Recommended intake

Vitamin C occurs as L-ascorbic acid and dihydroascorbic acid in fruits, vegetables and potatoes, as well as in processed foods to which it has been added as an antioxidant. The only wholly undisputed function of vitamin C is the prevention of scurvy. Although this is the physiological rationale for the currently recommended intake levels, there is growing evidence that vitamin C may provide additional protective effects against other diseases including cancer, and the recommended dietary allowance (RDA) may be increased in the near future. Scurvy develops in adults whose habitual intake of vitamin C falls below 1 mg/d, and under experimental conditions 10 mg/d is sufficient to prevent or alleviate symptoms (Bartley et al., 1953). The RDA is 60 mg per day in the USA, but plasma levels of ascorbate do not achieve saturation until daily intakes reach around 100 mg (Bates et al., 1979). Most of the ascorbate in human diets is derived from natural sources, and consumers who eat five portions, or about 400-500 g, of fruits and vegetables per day could obtain as much as 200 mg of ascorbate. 

Adequate fluid intake is also important the recommended intake for people who do not require fluid restriction is 6 to 8 eight-ounce glasses of water daily. 

The figure comes from a series of reports issued by the Institute of Medicine over the past decade. The experts who authored these reports revisited the question of recommended daily allowances and other measures of nutrient adequacy, and made recommendations regarding macronutrients (proteins, carbohydrates, fats and oils) and for micronutrients (vitamins and minerals). The Institute has had a long history of developing recommended intake levels, but in the recent... 

The recommended intake of vitamin D is 400 to 800 units daily. Alendronate/cholecalciferol is intended to provide 7 days worth of 400 units daily vitamin D in a single, once-weekly dose. 

Cobalt in small amounts is an essential element associated with vitamin B12, but at high levels can be toxic. There are no daily recommended intake levels for cobalt. Intestinal bacteria use cobalt to produce cobalamin, which in turn is an essential component of vitamin B12. Industrially, cobalt is used in pigments, permanent magnets, and as an alloy to harden metals as in tungsten carbide blades or drills. 

As older men age, Ca intakes that were previously comparable to recommended intakes markedly decline and become inadequate. Qn average, men over the age of 60 have Ca intakes that are 44% lower than what is recommended, and median intakes are even lower. Inadequate data in men and women >70 years of age preclude determination of an AI based on maximal Ca retention for this age group therefore, data are currently extrapolated from 51- to 70-year olds (Standing Committee of the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, and Institute of Medicine, 1997). 

Calcium has earned a reputation as one of the most at-risk nutrients (Foote et ah, 2004) and in 2005 the Dietary Guidelines Advisory Committee classified Ca as a shortfall nutrient because average Ca intake often falls to <60% of the recommended intake in subsets of the population (Kennedy and Meyers, 2005). The pressing need to improve the Ca status of Americans has been highlighted by the Healthy People 2010 Objective, an initiative that endeavors to increase, to at least 75%, the number of US individuals 2 years or older that meet current Ca recommendations (Looker, 2003). The general population requires ongoing education to more fully appreciate the relevance of Ca in relation to current and future health, the imminent risks associated with habitual inadequate intakes, and practical means by which to achieve recommended intakes. 

The main action of vitamin E in human tissue is to prevent oxidation of polyunsaturated fatty acids (PUFA), thereby protecting lipid and phospholipids in membranes. Vitamin E interacts syn-ergically with other nutrients, such as vitamin C, selenium, and zinc, which are also involved in the oxidation pathway. The recommended intake is strongly related to the quantity of PUFA consumption. Some studies [454-456] on animal models and epidemiological trials in human suggest... 

Food and Nutrition Board. (2004). Dietary Referenee Intakes (DRIs) Recommended Intakes for Individuals, Elements. http //www.nap.edu. The National Aeademies Press, Washington, D.C. 

Recommended dietary allowances (RDA) for vitamins are recommended intake of various vitamin to ensure the good health of a high proportion of the human population. The RDA values quoted below refer to the United States population (Whitney and Rolfes, 1996). Reference nutrient intake... 

Reports of specific amino acid toxicides from normal eating patterns are rare. Although all amino acids except alanine have been shown in be toxic, the probability of intoxication is vety remote. Humans seem able to tolerate all amino acids in excess of 10 times the recommended intake. 

Supplement your diet with calcium, if necessary, to obtain the daily recommended intake. 

Although dietary lead intakes in the UK are currently well within recommended intakes, it is the UK Government s policy to ensure that exposure to lead is reduced wherever practicable and, more specifically, to reduce blood lead levels in children to below 10 pg/dl. Food is one of the major sources of lead exposure in the UK the others are air (mainly lead dust originating from petrol) and drinking water. Exposure from all of these sources has been reduced, as demonstrated by the reduction in blood levels over the past 15 years.10 The decrease in dietary exposure reflects the success of the measures taken to reduce lead exposure and contamination of food, such as the use of lead-free petrol, welded food cans, and the banning of tin-coated lead capsules for wine bottles. 

The recommended ratio of phosphorus to calcium is 1 1, except in infants it is 2 1. For older infants, the recommended intake of phosphorus is increased to 80% of the calcium requirement, so that the ratio is similar to cow s milk (Harper 1969). Both phosphorus and calcium are distributed similarly in foods, hence a sufficient intake of calcium ensures a sufficient intake of phosphorus. The exception is cows milk, which contains more phosphorus than calcium (Harper 1969). The adult daily requirement for phosphorus is about 700 mg. A balanced diet provides sufficient amounts of phosphorus because it is commonly found in foods (phosphoproteins and phospholipids, inorganic phosphate), especially milk and milk products, wheat, meats and fish (Latner 1975). In the body, normal serum (inorganic) phosphorus levels are 4-7 mg/100 mL in children and 3-4.5 mg/100 mL in adults and the elderly. In body fluids and tissues, normal serum phosphorus levels found are 40, 170-250, 360, and 22,600 mg/100 mL in blood, muscle, nerve, and both bones and teeth, respectively (Harper 1969 Tietz 1970). 

The intakes are given as the mean and 95th percentile values or, for Se, as the mean and 5th percentile values. The PTWI and the Nordic Nutrition Recommendations (NNR) indicate upper tolerable and target intakes, respectively. For Ni neither recommended intake nor PTWI value exists. 

SINU, Societa Italiana di Nutrixzione Umana, Recommended intake values of energy and nutrients for the Italian population, 1996, http //www.sinu.it/lam.asp. 

Plasma zinc levels are commonly decreased in the elderly (Gil). These authors reported mean ( SD) plasma levels in normal young adults at 12.7 ( 1.4) mmol/liter versus 10.5 ( 4.7) mmol/liter in the elderly intracellular levels (neutrophils) were 1.26 ( 0.28) and 0.95 ( 0.26) nmol/mg protein, respectively. This deficiency is most often due to lack of dietary lean meat, poultry, and fish. As a result, zinc intake is frequently less than the minimum recommended intake of 15 mg/day. Moreover, Zn deficiency is particularly common in individuals with diabetes mellitus, liver and renal diseases, malabsorption, alcohol abuse, and those taking diuretic medications (K13). Interestingly, many of the signs and symptoms of Zn deficiency are the same as those often attributed to the aging process (Table 3). 

The report of a WHO Expert Committee (1) emphasized the need for information on the bioavailability of zinc, since the recommended intake was dependent on this important factor. Although zinc deficiency in humans was initially reported from Iran and Egypt, adverse effects of marginal or low intakes of zinc by infants and children have subsequently been reported from other parts of the world (2). Apparently the zinc intakes in Iran and Egypt were adequate but the bioavailability was adversely affected by the high level of phytate and fibre in the diet (2). The zinc content of the modern diet is decreased by the use of refined... 

Notwithstanding the problems involved in determining requirements for vitamins, most national authorities (as well as the United Nations FAO/WHO and the European Commission) publish, and periodically revise, tables of recommended intakes of nutrients or dietary reference values. 

Table 1 Dietary reference intakes recommended intakes for individuals, Food, and Nutrition Board, The Institute of Medicine, National Academies... 

Levine, M., Rumsey,S., Wang, Y, Park, J., Kwon,0., and Amano, N. (1997). In situ kinetics An approach to recommended intake of vitamin C, Methods Lnzi/moL 281, Part K, 425-437. 

A fatal case of hypervitaminosis A involved a premature neonate who died after having ingested 30 000 micrograms RE/day (90 000 lU/day), that is 60 times the recommended intake of vitamin A, for 11 days. On autopsy the skeleton showed marked alterations of endochondral bone formation. There was also evidence of accelerated resorption of bone, hypercalcemia, and metastatic calcification of the skin, soft tissues, and organs (59). 

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