Theme 3 Applied Lecture1

Managing Lactose Intolerance

Overview

The lecture focuses on managing lactose intolerance, particularly how lactose is digested and what happens when individuals cannot digest it effectively. Lactose, a sugar found in dairy products, serves as a primary energy source. Understanding lactose digestion is crucial for individuals suffering from lactose intolerance.

Digesting Lactose

  • Lactose: A sugar commonly found in milk and dairy products, acting as a significant source of energy.

  • Broken down into its monosaccharides: glucose and galactose.

Role of Lactase

  • Lactase: An enzyme classified as a β-galactosidase. It catalyzes the hydrolysis of lactose into glucose and galactose.

  • Located on the apical surface of intestinal enterocytes, allowing for effective absorption into the bloodstream.

Metabolism of Lactose

  • Upon hydrolysis of lactose by lactase:

    • Glucose enters glycolysis as Glucose-6-P.

    • Galactose is converted via multiple steps:

      • Galactokinase converts it to Galactose-1-P.

      • Further processed to UDP-Glucose by Gal-1-P uridyltransferase.

      • UDP-Gal epimerase converts UDP-Glucose to UDP-Galactose.

  • This metabolic pathway is crucial for energy extraction from lactose.

Lactase Production and Persistence

  • Lactase production generally decreases after weaning in most mammals, including ~65% of humans, indicating an evolutionary adaptation.

  • Certain populations developed mutations in the regulatory gene MCM6, which keeps the lactase gene on, allowing continued lactase production into adulthood.

  • This trait is particularly high in historically pastoral populations (e.g., Swedes, Danes).

Lactose Intolerance and Congenital Deficiency

  • Some individuals may be born with congenital lactase deficiency, leading to an inability to digest lactose.

  • Symptoms include excessive fermentation in the intestine, leading to gas, bloating, cramps, nausea, and diarrhea.

  • The LCT gene responsible for lactase production can have mutations causing this deficiency.

Galactosemia vs. Lactose Intolerance

  • Galactosemia: A disorder caused by inherited mutations affecting the metabolism of galactose, leading to toxic accumulation.

  • Confused with lactose intolerance but results from different genetic mutations (GALT, GALE, GALK1) affecting galactose processing enzymes.

Treatment Options

  • For Galactosemic individuals: Strict avoidance of galactose in the diet.

  • For Lactose intolerant individuals: Options include:

    • Omitting lactose, being selective with dairy products.

    • Use of lactase supplements that facilitate lactose digestion.

Microbial Fermentation and Dairy Production

  • Products like yogurt and cheese benefit from fermentation by lactic acid bacteria (e.g., Lactobacillus, Lactococcus, Bifidobacteria), leading to lower lactose content.

  • Fermentation not only lowers lactose but also helps in protein precipitation to form cheese.

Dietary Aids

  • Lactase supplements: Available commercially, often derived from fungi, assist in lactose digestion when consumed before dairy intake.

  • The industry surrounding these supplements is vast and offers multiple products.

Industrial Production of Lactose-Free Products

  • Lactose-free dairy products involve pretreating milk with lactase enzymes extracted from various microorganisms, which function effectively at neutral pH levels, enhancing product palatability without residual lactose.

Conclusion

Understanding lactose intolerance extends to genetic underpinnings, enzyme function, and available dietary modifications, highlighting the intricate relationship between diet and biology.