Tissues become saturated when the intake is about 0.35 mg per 4.184 MJ and excess is excreted in urine.
Sources
To produce 4.184 MJ of energy from food, 0.4 mg thiamin have to be provided. Therefore, if a food is being a source of thiamin, it must provide more of the vitamin than is required for obtaining the energy it is supplying. Thiamine is found in a wide variety of foods at low concentrations. Yeast and pork meat are the most highly concentrated sources of thiamine. Cereal grains, however, are the most important dietary sources of thiamine in the diet as these foods are consumed readily in most diets. Of the cereal grains, whole grains contain more thiamine than refined grains, as thiamine is found mostly in the outer layers of the grain and in the germ.
Requirement of thiamin
The requirement for thiamin is expressed per 4.184 MJ (1000kcal) ingested. Tissues become saturated when the intake is about 0.35 mg per 4.184 MJ and excess is excreted in urine.
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