Raising Milk Energy Content Retards Gastric Emptying of Lactose in Lactose-Intolerant Humans with Little Effect on Lactose Digestion

Abstract

Lactose digestion improves when the energy content of a meal is raised, perhaps due to delayed gastric emptying; however, this has not been demonstrated directly. It is not known whether lactose-intolerant subjects should consume full-fat or high energy milk instead of half-skimmed milk. In this study, breath 13CO2 and hydrogen (H2) measurements were combined to assess simultaneously the effect of increasing milk energy content on gastric emptying, digestion, and tolerance of lactose. On two separate days, 11 adult lactose maldigesters ingested, in the fasting state, a single dose of 710 kJ half-skimmed milk or 1970 kJ high energy milk. Both contained 18 g lactose and were supplemented with 100 mg 13C-glycine for breath 13CO2 measurement. For 6 h after milk ingestion, samples of expired breath were collected, and subjects scored their symptoms on a four-grade questionnaire. Gastric emptying was measured from excretion of breath 13CO2. The mean gastric emptying half-time was significantly longer after ingestion of high energy milk than after half-skimmed milk (84 +/- 4 vs. 64 +/- 4 min, P = 0.004). The mean area under the breath H2 excretion curve measured for 6 h was 330 +/- 61 microL/L after subjects consumed high energy milk vs. 470 +/- 82 microL/L after they consumed half-skimmed milk (P = 0.07). Mean symptom scores did not differ after ingestion of the two milks, but only two subjects experienced disturbing symptoms after high energy milk ingestion compared with five subjects after ingestion of half-skimmed milk (P = 0.56). Although ingestion of high energy milk delayed the gastric emptying of lactose for significantly longer than the ingestion of half-skimmed milk (P < 0.01), it did not lead to significant improvement in symptoms and reflected only a trend toward improved lactose digestion (P = 0.07), as measured by the area under the breath H2 excretion curve. These results indicate that it is not beneficial for most lactose-intolerant subjects to replace consumption of half-skimmed milk by milk with a higher energy content.