Vitamin status

Safety. No toxicity has been associated with acute or chronic intakes of vitamin B 2 Hi doses of 100 and 1 mg, respectively. Vitamin B 2 absorption is both limited and affected by vitamin status. Therefore, absorption is reduced with improved status, lessening the risk of toxicity. 

BATES C J, RUTISHAUSER I H E, BLACK A E, PAUL A A, MANDAL A R and PATNAIK B K (1979) Longterm vitamin status and dietary intake of healthy elderly subjects , ilrii/iVMfr, 42,43-56. 

Fernandez-Banares, F., Abad-Lacruz, A., Xiol, X., Gine, J.J., Dolz, C., Cabre, E., Esteve, M., Gonzales-Huix and Gassull, M.A. (1989). Vitamin status in patients with inflammatory bowel disease. Am. J. Gastroenterol. 85, 744-748. 

Age, calcium intake, hormonal status, exercise and vitamin status have all been implicated in the development of osteoporosis. Estrogen levels represent an important factor in skeletal calcium retention and homeostasis. In therapeutic trials in which post-menopausal women were given daily doses of estrogens, such therapy has been demonstrated to be partially effective in reducing the rate of bone resorption. However, this therapy has the concomitant hazard of endometrial cancer (10). Vitamin D and its hormones have been given considerable attention in the more recent studies. Without adequate dietary and tissue levels of such vitamins, calcium absorption and bone status will be impaired. 

Selhub J, Jacques PF, Wilson PW, Rush D, Rosenberg IH (1993) Vitamin status and intake as primary determinants of homocysteinemia in an elderly population. JAMA 270 2693-2698... 

Thurnham, D. I. (1981) Red cell enzyme tests of vitamin status do marginal deficiencies have any physiological signifi-... 

As the discovery of the vitamins progressed, it was realized that Factor B consisted of a number of chemically and physiologically distinct compounds. Before they were identified chemically, they were given a logical series of alphanumeric names Bi, B2, and so forth. As can be seen from Table 1.2, a number of compounds were assigned vitamin status, and were later shown either not to be vitamins, or to be compounds that had aheady been identified and given other names. 

There are no functional tests of pantothenic acid nutritional status that are generally applicable. Deficiency of pantothenic acid impairs the ability to acetylate a variety of drugs, such as p-aminobenzoic acid, but this has not been developed as an index of vitamin status. The capacity to acetylate drugs is genetically determined neither experimental pantothenate deficiency nor the administration of supplements affects the determination of fast or slow acetylator status (Pietrzik et al., 1975 Vas et al., 1990). 

Selhub J, Jacques PF Bostom AG, Wilson PW, and Rosenberg IH (2000) Relationship between plasma homocysteine and vitamin status in the Framingham study population. Impact of folic acid fortification. Public Health Review 28, 117-45. 

However, the sheer complexity of a pathway is not an indicator for the vitamin status of a given class of compounds, as opposed to endogenous biosynthesis in mammals. Thus, animals biosynthesize molybdopterin, which is a cofactor involved in certain redox reactions, from basic building blocks using at least... 

Several coenzymes comprising a pyrimidine ring motif are derived from GTP (22) (Fig. 3). Specifically, this group comprises two members of the B vitamin group, riboflavin (vitamin B2) (24) and folic acid/tetrahydrofolate (33). Two other members of the group, tetrahydrobiopterin (31) and molybdopterin (8), are biosynthesized de novo in animals and do not have vitamin status (20, 21). 

Plasma PLP levels have been used frequently as an indicator of vitamin status. Vitamin compciunds can be separated from each other and measured individually by high-pressure liquid chromatography (UPLC), where, after separation, the vitamins are detected by fluorescence (Tsuge, 1997). Great care needs tt> be taken... 

Vitamin status can be assessed by a direct test for the levels of 25-(OHin the serum, This competitive binding test involves three components (1) a serum sample, (2) radioactive 25-hydroxy[ Hjvitamin Dj, and (3) vitamin D-binding protein. The source of vitamin D-binding protein may be sheep serum. The functional tests for deternrination of vitamin D irvdude the diagnostic tests for rickets and osteomalacia. A test for osteomalacia, for example, may include measurement of the width of the osteoid in a bone biopsy. The osteoid is described later. 

Flavins are lost from the body as intael riboflavin, rather than as a breakdown product of riboflavin. Hence, vitamin status may be assessed by measuring the level of urinary riboflavin. Generally, the loss of 30 ig of riboflavin/g creatinine or less per day indicates a deficiency. This metht>d of assessment is not preferred because it is influenced by a number of factors unrelated to vitamin status. Another problem with this method is its great sensitivity to a short-term deficiency thus, it does not necessarily reflect the true concentrations of FAD and FMN in tissues. The most reliable way to assess riboflavin status is by a functional test. The test involves the assay of glutathione reductase, using red blood cells as the source of... 

Glutathione is discussed further in the section on selenium and glutathione in Chapter 10. The enzyme assay is conducted using glutathione reductase extracted from red blood cells with and without added FAD. Chmnic consumption of a diet deficient in riboflavin allows the continued synthesis of a variety of flavoproteins, but results in the accumulation of apoenzyme without its conversion to holoen-zyme. Addition of chemically pure FAD to a biological fluid containing apoenzyme results In the stimulation of enzyme activity because of the formation of the holoenzyme. It is this stimulation of enzyme activity that is used to determine vitamin status in humans. 

FIGURE 9.75 Results of the FAD sHmuJation test used to assess vitamin status in high school Students. (Redrawn with permission from Sauberlich el a ., 1972.)... 

Shane, B, and Contractor, S-1 (1975), Assessment of vitamin status. Studies on pregnant women and oral contraceptive users. Ant. J. din. Wm/t. 28, 739-747. 

Vitamins are not infrequently used by medical workers as placebos against poorly defined general malaise, often without consideration of the patient s actual vitamin status (3). Self-medication with vitamin supplements is very common in most countries, and commonly the users are not objectively vitamin deficient (4). In general, physicians in an industrialized society can expect that about half of their adult patients will currently be taking vitamin supplements (5) among athletes 75% have been found to use supplements (6). 

The existence of apoenzyme and holoenzyme forms of various enzymes is of use to the clinician. The proportion of a specific enzyme occurring in apoenzyme and holoenzyme forms is used to assess vitamin status in the cases of vitamin Bg, thiamin, and riboflavin. Vitamin status is determined by measuring the percentage stimulation of enzyme activity that occurs after adding the appropriate cofactor to a biological sample (blood) containing the enz3me of interest. 

FIGURE 9 0 Neutrophils. The examination of neutrophils is used to diagnose vitamin status. 

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