C Supplements

Vitamin C is the most often sold single supplement in the United States (Sauberlich, 1994). According to U.S. national surveys in the 1980s, about 35 to 40% of the adult population reported taking supplements within the last 14 days (Subar and Block, 1990). In a 1987 survey, about 8% were taking vitamin C daily (Subar and Block, 1990). The median additional intake of supplemental vitamin C in this survey was about 60 mg per day. In the Physicians Health Study, a randomized trial 

In other countries the use of supplements is also increasing. A national survey in the mid-1980s in West Germany revealed that up to 10% (strata of women above 65 years) indicated a regular use of vitamin supplements (Heseker et al,y 1994). 

It has been shown that regular use of vitamin C supplements increases blood concentrations by 0.36 to 0.46 mg/dl (Dickinson et aL, 1994). There also seems to be no differences in bioavailability between dietary and supplemental vitamin C (Mangels et al., 1993). Therefore, theoretically, results from epidemiological investigations regarding the effect of vitamin C supplements on risk in observational studies should be considered a significant contribution to the evidence of a causal relationship since the pure substance is applied. 

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Carbon. Determination of 8 has been carried out by GC separation of the analytes followed by high-temperature oxidation. Although oxidation with CuO at 850°C has been used, use of NiO at 1050°C supplemented by O2 is preferable, and it is important to remove HjO before isotopic analysis (Merritt et al. 1995). 

In a recent study, serum ascorbate concentrations were significantly reduced in a group of elderly diabetic patients (w = 40, mean age 69 years) in comparison with an age-matched group of non-diabetic controls ( = 22, mean age 71 years), and this reduction was more pronounced in those patients with microangiopathy (Sinclair et al., 1991). Diabetic patients were shown to have a high serum dehydroascorbate/ascorbate ratio indicative of increased oxidative stress. Ascorbate deficiency was partially corrected by vitamin C supplementation, 1 g daily by mouth, but the obvious disturbance in ascorbate metabolism in the diabetic patients was accentuated, since serum ascorbate concentrations fell (after the initial rise) despite continued vitamin C supplementation (Fig. 12.3). 

Water-soluble vitamins removed by hemodialysis (HD) contribute to malnutrition and vitamin deficiency syndromes. Patients receiving HD often require replacement of water-soluble vitamins to prevent adverse effects. The vitamins that may require replacement are ascorbic acid, thiamine, biotin, folic acid, riboflavin, and pyridoxine. Patients receiving HD should receive a multivitamin B complex with vitamin C supplement, but should not take supplements that include fat-soluble vitamins, such as vitamins A, E, or K, which can accumulate in patients with renal failure. 

Lead was found to decrease tissue levels of vitamin C in a study in rats (Vij et al. 1998). Since vitamin C is required for the synthesis of heme, the authors suggested that some hematological effects of lead (e.g., inhibition of ALAD) may be due at least partially to a lead-induced decrease in bioavailability or increased demand of vitamin C. Supplementation with vitamin C almost completely restored ALAD activity in blood and liver. 

Turner, R. C. Supplemental Limnological Studies at Richard B. Russell and Clarks Hill Lakes, 1983-1985 Kennedy, R. H., Ed. Misc. Paper EL-87-2, U.S. Army Engineers Waterways Experiment Station, Vicksburg, MS, 1987 pp 128-139. 

It is found in citrus fruits and brighdy coloured vegetables, such as peppers and broccoli. Many people take vitamin C supplements, which are readily available from supermarkets and pharmacies (Figure 15.14). Although vitamin C is destroyed by exposure to air and heat, the average person usually reaches the recommended daily allowance of 60 mg through food. 

Morton, D.J., Barrett-Connor, E.L., and Schneider, D.L. 2001. Vitamin C supplement and bone mineral density in postmenopausal women. J. Bone Miner. Res. 16, 135-140. 

A7. Alessio, H. M., Goldfarb, A. H., and Cao, G., Exercise-induced oxidative stress before and after vitamin C supplementation. Int. J. Sport Nutr. 7, 1-9 (1997). 

A12. Anderson, D., Factors that contribute to biomarker responses in humans including a study in individuals taking vitamin C supplementation. Mutat. Res. 480-481, 337—347 (2001). 

NHScf 12 yr 14,968 F The use of specific vitamin E supplements but not specific vitamin C supplement may be relate to modest cognitive benefits in older women (193)... 

CCS Case-control 4750 M-F Use of vitamin E and C supplements in combination reduces the prevalence of Alzheimer s disease (208)... 

Burr ML, Hurley RJ, Sweetnam PM. Vitamin C supplementation of old people with low blood levels. Gerontol Clin I 975 17 236-243. 

Hunt C, Chakravorty NK, Annan G, The clinical and biochemical effects of vitamin C supplementation in short-stay hospitalized geriatric patients, Int J Vitam Nutr Res 1984 54 65-74. 

Losonczy KG, Harris TB, Havlik RJ. Vitamin E and vitamin C supplement use and risk of all-cause coronary heart disease... 

Gmelin Handbook of Inorganic Chemistry, System No. 65, Palladium. Main Volume (a) Section 1. The Element, 1939 (b) Section 2, Compounds, 1942 (c) Supplement Volume Part B. Compounds Section 2, Palladium Compounds, 1986. 

Regardless of whether or not high intakes of ascorbate have any beneficial effects, large numbers of people habitually take between 1 to 5 g per day of vitamin C supplements, and some take considerably more. The U.S. /Canadian tolerable upper level of intake is 2 g per day (Institute of Medicine, 2000). 

As discussed in Section 13.3.6, ascorbate may act to inhibit the formation of carcinogenic nitrosamines from nitrite and dietary amines, and thus reduce the risk of cancer. There is some evidence that vitamin C supplements are protective against the development of gastric cancer. 

Bruno RS, Leonard SW, Atkinson J, Montine TJ, Ramakrishnan R, Bray TM, Traber MG. Faster plasma vitamin E disappearance in smokers is normalized by vitamin C supplementation. Free Radic. Biol. Med. 2006 40 689. 

Given that most individuals receive a reasonable amount of vitamin C from their diet, it is likely that the greatest benefit of vitamin C supplementation for treatment of the common cold will be seen in specific groups such as those with low dietary intakes of vitamin C. This will include children, young men, the elderly and in those undertaking heavy physical... 

Mashour S, Turner JF Jr, Merrell R. Acute renal failure, oxalosis, and vitamin C supplementation a case report and review of the literature. Chest 2000 118(2) 561-3. 

Ono K. Secondary hyperoxalemia caused by vitamin C supplementation in regular hemodialysis patients. CUn Nephrol 1986 26(5) 239 3. 

Ono K, Ono H, Ono T, Kikawa K, Oh Y. Effect of vitamin C supplementation on renal oxalate deposits in five-sixths nephrectomized rats. Nephron 1989 51(4) 536-9. 

Vitamin C (ascorbic acid) is essential in the development and maintenance of cells and tissues. It cannot be synthesized in the body and so is an essential requirement in the diet. Good food sources are vegetabies and citrus fruits. Deficiency eventually leads to scurvy but before that, there is a decreased resistance to infection, and other disorders are seen particularly with the elderly. Vitamin C supplements are rarely necessary with a normal diet. There have been claims that pharmacological doses help prevent colds, and it is incorporated into a number of cold remedies. 

Vitamin C positively influences coUagen production, and increases osteoblast formation and osteoclast formation and survival. Some, but not aU, observational studies showed that vitamin C supplementation (1000 mg or more) was associated with higher BMD than that of nonusers. Again, it is premature to suggest routine supplementation. 

Forette F, Seux M-L, Staessen JA et al. Prevention of dementia in randomised double-blind placebo-controlled systolic hypertension in Europe (Syst-Eur) trial. Lancet 1998 351 1347-51 Morris MC, Beckett LA, Scherr PA et al. Vitamin E and vitamin C supplement use and risk of incident Alzheimer disease. Alzheimer Dis Assoc Disord 1998 12 121-6 National Institute for Clinical Excellence Technology Appraisal Guidance No. 19. Guidance on the use of donepezil, rivastigmine and galantamine for the treatment of Alzheimer s disease, 2001. http //www. nice, org. uk/... 

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