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Showing papers on "Ascorbic acid published in 1996"


Journal ArticleDOI
TL;DR: The FRAP assay offers a putative index of antioxidant, or reducing, potential of biological fluids within the technological reach of every laboratory and researcher interested in oxidative stress and its effects.

17,394 citations


Journal ArticleDOI
TL;DR: In this article, a large group of flavonoids from all major structural subclasses were tested on their ability to inhibit doxorubicin (enzymatically)-induced microsomal lipid peroxidation (LPO) and to chelate Fe2+.

1,195 citations


Journal ArticleDOI
01 Dec 1996-Urology
TL;DR: From the current data it appears that no single adjuvant will be able to enhance the fertilizing capacity of sperm in infertile men, and a combination of the possible strategies that are not toxic at the dosage used would be a feasible approach.

908 citations


Journal ArticleDOI
TL;DR: It is concluded that endothelial dysfunction in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus can be improved by administration of the antioxidant, vitamin C, and support the hypothesis that nitric oxide inactivation by oxygen-derived free radicals contributes to abnormal vascular reactivity in diabetes.
Abstract: Endothelium-dependent vasodilation is impaired in humans with diabetes mellitus. Inactivation of endothelium-derived nitric oxide by oxygen-derived free radicals contributes to abnormal vascular reactivity in experimental models of diabetes. To determine whether this observation is relevant to humans, we tested the hypothesis that the antioxidant, vitamin C, could improve endothelium-dependent vasodilation in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus. We studied 10 diabetic subjects and 10 age-matched, nondiabetic control subjects. Forearm blood flow was determined by venous occlusion plethysmography. Endothelium-dependent vasodilation was assessed by intraarterial infusion of methacholine (0.3-10 micrograms/min). Endothelium-independent vasodilation was measured by intraarterial infusion of nitroprusside (0.3-10 micrograms/min) and verapamil (10-300 micrograms/min). Forearm blood flow dose-response curves were determined for each drug before and during concomitant intraarterial administration of vitamin C (24 mg/min). In diabetic subjects, endothelium-dependent vasodilation to methacholine was augmented by simultaneous infusion of vitamin C (P = 0.002); in contrast, endothelium-independent vasodilation to nitroprusside and to verapamil were not affected by concomitant infusion of vitamin C (P = 0.9 and P = 0.4, respectively). In nondiabetic subjects, vitamin C administration did not alter endothelium-dependent vasodilation (P = 0.8). We conclude that endothelial dysfunction in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus can be improved by administration of the antioxidant, vitamin C. These findings support the hypothesis that nitric oxide inactivation by oxygen-derived free radicals contributes to abnormal vascular reactivity in diabetes.

883 citations


Journal ArticleDOI
TL;DR: This presentation discusses the role of catalytic metals in free radical-mediated oxidations, ascorbate as both a pro-oxidant and an antioxidant, use of asCorbate to determine adventitious catalytic metal concentrations, and uses of ascorBate radical as a marker of oxidative stress.
Abstract: Trace levels of transition metals can participate in the metal-catalyzed Haber-Weiss reaction (superoxide-driven Fenton reaction) as well as catalyze the oxidation of ascorbate. Generally ascorbate is thought of as an excellent reducing agent; it is able to serve as a donor antioxidant in free radical-mediated oxidation processes. However, as a reducing agent it is also able to reduce redox-active metals such as copper and iron, thereby increasing the pro-oxidant chemistry of these metals. Thus ascorbate can serve as both a pro-oxidant and an antioxidant. In general, at low ascorbate concentrations, ascorbate is prone to be a pro-oxidant, and at high concentrations, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the "position" of this crossover effect is a function of the catalytic metal concentration. In this presentation, we discuss: (1) the role of catalytic metals in free radical-mediated oxidations; (2) ascorbate as both a pro-oxidant and an antioxidant; (3) catalytic metal catalysis of ascorbate oxidation; (4) use of ascorbate to determine adventitious catalytic metal concentrations; (5) use of ascorbate radical as a marker of oxidative stress; and (6) use of ascorbate and iron as free radical pro-oxidants in photodynamic therapy of cancer.

851 citations


Journal ArticleDOI
TL;DR: In this paper, the hypothesis that dietary antioxidant vitamins and flavonoids account for this observation was investigated in a prospective study, where a cohort of 552 men aged 50 to 69 years was examined in 1970 and followed up for 15 years.
Abstract: Background: Epidemiological studies suggested that consumption of fruit and vegetables may protect against stroke. The hypothesis that dietary antioxidant vitamins and flavonoids account for this observation is investigated in a prospective study. Methods: A cohort of 552 men aged 50 to 69 years was examined in 1970 and followed up for 15 years. Mean nutrient and food intake was calculated from crosscheck dietary histories taken in 1960, 1965, and 1970. The association between antioxidants, selected foods, and stroke incidence was assessed by Cox proportional hazards regression analysis. Adjustment was made for confounding by age, systolic blood pressure, serum cholesterol, cigarette smoking, energy intake, and consumption of fish and alcohol. Results: Forty-two cases of first fatal or nonfatal stroke were documented. Dietary flavonoids (mainly quercetin) were inversely associated with stroke incidence after adjustment for potential confounders, including antioxidant vitamins. The relative risk (RR) of the highest vs the lowest quartile of flavonoid intake (≥28.6 mg/d vs Conclusions: The habitual intake of flavonoids and their major source (tea) may protect against stroke. (Arch Intern Med. 1996;154:637-642)

840 citations


Journal ArticleDOI
TL;DR: There is a need to increase the understanding of this enigmatic molecule since it could be involved in a wide range of important functions from antioxidant defence and photosynthesis to growth regulation.

794 citations


Journal ArticleDOI
TL;DR: In this article, various surface modification procedures were used on glassy carbon (GC) electrodes to yield surfaces with low oxide content or which lack specific oxide functional groups, and monolayers of several different adsorbates were formed on GC surfaces before electrochemical evaluation.
Abstract: Various well-established and novel surface modification procedures were used on glassy carbon (GC) electrodes to yield surfaces with low oxide content or which lack specific oxide functional groups. In addition, monolayers of several different adsorbates were formed on GC surfaces before electrochemical evaluation. Both the nonspecific monolayer adsorbates and reagents which chemisorb to specific functional groups were observed on the surface with Raman and photoelectron spectroscopy. The various GC surfaces were then evaluated for their electron transfer reactivity with nine redox systems in aqueous electrolyte, including Ru(NH3)62+/3+, Fe(CN6)3-/4-, ascorbic acid, and Feaq3+/2+. The nine systems were categorized according to their kinetic sensitivity to surface modification. Several, including Ru(NH3)62+/3+, are insensitive to surface modifications and are considered outer sphere. Feaq3+/2+, Vaq2+/3+, and Euaq2+/3+ are catalyzed by surface carbonyl groups and are very sensitive to the removal of surface...

669 citations


Journal ArticleDOI
TL;DR: Ascorbic acid reverses endothelial vasomotor dysfunction in the brachial circulation of patients with coronary artery disease and suggests that endothelial dysfunction may respond to antioxidant therapy.
Abstract: Background In the setting of atherosclerosis, endothelial vasomotor function is abnormal Increased oxidative stress has been implicated as one potential mechanism for this observation We therefore hypothesized that an antioxidant, ascorbic acid, would improve endothelium-dependent arterial dilation in patients with coronary artery disease Methods and Results Brachial artery endothelium-dependent dilation in response to hyperemia was assessed by high-resolution vascular ultrasound before and 2 hours after oral administration of either 2 g ascorbic acid or placebo in a total of 46 patients with documented coronary artery disease Plasma ascorbic acid concentration increased 25-fold 2 hours after treatment (46±8 to 114±11 μmol/L, P=001) In the prospectively defined group of patients with an abnormal baseline response (<5% dilation), ascorbic acid produced marked improvement in dilation (20±06% to 97±20%), whereas placebo had no effect (11±15% to 17±15%, P=003 for ascorbic acid versus placebo)

589 citations


Journal Article
TL;DR: The hypothesis that fruit and vegetables exert a cancer-protective effect via a decrease in oxidative damage to DNA is supported via a reduction in endogenous oxidative base damage in the lymphocyte DNA of both smokers and nonsmokers.
Abstract: The association between high intake of fruit and vegetables and low incidence of certain cancers is well established. Dietary antioxidants present in these foods are thought to decrease free radical attack on DNA and hence to protect against mutations that cause cancer, but this causal mechanism remains conjectural. We have adopted a molecular epidemiological approach to this question, based on a modified alkaline single-cell gel electrophoresis assay ("comet assay") which specifically detects oxidation of pyrimidines in the DNA of human lymphocytes. In a survey of men 50-59 years of age living in the northeast of Scotland, smokers initially showed significantly more base damage than nonsmokers. Correlations between oxidative base damage and plasma concentrations of various antioxidants were generally negative but not statistically significant. Supplementation of the diet for 20 weeks with vitamin C (100 mg/day), vitamin E (280 mg/day), and beta-carotene (25 mg/day) resulted in a highly significant (P < 0.002) decrease in endogenous oxidative base damage in the lymphocyte DNA of both smokers and nonsmokers. In addition, lymphocytes of antioxidant-supplemented subjects showed an increased resistance to oxidative damage when challenged in vitro with H2O2. These findings strongly support the hypothesis that fruit and vegetables exert a cancer-protective effect via a decrease in oxidative damage to DNA.

563 citations


Journal ArticleDOI
TL;DR: Oxidative activation offers a novel route for the involvement of TGF beta in tissue processes in which ROS are implicated and endows LTGF beta with the ability to act as a sensor of oxidative stress and to function as a signal for orchestrating the response of multiple cell types.
Abstract: Transforming growth factor beta 1 (TGF beta) is a multifunctional cytokine that orchestrates response to injury via ubiquitous cell surface receptors. The biological activity of TGF beta is restrained by its secretion as a latent complex (LTGF beta) such that activation determines the extent of TGF beta activity during physiological and pathological events. TGF beta action has been implicated in a variety of reactive oxygen-mediated tissue processes, particularly inflammation, and in pathologies such as reperfusion injury, rheumatoid arthritis, and atherosclerosis. It was recently shown to be rapidly activated after in vivo radiation exposure, which also generates reactive oxygen species (ROS). In the present studies, the potential for redox-mediated LTGF beta activation was investigated using a cell-free system in which ROS were generated in solution by ionizing radiation or metal ion-catalyzed ascorbate reaction. Irradiation (100 Gray) of recombinant human LTGF beta in solution induced 26% activation compared with that elicited by standard thermal activation. Metal-catalyzed ascorbate oxidation elicited extremely efficient recombinant LTGF beta activation that matched or exceeded thermal activation. The efficiency of ascorbate activation depended on ascorbate concentrations and the presence of transition metal ions. We postulate that oxidation of specific amino acids in the latency-conferring peptide leads to a conformation change in the latent complex that allows release of TGF beta. Oxidative activation offers a novel route for the involvement of TGF beta in tissue processes in which ROS are implicated and endows LTGF beta with the ability to act as a sensor of oxidative stress and, by releasing TGF beta, to function as a signal for orchestrating the response of multiple cell types. LTGF beta redox sensitivity is presumably directed toward recovery of homeostasis; however, oxidation may also be a mechanism of LTGF beta activation that can be deleterious during disease mechanisms involving chronic ROS production.

Journal ArticleDOI
TL;DR: The present studies demonstrate that the antioxidant vitamin C markedly improves endothelium-dependent responses in chronic smokers, and supports the concept that endothelial dysfunction in Chronic smokers is at least in part mediated by enhanced formation of oxygen-derived free radicals.
Abstract: Background Chronic smoking is associated with endothelial dysfunction, an early stage of atherosclerosis. It has been suggested that endothelial dysfunction may be a consequence of enhanced degradation of nitric oxide secondary to formation of oxygen-derived free radicals. To test this hypothesis, we investigated the effects of the antioxidant vitamin C on endothelium-dependent responses in chronic smokers. Methods and Results Forearm blood flow responses to the endothelium-dependent vasodilator acetylcholine (7.5, 15, 30, and 60 μg/min) and the endothelium-independent vasodilator sodium nitroprusside (1, 3, and 10 μg/min) were measured by venous occlusion plethysmography in 10 control subjects and 10 chronic smokers. Drugs were infused into the brachial artery, and forearm blood flow was measured for each drug before and during concomitant intra-arterial infusion of the antioxidant vitamin C (18 mg/min). In control subjects, vitamin C had no effect on forearm blood flow in response to acetylcholine and sodium nitroprusside. In contrast, in chronic smokers the attenuated forearm blood flow responses to acetylcholine were markedly improved by concomitant administration of vitamin C, whereas the vasodilator responses to sodium nitroprusside were not affected. Conclusions The present studies demonstrate that the antioxidant vitamin C markedly improves endothelium-dependent responses in chronic smokers. This observation supports the concept that endothelial dysfunction in chronic smokers is at least in part mediated by enhanced formation of oxygen-derived free radicals.

Journal ArticleDOI
TL;DR: D dopamine in high concentrations binds to protein in the striatum, an event that is correlated with the specific loss of dopaminergic terminals in Parkinson's disease, and is suggested to be caused by an imbalance between the oxidation of dopamine and the availability of antioxidant defenses.
Abstract: We have examined the biochemical and histological effects of high concentrations of dopamine (0.05-1.0 micromol) injected into the rat striatum. Twenty-four hours after such injections, the oxidation products of dopamine and dihydroxyphenylacetic acid were detected as both free and protein-bound cysteinyl dopamine and cysteinyl dihydroxyphenylacetic acid. Protein-bound cysteinyl catechols were increased 7- to 20-fold above control tissue levels. By 7 days postinjection, the protein-bound cysteinyl catechols were still detectable, although reduced in concentration, whereas the free forms could no longer be measured. Histological examination of striatum at 7 days revealed a central core of nonspecific damage including neuronal loss and gliosis. This core was surrounded by a region containing a marked reduction in tyrosine hydroxylase immunoreactivity but no apparent loss of serotonin or synaptophysin immunoreactivity. When dopamine was injected with an equimolar concentration of either ascorbic acid or glutathione, the formation of protein-bound cysteinyl catechols was greatly reduced. Moreover, the specific loss of tyrosine hydroxylase immunoreactivity associated with dopamine injections was no longer detectable, although the nonspecific changes in cytoarchitecture were still apparent. Thus, following its oxidation, dopamine in high concentrations binds to protein in the striatum, an event that is correlated with the specific loss of dopaminergic terminals. We suggest that the selective degeneration of dopamine neurons in Parkinson's disease may be caused by an imbalance between the oxidation of dopamine and the availability of antioxidant defenses.

Journal ArticleDOI
TL;DR: Ascorbic acid has a multiplicity of antioxidant properties, but it can exert pro-oxidant effects in vitro, usually by interaction with transition metal ions, and it is as yet uncertain that these pro-oxide effects have any biological relevance.
Abstract: Ascorbic acid has a multiplicity of antioxidant properties, but it can exert pro-oxidant effects in vitro, usually by interaction with transition metal ions. It is as yet uncertain that these pro-oxidant effects have any biological relevance: some of the available data are summarized.

Journal ArticleDOI
TL;DR: Results show that sorghum does not have consistently higher or lower antioxidant levels than sunflower, and that antioxidant responses to drought differ in C3 and C4 plants.
Abstract: To determine if antioxidant responses to drought differ between C3 and C4 plants, we grew Sorghum bicolor (C4 ) and Helianthus annuus (C3 ) under either watered or dry conditions in a growth chamber. Levels of leaf enzymatic antioxidants (ascorbate peroxidase, catalase, guaiacol peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase and superoxide dismutase), nonenzymatic antioxidants (ascorbate, glutathione and carotenoids) and stress parameters (Chl and malondialdehyde [MDA]) were determined. Under watered and drought conditions, Chl contents and leaf relative water contents (RWC) were higher in sorghum than in sunflower; however, MDA levels were higher in sunflower than in sorghum. Under watered conditions, inherent levels of antioxidants were not consistently higher or lower in sorghum than in sunflower. In response to drought, levels of antioxidants, Chl and MDA showed increase, decrease or remained unchanged depending on crop, duration of drought and kind of antioxidants. Duration of drought was divided arbitrarily into three stages. At an early stage of drought (watering had stopped for 3-4 d) when soil water content (WC) and leaf RWC had decreased only in sunflower, drought generally did not affect levels of antioxidants and stress parameters. At a middle stage of drought (watering had stopped for 5-6 d) when soil WC had decreased for both sorghum and sunflower but leaf WC and RWC had decreased only in sunflower, drought changed levels of some antioxidants in sunflower and sorghum. At a late stage of drought (watering had stopped for 7-8 d) when soil WC, leaf WC and RWC had decreased in sorghum and sunflower, most parameters studied were affected by drought. Because of the differential effect of drought, levels of antioxidants were not consistently higher or lower in sorghum than in sunflower under drought. These results show that, under both drought and watered conditions, sorghum does not have consistently higher or lower antioxidant levels than sunflower, and that antioxidant responses to drought differ in C3 and C4 plants.

Journal ArticleDOI
TL;DR: It is shown that the soz1 mutant is hypersensitive to both sulfur dioxide and ultraviolet B irradiation, thus implicating ascorbate in defense against varied environmental stresses and indicating that screening for ozone-sensitive mutants is a powerful method for identifying physiologically important antioxidant mechanisms and signal transduction pathways.
Abstract: L-ascorbic acid (vitamin C) is a powerful reducing agent found in millimolar concentrations in plants, and is proposed to play an important role in scavenging free radicals in plants and animals. However, surprisingly little is known about the role of this antioxidant in plant environmental stress adaptation or ascorbate biosynthesis. We report the isolation of soz1, a semi-dominant ozone-sensitive mutant that accumulates only 30% of the normal ascorbate concentration. The results of genetic approaches and feeding studies show that the ascorbate concentration affects foliar resistance to the oxidizing gas ozone. Consistent with the proposed role for ascorbate in reactive oxygen species detoxification, lipid peroxides are elevated in soz1, but not in wild type following ozone fumigation. We show that the soz1 mutant is hypersensitive to both sulfur dioxide and ultraviolet B irradiation, thus implicating ascorbate in defense against varied environmental stresses. In addition to defining the first ascorbate deficient mutant in plants, these results indicate that screening for ozone-sensitive mutants is a powerful method for identifying physiologically important antioxidant mechanisms and signal transduction pathways. Analysis of soz1 should lead to more information about the physiological roles and metabolism of ascorbate.

Journal Article
TL;DR: It is concluded that H. pylori infection is accompanied by the formation of endogenous reactive nitrogen intermediates, which may contribute to DNA damage and apoptosis and in patients supplemented with either ascorbic acid or beta-carotene, there was a trend toward a reduction in apoptosis.
Abstract: Helicobacter pylori infection is a known risk factor for gastric cancer. We hypothesized that H. pylori infection would lead to the sustained production of the reactive nitrogen species nitric oxide and peroxynitrite as part of the host immune response. We further hypothesized that H. pylori infection would lead to increased apoptosis of gastric epithelial cells, possibly in response to free radical-mediated DNA damage. Using immunohistochemistry, we stained and scored gastric antral biopsies from 84 Colombian patients with nonatrophic gastritis before and after treatment for H. pylori infection. We examined expression of inducible nitric oxide synthase (iNOS); nitrotyrosine, a marker for peroxynitrite; and DNA fragmentation, a marker for apoptosis. Patients were treated with triple therapy (amoxicillin, 500 mg three times a day for 2 weeks; metronidazole, 400 mg three times a day for 2 weeks; and bismuth subsalicylate, 262 mg four times a day for 2 weeks, followed by 262 mg every day for 4-12 months). Eradication of H. pylori infection resulted in a significant reduction in iNOS and nitrotyrosine staining and a marginally significant reduction in apoptosis. Dietary supplementation with beta-carotene (30 mg every day for 4-12 months) resulted in a significant decrease in iNOS staining. Supplementation with ascorbic acid (1 g twice a day for 4-12 months) led to a significant reduction in nitrotyrosine staining. In patients supplemented with either ascorbic acid or beta-carotene, there was a trend toward a reduction in apoptosis, but this was not statistically significant. We conclude that H. pylori infection is accompanied by the formation of endogenous reactive nitrogen intermediates, which may contribute to DNA damage and apoptosis. In addition to antimicrobial therapy, dietary supplementation with beta-carotene and ascorbic acid may prevent the formation of these potential carcinogens.

Journal ArticleDOI
TL;DR: In order to make a compressed tablet which can rapidly disintegrate in the oral cavity, microcrystalline cellulose and low-substituted hydroxypropylcellulose were used as disintegrants, and ethenzamide and ascorbic acid were chosen as poorly and easily water soluble model drugs, respectively.
Abstract: In order to make a compressed tablet which can rapidly disintegrate in the oral cavity, microcrystalline cellulose and low-substituted hydroxypropylcellulose were used as disintegrants, and ethenzamide and ascorbic acid were chosen as poorly and easily water soluble model drugs, respectively. The mixture of microcrystalline cellulose and low-substituted hydroxypropylcellulose was compressed at 100--500 kgf in the absence of an active ingredient. The properties of these tablets, such as hardness, porosity, the time required for complete wetting of a tested tablet (wetting time), water uptake and disintegration time determined by a new disintegration apparatus, were investigated to elucidate the wetting and disintegration characteristics of these tablets, When the MCC/L-HPC ratio was in the range of 8:2 to 9:1, the shortest disintegration time was observed. The disintegration of tablets containing ethenzamide or ascorbic acid was examined next. Tablet disintegration time in the oral cavity was also tested, and good correlation between the disintegration behaviors in vitro and in the oral cavity was recognized.

Journal ArticleDOI
TL;DR: The possibility that paternal smoking causes mutations in sperm that lead to cancer, birth defects, and genetic diseases in offspring is discussed.
Abstract: Our previous studies have shown that men with low ascorbate intake have markedly increased oxo8dG in the DNA of their sperm. Because cigarette smoke is high in oxidants and depletes plasma and tissue antioxidants, oxidative DNA damage in sperm and tocopherol and ascorbate levels in seminal plasma were determined in smokers and non-smokers. The level in sperm DNA of oxo8dG, an oxidative lesion of guanine, was 50% higher in smokers compared to nonsmokers (p = 0.005). The concentration of alpha-tocopherol in seminal plasma was decreased in smokers by 32% (p = 0.03). Smoking and low antioxidant levels increase oxidative damage to sperm DNA. We discuss the possibility that paternal smoking causes mutations in sperm that lead to cancer, birth defects, and genetic diseases in offspring.

Journal ArticleDOI
TL;DR: In this article, the antioxidant properties of tocopherols and ascorbic acid in edible oils, and the impact of interfacial phenomena on their activities in emulsions and the effects of edible oil processing are reviewed.

Journal ArticleDOI
TL;DR: Overall, the present data suggest that protection against oxidative damage and related disease is best served by the variety of antioxidant substances found in fruit and vegetables.

Journal ArticleDOI
TL;DR: In this population, intake of vegetables appears to decrease premenopausal breast cancer risk, and this effect may be related to beta-carotene and lutein + zeaxanthin in vegetables.
Abstract: Background: Given the international variations in breast cancer incidence rates and the changes in breast cancer incidence among migrant populations, it has been hypothesized that diet is a factor influencing risk of this disease. Many studies indicate that a diet high in vegetables and fruits may protect against breast cancer. Purpose: We conducted a case-control study of diet, including the intake of non-food supplements, and premenopausal breast cancer risk. We evaluated in detail usual intake of vegetables and fruits (each measured as the total reported grams consumed for all queried vegetables and fruit), vitamins C and E, folic acid, individual carotenoids, and dietary fiber with its components. Methods: Case patients (n = 297) were identified through pathology records from hospitals in Erie and Niagara counties in western New York. They consisted of premenopausal women 40 years of age or older who were diagnosed with breast cancer from November 1986 through April 1991. Control subjects (n = 311), frequency-matched to case patients on the basis of age and county of residence, were randomly selected from New York State Department of Motor Vehicles records. In-person interviews included detailed reports of usual diet in the period 2 years before the interview. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: There was a reduction in risk associated with high intake of several nutrients. With the lowest quartile of intake as the referent, adjusted ORs for the highest quartile of intake for specific nutrients were as follows: vitamin C (OR = 0.53; 95% CI = 0.33-0.86), a-tocopherol (OR = 0.55; 95% CI = 0.34-0.88), folic acid (OR = 0.50; 95% CI = 0.310.82), a-carotene (OR = 0.67; 95% CI = 0.42-1.08) and Pcarotene (OR = 0.46; 95% CI = 0.28-0.74), lutein + zeaxanthin (OR = 0.47; 95% CI = 0.28-0.77), and dietary fiber from vegetables and fruits (OR = 0.48; 95% CI = 0.300.78). No association with risk was found for p-cryptoxanthin, lycopene, or grain fiber. Fruits were weakly associated with a reduction in risk (fourth quartile OR = 0.67; 95% CI = 0.42-1.09). No association was found between breast cancer risk and intake of vitamins C and E and folic acid taken as supplements. A strong inverse association between total vegetable intake and risk was observed (fourth quartile OR = 0.46; 95% CI = 0.28-0.74). This inverse association was found to be independent of vitamin C, a-tocopherol, folic acid, dietary fiber, and a-carotene. Adjusting for P-carotene or lutein + zeaxanthin somewhat attenuated the inverse association with vegetable intake. Conclusions: In this population, intake of vegetables appears to decrease premenopausal breast cancer risk. This effect may be related, in part, to P-carotene and lutein + zeaxanthin in vegetables. It appears, however, that, of the nutrients and food components examined, no single dietary factor explains the effect. Evaluated components found together in vegetables may have a synergistic effect on breast cancer risk; alternatively, other unmeasured factors in these foods may also influence risk. [J Natl Cancer Inst 1996;88:340-8] Given the international variation in breast cancer incidence rates and the changes in incidence among migrant populations (/), it has been hypothesized that diet is a factor influencing risk of this disease. There has been considerable attention paid to the hypothesis that fat intake is related to increased risk of breast cancer (2). While less research has focused on other dietary constituents, a number of studies (3-9) would appear to indicate that a diet high in vegetables and fruits may protect against breast cancer. While a few studies (10-12) have failed to find a relation, the finding of a protective effect of fruits and vegetables is relatively consistent and, therefore, provocative in terms of breast cancer prevention. The role of vegetables, fruits, and the nutrients and other dietary components found in these foods re

Journal ArticleDOI
TL;DR: In this review the process of lipid peroxidation and the atherogenicity of peroxidied lipids are discussed, and the most commonly used laboratory test for lipid per oxidation, the thiobarbituric acid reacting substances (TBARS) test is presented.
Abstract: In this review the process of lipid peroxidation and the atherogenicity of peroxidied lipids are discussed. Recent findings with regard to the effect of selected dietary factors on susceptibility of lipids to oxidative stress and on antioxidant defences are analysed with particular reference to their potential use in the prevention and treatment of atherogenesis and, by extension, coronary heart disease. Laboratory methods of assessing antioxidant defences, lipid peroxidation and the effects of lipid peroxidation are also reviewed and discussed with particular reference to their ability to assess in vivo oxidative stress and lipid peroxidation status. A range of oxidative stress indices are presented and their limitations discussed, but the main focus is on the most commonly used laboratory test for lipid peroxidation, the thiobarbituric acid reacting substances (TBARS) test. Finally, the influence of selected dietary factors on measured peroxidation status is discussed, with particular reference to the antioxidant vitamins C (ascorbic acid) and E (alpha tocopherol) and the type of fatty acids (mono- and poly-unsaturated) in the diet.

Journal ArticleDOI
TL;DR: High intake of antioxidant micronutrients, especially vitamin C, may reduce the risk of cartilage loss and disease progression in people with OA, and no effect of antioxidant nutrients on incident OA is found.
Abstract: Objective. Cumulative damage to tissues, mediated by reactive oxygen species, has been implicated as a pathway that leads to many of the degenerative changes associated with aging. We hypothesized that increased intake of antioxidant micronutrients might be associated with decreased rates of osteoarthritis (OA) in the knees, a common age-related disorder. Methods. Participants in the Framingham Osteoarthritis Cohort Study underwent knee evaluations by radiography at examinations 18 (1983–1985) and 22 (1992–1993). Usual dietary intake was assessed using the Food Frequency Questionnaire, administered at examination 20 (1988–1989). Knees without OA at baseline (Kellgren and Lawrence [K&L] grade ⩾1) were classified as having incident OA if they had a K&L grade ⩽2 at followup. Knees with OA at baseline were classified as having progressive OA if their score increased by ⩽1 at followup. Knees were also classified as having cartilage loss or osteophyte growth if their maximal joint space narrowing or osteophyte growth score increased by ⩽1 (range 0–3). The association of vitamin C, beta carotene, and vitamin E intake, ranked in sex-specific tertiles, with incidence and progression of OA was compared with that of a panel of nonantioxidant vitamins, B1, B6, niacin, and folate, using logistic regression and generalized estimation equations to adjust for correlation between fellow knees. The lowest tertile for each dietary exposure was used as the referent category. Odds ratios (OR) were adjusted for age, sex, body mass index, weight change, knee injury, physical activity, energy intake, and health status. Results. Six hundred forty participants received complete assessments. Incident and progressive OA occurred in 81 and 68 knees, respectively. We found no significant association of incident OA with any nutrient. A 3-fold reduction in risk of OA progression was found for both the middle tertile (adjusted OR = 0.3, 95% confidence interval [95% CI] 0.1–0.8) and highest tertile (adjusted OR = 0.3, 95% CI 0.1–0.6) of vitamin C intake. This related predominantly to a reduced risk of cartilage loss (adjusted OR = 0.3, 95% CI 0.1–0.8). Those with high vitamin C intake also had a reduced risk of developing knee pain (adjusted OR = 0.3, 95% CI 0.1–0.8). A reduction in risk of OA progression was seen for beta carotene (adjusted OR = 0.4, 95% CI 0.2–0.9) and vitamin E intake (adjusted OR = 0.7, 95% CI 0.3–1.6), but was less consistent. No significant associations were observed for the nonantioxidant nutrients. Conclusion. High intake of antioxidant micronutrients, especially vitamin C, may reduce the risk of cartilage loss and disease progression in people with OA. We found no effect of antioxidant nutrients on incident OA. These preliminary findings warrant confirmation.

Journal ArticleDOI
TL;DR: Whether the antioxidant mechanism explains their relationship with risk for acute and chronic disease in epidemiologic studies remains to be determined and will have an impact on both clinical dietetics practice and public health nutrition guidelines.
Abstract: Under normal circumstances, free radicals that are produced through biological processes and in response to exogenous stimuli are controlled by various enzymes and antioxidants in the body Laboratory evidence suggests that oxidative stress, which occurs when free radical formation exceeds the ability to protect against them, may form the biological basis of several acute medical problems, such as tissue injury after trauma, and chronic conditions, such as atherosclerosis and cancer A potential role for the antioxidant micronutrients (vitamin C, vitamin E, and the carotenoids) in modifying the risk for conditions that may result from oxidative stress has stimulated intense research efforts, increased interest in micronutrient supplements, and heightened consumer interest in these compounds Much remains to be learned, however, about the bioavailability, tissue uptake, metabolism, and biological activities of these micronutrients These biological characteristics will ultimately determine their clinical usefulness in modulating oxidative stress Also, whether the antioxidant mechanism explains their relationship with risk for acute and chronic disease in epidemiologic studies remains to be determined Increased knowledge in this area of nutrition science will have an impact on both clinical dietetics practice and public health nutrition guidelines J Am Diet Assoc 1996; 96:693–702

Journal ArticleDOI
TL;DR: There is a marked increase in anti-TNF activity and a decrease of antioxidant defense in patients at risk of developing multiple organ failure and the predictive value of plasma concentrations of circulating TNF-soluble receptors and vitamin C in this type of patient needs further evaluation.
Abstract: ObjectivesThe aims of this study were: a) to evaluate plasma concentrations of cytokines and their soluble receptors, as well as antioxidant substances in patients at high risk of developing multiple organ failure; b) to investigate early change; and c) to examine the possible prognostic value of th

Journal ArticleDOI
TL;DR: The findings indicate that antioxidant defenses could be considerably compromised in these very sick patients and the potential of these species to damage DNA and lipid membranes could be increased and compromise recovery.

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TL;DR: The ability of caffeine to inhibit oxidative damage induced by these reactive species in membranes suggest one more positive attribute of caffeine, whose daily intake as coffee may be considerable in most populations.

Journal ArticleDOI
TL;DR: An increase in the consumption of animal fats among patients with PD is consistent with the hypothesis that oxidative stress and lipid peroxidation are important in the pathogenesis of this disease.
Abstract: Oxidative stress plays an important role in the pathogenesis of Parkinson's disease (PD). In a population-based, case-control study we examined whether dietary intake of antioxidants and other oxidative compounds was associated with PD. Dietary intake was assessed by a semiquantitative food-frequency questionnaire in 110 PD case patients and 287 control subjects. A higher caloric intake was observed in patients with PD and did not vary with increasing duration of symptoms. Energy-adjusted fat intake was significantly higher among patients with PD than control subjects (p for trend = 0.007). Intake of protein (p for trend = 0.17) and carbohydrates (p for trend = 0.46) did not differ in patients and control subjects. Analyses of the primary sources of fat indicated that increasing intake of animal fats were strongly related to PD (odds ratio, 5.3; 95% confidence interval, 1.8-15.5; p for trend = 0.001). No significant differences were observed for intake of vitamins with antioxidant activity. An increase in the consumption of animal fats among patients with PD is consistent with the hypothesis that oxidative stress and lipid peroxidation are important in the pathogenesis of this disease. No effect of vitamins with antioxidant activity, either from food or supplements, was observed.

Journal ArticleDOI
09 Mar 1996-BMJ
TL;DR: The relation between cognitive function and risk of death from stroke suggests that cerebrovascular disease is an important cause of declining cognitive function, and vitamin C status may be a determinant of cognitive function in elderly people through its effect on atherogenesis.
Abstract: Objectives: To investigate the relation between cognitive function and cause specific mortality in people aged 65 and over. Design: A 20 year follow up study of a cohort of randomly selected elderly people living in the community who in 1973-4 had taken part in a nutritional survey funded by the Department of Health and Social Security. Setting: Eight areas in Britain (five in England, two in Scotland, and one in Wales). Subjects: 921 men and women whose cognitive function was assessed by a geriatrician in 1973-4 and for whom data on health, socioeconomic circumstances, and diet had been recorded. Results: Cognitive impairment was associated with increased mortality, in particular death from ischaemic stroke. Those who scored 7 or less on the Hodkinson mental test had a relative risk of dying from stroke of 2.8 (95% confidence interval 1.4 to 5.5), compared with those who gained the maximum score (10), after adjustment for age, sex, blood pressure, serum cholesterol concentration, and vitamin C intake. These associations were independent of illness or social class. At the time of the nutritional survey, cognitive function was poorest in those with the lowest vitamin C status, whether measured by dietary intake or plasma ascorbic acid concentration. The relation between vitamin C status and cognitive function was independent of age, illness, social class, or other dietary variables. Conclusion: The relation between cognitive function and risk of death from stroke suggests that cerebrovascular disease is an important cause of declining cognitive function. Vitamin C status may be a determinant of cognitive function in elderly people through its effect on atherogenesis. A high vitamin C intake may protect against both cognitive impairment and cerebrovascular disease. Key messages Key messages In this prospective study of 921 elderly people cognitive impairment was a strong predictor of death from ischaemic stroke Low vitamin C intake and low plasma ascorbate concentrations were also important risk factors for death from stroke Cognitive performance was poorest in people with the lowest vitamin C status A high vitamin C intake may protect against both cognitive impairment and cerebrovascular disease