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(Gut 1997; 41: 70-76)

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Studies attempting to evaluate protein assimilation in humans have hitherto relied on either ileostomy subjects or intubation techniques. The availability of stable isotope-labeled protein allowed us to determine the amount and fate of dietary protein escaping digestion and absorption in the small intestine of healthy volunteers using noninvasive tracer techniques. Ten healthy volunteers were studied once after ingestion of a cooked test meal, consisting of 25 g of (13)C-, (15)N-, and (2)H-labeled egg protein, and once after ingestion of the same but raw meal. Amounts of 5.73% and 35.10% (P < 0.005) of cooked and raw test meal, respectively, escaped digestion and absorption in the small intestine. A significantly higher percentage of the malabsorbed raw egg protein was recovered in urine as fermentation metabolites. These results 1) confirm that substantial amounts of even easily digestible proteins may escape assimilation in healthy volunteers and 2) further support the hypothesis that the metabolic fate of protein in the colon is affected by the amount of protein made available.

It is thought that Helicobacter pylori infection may influence growth rate in children. The aim of this study was to evaluate the prevalence of H pylori infection in healthy Italian children, and to look for diVerences in height between infected and non-infected subjects. Two hundred and sixteen children, aged 3 to 14 years, were tested for H pylori infection by 13 C-urea breath test. Centile values for height were calculated. Composite indices for socioeconomic class and household crowding were also determined. Forty nine of 216 children (22.7%) were H pylori positive. The prevalence of infection increased with age. Eight of 49 H pylori positive children (16.3%) were below the 25th centile for height, compared with 13 of 167 H pylori negative children (7.8%). This diVerence became significant in children aged 8.5 to 14 years; in this group (n = 127), eight of 31 infected children (25.8%) were below the 25th centile for height, compared with eight of 96 noninfected children (8.3%). A significant correlation was found between socioeconomic conditions, household crowding, and H pylori status. By using stepwise logistic regression, only the centile value for height was significantly related to H pylori status in older children. Thus H pylori infection was associated with growth delay in older children, poor socioeconomic conditions, and household overcrowding. This finding is consistent with the hypothesis that H pylori infection is one of the environmental factors capable of aVecting growth.

Egg proteins contribute substantially to the daily nitrogen allowances in Western countries and are generally considered to be highly digestible. However, information is lacking on the true ileal digestibility of either raw or cooked egg protein. The recent availability of stable isotope-labeled egg protein allowed determination of the true ileal digestibility of egg protein by means of noninvasive tracer techniques. Five ileostomy patients were studied, once after ingestion of a test meal consisting of 25 g of cooked 13C- and 15N-labeled egg protein, and once after ingestion of the same test meal in raw form. Ileal effluents and breath samples were collected at regular intervals after consumption of the test meal and analyzed for 15N- and 13C-content, respectively. The true ileal digestibility of cooked and raw egg protein amounted to 90.9 +/- 0.8 and 51.3 +/- 9.8%, respectively. A significant negative correlation (r = -0.92, P < 0.001) was found between the 13C-recovery in breath and the recovery of exogenous N in the ileal effluents. In summary, using the 15N-dilution technique we demonstrated that the assimilation of cooked egg protein is efficient, albeit incomplete, and that the true ileal digestibility of egg protein is significantly enhanced by heat-pretreatment. A simple 13C-breath test technique furthermore proved to be a suitable alternative for the evaluation of the true ileal digestibility of egg protein.