GASTRIC EMPTYING IN FORMULA FED AND BREAST FED INFANTS MEASURED WITH THE 13C OCTANOIC ACID BREATH TEST.

The 13C octanoic acid breath test, a non-invasive method to measure gastric emptying, was used to compare the gastric emptying rate of formula fed infants with that of breast fed infants. Octanoic acid, a medium chain triglyceride (MCT) marked with the stable isotope 13C is immediately absorbed in the duodenum. Because gastric emptying is the rate-limiting step of the absorption of MCT, the fraction of 13C expired in the breath indicates the rate of gastric emptying. Twenty newborn infants (12 M, 8 F) were investigated with consent from the parents. The babies had a mean gestational age at birth of 33 weeks (range: 27 - 41) and a birthweight of 2105 g (range: 960 - 4100). Their mean weight at the day of the test was 2451 g (range: 1998 - 4140) and the mean age was 24 days (range: 7 - 74). Each infant received a test meal after a fasting period of maximum 3 hours: 11 infants were fed formula milk (Nutrilon Premium, NV Nutricia, Zoetermeer, The Netherlands) with 13C octanoic acid and 9 babies received their mother's milk that had been expressed to allow mixing with 13C octanoic acid. After taking two basal breath samples and ingestion of the feed, breath samples were taken using a masal prong, every 5 minutes during the first half hour and every 15 minutes during the next 3.5 hours. Analysis of the expired 13C fraction in the breath samples was performed using the isotope ratio mass spectrometry and resulted in a gastric emptying curve and gastric emptying parameters. The mean half-emptying time, obtained by the 13C octanoic acid breath test was 69 minutes (range: 36 - 98 min) for the formula fed infants and was 46 minutes (range: 24 - 86) for the breast fed infants. The difference between the half-emptying times is highly significant (t-test, p < 0.01). The gastric emptying coefficient (GEC) in the breast fed group was 3.03 and in the formula fed group 3.22. The difference between the GEC is significant (t-test, p < 0.05). The 13C octanoic acid breath test documented a faster gastric emptying of human milk than formula. This finding is in accordance with earlier, more invasive studies, using dilution techniques. The 13C octanoic acid breath test is a safe and non-invasive method for measuring gastric emptying in small infants, allowing comparison between various feeding methods.