Recommended Dietary Allowances 10th Edition (1989) / Chapter Skim
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Fat-Soluble Vitamins
Fat-Soluble Vitamins
Pages 78-114
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From page 78... ...
precursors of vitamin A such as Q-carotene, a-carotene, and cryptoxanthin formed by plants and present in some animal fats. The structural requirements for vitamin A biological activity are very strict and apply both to retinoids and to carotenoids (Wolf and Johnson, 19601.
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From page 79... ...
, whereas carotenoid absorption falls markedly to levels as lowers 10% or less (Bauernfeind, 1972; Olson, 1972~. Absorbed retinol is largely esterified in intestinal mucosal cells and incorporated into chylomicrons, as is the portion of absorbed ,B-carotene and other biologically active carotenoids that is not cleaved in intestinal cells.
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From page 80... ...
Although rare in the United States, vitamin A deficiency is a major nutritional problem in some parts of the nonindustrialized world, causing a number of the more than 500,000 new cases of active corneal lesions that occur annually in children (FAO, 1988~. The Nutritional Relationship Between Preformed Vitamin A, Biologically Active Retinoids, and Carotenoid~s Vitamin A activity is often expressed as international units (IU)
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From page 81... ...
Dietary Sources and Usual Intakes The richest sources of preformed retinal are liver and fish liver oils, and appreciable quantities are also present in whole and fortified milk and in eggs. Biologically active carotenoids are found in abundance in carrots and in dark-green leafy vegetables such as spinach (USDA, 1976 - 1989~.
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From page 82... ...
Vitamin A deficiency symptoms included dryness of skin, impaired dark adaptation, eye discomfort, and low plasma retinol levels (~15 ~g/dl)
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From page 83... ...
There was considerable variation among them in the time of occurrence of vitamin A deficiency signs. Abnormal electroretinograms occurred at plasma retinol levels of 4 to 11 ~g/dl and impaired dark adaptation was observed at plasma retinol levels of 3 to 25 ~g/dl, whereas follicular hyperkeratosis was found at plasma retinol levels of 7 to 37 ~g/dl.
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From page 84... ...
Clinical observations, radiometric findings on body pools of vitamin A, and vitamin A utilization rates suggest that the maintenance of a plasma retinol level above 20 ~g/dl appears to be essential, while a plasma level above 30 ~g/dl would be desirable to ensure modest body stores of the vitamin. These plasma levels would be associated with utilization rates of vitamin A of 570 to 1,250 ~g/day found for the eight adult men in the study of Sauberlich et al.
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From page 85... ...
To maintain maternal liver reserves, account for normal variation in milk volume, and provide a margin of safety, therefore, a daily increment of 500 RE is recommended during the first 6 months of lactation. Inasmuch as the mean daily human milk volume falls to 600 ml after 6 months, a daily increment of 400 RE should suffice during this later period.
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From page 86... ...
Thereafter, RDA values are extrapolated to the adult level on the basis of body weight. Allowances of 400, 500, and 700 RE daily are recommended for the age groups of 1 to 3, 4 to 6, and 7 to 10 years, respectively, with no distinction between males and females.
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From page 87... ...
At this time, it is not possible to draw any conclusions about how this information relates to setting RDAs for vitamin A, but it does suggest that a generous intake of carotenoidrich foods may be of benefit. Excessive Intakes and Toxicity When ingested in very high doses, either acutely or chronically, preformed vitamin A causes many toxic manifestations, including headache, vomiting, diplopia, alopecia, dryness of the mucous membranes, desquarnation, bone abnormalities, and liver damage (Bauernfeind, 19801.
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From page 88... ...
1987. Vitamin A relative dose response test: validation by intravenous injection in children with liver disease.
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From page 89... ...
1987. Vitamin A intake and plasma retinol levels in healthy elderly men and women.
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From page 90... ...
1980. Recommended Dietary Allowances, 9th revised ed.
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From page 91... ...
85-4. Nutrition Monitoring Division, Human Nutrition Information Service.
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1987a. Dietary intakes of vitamin A precursors by rural Gambian pregnant and lactating women.
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From page 93... ...
Abnormalities in calcium homeostasis and bone metabolism can also occur when the conversion of vitamin D to biologically active forms is compromised due to disease states. For example, rickets and osteomalacia are often found in patients with kidney failure (Haussler and McCain, 19771.
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From page 94... ...
Calculations based on reference aVitamin D occurs as cholecalciferol or ergocalciferol in foods and fortified food products. Since the chemical forms are generally not separately identified, the vitamin D content of foods and dietary intakes are given in micrograms of cholecalciferol for slmpllclty.
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From page 95... ...
Data from USDA's 1977 - 1978 Nationwide Food Consumption Survey indicate that 1.25 to 1.75 ~g/day (50 to 70 IU) is the usual dietary intake in the United States (USDA, 1983~.
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From page 96... ...
In full-term infants fed human milk, bone mineral content, total and ionized calcium in serum, and serum phosphorus and alkaline phosphatase values were similar to those in a comparison group fed infant formula containing 10 fig (400 IU) of vitamin D per quart, but serum 25~0H)
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1949. Comparative efficacy of vitamin D preparations in prophylactic treatment of premature infants.
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From page 98... ...
1987. Nationwide Food Consumption Survey Continuing Survey of Food Intakes by Individuals: Women 19-50 Years and Their Children 1-5 Years, 4 Days, 1985.
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From page 99... ...
premature, very low birth weight infants in whom low plasma vitamin E levels have been associated with some, but not all, of their medical problems (Anonymous, 1988; Bieri et al., 1983; Farrell, 1980)
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From page 100... ...
Function and Metabolism Tocopherols are known chemically as antioxidants, i.e., they prevent propagation of the oxidation of unsaturated fatty acids by trapping peroxyl free radicals. It is widely accepted that this is the basic function of vitamin E in animal tissues, where tocopherol is found in cellular membranes associated with polyunsaturated fatty acids (PUFA)
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From page 101... ...
When plasma vitamin E is considerably below normal, red cells become susceptible to excessive hemolysis (Leonard and Losowsky, 1971~. Dietary Sources and Usual Intakes The tocopherol content of foods varies greatly, depending on processing, storage, and preparation procedures during which large losses may occur (BauernfeincI, 1 980; Dicks, 1 965~.
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From page 102... ...
In heart tissue, for example, lipids contain greater concentrations of highly unsaturated fatty acids than do most other tissues. When the primary PUFA in the diet is linoleic acid, as in most U.S.
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From page 103... ...
Most surveys of physically active elderly populations have not shown plasma vitamin E levels to be different from those of younger adults. In a recent study of subjects over 80 years of age, however, slightly lower values were found than in a middle-aged control group.
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From page 104... ...
Premature infants present problems somewhat different f rom those of full-term infants of normal weight. Because of their low body stores of tocopherol, their reduced intestinal absorption (Gross and Melhorn, 1972)
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1962. Interrelations between vitamin E and polyunsaturated fatty acids in animals.
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1966. Syndrome in premature infants associated with low plasma vitamin E levels and high polyunsaturated fatty acid diet.
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From page 107... ...
CSFII. Nationwide Food Consumption Survey Continuing Survey of Food Intakes by Individuals: Men 19-50 Years, 1 Day, 1985.
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From page 108... ...
In humans, the total body pool of vitamin K is small, and its turnover is rapid (Bjornsson et al., 1980; Olson, 1984~. Liver stores of vitamin K appear to consist of only about 10% phylloquinone and approximately 90% of various menaquinones, which are probably synthesized by intestinal bacteria (Shearer et al., .1988~.
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From page 109... ...
The vitamin K intake in a single day is not a reliable indicator of its average intake by an individual over an extended period, and diets largely free of green leafy vegetables may still contain adequate amounts of vitamin K Recommended Allowances Adults The major criterion for assessing the adequacy of vitamin K status in adult humans is the maintenance of plasma prothrombin concentrations in the normal range, i.e., from 80 to 120 1lg/ml (Blanchard et al., l 981)
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From page 110... ...
and treated with neomycin for 4 weeks, daily intravenous dosages of 1.5 fig of vitamin K per kilogram of body weight restored normal plasma prothrombin levels, whereas 0.1 ~g/kg daily did not (Frick et al., 1967~. In a study of four adults fed 0.4 ~g/kg daily and treated with antibiotics for 5 weeks, plasma concentrations of prothrombin fell but remained at 70% or more of normal values (O'Reilly, 1971)
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From page 111... ...
Because human milk contains low levels of vitamin K (2 log/ liter) and the intestinal flora are limited, exclusively breastfed infants who do not receive vitamin K prophylaxis at birth are at very real risk of developing fatal intracranial hemorrhage secondary to vitamin K deficiency (Lane et al., 1983~.
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From page 112... ...
Adults treated chronically with broad-spectrum antibiotics or on longterm hyperalimentation, and patients with chronic biliary obstruction or with lipid malabsorption syndromes, are particularly sensitive to vitamin K deficiency (Olson, 1982, 1984; Olson and Suttie, 1977; Suttie, 1984~. Excessive Intakes and Toxicity Even when large amounts of vitamin K are ingested over an extended period, toxic manifestations have not been observed (Owen, 1971~.
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From page 113... ...
in human milk, cow's milk and infant formula foods determined by high-performance liquid chromatography.
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From page 114... ...
2. Nutrition Monitoring Division, Human Nutrition Information Service.
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