Biogeochemistry of selenium and its impact on food chain quality and human health

Objective: The British Nutrition Foundation was recently commissioned by the Food Standards Agency to conduct a review of the government's research programme on Antioxidants in Food . Part of this work involved an independent review of the scientific literature on the role of antioxidants in chronic disease prevention, which is presented in this paper. Background: There is consistent evidence that diets rich in fruit and vegetables and other plant foods are associated with moderately lower overall mortality rates and lower death rates from cardiovascular disease and some types of cancer. The ‘antioxidant hypothesis’ proposes that vitamin C, vitamin E, carotenoids and other antioxidant nutrients afford protection against chronic diseases by decreasing oxidative damage. Results: Although scientific rationale and observational studies have been convincing, randomised primary and secondary intervention trials have failed to show any consistent benefit from the use of antioxidant supplements on cardiovascular disease or cancer risk, with some trials even suggesting possible harm in certain subgroups. These trials have usually involved the administration of single antioxidant nutrients given at relatively high doses. The results of trials investigating the effect of a balanced combination of antioxidants at levels achievable by diet are awaited. Conclusion: The suggestion that antioxidant supplements can prevent chronic diseases has not been proved or consistently supported by the findings of published intervention trials. Further evidence regarding the efficacy, safety and appropriate dosage of antioxidants in relation to chronic disease is needed. The most prudent public health advice remains to increase the consumption of plant foods, as such dietary patterns are associated with reduced risk of chronic disease.

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A review of the epidemiological evidence for the 'antioxidant hypothesis'.

Selenium and coronary heart disease: a meta-analysis

Antioxidants and disease prevention

The independent association of serum concentrations of saturated and polyunsaturated fatty acids, apolipoproteins Al and B, selenium and vitamins A and E with the risk of death from coronary artery disease (CAD) was studied in 92 persons with no previous myocardial infarction, who died from CAD during a 5-year follow-up, and their 92 1-to-1 matched controls. Case-control pairs came from a randomly drawn population sample of approximately 12,000 persons aged 30 to 64 years from 2 provinces of eastern Finland, an area with exceptionally high CAD mortality. Control subjects were matched for sex, age, serum cholesterol, mean arterial pressure, tobacco consumption and history of cardiovascular diseases. The persons who died of CAD had lower serum esterified arachidonic acid concentrations before follow-up than the control subjects (41 vs 48 mg/liter, p = 0.05), and this difference was greater for pairs with no chest pain on effort (36 vs 50 mg/liter, p

Serum fatty acids, apolipoproteins, selenium and vitamin antioxidants and the risk of death from coronary artery disease.

A longitudinal case-control study of 33 patients with one or more risk factors for coronary heart disease and 64 controls showed that the serum selenium concentration (range 0.63-1.33 mumol/l (50-105 micrograms/l] was not associated with development of clinical manifestations of coronary heart disease during a follow up of five to seven years. The content of polyunsaturated fatty acids, especially eicosapentaenoic acid, in serum cholesterol esters and phospholipids was positively correlated with selenium concentration. As a low content of polyunsaturated fatty acids in serum lipids was an independent risk factor for coronary heart disease in these subjects it may be hypothesised that the high coronary risk in subjects with a very low serum selenium concentration (less than 0.57 mumol/l (less than 45 micrograms/l] might be due not to selenium deficiency but to the coexisting low concentrations of polyunsaturated fatty acids in serum.

G Alfthan

Papers

Serum selenium concentration related to myocardial infarction and fatty acid content of serum lipids.