Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis

Bjelaković, Goran; Nikolova, Dimitrinka; Simonetti, Rosa G; Gluud, Christian

doi:10.1016/s0140-6736(04)17138-9

Cited by 548 publications

(386 citation statements)

References 55 publications

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“…Yu et al (63) , Bjelakovic et al (64) In US patients with relatively low Se status (plasma Se < 85 mg/l) HIV infection progresses more rapidly to AIDS with higher mortality Baum et al (65) , Campa et al (66) In a Tanzanian observational study of 949 HIV-positive pregnant women mortality decreases with increase in plasma Se ( > 85 mg/l) over 5-year follow-up period Kupka et al (67) Cancer Inverse relationship between crop and human Se status and cancer incidence in North America…”

Section: Antiviral Effects and Hivmentioning

confidence: 99%

Symposium on ‘Geographical and geological influences on nutrition’ Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

2009

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Se is essential to human and animal health but can be toxic in excess. An interest in its geochemistry has developed alongside a greater understanding of its function in a number of health conditions. Geology exerts a strong control on the Se status of the surface environment; low-Se rock-types (0·05–0·09 mg Se/kg) make up the majority of rocks occurring at the Earth's surface, which in turn account for the generally low levels of Se in most soils. However, there are exceptions such as associations with sulfide mineralisation and in some types of sedimentary rocks (e.g. black shales) in which contents of Se can be much higher. Baseline geochemical data now enable a comparison to be made between environmental and human Se status, although a direct link is only likely to be seen if the population is dependent on the local environment for sustenance. This situation is demonstrated with an example from the work of the British Geological Survey in the Se-deficiency belt of China. The recent fall in the daily dietary Se intake in the UK is discussed in the context of human Se status and declining use of North American wheat in bread making. Generally, US wheat has ten times more Se than UK wheat, attributed to the fact that soils from the wheat-growing belt of America are more enriched in Se to a similar order of magnitude. In agriculture effective biofortification of crops with Se-rich fertilisers must be demonstrably safe to the environment and monitored appropriately and baseline geochemical data will enable this process to be done with confidence.

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Section: Antiviral Effects and Hivmentioning

confidence: 99%

Symposium on ‘Geographical and geological influences on nutrition’ Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

2009

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“…Again, there are few data relating to intestinal infectious disease, but there is scant evidence that antioxidant supplementation reduces all-cause mortality (including from other infectious diseases) or gastrointestinal cancer (60,61) .…”

Section: Other Antioxidantsmentioning

confidence: 99%

Nutrition, intestinal defence and the microbiome

Kelly

2010

Proc. Nutr. Soc.

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The interaction between nutrition and infection was the subject of important work by several groups in the 1960s. The explosion of knowledge in immunology, including innate immunity, has led to increased understanding of the impact of nutrition on host defence, but much more work needs to be done in this area. In the last decade an increasing volume of work has opened up the previously obscure world of human endogenous flora. This work suggests that the microbiome, the total genetic pool of the microbiota, contributes to the already complex interaction between nutrition and infectious disease. The established concept that nutritional status, host defence and infection all impact on each other now has to be expanded into a multiple interaction, with the microbiota interacting with all three other elements. There is good evidence that the microbiome programmes host defence and drives a metabolome that impacts on energy balance, and indeed on some micronutrients. In turn, host defence shapes the microbiome, and nutritional status, particularly micronutrient status, helps determine several elements of host defence. While interventions in this area are in their infancy, the understanding of interactions that already have an enormous impact on global health is now at a threshold. The present review explores the evidence for these interactions with a view to putting potential interventions into the context of a conceptual framework.

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“…Arguably excess quantity of antioxidant in tissues may lead to deleterious consequences. Many high quality recent studies are available in support [28,[54][55][56][57][58]. However, many issues are still unresolved or controversial.…”

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confidence: 99%

Reconvene and Reconnect the Antioxidant Hypothesis in Human Health and Disease

Singh

Chandra

Mahdi

et al. 2010

Indian J Clin Biochem

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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 overar...

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Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis

Cited by 548 publications

References 55 publications

Symposium on ‘Geographical and geological influences on nutrition’ Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

Symposium on ‘Geographical and geological influences on nutrition’ Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

Nutrition, intestinal defence and the microbiome

Reconvene and Reconnect the Antioxidant Hypothesis in Human Health and Disease

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