Vitamin nutritional requirement

Nutritional Requirements. The nutrient requirements of mammalian cells are many, varied, and complex. In addition to typical metaboHc requirements such as sugars, amino acids (qv), vitamins (qv), and minerals, cells also need growth factors and other proteins. Some of the proteins are not consumed, but play a catalytic role in the cell growth process. Historically, fetal calf semm of 1—20 vol % of the medium has been used as a rich source of all these complex protein requirements. However, the composition of semm varies from lot to lot, introducing significant variabiUty in manufacture of products from the mammalian cells. 

The nutritional requirement for vitamin Bjg is low. Adult humans require only about 3 micrograms per day, an amount easily acquired with normal eating habits. However, because plants do not synthesize vitamin Bjg, pernicious anemia symptoms are sometimes observed in strict vegetarians. 

The mean dietary intake of soy isoflavones in Asian populations consuming soy-based diets ranges from 20-40 mg isoflavones/day, with upper percentile consumer intakes of 70 mg/day (corresponding to around 1 mg/kg body weight). In the six month intervention studies in Western postmenopausal women, the effective dose for improved BMD was around 80-90 mg/day, while in the one year, randomized, double-blind, placebo controlled clinical trial, the effective dose was 54 mg/day. Overall, the dietary recommendation is to consume 50 mg isoflavones/day in combination with standard nutritional requirements for calcium and vitamin D. 

A complete synthetic media for the growth of Tetrahymena pyriformis E., a protozoan whose nutritional requirements closely simulate those of mammals, was irradiated at Michigan (B16). When the medium failed to support the growth of Tetrahymena, the essential vitamins and amino acids were individually irradiated in solution. All vitamins were altered structurally by less than sterilization doses. The amino acids proved stable under the same conditions. 

The animals basic nutritional requirements must be met, with regard to the levels of minerals and vitamins, to ensure their health and welfare. In some countries, supplementation with vitamins, trace elements and minerals is not a routine practice, whether certified organic or not. Another aspect of the interaction between animal health and nutrition regarding worm control is feeding with bioactive forages, which, for example Hoste et al. (2004) and Thamsborg et al (2005) describe, based on an EU-funded project WORMCOPS. 

To some extent the vitamin E requirement may be lessened by the presence in the diet of synthetic antioxidants and by selenium. Much evidence supports a relationship between the nutritional need for selenium and that for vitamin E. Lack of either causes muscular dystrophy in many animals as well as severe edema (exudative diathesis) in chicks. Since vitamin E-deficient rats have a low selenide (Se2 ) content, it has been suggested that vitamin E protects reduced selenium from oxidation.) Vitamin C (ascorbic acid), in turn, protects vitamin E. 

Although all heterotrophs depend on preformed organic compounds, they differ markedly in the numbers and types of compounds they require. Some species can make all required compounds when supplied with a single carbon source others have lost some or many biosynthetic capabilities. Mammals must obtain about half of their amino acids from external sources. They also are unable to make several metabolic cofactors, as evidenced by their well-known nutritional requirements for vitamins. Some bacteria and some parasites have even more extensive nutritional requirements than mammals. 

Phase II Reactions. As with phase I reactions, phase II reactions usually depend on several enzymes with different cofactors and different prosthetic groups and, frequently, different endogenous cosubstrates. All of these many components can depend on nutritional requirements, including vitamins, minerals, amino acids, and others. Mercapturic acid formation can be cited to illustrate the principles involved. The formation of mercapturic acids starts with the formation of glutathione conjugates, reactions catalyzed by the glutathione -transferases. 

To evaluate nutrition requirements, the reader needs a basic understanding of nutrients and the parameters that affect their needs. Nutrients are chemical substances needed to maintain life which are supplied to the body in food or drinks. The nutrients include vitamins, minerals, carbohydrates, fats, proteins, and water. These classifications of nutrients encompass approximately 45 different chemicals that are involved in every function or structure of the body. Wiile some of these functions that are directly influenced by exercise will be discussed in the subsequent chapters, a complete listing of these functions is beyond the scope of this book. For a more thorouc(i review of nutrient functions, the reader is referred to any one of a number of excellent nutrition references (5-6,15-16). 

The same criteria used to define requirements can also be used to assess vitamin nutritional status. 

The U.S./Canadian tolerable upper level is set at 1,000 mg per day, based on reports of prolonged prothrombin time in people receiving anticoagulants and consuming 1,100 to 2,100 mg of vitamin E per day. It is noteworthy that although the report specifically excluded the 2S isomers of synthetic a-tocopherol from calculations of nutritional requirements, this tolerable upper level includes all forms of the vitamin, regardless of their tissue retention and biological activity (Institute of Medicine, 2000). 

Early studies of vitamin Be requirements used the development of abnormalities of tryptophan or methionine metabolism during depletion, and normalization during repletion with graded intakes of the vitamin. Although tryptophan and methionine load tests are unreliable as indices of vitamin Be status in epidemiological studies (Section 9.5.4 and Section 9.5.5), under the controlled conditions of depletion/repletion studies they do give a useful indication of the state of vitamin Be nutrition. More recent studies have used more sensitive indices of status, including the plasma concentration of pyridoxal phosphate, urinary excretion of 4-pyridoxic acid, and erythrocyte transaminase activation coefficient. 

Bender DA (1989) Vitamin Be requirements and recommendations. European Journal of Nutrition 43, 289-309. 

Levine M, Dhariwal KR, Welch RW, Wang Y, and Park JB (1995) Determination of optimal vitamin C requirements in humans. American Journal of Clinical Nutrition 62,1347S-56S. 

Estimation of the vitamin Be requirements of infants presents a problem, and there is a clear need for further research. Eiuman milk, which must be assumed to be adequate for infemt nutrition, provides only 2.5 to 3.5 /rg of vitamin Be per g of protein- lower them the requirement for adults. Although their requirement for catabolism of amino acids may be lower than in adults (because they have net new protein synthesis), they must also increase their body content of the viteimin as they grow. Coburn (1994) noted that tbe requirement for growth in a number of animal species was less tban tbat to maintain saturation of transaminases or minimum excretion of tryptophan metabolites after a test dose and was about 15 nmol per g of body weight gain across a range of species. 

Pietrzik K, Hesse CH, Zui Wiesch ES, and Hotzel D (1975) Urinary excretion of pantothenic acid as a measurement of nutritional requirements. International Journal of Vitamin and Nutrition Research 45,153-62. 

Valk EE and Hornstra G (2000) Relationship between vitamin E requirement and polyunsaturated fatty acid intake in man a review. International Journal of Vitamin and Nutrition Research 70, 31-42. 

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