THE EFFECT OF AGE AND GENDER ON THE METABOLIC DISPOSAL OF [1-C-13]PALMITIC ACID

Objective: To examine the effect of age and gender on the metabolic di sposal of [1-C-13] palmitic acid. Design: Cross-sectional. Setting: Cl inical Nutrition and Metabolism Unit at Southampton General Hospital, Institute of Human Nutrition, University of Southampton. Subjects and measurements: Twelve children (5 boys and 7 girls; aged 5-10 y) and si x men (BMI 23.3 +/- 2.6 kg/m(2); aged 20-30 y) were recruited, Followi ng oral administration of a bolus dose of [1-C-13]palmitic acid (10 mg /kg body weight) consumed with a test meal (1667 kJ) the excretion of C-13-label was measured on breath as (13) CO2 over 24 h and in stool o ver 5 d to account for differences in absorption of [1-C-13]palmitic a cid. The C-13-enrichment of samples was determined by continuous flow- isotope ratio mass spectometry. Net substrate oxidation was estimated from gaseous exchange measurements in the postabsorptive state and ove r 6 h postprandially. Results: The excretion of (CO2)-C-l3 on breath v aried between subjects both in the pattern and amount excreted over 24 h, Breath (CO2)-C-13 was not different between boys (61.0 +/- 22.4% o f absorbed dose) and girls (54.2 +/- 17.9% of absorbed dose). The excr etion of breath (CO2)-C-13 was less in the men (35.1 +/- 9.3% of absor bed dose; P = 0.005) and that observed previously by our group in wome n (30.7 +/- 6.7% of absorbed dose; P = 0.005) than in the children. Ne t fat oxidation was greater in the children in both the postabsorptive (2.43 +/- 78 g/h) and postprandial (1189 +/- 3.13 g/6 h) states than in the men (0.93 g/h +/- 1.50; P = 0.016; 9.86 +/- 10.53 g/6 h; NS) an d women studied previously (0.53 +/- 0.68 g/h; P = 0.003; 0.03 +/- 3.2 1 g/6 h; P = 0.00l). Conclusions: Our observations that children oxidi sed nearly twice the amount of [1-C-13] palmitic acid than adults in c onjunction with greater net fat oxidation In children than adults in b oth the postabsorptive and postprandial states should he considered be fore current UK dietary recommendations for fat and saturated fats. de veloped for adults, are applied to growing children. For dietary recom mendations to be developed further more information is required, parti cularly in groups of infants and the elderly, about the factors that i nfluence the postprandial handling of dietary fat.