DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. Intake recommendations for thiamin and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies (formerly National Academy of Sciences). For adults, excretion of less than 100 mcg/day thiamin in urine suggests insufficient thiamin intake, and less than 40 mcg/day indicates an extremely low intake. Another commonly used measure of thiamin status is urinary thiamin excretion, which provides data on dietary intakes but not tissue stores. The result is typically 0%–15% in healthy people, 15%–25% in those with marginal deficiency, and higher than 25% in people with deficiency. The result, known as the "TDP effect," reflects the extent of unsaturation of transketolase with TDP. Thiamin status is often measured indirectly by assaying the activity of the transketolase enzyme, which depends on TDP, in erythrocyte hemolysates in the presence and absence of added TDP. Levels of thiamin in the blood are not reliable indicators of thiamin status. TDP serves as an essential cofactor for five enzymes involved in glucose, amino acid, and lipid metabolism.
#Give thiamine before glucose free#
Bacteria in the large intestine also synthesize free thiamin and TDP, but their contribution, if any, to thiamin nutrition is currently unknown. The vitamin has a short half-life, so people require a continuous supply of it from the diet.Ībout 80% of the approximately 25–30 mg of thiamin in the adult human body is in the form of thiamin diphosphate (TDP also known as thiamin pyrophosphate), the main metabolically active form of thiamin. Humans store thiamin primarily in the liver, but in very small amounts. The remaining dietary thiamin is in free (absorbable) form. Most dietary thiamin is in phosphorylated forms, and intestinal phosphatases hydrolyze them to free thiamin before the vitamin is absorbed. Ingested thiamin from food and dietary supplements is absorbed by the small intestine through active transport at nutritional doses and by passive diffusion at pharmacologic doses. This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells. Thiamin is naturally present in some foods, added to some food products, and available as a dietary supplement.
Thiamin (or thiamine) is one of the water-soluble B vitamins.
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