Exploring novel applications for lactose in human nutrition

Odell, Oliver J. ORCID: 0000-0002-5389-1746 (2022). Exploring novel applications for lactose in human nutrition. University of Birmingham. Ph.D.

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Abstract

Lactose is a disaccharide of glucose and galactose, found exclusively in dairy. Despite its common presence in the human diet, little is known about its possible roles in sports nutrition, and whether there are any potential applications for this carbohydrate. The aim of the thesis was to identify possible applications for lactose in a sports nutrition context. Therefore, Chapter 3 was conducted to determine whether ingested lactose can be readily oxidised during moderate intensity exercise compared to sucrose, which is a commonly ingested carbohydrate in sports nutrition. Both carbohydrates exhibited similar exogenous carbohydrate oxidation rates, demonstrating that lactose can act as a viable source of substrate for exercise metabolism. Interestingly, lactose resulted in less pronounced suppression of fat oxidation than sucrose, with a concomitant reduction in endogenous carbohydrate oxidation. Lactose did not elicit gastrointestinal discomfort to a greater extent than sucrose or plain water ingestion, the potential for which had been a key concern. Following observations of endogenous carbohydrate sparing, Chapter 4 aimed to determine whether lactose ingestion resulted in hepatic, or muscular glycogen sparing. The execution of this study was limited by COVID-19 restrictions, meaning that it functioned as a pilot study to investigate an improved 13C oral tracer methodology for assessing substrate utilisation. The limited data generated implied that the glycogen sparing observed was of hepatic origin. Chapter 5 investigated lactose in a post-exercise setting for the recovery of liver glycogen. Galactose and fructose, when ingested with glucose have been shown to accelerate liver glycogen repletion. Therefore lactose, as the major dietary source of galactose, was used to determine if galactose and fructose, alongside glucose, were better at restoring liver glycogen than glucose and fructose. Although liver glycogen synthesis rates were high in both conditions, there was no clear benefit for ingesting the full spectrum of dietary monosaccharides above sucrose (glucose-fructose) ingestion on liver glycogen synthesis. In conclusion, the thesis presents novel insights into the metabolism of lactose in a variety of exercise contexts providing new possible applications for lactose in sports nutrition.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):