Under-reporting of dietary intake by smoking and non-smoking subjects counselled for hypercholesterolaemia.

Objective: We asked whether under-reporting of energy and cigarette smoking were associated with choice of foods and dietary composition amongst subjects with hypercholesterolaemia who had received dietary instruction to lower serum cholesterol.

Methods: Dietary intake was assessed with a 4-day weighed food record in 205 women and 141 men, aged 20-73 years, being treated at a lipid clinic (tertiary referral centre). Under-reporting was assessed by calculating the ratio of energy intake (EI) to estimated basal metabolic rate (BMR).

Results: The median EI/BMR was 1.1 for both men and women. EI/BMR did not differ according to smoking status, but correlated negatively with body mass index (Spearman's rho = -0.32, P = 0.0001). EI/BMR was inversely associated with energy-adjusted intakes of potatoes, vegetables, fish and low-fat meats, and positively associated with intakes of nuts, potato crisps, chocolate, sour and ice cream, oils, fatty meat spreads, cakes and biscuits, and with alcohol. Thus, low EI/BMR was associated with increased energy-adjusted intakes of protein, thiamine, riboflavin, niacin, iron and cholesterol and with decreased intakes of sugar, poly- and monounsaturated fats and vitamin E (all P < 0.05). Cigarette smokers had a higher energy percentage (E%) from fat than non-smokers (29 +/- 6 vs. 26 +/- 6), a lower E% from carbohydrates (50 +/- 7 vs. 54 +/- 7) and a lower intake of vitamin C (11 +/- 7 vs. 16 +/- 9 mg MJ-1; all P = 0.0001), reflecting an increased intake of fatty meats and a decreased intake of skimmed cheese, fruit, rice and pasta, and cakes and biscuits (all P < 0.05).

Conclusions: Weighed dietary records reflected a 'healthier' intake of fat, protein, sugar, alcohol and some micronutrients amongst under-reporters, suggesting that self-reported dietary intakes are biased in patients with hypercholesterolaemia. Lack of responsiveness to the diet should not be assumed when dietary data are based on self-report. Smokers report a higher intake of fat and lower intake of vitamin C than non-smokers, even after dietary counsel, and may require more intensive interventions to optimize the diet.