Vitamin in human nutrition

Pure NADP+ was isolated from red blood cells in 1934 by Otto Warburg and W. Christian, who had been studying the oxidation of glucose 6-phosphate by erythrocytes.13 They demonstrated a requirement for a dialyzable coenzyme which they characterized and named triphosphopyridine nucleotide (TPN+, but now officially NADP+ Fig. 15-1). Thus, even before its recognition as an important vitamin in human nutrition, nicotinamide was identified as a component of NADP+. 

Interestingly, vitamin C, or ascorbic acid, is a vitamin in human nutrition, since a necessary enzyme is missing to convert what is called gulonolactone to yield ascorbic acid (Ungar, in Devlin, 1986, p. 719), whereas in animals such as the rat or dog, this enzyme is naturally present, so that ascorbic acid could then be called a hormone.)... 

The importance of vitamin D—the sunshine vitamin—in human nutrition lies in the role of regulating calcium and phosphorus metabolism. Vitamin D promotes intestinal absorption of calcium and phosphorus and influences the process of bone mineralization. In the absence of vitamin D, mineralization of bone matrix is impaired, resulting in rickets in children and osteomalacia in adults. Although rickets is rare in the United States, it is still prevalent in many countries. 

Edgar S. Gordon, "Pantothenic Acid in Human Nutrition," in E. A. Evans, Jr., ed, The Biological Action of the Vitamins, The University of Chicago Press, Chicago, 111., 1942. pp. 136143. 

The requirement for vitamins in humans and other animals is the result of mutations in the enzymes involved in biosynthetic coenzymes. As intermediates of coenzyme biosynthesis are available in suf cient amounts in the diet of heterotrophic animals (see p. 112), the lack of endogenous synthesis did not have unfavorable effects for them. Microorganisms and plants whose nutrition is mainly autotrophic have to produce all of these compounds themselves in order to survive. 

G. F. M. Ball, Water-Soluble Vitamin Assay in Human Nutrition, Chapman Hall, Cornwell, U.K., 1994. 

The combined dehydrogenation and decarboxylation of pyruvate to the acetyl group of acetyl-CoA (Fig. 16-2) requires the sequential action of three different enzymes and five different coenzymes or prosthetic groups—thiamine pyrophosphate (TPP), flavin adenine dinucleotide (FAD), coenzyme A (CoA, sometimes denoted CoA-SH, to emphasize the role of the —SH group), nicotinamide adenine dinucleotide (NAD), and lipoate. Four different vitamins required in human nutrition are vital components of this system thiamine (in TPP), riboflavin (in FAD), niacin (in NAD), and pantothenate (in CoA). We have already described the roles of FAD and NAD as electron carriers (Chapter 13), and we have encountered TPP as the coenzyme of pyruvate decarboxylase (see Fig. 14-13). 

BV Siegel, DM Klurfeld. Vitamin C and the immune response in health and disease. Nutrition and Immunology. In Human Nutrition A Comprehensive Treatise, vol. 8. New York Plenum, 1993, pp 167-196. 

GFM Ball. Water-Soluble Vitamin Assays in Human Nutrition. London Chapman Hall, 1994, pp 142-386. 

Fruit juice is important in human nutrition far beyond its use as a refreshing source of liquid. Many fruits contain a variety of minor ingredients, particulary vitamins and minerals, as well as carbohydrates, which are the predominant solid component. Although fruit contains small amounts of protein and fat, these are not important ingredients of juices. 

Vitamin A, a fat-soluble vitamin, is indicated for severe vitamin A deficiency with xerophthalmia. (See the section Importance of Vitamin A in Human Nutrition. )... 

Although, owing to the wide distribution of vitamin Bg in nature, clinical deficiency symptoms are seldom observed, there is little doubt that pyridoxine is essential in human nutrition. Pyridoxine is absorbed from the gastrointestinal tract and is converted to the active form pyri-doxal phosphate. Absorption is decreased in gastrointestinal diseases and also in subjects taking isoniazid (3). It is excreted in the urine as 4-pyridoxic acid (2). The metabolism of vitamin Bg in human beings has been investigated (56). 

The literature related to the carotenes and xanthophylls is very large because of its importance in human nutrition. However, the scope of the literature devoted to Vitamin A2 is minuscule by comparison. The literature devoted to Vitamin A3 is even smaller. 

Fats occur naturally in food and play a significant role in human nutrition. Fats are used to store energy in the body, insulate body tissues, cushion internal organs, and transport fat-soluble vitamins in the blood. Fats also play in an important role in food preparation They enhance food flavor and food texture, make baked products tender, and conduct heat during cooking. 

D-Pantolactone (Figure 6.3.1) is an important intermediate in the production of d-pantothenic acid, also called vitamin B5. Deficiency of pantothenic acid can result in symptoms such as pathological changes of the skin and mucosa, disorders in the gastrointestinal tract and nervous system, organ changes, and hormonal disorders. Pantothenic acid is used mainly in feed for chicken and pigs and also as a vitamin supply in human nutrition. Its commercial form, the calcium salt, is produced worldwide on a multi-thousand ton scale. 

Vitamins are minor components of foods that play an essential role in human nutrition. Many vitamins are unstable under certain conditions of processing and storage (Table 9-1), and their levels in processed foods, therefore, may be considerably reduced. Synthetic vitamins are used extensively to compensate for these losses and to restore vitamin levels in foods. The vitamins are usually divided into two main groups, the water-soluble and the fat-soluble vitamins. The occurrence of the vitamins in the various food groups is related to their water-or fat-solubility. The relative importance of certain types of foods in supplying some of the important vitamins is shown in Table 9-2. Some vitamins function as part of a coenzyme, without which the enzyme would be ineffective as a biocatalyst. Frequently, such coenzymes are phosphorylated forms of vitamins and play a role in the metabolism of fats, proteins, and carbohydrates. Some vitamins occur in foods as provitamins—compounds that are not vitamins but can be changed by the body into vitamins. Vitamers are members of the same vitamin family. 

Figure 9-14 Relation Between Extraction Rate and Proportion of Total Vitamins of the Grains Retained in Flour. Source Reprinted with permission from W.R. Aykroyd and J. Doughty, Wheat in Human Nutrition, 1970, Food and Agriculture Organization of the United Nations.

Plants represent a very important role in human nutrition, due to the large quantities of proteins, carbon hydrates, lipids, vitamins, antioxidants and mineral salts that its can supply. Sometimes the nutritional aspect can be associated with the flavour and fragrance of the extracts producing a high value products. In recent years one can observe an increase in research for natural sources, in particular from plant matrices, of additives with application in the food, cosmetic and pharmaceutical industries. 

Lecithin is the main dietary source of choline. The U.S. National Academy of Science s (NAS) Food and Nutrition Board recently underscored the importance of lecithin in human nutrition by assigning chohne (the vitamin component of PC) a dietary reference intake (DRI) in 1998 (244). Although it is true that lecithin and choline are present in a variety of foods, the specific amount of lecithin and choline in foods is currently unknown. At this time, no comprehensive analysis of choline in the food supply exists. Such an analysis is, however, underway and it is estimated that the extensive USDA database of foods will be fully analyzed for choline content by 2005. The analysis will include all forms of choline found in food. 

Ball GFM. Pantothenic acid. Water-soluble vitamin assays in human nutrition. New York Chapman and Hall, 1994. 

The concentration of ascorbate in the human plasma is 25 pM and above. Cells take up ascorbate by a Na -coupled uptake mechanism against a concentration gradient. A marked stereo-selectivity for L-ascorbic acid relative to D-isoascorbic acid in their cellular transport has been shown by Franceschi et al. [12]. The same transport is also important in the intestine. The nutritional supply of ascorbic acid is the only source for this vitamin in humans, primates, and guinea pigs. Other mammals are able to produce ascorbic acid. There exists sufficient evidence for an active role of ascorbate as an antioxidant in vivo. Decreased ascorbic acid will increase lipid peroxidation and decrease vitamin E and is connected with oxidative DNA damage. The supply of ascorbate in some cases will reduce the amount of oxidative damage in diseases that... 

D-(+)-Biotin (1), a biocatalyst of reversible metabolic reactions of carbon dioxide transport in organisms, is one of the water-solnble B-complex gronp of vitamins and has immense commercial importance in ponltry feeds and animal nntrition. Componnd 1 was isolated from egg yolk, liver and milk concentrates. " It is an important vitamin for human nutrition and animal health. " Its structure was determined and confirmed by the first total synthesis. Its absolute configuration by X-ray crystallographic analysis was established. Syntheses of biotin from noncarbohydrate and its analogues from carbohydrate and noncarbohydrate have been reported. " Syntheses from carbohydrate precursors are discussed in this part. 

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