Recommended Dietary Allowances 10th Edition (1989) / Chapter Skim
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Water-Soluble Vitamins
Water-Soluble Vitamins
Pages 115-173
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From page 115... ...
, folic acid (Stokes et al., 1975) , histamine (Clemetson, 1980)
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From page 116... ...
, but at large doses, degradation within the intestine may be substantial (Kallner et al., 1985~. Dietary Sources and Usual Intakes Vegetables and fruits contain relatively high concentrations of vitamin C, e.g., green and red peppers, collard greens, broccoli, spinach, tomatoes, potatoes, strawberries, and oranges and other citrus fruits.
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From page 117... ...
vitamin C values of less than 0.2 ma/ d1, leukocyte concentrations of less than 2 1lg/108 cells, and a body pool size of less than 300 mg (Hodges et al., 1969, 1971; Sauberlich, 1981~. To eliminate clinical signs of scurvy in several groups of male subjects, vitamin C intakes ranging from 6.5 to 10 mg/day were required (Baker et al., 1971; Bartley et al., 1953; Hodges et al., 1969, 1971~.
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From page 118... ...
the average depletion rates and the steady state turnover rates at a pool size of 1,500 ma; (3) the less than complete absorption of ascorbic acid, estimated at 85~o for usual intakes; and (4)
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From page 119... ...
To offset losses from the mother's body pool during pregnancy, a 10 mg/day increment in the maternal vitamin C RDA is recommended during pregnancy. The concentration of vitamin C in human milk varies widely (3 to 10 mg/dl)
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Other Consiclerations Usual daily dietary intakes of vitamin C (25 to 75 ma) can enhance the intestinal absorption of dietary nonheme iron by two- to fourfold (Cook and Monsen, 1977; Rossander et al., 1979~.
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1985. Effects of different levels of vitamin C intake on the vitamin C concentration in human milk and the vitamin C intakes of breast-fed infants.
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1982. Nutritional status in a healthy elderly population: vitamin C
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1975. Comparison of the nutritional status of pregnant adolescents with adult pregnant women.
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1981. The effects of ascorbic acid, vitamin Be;, vitamin Bit, and folic acid supplementation on the breast milk and maternal nutrition status of low socioeconomic lactating women.
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From page 125... ...
Reduced TPP saturation of erythrocyte transketolase has also been observed in animals and humans fed diets low in thiamin (Sauberlich et al., 19791. Clinical signs of deficiency have been noted when less than 7% (70 Age of a 1 mg dose of thiamin is excreted in the urine in a dose-retention test (Horwitt et al., 1948~.
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From page 126... ...
. Recommended Allowances Allowances for thiamin have been based on assessment of the effects of varying levels of dietary thiamin on the occurrence of clinical signs of deficiency, on the excretion of thiamin or its metabolites, and on erythrocyte transketolase activity.
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From page 127... ...
or indirectly (Berit-Kjosen and Seim, 1977~. When healthy subjects were studied under controlled experimental conditions, good correlations of urinary excretions with the erythrocyte transketolase activity and TPP stimulation of transketolase were recorded (Sauberlich et al., 1970, 1979; Wood et al., 1980~.
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From page 128... ...
Although thiamin is essential for the metabolism of carbohydrate and certain amino acids, but not for fat and the remaining protein fraction, it is difficult in practice to separate energy intake Into these components; hence, the thiamin recommendation is expressed by convention in terms of total caloric intake. Pregnancy and Lactation Studies of urinary excretion of thiamin blood thiamin levels, and erythrocyte transketolase activity all indicate that the requirement for thiamin in women increases during pregnancy (Heller et al., 1974; Kaminetzky et al., 1973; Lockhart et al.
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From page 129... ...
, urinary excretion of thiamin and whole blood thiamin levels in a group of preadolescent children indicated that intakes approximating 0.3 mg/1,000 kcal were adequate. In a study of the urinary thiamin excretion of 16- to 18year-old girls, Hart and Reynolds (1957)
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116. Report of the Committee on Nutritional Aspects of Ageing, Food and Nutrition Board, Division of Biology and Agriculture.
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1946. Thiamine excretions and blood levels of young women on diets containing varying levels of the B vitamins, with some observations on niacin and pantothenic acid.
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From page 132... ...
In men, urinary excretion of less than 10% of riboflavin intake may reflect potential riboflavin deficiency (Horwitt et al., 1950~. When urine collections are difficult to obtain, the estimates of the riboflavin present in erythrocytes can provide some indication of riboflavin nutrition (Bates et al., 1981; Bessey et al., 1956~.
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From page 133... ...
Because riboflavin is essential to the functioning of vitamins Be and niacin, some symptoms attributed to riboflavin deficiency are actually due to the failure of systems requiring these other nutrients to operate effectively (McCormick, 1988~. Dietary Sources and Usual Intakes Animal protein sources such as meats, poultry, fish, and, especially, dairy products are good sources of riboflavin.
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From page 134... ...
Periods of hard work have been shown to decrease urinary excretion of riboflavin in young men (Tucker et al., 1960) , and moderate exercise has been shown to increase the EGR activity ratio and to decrease riboflavin excretion in young women consuming levels of riboflavin at about the RDA (Belko et al., 1983~.
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1981. Riboflavin status in Gambian pregnant and lactating women and its implications for Recommended Dietary Allowances.
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1950. Correlation of urinary excretion of riboflavin with dietary intake and symptoms of ariboflavinosis.
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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 138... ...
In four studies in which niacin status was judged by urinary excretion of niacin metabolites, the quantities of supplementary tryptophan required to give the same response as 1 mg of niacin ranged from 39 to 86 mg (Goldsmith et al., 1961; Horwitt et al., 1956; Patterson et al., 1980; Vivian, 1964~. The convention is to consider 60 mg of tryptophan as equivalent to 1 mg of niacin, and to regard each to be 1 niacin equivalent (NE)
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From page 139... ...
When these subjects were fed diets containing approximately 200 mg of tryptophan and varying levels of niacin, there was a significant increase in urinary niacin metabolites whenever they were given 8 to 10 mg of niacin (Goldsmith et al., 19551. These results suggest that a daily intake of 11.3 to 13.3 NEs (200 mg of tryptophan + 8 to 10 mg of niacin)
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From page 140... ...
The increase in the urinary excretion of N'methylnicotinamide, also observed in pregnant women (Horwitt et al., 1981) , reflects an enchanced capacity for the biosynthesis of nicotinate ribonucleotide from tryptophan.
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. mentat~on on urinary excretion of tryptophan metabolites by pregnant women.
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I Nitrogen balances, blood pyridine nucleotides and urinary excretion of N~-methylnicotinamide and Ni-methyl-2-pryridone-5carboxamide on a low-niacin diet.
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. Vitamin B6 nutriture is best assessed by a combination of these assessment methods (e.g., plasma PLP levels, urinary excretion of 4-PA, and the response of urinary metabolites to a 2-g tryptophan load test)
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, who measured urinary excretion of 4-PA and vitamin B6 as well as plasma PLP levels in 41 adult females, reported acceptable levels of each indicator at dietary intakes of 1.25 and 1.5 mg (0.0125 and 0.015 mg/g of protein)
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From page 145... ...
The concentration of vitamin B6 in human milk is approximately 0.01 to 0.02 mg/liter during the first days of lactation and gradually increases to 0.10 to 0.25 mg/liter (Coursin, 1955; Karlin, i959; Kirksey and West, 1978; West and Kirksey, 19761. The vitamin B6 content of milk reflects the nutritional status of the mother (Karlin, 1959; Kirksey and West, 1978; Roepke and Kirksey, 1979; Thomas et al., 1979; West and Kirksey, 1976~.
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From page 146... ...
The present subcommittee maintains the vitamin B6 recommendations of the ninth edition of the RDA 0.3 mg/day during the first 6 months of infancy and 0.6 mg/day for older infants. Studies on the nutritional status of children and adolescents in relation to their intake of vitamin B6 are limitecl.
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From page 147... ...
Tuvemo.1972. Pyridoxal phosphate and folic acid concentration in blood and erythrocyte aspartate aminotransferase activity during pregnancy.
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1978. Relationship between vitamin B6 intake and the content of the vitamin in human milk.
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85-3. Nutrition Monitoring Division, Human Nutrition Information Service.
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29:961-969. FOLATE Folate and folacin are generic descriptors for compounds that have nutritional properties and chemical structures similar to those of folic acid (pteroylglutamic acid, or PGA)
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From page 151... ...
diet is about one-half that of crystalline folic acid, which is efficiently absorbed (Sauberlich et al., 1987~. Assessment of Folate Status Well-nourished individuals excrete daily up to 40 fig of folate in the urine (Herbert, 1968)
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One involves determining a minimum requirement for pure folic acid and increasing this amount to cover bioavailability, individual variation, and the need for adequate reserves. A second approach is evaluation of the average intake of food folate among persons in good folate status.
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From page 153... ...
(1970) reported a reduced incidence of premature births in women given supplementary folic acid; an oral PGA supplement of 500 ~g/day was associated with a 50% reduction in the incidence of small-for-date births among 134 pregnant women in India (Iyengar and Rajalakshmi, 1975~.
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From page 154... ...
. In women with poor folate stores and whose diet was essentially devoid of folate, the progression of folate deficiency was as effectively prevented by administering a supplement of 300 fig of PGA daily in maize meal (a food that reduced availability by 44%, i.e., the effective dose was 168 fig of PGA)
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From page 155... ...
Megaloblastic anemia due to dietary folate deficiency is rare in children. Those who drink vegetable or fruit juice or eat fresh uncooked fruits or vegetables each day maintain adequate folate status; deficiency has been observed among children whose entire diet consists of fine-particulate foods cooked for a long time (Herbert, 1981)
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1975. Minimal daily requirement of folic acid in normal Indian subjects.
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1975. Folic acid absorption in pregnancy.
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1961. Megaloblastic anemia in scurvy with response to 50 micrograms of folic acid daily.
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The dominant forms in meat are adenosyl- and hydroxocobalamin, whereas dairy products, including human milk, contain mainly methyl- and hydroxocobalamin (Gimsing and Nex, 1983~. Dietary Sources and Usual Intakes Bacteria, fungi, and algae can synthesize vitamin Be, but yeasts, higher plants, and animals cannot.
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From page 160... ...
,-folate interaction and may relate to the similarity in B.., and folate deficiency signs (Herbert and Colman, 1988~. The other cobalamin coenzyme, deoxyadenosylcobalamin, catalyzes the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A, a reaction in the pathway for the degradation of certain amino acids and odd-chain fatty acids.
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From page 161... ...
The daily loss of vitamin B., is approximately 0.1% (range, 0.05 to 0.2%) of the body pool, regardless of pool size (Heyssel et al., 1966~.
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From page 162... ...
Estimates of requirement are necessarily dependent on a judgment as to desirable pool size. Recommended Allowances Adults A dietary intake of 1 fig daily can be expected to sustain average normal adults.
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From page 163... ...
At 6 months postpartum, 0.6 ~g/liter was found in the milk of wellno',risher1 women in the United States (Thomas et al., 1980~. This would mean a loss of 0.45 fig in 750 ml of human milk, or 0.56 fig/ day at the upper level of production.
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1988. Folic acid and vitamin Bit.
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From page 165... ...
1986. Nationwide Food Consumption Survey Continuing Survey of Food Intakes by Individuals: Men 19 - 50 Years, 1 Day, 1985.
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From page 166... ...
Low activity of biotin enzymes results in the urinary excretion of organic acids (the nature of which is determined by the metabolic step that is blocked) , skin rash, and hair loss.
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From page 167... ...
Estimated Safe and Adequate Daily Dietary Intakes Adults The lack of definitive studies of biotin requirements make it difficult to estimate an allowance. A daily dose of 60 fig has maintained adults on total parenteral nutrition symptom-free for 6
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From page 168... ...
This range is lower than that recommended in the previous edition of the RDA, because improved analytical methods for biotin have reduced the estimates of daily intakes compatible with good health. Pregnancy and Lactation Blood biotin levels are significantly lower in pregnant than in nonpregnant women and fall progressively throughout gestation.
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From page 169... ...
34:699 - 716. PANTOTHENIC ACID Pantothenic acid, a B-complex vitamin, plays its primary physiological roles as a component of the coenzyme A molecule and within the 4'-phosphopantetheine moiety of the acyl carrier protein of fatty acid synthetase, which serves in acyl-group activation and transfer reactions (McCormick, 1988~.
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7 ~ 7 — _ _ _ _ _ ~ __ ~ Dietary Sources and Usual Intakes Pantothenic acid is widely distributed among foods. It is especially abundant in animal tissues, whole grain cereals, and legumes.
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In a small group of pregnant, postpartum, and nonpregnant teenagers, the calculated dietary intakes were lower, ranging from 1.1 to 7.2 mg/day (Cohenour and Calloway, 1972~. Estimated Safe and Adequate Daily Dietary Intakes Adults Urinary excretion generally correlates with dietary intake of pantothenic acid, although individual variation is large.
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From page 172... ...
1981. Pantothenic acid content of human milk.
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1984. Effect of pantothenic acid status on the content of the vitamin in human milk.
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