The effect of age and gender on the metabolic disposal of [1-¹³C]palmitic acid

Abstract

Objective: To examine the effect of age and gender on the metabolic disposal of [1-¹³C] palmitic acid.

Design: Cross-sectional.

Setting: Clinical 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 six men (BMI 23.3±2.6 kg/m²; aged 20–30 y) were recruited. Following oral administration of a bolus dose of [1-¹³C]palmitic acid (10 mg/kg body weight) consumed with a test meal (1667 kJ) the excretion of ¹³C-label was measured on breath as ¹³CO₂ over 24 h and in stool over 5 d to account for differences in absorption of [1-¹³C]palmitic acid. The ¹³C-enrichment of samples was determined by continuous flow-isotope ratio mass spectrometry. Net substrate oxidation was estimated from gaseous exchange measurements in the postabsorptive state and over 6 h postprandially.

Results: The excretion of ¹³CO₂ on breath varied between subjects both in the pattern and amount excreted over 24 h. Breath ¹³CO₂ was not different between boys (61.0±22.4% of absorbed dose) and girls (54.2±17.9% of absorbed dose). The excretion of breath ¹³CO₂ was less in the men (35.1±9.3% of absorbed dose; P=0.005) and that observed previously by our group in women (30.7±6.7% of absorbed dose; P=0.005) than in the children. Net fat oxidation was greater in the children in both the postabsorptive (2.43±0.78 g/h) and postprandial (11.89±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) and women studied previously (0.53±0.68 g/h; P=0.003; 0.03±3.21 g/6 h; P=0.001).

Conclusions: Our observations that children oxidised nearly twice the amount of [1-¹³C] palmitic acid than adults in conjunction with greater net fat oxidation in children than adults in both the postabsorptive and postprandial states should be considered before current UK dietary recommendations for fat and saturated fats, developed for adults, are applied to growing children. For dietary recommendations to be developed further more information is required, particularly in groups of infants and the elderly, about the factors that influence the postprandial handling of dietary fat.

Sponsorships: This work was supported by The Ministry of Agriculture, Fisheries and Food, Scientific Hospital Supplies, UK Ltd. and The Wessex Medical Trust.