THE DETERMINANTS OF PLASMA BETA-CAROTENE - INTERACTION BETWEEN SMOKING AND OTHER LIFE-STYLE FACTORS

Objective: To assess the effect of cigarette smoking on the relationsh ip between dietary intake and circulating levels of beta-carotene. Des ign: A secondary analysis of data collected for the Diet and Nutrition al Survey of British Adults by The Department of Health and The Minist ry of Agriculture, Fisheries and Food; the study was a cross-sectional survey of a representative sample of the British population. Setting: The study was conducted on a free living adult (16-64 years of age) p opulation resident in Great Britain. Subjects: 1483 subjects completed a seven day weighed inventory and provided a blood sample. Results: S mokers had statistically significantly lower dietary intakes and circu lating levels of beta-carotene than non-smokers. At the same level of dietary intake, smokers were more likely to have lower circulating lev els than non-smokers. For every 1000 mu g change in dietary intake, th ere was a 0.01 mu mol/l change in plasma beta-carotene in smokers and a 0.04 mu mol/l change in non-smokers. The effect of smoking on circul ating levels of beta-carotene persisted after adjusting for other fact ors. Conclusions: The results suggest that smoking places extra demand s on the host; the higher risk of heart disease for smokers may be due to a combination of an increased inflammatory response, reduced host defences, and increased levels of circulating LDL. Failure to take acc ount of the interaction between risk factors may distort the estimates of the relative importance of each factor when considered in isolatio n.