Ascorbic acid intake

The adrenal glands and pituitary glands have the highest tissue concentration of ascorbic acid. The brain, Hver, and spleen, however, represent the largest contribution to the body pool. Plasma and leukocyte ascorbic acid levels decrease with increasing age (152). Elderly people require higher ascorbic acid intakes than children to reach the same plasma and tissue concentration (153). 

NT196 Ueta, E., Y. Tadokoro, T. Yamamoto, et al. The effect of cigarette smoke exposure and ascorbic acid intake on gene expression of antioxidant enzymes and other related enzymes in the livers and lungs of Shionogi rats with osteogenic disorders. Toxicol Sci 2003 73(2) 339-347. 

There have been several epidemiological and several case reports inversely relating ascorbic acid intake from food to human cancer mortality. These studies are interesting, but may be confounded with the fact that the same ascorbic acid containing foods, namely fruits and vegetables, also contain large amounts of vitamin A and fiber. Both vitamin A and fiber have been inversely related to human cancer mortality and have been shown to inhibit several types of chemically-induced carcinogenesis in animals. Therefore, the possible anti cancer effect of ascorbic acid may be due to other factors. 

Head and Hansen (415) added L-ascorbic acid (42.3 mg/L) to whole, chocolate, and low fat (1%) fluid milks to increase the ascorbic acid intake of school children. Three milk treatments were examined (C) pasteurized milk, (E) pasteurization (74°C for 16 s) after ascorbic acid addition, and (F) ascorbic acid addition after pasteurization. Storage (4°C) retention of ascorbic acid (Figure 9) was good, and the taste reactions of children were favorable. Previously Weinstein et al. (416) and Anderson et al. (417) had reported on ascorbic acid nutrified fluid milk to which ascorbic acid was added at 50 and 200 mg/L, respectively. Infant milks nutrified with ascorbic acid were investigated by Cameron (418) during the preparatory procedures prior to infant feeding. 

Zinc and Ascorbic Acid Metabolism and Excretion. Iron has an oxidizing effect on ascorbic acid, reducing its urinary excretion therefore, Keltz et al. (61) questioned whether zinc would show a similar effect. Human subjects were fed a diet containing either 11.5 or 19.5 mg of zinc/d for 7-d balance periods. Daily ascorbic acid intake was 100 mg. Consistent with the findings from iron-loaded Africans, the higher zinc intake caused a significant 30% decrease in urinary ascorbate excretion. No explanation for the zinc-related reduction in ascorbic acid beyond the analogy with the iron-loaded individuals is readily available. 

Table 3B ASCORBIC ACID INTAKE MALES HANES 2, 1976-1980 All Income Levels Percentile Mean 50th 25th 10th (mg) Income 50th Below Poverty 25th 10th ...

Level of ascorbic acid in the diet has been found to be an important factor in determining non-heme iron absorption (6,10,11). Ascorbic acid intake has been found to be more closely correlated to several biochemical parameters of iron nutritional status than was total iron Intake (12). However, timing of consumption is equally important. If non-heme iron absorption is to be increased via this factor, then both the non-heme iron and the ascorbic acid must be consumed at the same time. Considering that important sources of ascorbic acid are all of plant origin, the chances that a shift from more animal-based foods to more plant-based foods will lead to Increased consumption of ascorbic acid are good indeed. However, this is not necessarily the case if the shift moves toward a diet based solely, for example, on highly polished cereals. 

Iron and ascorbic acid intake of adult vegetarian men and women in comparison to the NRC RDA s were also reported by Brown and Bergan (26). Similarly, as in the previously reported study by Tober and Cook, vegetarian men had mean iron intakes of 148% of the NRC RDA s but the figure for vegetarian women was only 62% of this standard. Mean ascorbic acid intakes were 164 and 165% of the standards for adult men and women. 

As shown in Table I, iron intakes of both groups was approximately the same with mean values being only about one-half the NRC RDA allowances for this age/sex group. However, ascorbic acid intake levels were high which might have helped in the utilization of the iron provided. Hemoglobin and hematocrit levels which are sometimes used as indexes of adequate iron... 

Pharmacokinetics. Approximately 10% of iron administered orally is absorbed in the duodenum and upper jejunum. Absorption of iron is decreased by food and achlorhydria. In patients with iron deficiency GI absorption may be increased, up to 25% to 30% however, this adaptive response may be impaired in patients with kidney disease. The heme form of oral iron binds to a different receptor in the GI tract than nonheme iron, is absorbed to a greater extent, and may be better tolerated. " Some oral iron formulations also include ascorbic acid to enhance iron absorption. While there is an association between ascorbic acid intake and oxalate formation, this association is generally not observed at doses of ascorbic acid contained in these iron formulations. ... 

Although scurvy is a rare disease, it is a constant threat to individuals or populations, especially during cultural changes. Adequate ascorbic acid intake is not insured without special effort in this direction. Woodruff (W12) pointed this out in commenting on the increasing incidence... 

I. Plasma Ascorbic Acid Levels. The measurement of plasma levels of ascorbic acid in populations has been used to provide more reliable data on average intakes than that obtained from the incidences of scurvy or from nutritional histories. It must be emphasized, however, that scurvy develops only in those individuals with plasma levels below those which can be accurately measured. Extensive studies have provided empirical correlations of expected plasma and white blood cell levels with different ascorbic acid intakes (L24, M24, S23). Other studies have also shown that both the ascorbic acid and the dehydroascorbic acid content of foods were equally effective in raising the plasma level of ascorbic acid (D8). 

At the conclusion of the Medical Research Council study, saturation tests were done on the subjects with long histories of accurately known ascorbic acid intakes. More than three daily test doses (10 mg/kg body weight) were necessary before a sharp rise occurred in urinary ascorbic acid excretion of subjects who had been receiving 20 mg/day or less, but again no distinction could be made in this way between the deficient and the protected individuals receiving the lower amounts. 

Kadiska, M.B., Hanna, P.M., Hernandez, L. and Mason, R.P. ( 1992) In vivo evidence of hydroxyl radical formation after acute copper and ascorbic acid intake electron spin resonance spin-trapping investigation. Mol. Pharmacol. 42 723-729. 

Brunnemann et al. (509) reported the measurement of the endogenous formation of NPRO in smokers and nonsmokers on a controlled diet, relatively low in proline and ascorbic acid. The NPRO in urine was determined in 24-h urine samples on days 3,6,9, and 12. Different groups in the study were administered proline and/or ascorbic acid at appropriate times during the experiment. Ascorbic acid intake reduced urinary levels of NPRO. Differences in NPRO excretion by smokers and nonsmokers on the controlled diet, ascorbic acid supplement, no proline supplement were not statistically significant. 

The mechanisms by which vitamins prevent illnesses are not weU understood, and the amounts needed to lower risks for certain disease conditions may be higher than the current recommended levels for preventing nutritional deficiencies. For example, the Institute of Medicine recommends that to prevent neural tube birth defects, women of child-bearing age should consume 400 Xg of folic acid per day (but not more than 1000 Xg/day) from fortified foods and/or dietary supplements in addition to folates obtained from a varied diet. " < Ascorbic acid intakes of 80-200mg daily (8-20 times the amounts needed to prevent scurvy) may be necessary to enhance certain physiological functions and minimize specific disease risks. " ... 

Jacob, R. A., Skala, J. H., Omaye, S. T., and Tumlund, J. R., 1987a, Effect of varying ascorbic acid intakes on copper absorption and ceruloplasmin levels of young men, J. Nutr. 117 2109-2115. 

VanderJagt, D. J., Garry, P. J., and Bhagavan, H. N., 1987, Ascorbic acid intake and plasma levels in healthy elderly people. Am. J. Clin. Nutr. 46 290-294. 

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