Antioxidants primary prevention

Chong, EW, Wong, TY, Kreis, AJ, Simpson, JA, and Guymer, RH, 2007. Dietary antioxidants and primary prevention of age related macular degeneration Systematic review and meta-analysis. BMJ 335, 755. 

The E vitamins consist of eight naturally occurring tocopherols, of which a-tocopherol is the most active (Figure 28.28). The primary function of vitamin E is as an antioxidant in prevention of the nonenzymic oxidation of cell components (for example, polyunsaturated fatty acids) by molec ular oxygen and free radicals. 

Cambridge Heart Antioxidant Study DATATOR Deprenyl and Tocopherol Antioxidative Therapy of Rarkinsonism FMC, Finnish Mobile Clinic Health Examination Survey GISSI, Gruppo Italiano Studio Soprawivenza Infarto HOPE, Heart Outcome Prevention Evaluation HPFS, Health Professional Follow-up Study NHS, Nurses Health Study PPR Primary Prevention Project SPACE, Secondary Prevention with Antioxidants of Cardiovascular disease in End-stage renal disease VEAPS, Vitamin E Atherosclerosis Prevention Study VECAT Vitamin E Cataract Age-related maculopathy Trial. 

There are many types of antioxidants. The most popular in composite materials are primary antioxidants or chain breaking antioxidants, and secondary antioxidants or preventative antioxidants. ... 

Two main types of antioxidants are available commercially primary antioxidants and secondary antioxidants. Primary or chain breaking antioxidants work by removing the free radical species, converting them to less reactive forms and thereby inhibiting the propagation process. Secondary or preventive antioxidants work by interfering with the formation of additional free radicals. 

Increased oxidant formation is a significant contribution to disease and often an indispensable requirement, but not just an epiphenomenon. In carcinogenesis, chemoprevention of exocyclic DNA adducts by antioxidants was demonstrated by Nair et al. (1996). Primary prevention of cancer is not only to avoid hazardous exposures but also involves the intake of protective agents and modulation of the host s defence mechanisms before the onset of malignancy. 

Low levels of vitamin Bg may cause hyperhomocysteinaemia since vitamin Bg acts as a cofactor for tra .s-sulfation of cysteine (Siri et al. 1998). There is evidence that an elevated homocysteine level is a risk factor for heart disease and stroke. Endo et al. (2006) reported that vitamin Bg deficiency induced the oxidant stress which accelerates atherosclerosis. They also highlighted that the antioxidant activity of vitamin Bg may suppress the homo-cysteine-induced atherosclerosis. Vitamin Bg levels may be important in the prevention of coronary heart disease intake of vitamin Bg above the current recommended dietary allowance has been shown to be instrumental in the primary prevention of coronary heart disease among women (Rimm et al. 1998). 

Clinical studies investigated the antioxidative effects of antioxidant supplementation of humans on ex vivo LDL oxidation [48-52], We have shown that dietary supplementation of p-carotene of healthy subjects resulted in a moderate inhibitory effect on the susceptibility of LDL to oxidative modification [53-55] in some, but not in all studied subjects. The combination of carotenoids with vitamin E, in contrast, demonstrated a synergistic inhibitory effect on LDL oxidation in all studied cases [56], We showed that supplementation of vitamin E of atherosclerotic apolipoprotein E-deficient mice (25 pg/mouse/day for 3 months) inhibited LDL oxidation by 40% and the atherosclerotic lesion area by 35% [57], In humans, unlike in animal models, both vitamin E and carotenoids did not significantly reduce atherosclerosis in primary prevention trials [58], This result may be related to insufficient absorption, insufficient potency, and inappropriate tissue distribution,... 

Antioxidants act either by radical trapping, interfering in the radical propagation, or by decomposition of the hydroperoxide formed. In this way they inhibit the formation of new radicals. The former are known as chain breaking or chain terminator antioxidants (primary antioxidants). The latter, the hydroperoxide decomposing agents, are also known as preventive antioxidants (secondary antioxidants). 

Table 1 Summary of large mterventlon trials >1000 subjects) Investigating the role of antioxidants and CVD In primary prevention ...

An average of 4 years of supplementation with 400 lU of vitamin E per day was found to exert no beneficial or harmful effect on CVD outcomes or on nephropathy. The Primary Prevention Project trial found no effect of vitamin E (300mg/day) supplementation for 3 or 4 years in diabetic subjects, and the Heart Protection Study, which included a number of people with diabetes, also reported no benefit of a combination of antioxidant vitamins on mortality or incidence of vascular disease. 

The detection and quantification of one or more of the above lipid peroxidation produas (primary and/or secondary) in appropriate biofluids and tissue samples serves to provide indices of lipid peroxidation both in ntro and in vivo. However, it must be stressed that it is absolutely essential to ensure that the products monitored do not arise artifactually, a very difiScult task since parameters such as the availability of catalytic trace metal ions and O2, temperature and exposure to light are all capable of promoting the oxidative deterioration of PUFAs. Indeed, one sensible precaution involves the treatment of samples for analysis with sufficient levels of a chainbreaking antioxidant [for example, butylated hydroxy-toluene (BHT)] immediately after collection to retard or prevent peroxidation occurring during periods of storage or preparation. 

The antioxidant and acid neutralization properties of most fuel stabilizer formulations help to prevent the initial formation of most acids. Compounds such as tertiary-alkyl primary amines, as shown by the example in FIGURE 6-5, are quite effective distillate fuel additives. These oil-soluble amines can be formulated into stabilizer formulations at relatively low concentrations and can provide a significant boost in overall performance of a fuel stabilizer. 

When the antioxidants were used in the cooked/stored samples, data indicated that they were very effective in inhibiting lipid oxidation and MFD. The chemical and off-flavor indicators were reduced and the on-flavor notes were increased. Thus, phenolic-type primary antioxidants that function as free radical scavengers are very effective tools for preventing lipid oxidation and MFD in ground beef. It should also be noted that the intensity of the desirable flavor notes remained at very high levels, which meant that the patties retained their beefy tastes. Therefore, for an antioxidant to be highly effective, it should not only prevent lipid oxidation, but it should also retain the desirable flavor properties of the food commodity. 

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