Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036474 (scurvy)
 685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There is an enormous amount of literature on vitamin C intake and health in animals, cell cultures, and humans. Beyond its function in collagen formation, ascorbic acid is known to increase absorption of inorganic iron, to have essential roles in the metabolism of folic acid and of some amino acids and hormones, and to act as an antioxidant. In recent years, research has increasingly focused on this latter function, stimulated by suggestions that "oxidative stress" may be a causal factor in the etiology of such diverse and important disorders of aging as cancer, cardiovascular disease, and cataract formation. The present evidence is strong enough to have convinced nutritionists that daily vitamin C intake should be many times higher than the amount needed to protect against scurvy, and this is reflected in the present Recommended Dietary Allowances. Suggestions that the recommended levels should be higher still are largely based on extrapolations from results of animal and tissue culture studies. How much ascorbic acid is necessary to achieve in humans the effects seen in animal studies is not clear. In general, the limited human studies have not been persuasive. The data are incomplete, and many of the studies have serious flaws. There are no toxicity studies of the type done for new compounds being considered for approval as therapy for major disease conditions. Intervention studies will be difficult, but are essential, and methods for tissue saturation measurement must be defined before new recommendations for the public are designed.
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PMID:Vitamin C (ascorbic acid): new roles, new requirements? 805 61

The current recommended dietary allowance (RDA) for vitamin C for adult nonsmoking men and women is 60 mg/d, which is based on a mean requirement of 46 mg/d to prevent the deficiency disease scurvy. However, recent scientific evidence indicates that an increased intake of vitamin C is associated with a reduced risk of chronic diseases such as cancer, cardiovascular disease, and cataract, probably through antioxidant mechanisms. It is likely that the amount of vitamin C required to prevent scurvy is not sufficient to optimally protect against these diseases. Because the RDA is defined as "the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all healthy individuals in a group," it is appropriate to reevaluate the RDA for vitamin C. Therefore, we reviewed the biochemical, clinical, and epidemiologic evidence to date for a role of vitamin C in chronic disease prevention. The totality of the reviewed data suggests that an intake of 90-100 mg vitamin C/d is required for optimum reduction of chronic disease risk in nonsmoking men and women. This amount is about twice the amount on which the current RDA for vitamin C is based, suggesting a new RDA of 120 mg vitamin C/d.
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PMID:Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. 1035 26

Vitamin deficiency syndromes such as scurvy and beriberi are uncommon in Western societies. However, suboptimal intake of some vitamins, above levels causing classic vitamin deficiency, is a risk factor for chronic diseases and common in the general population, especially the elderly. Suboptimal folic acid levels, along with suboptimal levels of vitamins B(6) and B(12), are a risk factor for cardiovascular disease, neural tube defects, and colon and breast cancer; low levels of vitamin D contribute to osteopenia and fractures; and low levels of the antioxidant vitamins (vitamins A, E, and C) may increase risk for several chronic diseases. Most people do not consume an optimal amount of all vitamins by diet alone. Pending strong evidence of effectiveness from randomized trials, it appears prudent for all adults to take vitamin supplements. The evidence base for tailoring the contents of multivitamins to specific characteristics of patients such as age, sex, and physical activity and for testing vitamin levels to guide specific supplementation practices is limited. Physicians should make specific efforts to learn about their patients' use of vitamins to ensure that they are taking vitamins they should, such as folate supplementation for women in the childbearing years, and avoiding dangerous practices such as high doses of vitamin A during pregnancy or massive doses of fat-soluble vitamins at any age.
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PMID:Vitamins for chronic disease prevention in adults: clinical applications. 1206 76

Prevention of disease rather than its alleviation or cure has always been the aim of healthcare professionals. While this goal has been achieved for many infectious diseases through improvements in hygiene and vaccination, as well as for acute deficiency diseases such as scurvy, less progress has been made with chronic diseases. These are increasing as the population ages. Chief among the chronic diseases on the increase are: Type 2 diabetes. Hypertension and cardiovascular disease, which are responsible for over 40 per cent of all deaths in the UK (DoH 1999). Obesity, which is a major cause of morbidity and predisposes to diabetes, cardiovascular disease and other chronic illnesses. Cancer. This article describes the nature, aetiology and prevention of the metabolic syndrome. Although not a disease, the metabolic syndrome is like smoking in that it strongly predisposes to disease and is preventable.
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PMID:The metabolic syndrome. 1295 75

Vitamin C is an essential micronutrient. Absence from the diet will result in the deficiency disease scurvy, typically characterised by weakening of collagenous structures. High intakes of vitamin C have been associated with decreased incidence or severity of a number of diseases, including cancer and cardiovascular disease. These beneficial effects may be attributed to its antioxidant properties, although the exact mechanisms of action remain elusive. It is also unclear what intake levels are required for optimal health benefits. The task of defining optimal intakes is hindered by the lack of a reliable functional marker of tissue vitamin C status in man. Many different pathways have been investigated, but none of them have measurable outcome variables relating directly to scorbutic changes. The bone-collagen formation pathway has the potential to provide a functional index of tissue vitamin C adequacy. Vitamin C acts as a cofactor for the enzyme lysyl hydroxylase, which is required for the hydroxylation of lysine residues in procollagen chains. Pyridinoline is a mature collagen cross-link formed from three hydroxylysine residues, deoxypyridinoline is formed from two hydroxylysine and one lysine residue. Guinea-pig studies have shown an alteration in the pyridinium cross-link ratios in response to graded vitamin C intakes (Tsuchiya & Bates, 1998). In order to investigate whether these changes can be seen in a human population group, a study was carried out in rural Gambia, where there is a marked seasonal variation in dietary vitamin C. The present review discusses the rationale behind the study and presents some preliminary results.
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PMID:Vitamin C and bone markers: investigations in a Gambian population. 1450 91

Lipoprotein(a), a variant of LDL carrying the adhesive glycoprotein apo(a), is a leading risk factor for cardiovascular disease. Lipoprotein(a) (Lp(a)) is found in humans and subhuman primates but rarely in lower mammals. Better understanding of the evolutionary advantage of this molecule should elucidate its physiological role. We developed a new mouse model with two characteristics of human metabolism: the expression of Lp(a) and the lack of endogenous ascorbate (vitamin C) production. We show that dietary deficiency of ascorbate increases serum levels of Lp(a). Moreover, chronic hypoascorbemia and complete depletion of ascorbate (scurvy) leads to Lp(a) accumulation in the vascular wall and parallels atherosclerotic lesion development. The results suggest that dietary ascorbate deficiency is a risk factor for atherosclerosis independent of dietary lipids. We provide support for the concept that Lp(a) functions as a mobile repair molecule compensating for the structural impairment of the vascular wall, a morphological hallmark of hypoascorbemia and scurvy.
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PMID:Hypoascorbemia induces atherosclerosis and vascular deposition of lipoprotein(a) in transgenic mice. 2606 92

Vitamin C is a powerful dietary antioxidant that has received considerable attention in the literature related to its possible role in heart health. Although classical vitamin C deficiency, marked by scurvy, is rare in most parts of the world, some research has shown variable heart disease risks depending on plasma vitamin C concentration, even within the normal range. Furthermore, other studies have suggested possible heart-related benefits to vitamin C taken in doses beyond the minimal amounts required to prevent classically defined deficiency. The objective of this review is to systematically review the findings of existing epidemiologic research on vitamin C and its potential role in cardiovascular disease (CVD). It is well established that vitamin C inhibits oxidation of LDL-protein, thereby reducing atherosclerosis, but the cardiovascular outcomes related to this action and other actions of vitamin C are not fully understood. Randomized controlled trials as well as observational cohort studies have investigated this topic with varying results. Vitamin C has been linked in some work to improvements in lipid profiles, arterial stiffness, and endothelial function. However, other studies have failed to confirm these results, and observational cohort studies are varied in their findings on the vitamin's effect on CVD risk and mortality. Overall, current research suggests that vitamin C deficiency is associated with a higher risk of mortality from CVD and that vitamin C may slightly improve endothelial function and lipid profiles in some groups, especially those with low plasma vitamin C levels. However, the current literature provides little support for the widespread use of vitamin C supplementation to reduce CVD risk or mortality.
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PMID:Vitamin C and Heart Health: A Review Based on Findings from Epidemiologic Studies. 2752 39

Vitamin C is essential to prevent scurvy in humans and is implicated in the primary prevention of common and complex diseases such as coronary heart disease, stroke, and cancer. This chapter reviews the latest knowledge about dietary vitamin C in human health with an emphasis on studies of the molecular mechanisms of vitamin C maintenance as well as gene-nutrient interactions modifying these relationships. Epidemiological evidence indicates 5% prevalence for vitamin C deficiency and 13% prevalence for suboptimal status even in industrialized countries. The daily intake (dose) and the corresponding systemic concentrations (response) are related in a saturable relationship, and low systemic vitamin C concentrations in observational studies are associated with negative health outcomes. However, there is no evidence that vitamin C supplementation impacts the risks for all-cause mortality, impaired cognitive performance, reduced quality of life, the development of eye diseases, infections, cardiovascular disease, and cancers. This might be related to the fact that prevention would not be realized by supplementation in populations already adequately supplied through dietary sources. Recent genetic association studies indicate that the dietary intake might not be the sole determinant of systemic concentrations, since variations in genes participating in redox homeostasis and vitamin C transport had been associated with lowered plasma concentrations. However, impact sizes are generally low and these phenomena might only affect individual of suboptimal dietary supply.
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PMID:Dietary Vitamin C in Human Health. 2947 24