Nutrient requirements Vitamins

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. 

Vitamins are a group of organic nutrients required in small quantities for a variety of biochemical functions and which, generally, cannot be synthesized by the body and must therefore be supphed in the diet. 

Deficiencies in nutrients such as folic acid and vitamin B12 may hinder this process of erythrocyte maturation.4,5 Folic acid and vitamin B12 are important nutrients required for the formation of DNA. In a setting where these nutrients are decreased, DNA synthesis is inhibited, and consequently, erythrocyte maturation also is inhibited.4,5 Poor diet can be a contributor to the deficiencies in these... 

Hematopoiesis, the production from undifferentiated stem cells of circulating erythrocytes, platelets, and leukocytes, is a remarkable process that produces over 200 billion new blood cells per day in the normal person and even greater numbers of cells in people with conditions that cause loss or destruction of blood cells. The hematopoietic machinery resides primarily in the bone marrow in adults and requires a constant supply of three essential nutrients—iron, vitamin B12,... 

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 lipids of the diet include TGs, phospholipids, cholesteryl esters, cholesterol, and the fat-scivble vitamins. These nutrients require special types of biochemical machinery to facilitate their assimilation and distributicrt within the body. The biochemical apparatus used includes bile salts, apolipoprotcins, serum albumin, and vitamin-binding proteins. Apolipopnoteins are the primary subject of this section. The term apolipoprotain is used when referrmg only to the protein, whereas the term lipoprotein refers to the complex of apolipoprotein and lipid. 

Greene HL, Hambidge KM, Schanler R, Tsang RC. Guidelines for the use of vitamins, trace elements, calcium, magnesium, and phosphorus in infants and children receiving total parenteral nutrition report of the Subcommittee on Pediatric Parenteral Nutrient Requirements from the Committee on Clinical Practice Issues of the American Society for Chnical Nutrition. Am J Clin Nutr 1988 48 1324-42. 

Individuals performing more strenuous activities requiring additional intake of calories also will require more nutrients including vitamins. 

Other Nutrients - Minerals, vitamins, and trace minerals are also required in most fermentations. 

COENZYMES Most coenzymes are derived from vitamins. Vitamins (organic nutrients required in small amounts in the human diet) are divided into two classes water-soluble and lipid-soluble. In addition there are certain vitamin-like nutrients (e.g., lipoic acid, carnitine, and p-aminobenzoic acid) that can be... 

Scurvy is now a preventable disease. In the recent past, it became possible to achieve such a practical result best by studying the principles of the problem. The nutritional science of the early twentieth century provided this basis in principle, and the nutritional problem is now essentially solved. An essential nutrient called vitamin C is ascorbic acid. We have amassed a wealth of information about its chemistry, occurrence, the requirements for it, and the deficiency state produced by its lack. 

An example of the difference between the AI and the EAR is provided by riboflavin. Very few data exist on the nutrient requirements of very young infants. However, human milk is the sole recommended food for the first 4 to 6 months, so the AI of the vitamin riboflavin for this life stage group is based on the amount in breast milk consumed by healthy full-term infants. Conversely, the riboflavin EAR for adults is based on a number of studies in humans relating dietary intake of riboflavin to biochemical markers of riboflavin status and development of clinical deficiency symptoms. 

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