Abstract
Studies of absorption and bioavailability of nutrients naturally enriched with 13C require accurate measurements of small increases of 13C in respiratory CO2 and stool carbon. Sensitivity of these measurements would be increased by reducing the natural background of 13C in these excreta. We have developed a 13C depleted infant formula based on lactose, whey, and casein from New Zealand cows which consume only C3 vegetation naturally low in 13C. This formula, designated CNRC3, was produced by Ross Laboratories and was comparable to a commercial 60/40 whey/casein product. To test the formula's ability to reduce baseline levels of 13C in infant excreta, 10 formula-fed infants 28 to 56 days old and free of metabolic disorders were enrolled in the 9 day study. Two stool samples were collected daily and stored frozen. Infants received their usual formula on days 1 and 2 and were switched to CNRC3 formula for days 3-9. On days 2 and 9, 7 breath samples were collected at 30-min intervals with a face mask. Breath and stool samples were analyzed for 13C content by gas-isotope-ratio mass spectrometry. Infants consuming commercial formula had breath δ 13C values of -21.1 ± 0.6 % over the 3-hr collection period; stool values were -21.6 ± 0.5 %. After 7 days on the CNRC3 formula, δ 13C values of breath declined by 5.6 % to -26.7 ± 0.7 %; stool values declined by 3.8 % to -25.4 ± 0.4 %. The reduced background of 13C achieved in CNRC3 formula can improve resolution of excess 13C in infant excreta by approximately 50%.
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Boutton, T., Hopkinson, J., Sekely, S. et al. A 13C-DEPLETED INFANT FORMULA USEFUL FOR METABOLIC STUDIES. Pediatr Res 21 (Suppl 4), 264 (1987). https://doi.org/10.1203/00006450-198704010-00583
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DOI: https://doi.org/10.1203/00006450-198704010-00583