Vitamins adequate intake

G.2 Recommended Dietary Allowances and Adequate Intakes, Vitamins (Reprinted with permission... 

If the concepts and facts presented in this paper are correct, a major kind of human cancer in many regions of the world, cancer of the stomach, is due to a type of nitroso compound, a nitrosoureido derivative, even though not a nitrosamine It is quite certain that the formation of such compounds can be blocked by vitamin C and vitamin E, as well as by some other substances such as gallates Thus, the primary prevention of cancer caused by nitroso compounds is readily accomplished through an adequate Intake of such harmless inhibitors with every meal from infancy onwards ... 

Polymeric formulas typically have low osmolality of 300 to 500 mOsm/kg. These formulas also usually supply essential vitamins and minerals in amounts similar to the Adequate Intakes or Recommended Dietary Allowances for these nutrients when the formula is delivered in amounts adequate to meet the macronutrient requirements of most patients. Many polymeric formulas are inexpensive relative to oligomeric formulas. Most polymeric formulas are lactose-free and gluten-free, as are most modern tube feeding products. Products designed to be used as oral supplements generally are polymeric and often have sucrose or other simple sugars added to improve taste. 

All individuals should have a balanced diet with adequate intake of calcium and vitamin D (Table 3-1). Table 3-2 lists dietary sources of calcium and vitamin D. If adequate dietary intake cannot be achieved, calcium supplements are necessary. 

Group and Ages Institute of Medicine Adequate Intake Elemental Calami (mgf Vitamin D (mibf ... 

Most experts believe the recommended adequate intakes for vitamin D are too low. 

Vitamins occur naturally in many foods and raw materials. However the natural contents are often supplemented in many food products to ensure an adequate intake, for example in infant formulae, breakfast cereals and clinical nutrition products. Vitamins are usually added as nutrients and thus not covered in this chapter but may also be added as food colours (riboflavin, carotenes). The reader should refer to the following references for recent developments in... 

We cannot live without the essential nutrients. The absence of vitamins and minerals from our diet threatens survival. Thus, the health risk of nutritional inadequacy (which takes many forms, depending upon the nutrient) is large at zero intake, and then decreases as intake increases risks are minimal when nutritionally adequate intakes are achieved (there are several measures of adequacy, not described here). 

Furthermore, the two pathways that normally degrade homocysteine are absent from the neurone and glial cells and so homocysteine can accumulate in the brain (Chapter 8, Appendix 8.2). Consequently, the maintenance of adequate intake of folic acid and vitamin over many years, to ensure low levels of homocysteine, may help to protect neurones and reduce the risk of development Alzheimer s disease. 

Nutrition Patients should maintain adequate nutrition, particularly an adequate intake of calcium and vitamin D. 

Reference Intakes (DRIs). In the past, the recommended dietary allowances (RDAs), which are the levels of intake of essential nutrients that are considered to be adequate to meet the known nutritional needs of practically all healthy persons, were the primary reference value for vitamins and other nutrients. The DRIs also include other reference values, such as the estimated average requirement (EAR) and the adequate intake (AI). The RDA, EAR, and AI reference standards define nutritional intake adequacy. Since these recommendations are given for healthy populations in general and not for individuals, special problems, such as premature birth, inherited metabolic disorders, infections, chronic disease, and use of medications, are not covered by the requirements. Separate RDAs have been developed for pregnant and lactating women. Vitamin supplementation may be required by patients with special conditions and for those who do not consume an appropriate diet. 

A varied diet containing a wide range of foodstuffs provides adequate intake of vitamins for most people, and supplementing these amounts will have no beneficial effect and may result in the toxicity associated with hypervitaminosis. The DRI also includes the tolerable... 

Pantothenate deficiency is rare, occurring only in cases of severe malnutrition characteristic symptoms include vomiting, intestinal distress, insomnia, fatigue and occasional diarrhoea. Pantothenate is widespread in foods meat, fish, poulty, whole-grain cereals and legumes are particularly good sources. Although no RDA or RNI value has been established for panthothenate, safe and adequate intake of this vitamin for adults is estimated to be 3-7 mg day-1. Pantothenate is non-toxic at doses up to 10 g day-1. 

Special Precautions Patients should maintain adequate intake of calcium and vitamin D Patients with enterocolitis may experience diarrhea Etidronate is not metabolized and is excreted intact via the kidney Pregnancy Category C ... 

Because the potential benefits outweigh the possibilities of harm, many experts recommend a daily multivitamin that does not exceed the RDA of it component vitamins. Multivitamins ensure an adequate intake for those vitamins—folic acid, vitamin B6, vitamin B12, and vitamin D—that are most likely to be deficient. However, the the evidence is insufficient to recommend for or against the use of supplements of vitamins A, C, or E multivitamins with folic acid or antioxidant combinations for the pre vention of cancer or cardiovascular disease. Most experts recommend against the use of p-carotene supplements, either alone or in combina Don, for the prevention of cancer or cardiovascular disease. 

When present in excess methionine is toxic and must be removed. Transamination to the corresponding 2-oxoacid (Fig. 24-16, step c) occurs in both animals and plants. Oxidative decarboxylation of this oxoacid initiates a major catabolic pathway,305 which probably involves (3 oxidation of the resulting acyl-CoA. In bacteria another catabolic reaction of methionine is y-elimination of methanethiol and deamination to 2-oxobutyrate (reaction d, Fig. 24-16 Fig. 14-7).306 Conversion to homocysteine, via the transmethylation pathway, is also a major catabolic route which is especially important because of the toxicity of excess homocysteine. A hereditary deficiency of cystathionine (3-synthase is associated with greatly elevated homocysteine concentrations in blood and urine and often disastrous early cardiovascular disease.299,307 309b About 5-7% of the general population has an increased level of homocysteine and is also at increased risk of artery disease. An adequate intake of vitamin B6 and especially of folic acid, which is needed for recycling of homocysteine to methionine, is helpful. However, if methionine is in excess it must be removed via the previously discussed transsulfuration pathway (Fig. 24-16, steps h and z ).310 The products are cysteine and 2-oxobutyrate. The latter can be oxidatively decarboxylated to propionyl-CoA and further metabolized, or it can be converted into leucine (Fig. 24-17) and cysteine may be converted to glutathione.2993... 

Table 38-2 summarizes the key aspects of vitamins needed throughout the body. Most of these vitamins cannot be synthesized within the body and must be ingested from an outside source.76 Eating certain foods on a regular basis will provide the body with an adequate supply of the specific vitamins it needs. Fruits and vegetables, for example, often serve as a source of dietary vitamins. Alternatively, there are myriad vitamin supplements that consumers can purchase and self-administer to insure adequate daily vitamin intake. 

Recommended daily requirement [RDA) or adequate intake CAQ for men and nonpregnant women over 20 years old. Recommended values for certain vitamins Ce.g., folic acid) may be higher in women who are pregnant. Values for children are typically lower, and are adjusted according to the child s age. 

Clinicians should therefore advise patients about the need for adequate dietary vitamin intake, but should also caution patients about the indiscriminate or excessive use of vitamin supplements. Patients with... 

During pregnancy and lactation, it is advisable to increase the maternal intake of vitamin A by about 25%. As the typical North American diet readily provides adequate intake of the vitamin, supplementation is not routinely indicated. 

How can pancreatic insufficiency contribute to the development of vitamin B12 deficiency despite the presence of adequate intake of vitamin B12 and normal secretion of intrinsic factor ... 

Table 30-2. Adequate Intakes of Calcium and Vitamin D at Different Ages ...

In the absence of inadequate endogenous synthesis, vitamin D must be obtained from dietary sources or from supplements. Few foods contain vitamin D except for the flesh of fatty fish (salmon, mackerel, sardines), fish liver oils, and eggs from hens fed feed enriched with vitamin D. In the United States, all commercially produced milk is fortified with vitamin D2 at a level of 400 IU/L (1 IU = 0.025 fig of vitamin D3). Therefore, in the United States (and other economically advanced countries) most dietary vitamin D is obtained from milk and other vitamin D2-fortified foods. Both vitamin D2 and vitamin D3 are converted at the same rate to 25-hydroxyvitamin D by a hydroxylase in the liver and are equally active as a prohormone. Because dietary uptake of vitamin D is dependent on normal fat absorption, conditions in which fat malabsorption is present can result in vitamin D deficiency. Because breast milk contains little vitamin D, vitamin D deficiency can occur in infants who are solely breastfed, are not exposed to adequate sunlight, and are not receiving vitamin D supplements. The adequate intake of vitamin D for children is 5 pg/day (200 IU/day) (Table 30-2). 

There is no recommended dietary allowance for this vitamin because of insufficient evidence to base one on. It is estimated that adult dietary intake in the United States ranges from 5 to 20 mg/day, and 5 to 10 mg/ day probably represents an adequate intake. 

The polypeptide parathormone is released from the parathyroid glands when the plasma Ca2+ level falls. It stimulates osteoclasts to increase bone resorption in the kidneys it promotes calcium reabsorption, while phosphate excretion is enhanced. As blood phosphate concentration diminishes, the tendency of Ca2+ to precipitate as bone mineral decreases. By stimulating the formation of vitamin D hormone, parathormone has an indirect effect on the enteral uptake of Ca2+ and phosphate. In parathormone deficiency, vitamin D can be used as a substitute that, unlike parathormone, is effective orally. Teriparatide is a recombinant shortened parathormone derivative containing the portion required for binding to the receptor. It can be used in the therapy of postmenopausal osteoporosis and promotes bone formation. While this effect seems paradoxical in comparison with hyperparathyroidism, it obviously arises from the special mode of administration the once daily s.c. injection generates a quasi-pulsatile stimulation. Additionally, adequate intake of calcium and vitamin D must be ensured. 

Figures for infants under 12 months are Adequate Intakes, based on the observed mean intake of infants fed principally on breast milk for nutrients other than vitamin K, figures are RDA, based on estimated average requirement +2 SD figures for vitamin K are Adequate Intakes, based on observed ...

Having decided an appropriate criterion of adequacy, which will differ from one vitamin to another, the problem is to determine what are adequate intakes to meet those criteria. Studies of vitamin requirements can be divided into the following four groups. 

Adequate Intake For some vitamins, notably biotin (Section 11.5) and pantothenic acid (Section 12.6), dietary deficiency is more-or-less unknown, and there are no data from which to estimate average requirements or derive reference intakes. In such cases, the observed range of intakes is obviously more than adequate to meet requirements, and the average intake is used to calculate an adequate intake figure. 

Dietary vitamin D makes little contribution to status, and the major factor is exposure to sunlight, a conclusion that is supported by the two-fold seasonal variation in plasma calcidiol in temperate regions (see Table 3.2). There are no reference intakes for young adults in the United Kingdom and Europe for house-bound elderly people, the reference intake is 10 /rg per day, based on the intake required to maintain a plasma concentration of calcidiol of 20 nmol per L (see Table 3.5). This will almost certainly require supplements of the vitamin, because average intakes are less than half this amount. The U.S./Canadian adequate intake is 5 /xg per day up to age 50, increasing to 10 /xg between 51 to 70, and 15 /xg over 70 years of age (Institute of Medicine, 1997). 

Deficiency of vitamins Bg, B12, or folate are aU associated with elevated plasma homocysteine, with vitamin Bg deficiency as a result of impaired activity of cystathionine synthetase (Section 9.5.5) and folate and vitamin B12 as a result of impaired activity of methionine synthetase (Section 10.3.4). In subjects with apparently adequate intakes of vitamins Bg and B12, supplements of these two vitamins have little or no effect on fasting plasma homocysteine, although additional vitamin Bg reduces the plasma concentration of homocysteine after a test dose of methionine. By contrast, supplements of... 

Although the minimum requirement for vitamin C is firmly established, there are considerable discrepancies between the reference intakes published by different national and international authorities (see Table 13.3), with figures ranging between 30 to 90 mg per day. This is the result of the use of different criteria of adequacy and reflects differences of opinion as to what represents an adequate intake of vitamin C. It is possible to produce arguments to support reference intakes of between 30 to 100 mg per day. 

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