An increased concentration of end products of lipid peroxidation is the evidence most frequently quoted for the involvement of free radicals in human disease. However, it is likely that increased oxidative damage occurs in most, if not all, human diseases and plays a significant pathological role in only some of them. For example, peroxidation appears to be important in atherosclerosis and in worsening the initial tissue injury caused by ischemic or traumatic brain damage. Oxidative stress can damage many biological molecules; indeed, proteins and DNA are often more significant targets of injury than are lipids, and lipid peroxidation often occurs late in the injury process. Many assays are available to measure lipid peroxidation, but no single assay is an accurate measure of the whole process. Application of simple diene-conjugate and thiobarbituric acid (TBA) assays to human tissues and body fluids can produce artifacts. An HPLC-based TBA test can eliminate some of these artifacts.

A wide variety of oxygen free radicals and other reactive oxygen species can be formed in the human body and in food systems. Transition metal ions accelerate free-radical damage. Antioxidant defenses, both enzymic and nonenzymic, protect the body against oxidative damage, but they are not 100% efficient, and so free-radical damage must be constantly repaired. Nonenzymatic antioxidants are frequently added to foods to prevent lipid peroxidation. Several lipid antioxidants can exert prooxidant effects toward other molecules under certain circumstances, and so antioxidants for food and therapeutic use must be characterized carefully. Methods of measuring oxidative damage and trapping free radicals in vivo are briefly discussed. Such methods are essential in checking proposals that increased intake of food-derived antioxidants (such as antioxidant vitamins) would be beneficial to humans.

Abstractcorbate might protect against the lung damage caused by cigarette smoking. 5 However, the Background -Fresh fruit consumption and vitamin C intake have been associated effects are not confined to smokers 1 3 and in one study appeared to be stronger in subjects with improved lung function in adults. Whether this is due to enhancement of lung who had never smoked and to be present in young adults, suggesting that other biological growth, to a reduction in lung function decline, or to protection against broncho-mechanisms may be required to explain reduced ventilatory function in subjects with a spasm is unclear. Methods -In a cross-sectional school low fruit intake.2 Strachan suggested that the relationship in adults might be an indirect rebased survey of 2650 children aged 8-11 from 10 towns in England and Wales the flection of an influence of diet on lung growth in childhood. In adults it has also been sugmain outcome measure was forced expiratory volume in one second (FEV 1 ) gested that any effect may be much greater amongst asthmatic subjects.1 standardised for body size and sex. Exposure was assessed by a food frequency We have examined the cross-sectional relationship between reported frequency of fresh questionnaire to parents and by measurement of plasma levels of vitamin C in a fruit, salad, and green vegetable consumption and lung function in 9-11 year old children subsample of 278 children. Results -FEV 1 was positively associated from 10 British towns. In addition we have examined the interactions with wheeze, and with frequency of fresh fruit consumption. After adjustment for possible confounding the relationship between plasma vitamin C levels and lung function in a subsample. We variables including social class and passive smoking, those who never ate any fresh have focused on fresh fruit because it is both an important source of vitamin C and may be fruit had an estimated FEV 1 some 79 ml (4.3%) lower than those who ate these more important in accounting for individual differences in intake, and because of the eviitems more than once a day (95% CI 22 to 136 ml). The association between FEV 1 and dence linking infrequent fresh fruit consumption to reduced lung function in adults. restricted to subjects who wheeze and to selected. Within each school 50 children aged identify the specific nutrient involved. Department of9-11 were invited to participate.