Recommended Dietary Allowances 10th Edition (1989) / Chapter Skim
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Trace Elements
Trace Elements
Pages 195-246
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From page 195... ...
. When the dietary supply of absorbable iron is sufficient, the intestinal mucosa regulates iron absorption in a manner that tends to keep body iron content constant.
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From page 196... ...
In the third stage, iron deficiency anemia, total blood hemoglobin levels are reduced below normal values for age and sex of the subject. Severe iron deficiency anemia is characterized by small red blood cells (microcytosis)
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From page 197... ...
The frequency of iron depletion as determined by measurement of serum ferritin, and of iron-deficient erythropoiesis as determined by transferrin saturation and protoporphyrin, is substantially greater than the frequency of iron deficiency anemia in the population surveyed in NHANES II (Bothwell et al., 1979; Dallman et al., 1984; Meyers et al., 1983~. Dietary Sources Iron is widely distributed in the U.S.
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From page 198... ...
(1978) have suggested a method for planning and evaluating iron intakes that takes account of the enhancement of nonheme iron absorption by ascorbic acid and the presence of meat in the diet.
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From page 199... ...
The subcommittee concluded that a dietary intake that achieves a target level of 300 mg of iron stores meets the nutritional needs of all healthy people. This level would be sufficient to provide the iron needs of an individual for several months, even when on a diet nearly devoid of iron.
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From page 200... ...
.1 1~' suggest that iron ln the diets typical of most populations of industrialized countries is relatively highly available, iron absorption ranging from 10 to 15%. Thus, at an intake of 15 mg/day, approximately 1.5 to 2.2 mg of absorbed iron could be available to replace iron losses in adult women.
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From page 201... ...
, the normal term infant can maintain satisfactory hemoglobin levels from human milk without other iron sources during the first 3 months of life. From birth to age 3 years, infants not breastfed should have an iron intake of approximately 1 mg/kg per day.
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From page 202... ...
may require higher amounts of food iron or a reliable source of ascorbic acid. Excessive Intakes and Toxicity in people without genetic defects that increase iron absorption, there are no reports of iron toxicity from foods other than long-term ingestion of home brews made in iron vessels (Walker and Arvidsson, 1953~.
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Application of the two-pool extrinsic tag method to measure heme and nonheme iron absorption from the whole diet.
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1976. Food iron absorption in human subjects.
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Report of the Subcommittee on Criteria for Dietary Evaluation, Coordinating Committee on Evaluation of Food Consumption Surveys, Food and Nutrition Board, Commission on Life Sciences. National Academy Press, Washington, D.C.
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From page 206... ...
Obligatory losses in young men fed a low-zinc diet of 0.3 mg/day were reduced to 0.67 mg/day and resulted in only a small negative balance. Because of such efficient regulation, a person's zinc requirement, whether determined by balance studies or by factorial calculations of endogenous losses, depends predominantly on that person's zinc status or body pool of mobilizable zinc.
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From page 207... ...
observed that increasing dietary intake of phosphorus greatly increased zinc requirements of humans in balance studies. Others have observed that the ingestion of additional phosphorus, as polyphosphates but not generally as orthophosphates, tended to depress zinc absorption slightly (Greger, 1988 J
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From page 208... ...
Such conditions are usually treated with massive zinc supplements; therefore, these therapeutic trials provide no quantitative information on which to base the zinc requirement to maintain optimal health. To estimate zinc requirements, the subcommittee assumed that the zinc status of healthy young adult men and women consuming mixed U.S.
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From page 209... ...
The increased zinc requirement of lactating women can be calculated from the amount of zinc lost each day in the different phases of lactation. The mean zinc content of human milk in the United States is approximately 1.5 and 1.0 mg/liter during the first and
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From page 210... ...
Average milk productions of 750 ml/day and 600 ml/day during the first and second 6 month periods, respectively, uses an extra 1.2 and 0.6 mg of absorbed zinc. Assuming an absorption efficiency of 20% and a coefficient of variation of 12.5% in milk production, the subcommittee recommends extra dietary intakes of 7 and 4 mg/day for the first and second 6 months of lactation.
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1981. Availability of zinc: loading tests with human milk, cow's milk, and infant formulas.
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From page 212... ...
Trace Elements in Human and Animal Nutrition, Vol.
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1983. Effect of dietary zinc sources and pregnancy on zinc utilization in adult women fed controlled diets.
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From page 214... ...
Dietary Sources and Usual Intakes The environmental levels of iodine and their contribution to the daily intake of animals and humans vary widely in the United States. In the coastal areas, seafoods, water, and iodine-containing mist from the ocean are important sources, whereas further inland, the iodine content of plant and animal products is variable, depending on the geochemical environment and on fertilizing, feeding practices, and food processing.
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From page 215... ...
It is customary to relate urinary iodine excretion, a reliable indicator of iodine intake and status, to the risk for goiter and other iodine deficiency disorders. An expert group of the Pan American Health Organization considered an excretion of more than 50 log of iodine per gram of creatinine as adequate for normal function, excretion of 25 to 50 ~g/g as associated with increased risk for hypothyroidism, and excretion of less than 25 Gag as indicative of serious risk for endemic cretinism (Querido et al., 1974~.
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From page 216... ...
Trace Elements in Human and Animal Nutrition, 5th ed. Academic Press, New York.
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From page 217... ...
Although the role of selenium in hydroperoxide destruction helps explain its close metabolic interrelationship with the antioxidant vitamin E, evidence for other possible functions is accumulating (Burk, 1983~. Direct evidence of a requirement for selenium in human nutrition was lacking until 1979, when Chinese scientists reported an association between low selenium status and Keshan disease, a cardiomyopathy that affects primarily young children and women of childbearing age (Keshan Disease Research Group, 1979a)
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From page 218... ...
Drinking water usually makes only a small contribution to selenium intake (WHO, 1987~. Studies in animals have shown that the bioavailability of selenium in certain fish is less than that in other foods (Mutanen, 19861.
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From page 219... ...
Therefore, the balance technique is of little help in delineating the selenium requirements of humans (Levander, 1987~. Another approach to estimating human selenium requirements is to examine dietary intakes in areas with and without selenium deficiency.
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From page 220... ...
. A so-called physiological human selenium requirement was estimated by following increases in plasma glutathione peroxidase activity in adult Chinese men with low selenium status (i.e., a daily dietary intake of approximately 10 Age, who were supplemented with graded doses of selenomethioni~ne (Yang et al., 1987~.
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From page 221... ...
The allowance during the second 6 months, calculated similarly, is 15 1lg/day. Moreover, these recommendations provide a substantial margin of safety, since infants in Finland and New Zealand suffer no observable ill effects of low selenium intake even though the average selenium content of human milk in those countries ranges from only 6 to 8 1lg/liter (Kumpulainen et al., 1983; Williams, 1983)
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1983. Manifestations of chronic selenium deficiency in a child receiving total parenteral nutrition.
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From page 223... ...
37:887 - 897. ' ' ' ~ P;~ |
From page 224... ...
~ ~ _ Evidence for Human Requirement Severe copper deficiency is rare in human beings (Cartwright and Wintrobe, 1964; Danks, 1988~. Copper depletion sufficient to cause hypocupremia has been observed during total parenteral nutrition (Strike, 1984)
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From page 225... ...
human fetus increases subDietary Sources and Usual Intakes Organ meats, especially liver, are the richest sources of copper in the diet, followed by seafoods, nuts, and seeds. The concentration of copper in drinking water is highly variable; it is much influenced by the interaction of the water's acidity with the piping system.
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From page 226... ...
Estimated Safe anti Adequate Daily Dietary Intakes Adults In the past, estimates of the copper requirement for humans were derived from metabolic balance studies. However, the balance technique can lead to false estimates of nutritional requirements because the efficiency of copper absorption is increased or decreased in response to low or high copper intakes, respectively (Turnlund et al., 1989~.
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From page 227... ...
Rather, the subcommittee recommends 1.5 to 3 mg/day as a safe and adequate range of dietary copper intake for adults. Infants and Children The average daily intake of copper by exclusively breastfed North American infants was 0.23 + .07 mg over the first 4 months of lactation (Butte et al., 1987)
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From page 228... ...
Excessive Intakes and Toxicity An FAD/WHO Expert Committee concluded that no deleterious effects can be expected in humans whose copper intake is 0.5 mg/kg body weight per day (FAD/WHO, 19711. Usual diets in the United States rarely supply more than 5 mg/day, and an occasional intake of up to 10 mg/day is probably safe for human adults.
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1985. Copper absorption from human milk, cow's milk, and infant formulas using a suckling rat model.
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1973. Trace Elements in Human Nutrition.
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From page 231... ...
Estimated Safe and Adequate Daily Dietary Intakes Adults Several short-term balance studies in adult humans fed different amounts of manganese have been conducted in an attempt to define the requirement for this trace element (reviewed by Freeland-Graves et al., 1987~. However, there are many problems with using the balance method to estimate trace element requirements (Freeland-Graves et al., 1988~.
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From page 232... ...
Given the apparent lack of manganese deficiency as a practical nutritional problem in adults, it would seem that current dietary intakes satisfy needs for the element. Therefore, a provisional daily dietary manganese intake for adults of 2.0 to 5.0 mg is recommended.
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1985. Studies in human lactation: zinc, copper, manganese, and chromium in human milk in the first month of lactation.
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Trace Elements in Human and Animal Nutrition, Vol.
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1973. Trace elements in human nutrition.
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From page 236... ...
. There is evidence that dental health has been improving, even in communities with low water fluoride concentrations, presumably because of increased fluoride intake from other sources (e.g., from foods processed with fluoridated water, topical fluoride applications by dentists, fluoride supplementation, and unintentional ingestion of fluoride dentifrices)
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From page 237... ...
, reflecting maternal intake. The low and high concentrations in human milk were found in samples from mothers drinking water with fluoride concentrations of 0.2 and 1.7 mg/liter, respectively.
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From page 238... ...
Estimated Safe and Adequate Daily Dietary f ntakes The estimated range of safe and adequate intakes of fluoride for adults is 1.5 to 4.0 mg/day. This takes into account the widely varying fluoride concentrations of diets consumed in the United States and includes both food sources and drinking water.
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Trace Elements in Human and Animal Nutrition, Vol.
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1983. Dietary intake of fluoride in the United Kingdom and fluoride content of some foodstuffs.
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From page 241... ...
This is in contrast to the average chromium intake of 33 and 25 Heyday from self-selected diets of adults in Beltsville, Maryland, in diets containing 2,300 and 1,600 kcal, respectively (Anderson and Kozlovsky, 19851. Estimated Safe and Adequate Dai1ty Dietary Intakes Because of the lack of methods to diagnose chromium status, it is difficult to estimate a chromium requirement.
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From page 242... ...
The safety of an intake of 200 fig has been established in long-term supplementation trials in human subjects receiving 150 ~g/day in addition to the dietary intake (Glinsmann and Mertz, 19661. Habitual dietary intakes of around 200 Friday have been reported in several studies; no adverse effects of such intakes are known.
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From page 243... ...
1977. Chromium deficiency, glucose intolerance and neuropathy reversed by chromium supplementation in a patient receiving long-term total parenteral nutrition.
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From page 244... ...
The first involved a patient on long-term total parenteral nutrition who developed a variety of symptoms, including amino acid intolerance, irritability, and, ultimately, coma (Abumrad et al., 19814. This person also displayed hypermethioninemia, increased urinary excretion of xanthine and sulfite, and decreased urinary excretion of uric acid and sulfate.
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From page 245... ...
Estimated Safe and Adequate Daiity Dietary Intakes Aside from the exceptions discussed above, no disturbances in uric acid or sulfate production have ever been related to molybdenum deficiency in humans. The human requirement apparently is so low that it is easily furnished by common U.S.
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From page 246... ...
Trace Elements in Human and Animal Nutrition, 5th ed, Vol.
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