Plasma Concentrations of Vitamin

Some biologically active vittimin Be is excreted in the urine, and a number of studies have assessed nutritional status by microbiological measurement of this excretion it is difficult to interpret the results in terms of underlying nutri-tiontil status rather than as a reflection of recent intake, although the excretion does fall in deficiency (Sauberlich et til., 1972, 1974). A possibly important source of error here is that minor rentil damage, resulting in albuminuria, will result in a considerable increase in urinary albumin-bound pyridoxtil phosphate. 

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Kayden, H.J. andTraber, M.G. (1993). Absorption, lipoprotein transport and regulation of plasma concentrations of vitamin E in humans. J. Lipid Res. 34, 343-358. 

Table 3.2 Plasma Concentrations of Vitamin D Metabolites nmol/L ...

The plasma concentration of vitamin C falls relatively rapidly during depletion studies, to undetectably low levels within 4 weeks of initiating a vitamin C-free diet, although clinical signs of scurvy may not develop for a further 3 to... 

A concern has been raised that phytosterol doses that are effective for cholesterol reduction may impair the absorption and lower blood concentrations of fat-soluble vitamins and antioxidants. A number of studies showed that phytosterols had no effect on plasma concentrations of vitamin D, retinol, or plasma-lipid-standardized alpha-tocopherol. Moreover, the reports of the effect of phytosterols on concentrations of blood carotenoids (lutein, lycopene, and alpha-carotene) are controversial. There seems to be general agreement that phytosterol doses >1 g/d significantly decrease LDL-C standardized beta-carotene concentrations however, it remains to be determined whether a reported 15-20% reduction in beta-carotene due to phytosterol supplementation is associated with adverse health effects. Noakes et al. found that consumption of one or more carotenoid-rich vegetable or fruit servings a day was sufficient to prevent lowering of plasma carotenoid concentrations in 46 subjects with hypercholesterolemia treated with 2.3 g of either sterol or stanol esters. 

M. Hultqvist, J. Hegbrant, C. Nilsson-Thorell, T. Lindhol, P. Nilsson, T. Linden and U. Hultqvist-Bengtsson, Plasma Concentrations of Vitamin C, Vitamin E and/or Malondialdehyde As Markers of Oxygen Free Radical Production Diuing Hemodialysis, Clinical Nephrology 47(1) (1997) 37-46. 

The normal range of plasma concentrations of vitamins Dj and is 1 to 2 ng/ml, 25-HydK3xy itamin P3 is the form of the vitamin present at highest concentrations, with normal values ranging from 8 to 40 ng/mJ, A value of 12 ng/ml has been used as a cutoff point to indicate itamin D deficiency, though some clinicians have used lower levels to indicate vitamin D deficiency. The hormonally active form of the vitamin, l,25-(OH)jD occurs at much lower levels (15-45 pg/ml). 

For the diagnosis of hypervitaminosis A, plasma concentrations and retinol-binding protein may be misleading. Cases have been reported of hepatic fibrosis, secondary to chronic ingestion of massive doses of vitamin A, where plasma concentrations of vitamin A and retinol-binding protein at the time of diagnosis were within the reference range (43). 

The effects of variations in pharmaceutical formulation on plasma concentrations of vitamin A have only been partly documented. Vitamin A in aqueous dispersion results in higher plasma concentrations than in oily formulations (88). 

Earlier studies suggested that oral contraceptives could lead to an increase in plasma concentrations of vitamin A (104), the inference being that increased vitamin A concentrations might have a negative effect on conception, and that this might provide an explanation for the reduced fertility sometimes seen during the period immediately following withdrawal of contraceptive steroids. More recent work has not supported this theory. 

Kayden, H.J. and Traber, M.G. 1993. Absorption, Lipoprotein Transport, and Regulation of Plasma Concentrations of Vitamin E in Humans. J. Lipid Res. 34 343-358. 

Erythrocyte and plasma folate concentrations are reduced in protein-calorie malnutrition, but the serum vitamin Bj2 concentration is unaffected or may even be slightly increased. The plasma concentrations of vitamins A and E are much reduced. Although the blood hemoglobin concentration is reduced, the serum iron concentration is initially little affected by malnutrition. 

Aksnes L, Aarskog D. Plasma concentrations of vitamin D metabolites in puberty effect of sexual maturation and implications for growth. J CMn Endocrinol Metab 1982 55 94-101. 

Vitamin requirements for ESKD patients receiving dialysis differ from those of a healthy person because of dietary modifications, kidney dysfunction, and dialysis therapy. The plasma concentrations of vitamins A and E are elevated in ESKD, while those of the water-soluble vitamins (81,82,8g, 812, niacin, pantothenic acid, folic acid, biotin, and vitamin C) tend to be low in this population, in large part due to the fact that many are dialyzable. The goal for vitamin supplementation in this population should be to prevent subclinical and frank deficiency and to avoid pathology from overdosage. Special vitamin supplements have been formulated for the dialysis population, which primarily include 8 vitamins with C and folic acid. 

Little information is available concerning alterations in vitamin requirements in ARF. Reduced plasma concentrations of vitamin A, ascorbate, vitamin D, and vitamin E have been reported in patients with ARF, whereas vitamin K concentrations are relatively increased. Losses of vitamins via dialysis also must be considered. Traditional HD clears several water-soluble vitamins such as folic acid, vitamins C and B12, and pyridoxine, but not the highly protein-bound vitamins A and D. The clinical significance of these findings in ARF is unknown. Currently, it seems prudent to administer vitamins at least daily in doses recommended by the Nutrition Advisory Group of the American Medical Association for patients receiving PN (see Chap. 137)." Administration of ascorbic acid should be restricted to under 200 mg/day to avoid secondary oxalosis which may worsen renal function." If the enteral route is used for nutritional support, vitamin administration should at least meet the recommended daily allowances (RDAs). 

Healthy newborn infants show decreased plasma concentrations of vitamin K-dependent clotting factors for a few days after birth, the time required to obtain an adequate dietary intake of the vitamin and to establish a normal intestinal flora. In premature infants and in infants with hemorrhagic disease of the newborn, the concentrations of clotting factors are particularly depressed, possibly reflecting vitamin K deficiency. Measurements of non-y-carboxylated prothrombin suggest that true vitamin K deficiency occurs in - 3% of live births. 

What is more frequent than vitamin E deficiency is vitamin E insufficiency, with suboptimal vitamin E supply in the diet or inefficient uptake and distribution of vitamin E. The normal average plasma concentration of vitamin E is 23.2 pM a plasma level below 11.6 pM is regarded as deficient. Certain diseases, like abe-talipojjroteinemia, chronic cholestatic liver disease, cystic fibrosis, chronic pancre-... 

Because this slight decrease in warfarin effects has been seen with raloxifene , (p.446), the authors suggested that it might be because oestrogenic compounds increase plasma concentrations of vitamin K-depend-ent clotting factors. ... 

Ferric ion is a necessary cofactor for lipoxygenase activity in platelets, and various chelators inhibit the enzyme (194,195]. The role of vitamin E in relation to platelet lipoxygenase is unclear. An inhibitory effect has been reported (196,197], whereas others have found no effect (198]. The lipoxygenase activity of human neutrophils (see below) has been reported to be enhanced by normal plasma concentrations of vitamin E, whereas higher concentrations are suppressive [199]. 

We were left then with conclusions that one might have anticipated namely, that patients with steatorrhea had a lowered plasma concentration of vitamin E and, as a reflection of this, an increased tendency of their... 

Study of 110 cases of angina pectoris plasma concentrations of vitamin C, E and carotene were significantly inversely related to the risk of angina pectoris. However, the relation of vitamin C to risk was substantially reduced after adjustment for smoking. Only vitamin E remained inversely related to the risk of angina (Riemersma a/., 1991). 

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