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

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.

Diet and cardiovascular disease in the UK: are the messages getting across?

Cardiovascular disease (CVD) is a leading cause of premature death in the UK and a major cause of ill health and disability. Whilst death rates from CVD have been falling since the late 1970s in the UK, levels of morbidity (such as angina) do not seem to be falling and may even be rising in some age-groups, especially as the population ages. There is broad consensus that lifestyle factors, including physical activity and diet, are fundamental determinants of heart disease risk. Current recommendations to reduce cardiovascular risk include maintaining a healthy body weight, eating five or more portions of fruit and vegetables each day, reducing intake of fat (particularly saturated fatty acids), reducing salt intake and eating one portion of oily fish per week. Although some improvements have been made in recent years (e.g. a reduction in total fat intake), national studies suggest that more effective campaigns are required to increase awareness of the benefits of these dietary changes. The present paper will discuss how the dietary messages relating to CVD are best communicated to the general public and will identify some of the main barriers to their implementation.

Achievement of dietary fatty acid intakes in long-term controlled intervention studies: approach and methodology.

OBJECTIVE: To describe the calculations and approaches used to design experimental diets of differing saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) compositions for use in a long-term dietary intervention study, and to evaluate the degree to which the dietary targets were met. DESIGN, SETTING AND SUBJECTS: Fifty-one students living in a university hall of residence consumed a reference (SFA) diet for 8 weeks followed by either a moderate MUFA (MM) diet or a high MUFA (HM) diet for 16 weeks. The three diets were designed to differ only in their proportions of SFA and MUFA, while keeping total fat, polyunsaturated fatty acids (PUFA), trans-fatty acids, and the ratio of palmitic to stearic acid, and n-6 to n-3 PUFA, unchanged. RESULTS: Using habitual diet records and a standardised database for food fatty acid compositions, a sequential process of theoretical fat substitutions enabled suitable fat sources for use in the three diets to be identified, and experimental margarines for baking, spreading and the manufacture of snack foods to be designed. The dietary intervention was largely successful in achieving the fatty acid targets of the three diets, although unintended differences between the original target and the analysed fatty acid composition of the experimental margarines resulted in a lower than anticipated MUFA intake on the HM diet, and a lower ratio of palmitic to stearic acid compared with the reference or MM diet. CONCLUSIONS: This study has revealed important theoretical considerations that should be taken into account when designing diets of specific fatty acid composition, as well as practical issues of implementation.