Dietary intake of individuals interested in eating a healthy diet: a validated study of intake before and after dietary advice.

The food intake of 37 adult volunteers (12 M, 25 F) interested in eating a healthy diet was measured on two occasions by the 7-day weighed record method. In week 1 subjects consumed their habitual diet and in week 2 attempted to follow dietary recommendations (DR). Intakes were compared with recommended dietary allowances (RDA) and with dietary guidelines (DG). Validation of recorded energy intakes against changes in body weight, and sodium, potassium and nitrogen intakes against urine excretions suggested reliable dietary records in both study weeks. Mean dietary intakes in week 1 met the RDA for all nutrients studied except for energy (which was close) and zinc (in females only). Daily energy intake was 2160 kcal (9.04 MJ) in week 1 and 1810 kcal (7.56 MJ) in week 2, and subjects lost weight during week 2. Absolute intakes of vitamins and minerals were similar in both study weeks, thus increasing nutrient density in week 2 and suggesting improved dietary quality. Mean dietary intakes in week 1 conformed more closely to DG than commonly reported and changed in the direction recommended in week 2. Mean daily intakes in week 1 and week 2 respectively were: fibre, 31 and 34 g; sodium 114 and 90 mmol; Na:K ratio, 1.37 and 1.10; alcohol, 3.3 and 2.3 per cent of total energy; fat, 38.7 and 34.2 per cent of food energy or 37.4 and 33.4 per cent of total energy. Intake of fibre increased with respect to energy but sodium intake per unit energy did not decrease. Energy intake was positively related to sodium, fibre and zinc intakes and influenced ease of conformity to DR for these nutrients. It is concluded that our motivated subjects were able to make short-term dietary changes consistent with DR. Whether or not these changes continue in the long term is the subject of a follow-up study.