Effects of antioxidant supplements and nutrients on patients with asthma and allergies (original) (raw)
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Antioxidant supplementation for health -a boon or a bane?
Antioxidants (vitamins E and C, β-carotene, superoxide dismutase [SOD], catalase etc.) are the substances that protect cells from the damage caused by free radicals, formed as a result of oxidative stress. Free radicals (O2−, H2O2, OH−, ROO− etc.) are generated during the cellular metabolism and also due to environmental effects (cigarette smoke, ionizing radiations). Excessive production of free radicals has been implicated in the causation and progression of several diseases, e.g., atherosclerosis, cancer, rheumatoid arthritis, diabetes, and cataract. The general belief is that since free radicals are bad for health, antioxidants are good. This led to an indiscriminate use and supplementation of antioxidants, which is currently a controversial issue. This review gives an updated information on the effects of supplementation of antioxidants (vitamins E and C, β-carotene, SOD, catalase etc.). While some studies suggest that antioxidants are benefi cial and protective, other interven...
Weighing the benefits of dietary antioxidant supplements
Journal of Food Technology, 2018
Evidence is building that consumption of large doses of dietary antioxidant supplements may not always render beneficial health effects and some may even have a negative effect. There are few reasons why this happens. Firstly, the role of free radicals causing various chronic diseases is not yet fully clear. There are also some beneficial actions conferred by free radicals in human physiology. Secondly, antioxidant capacity in the body coupled with immune system may resist the action of dietary antioxidants. Lastly, the dosage of antioxidants taken may be inappropriate. Some misconceptions about free radicals and antioxidants are discussed. In fact, low to moderate level of prooxidants might sometimes be better in stimulating the endogenous antioxidant enzyme defence system for overall human health. Consumption of natural foods rich in antioxidants such as fruits, vegetables, nuts, and grains, among others, may provide a better option for health promotion instead of taking high dosages of dietary antioxidant supplements.
Antioxidant Supplements and Oxidative Stress: The debate extends to the Middle East
Sultan Qaboos University Medical Journal [SQUMJ]
ree radicals are atoms that contain an unpaired valence electron that renders them chemically unstable and highly reactive. Free radicals are capable of damaging biological molecules such as nucleic acids, proteins, carbohydrates and lipids leading to cell damage and/or cell death. 1 These atoms result from normal metabolic processes in the human body as well as from environmental exposure to harmful rays, ozone, cigarette smoking, air pollutants and industrial chemicals. 1 Antioxidants are compounds that donate electrons to neutralise free radicals and prevent their detrimental effects. Diet is an important source of antioxidants as fruits and vegetables are rich in antioxidants such as polyphenols, vitamin E, vitamin C and minerals such as selenium. Glutathione is a major endogenous antioxidant which is produced in the intracellular compartment. 2 The balance between the oxidising effects of free radicals and the reducing power of antioxidants is referred to as "redox homeostasis". 3 Oxidative stress in humans occurs as a result of the imbalance between free radical production in cells and tissues and the ability of natural antioxidant defences to detoxify them. Exposure to oxidative stress has escalated in modern societies as a result of increased exposure to harmful oxidants in various aspects of life-including diet, industrial pollution, chemicals, medications, smoking, pesticides and many more. Imbalance in the redox state renders the human body more vulnerable to an array of disorders and chronic diseases such as cancer, heart disease, neurological disorders and other diseases linked to aging and disturbed immune function. 4-6 The International Society of Antioxidants in Nutrition and Health (ISANH) is a non-profit organisation based in Paris, France. 7 The general aim of this society is to address various factors affecting the redox balance in health and disease, particularly the role of natural and supplemental antioxidants. ISANH conducts regular
BioFactors, 2008
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Reconvene and reconnect the antioxidant hypothesis in human health and disease
Indian Journal of Clinical Biochemistry, 2010
The antioxidants are essential molecules in human system but are not miracle molecules. They are neither performance enhancers nor can prevent or cure diseases when taken in excess. Their supplemental value is debateable. In fact, many high quality clinical trials on antioxidant supplement have shown no effect or adverse outcomes ranging from morbidity to all cause mortality. Several Chochrane Meta-analysis and Markov Model techniques, which are presently best available statistical models to derive conclusive answers for comparing large number of trials, support these claims. Nevertheless none of these statistical techniques are flawless. Hence, more efforts are needed to develop perfect statistical model to analyze the pooled data and further double blind, placebo controlled interventional clinical trials, which are gold standard, should be implicitly conducted to get explicit answers. Superoxide dismutase (SOD), glutathione peroxidase and catalase are termed as primary antioxidants as these scavenge superoxide anion and hydrogen peroxide. All these three enzymes are inducible enzymes, thereby inherently meaning that body increases or decreases their activity as per requirement. Hence there is no need to attempt to manipulate their activity nor have such efforts been clinically useful. SOD administration has been tried in some conditions especially in cancer and myocardial infarction but has largely failed, probably because SOD is a large molecule and can not cross cell membrane. The dietary antioxidants, including nutrient antioxidants are chain breaking antioxidants and in tandem with enzyme antioxidants temper the reactive oxygen species (ROS) and reactive nitrogen species (RNS) within physiological limits. Since body is able to regulate its own requirements of enzyme antioxidants, the diet must provide adequate quantity of non-enzymic antioxidants to meet the normal requirements and provide protection in exigent condition. So far, there is no evidence that human tissues ever experience the torrent of reactive species and that in chronic conditions with mildly enhanced generation of reactive species, the body can meet them squarely if antioxidants defense system in tissues is biochemically optimized. We are not yet certain about optimal levels of antioxidants in tissues. Two ways have been used to assess them: first by dietary intake and second by measuring plasma levels. Lately determination of plasma/serum level of antioxidants is considered better index for diagnostic and prognostic purposes. The recommended levels for vitamin A, E and C and beta carotene are 2.2-2.8 lmol/l; 27.5-30 lmol/l; 40-50 lmol/l and 0.4-0.5 lmol/l, respectively. The requirement and recommended blood levels of other dietary antioxidants are not established. The resolved issues are (1) essential to scavenge excess of radical species (2) participants in redox homeostasis (3) selective antioxidants activity against radical species (4) there is no universal antioxidant and 5) therapeutic value in case of deficiency. The overarching issues are (1) therapeutic value as adjuvant therapy in management of diseases (2) supplemental value in developing population (3) selective interactivity of antioxidant in different tissues and on different substrates (4) quantitative contribution in redox balance (5) mechanisms of adverse action on excess supplementation (6) advantages and disadvantages of prooxidant behavior of antioxidants (7) behavior in cohorts with polymorphic differences (8) interaction and intervention in radiotherapy, diabetes and diabetic complications and cardiovascular diseases (9) preventive behavior in neurological disorders (10) benefits of non-nutrient dietary antioxidants (11) markers to assess optimized antioxidants status (12) assessment of benefits of supplementation in alcoholics and heavy smokers. The unresolved and intriguing issues are (1) many compounds such as vitamin A and many others possessing both antioxidant and non-antioxidant properties contribute to both the activities in vivo or exclusively only to non-antioxidant activity and (2) since human tissues do not experience the surge of FR, whether there is any need to develop stronger synthetic antioxidants. Theoretically such antioxidants may do more harm than good.
Recent evidence does not support a causational relationship between antioxidant supplements and reduced risk of coronary heart disease and other age-related pathologies. Advances in the understanding of the complex interactions between reactive oxygen species (ROS) and antioxidants “in vivo” and of the role of mitochondria in the adaptive response to oxidative stress suggest that physiological production of ROS in mitochondria is one of the most essential contributions to the maintenance of health and longevity. Through mechanisms linked to the concept of mitochondrial hormesis, a moderate transient increase in ROS formation increases the body's antioxidant defences by activating enzymes sensitive to oxidative stress and redox-sensitive transcription factors, while high doses of antioxidants may inhibit this adaptive response.
Dietary Antioxidants and Asthma in Adults
American Journal of Respiratory and Critical Care Medicine, 2001
Background: Several antioxidant nutrients have been reported to be inversely associated with asthma. A study was undertaken to assess the independent associations of these nutrients with asthma in adults. Methods: A nested case-control study was performed in 515 adults with physician diagnosed asthma and 515 matched controls using dietary data obtained from 7 day food diaries. The main outcome measures were physician diagnosed asthma and current symptomatic asthma (diagnosed asthma and self-reported wheeze within the previous 12 months). Results: Cases were similar to controls in age, sex, social class, and daily energy intake but had a lower median intake of fruit (132.1 v 149.1 g/day, p(0.05). 51.5% of the population reported zero consumption of citrus fruit; relative to these individuals, people who consumed .46.3 g/day had a reduced risk of diagnosed and symptomatic asthma (OR adjusted for potential confounders 0.59 (95% CI 0.43 to 0.82) and 0.51 (95% CI 0.33 to 0.79), respectively). In nutrient analysis, dietary vitamin C and manganese were inversely and independently associated with symptomatic asthma (adjusted OR per quintile increase 0.88 (95% CI 0.77 to 1.00) for vitamin C and 0.85 (95% CI 0.74 to 0.98) for manganese), but only manganese was independently associated with diagnosed asthma (OR 0.86 (95% CI 0.77 to 0.95)). Adjusted plasma levels of vitamin C were significantly lower in symptomatic cases than in controls (54.3 v 58.2 mmol/l, p = 0.003). Conclusions: Symptomatic asthma in adults is associated with a low dietary intake of fruit, the antioxidant nutrients vitamin C and manganese, and low plasma vitamin C levels. These findings suggest that diet may be a potentially modifiable risk factor for the development of asthma.
Nutrients, 2010
A recent meta-analysis of selected randomized clinical trials (RCTs), in which population groups of differing ages and health status were supplemented with various doses of -carotene, vitamin A, and/or vitamin E, found that these interventions increased all-cause mortality. However, this meta-analysis did not consider the rationale of the constituent RCTs for antioxidant supplementation, none of which included mortality as a primary outcome. As the rationale for these trials was to test the hypothesis of a potential benefit of antioxidant supplementation, an alternative approach to a systematic evaluation of these RCTs would be to evaluate this outcome relative to the putative risk of greater total mortality. Thus, we examined these data based on the primary outcome of the 66 RCTs included in the meta-analysis via a decision analysis to identify whether the results provided a positive (i.e., benefit), null or negative (i.e., harm) outcome. Our evaluation indicated that of these RCTs, 24 had a positive outcome, 39 had a null outcome, and 3 had a negative outcome. We further categorized these interventions as primary (risk reduction in healthy populations) or secondary (slowing pathogenesis or preventing recurrent events and/or cause-specific mortality) prevention or therapeutic (treatment to improve quality of life, limit complications, and/or provide rehabilitation) studies, and