Related Experiment Video
Updated: Aug 12, 2026
04:41
Measuring Lactase Enzymatic Activity in the Teaching Lab
Published on: August 6, 2018
A study of lactose absorption capacity in twins
Human Genetics
|January 1, 1984
Summary
Lactose absorption is primarily inherited, with genetic factors strongly influencing lactase phenotypes. The blood galactose test proved most effective in distinguishing lactose absorbers from lactose malabsorbers.
Area of Science:
- Human Genetics
- Gastroenterology
- Nutritional Science
Background:
- Lactose malabsorption is common, affecting a significant portion of the adult population worldwide.
- Understanding the genetic basis of lactase persistence and non-persistence is crucial for public health and personalized nutrition.
- Previous studies suggest a genetic component to lactase phenotypes, but definitive inheritance patterns require robust twin studies.
Purpose of the Study:
- To investigate the monogenic Mendelian inheritance of lactase phenotypes (lactose absorber vs. lactose malabsorber).
- To compare the efficacy of three common lactose tolerance tests: breath hydrogen, blood glucose, and blood galactose.
- To assess the concordance and constancy of lactose intolerance symptoms in relation to phenotype.
Main Methods:
- A lactose tolerance test using breath hydrogen determination was administered to 102 healthy Hungarian twin pairs (52 monozygous, 50 dizygous).
- Three lactose tolerance tests (breath hydrogen, blood glucose, blood galactose) were compared in 49 concordant twin pairs.
- Statistical analysis included Hardy-Weinberg equilibrium calculations and comparison of intrapair correlation coefficients.
Main Results:
- All monozygous twin pairs were concordant for lactase phenotype, supporting a strong genetic influence.
- The blood galactose test demonstrated the highest diagnostic accuracy, showing significant differences between MZ and DZ twins and no overlap between phenotypes.
- Breath hydrogen and blood glucose tests showed less distinct separation between lactose absorbers and malabsorbers, with some overlapping results.
Conclusions:
- Lactase phenotypes exhibit monogenic Mendelian inheritance, strongly supported by twin study concordance rates.
- The blood galactose test is the most reliable method for phenotyping lactose absorption capacity among the tested methods.
- Genetic factors play a predominant role in determining an individual's ability to absorb lactose.
Related Concept Videos
01:00Punnett Squares
Overview
01:27Glucose Transporters
Glucose transporters facilitate the transport of glucose across the cell membrane. In addition to glucose, some glucose transporters can also aid the movement of other hexoses such as fructose, mannose, and galactose.
Facilitated diffusion-glucose transporters (GLUTs) are encoded by the solute-linked carrier (SLC) family 2, subfamily A gene family, or SLC2A. The 14 GLUT protein members are distributed into three classes:
Facilitated diffusion-glucose transporters (GLUTs) are encoded by the solute-linked carrier (SLC) family 2, subfamily A gene family, or SLC2A. The 14 GLUT protein members are distributed into three classes:
01:26Glucose Absorption Into the Small Intestine
Complex carbohydrates consumed cannot be absorbed into the small intestine in their original form. First, they must be hydrolyzed to a monosaccharide form such as glucose or galactose. These monosaccharides are then transported across the intestinal membrane and into the blood via transcellular transport. The intestinal epithelial cells allow the movement of these monosaccharides with a defined 'entry' through membrane transporter proteins present on their apical membrane and 'exit' via the...
01:25Carbohydrate Absorption
Carbohydrates are essential macronutrients that serve as the body's primary energy source. Their digestion begins in the mouth, where salivary amylase partially breaks down complex carbohydrates such as starch into smaller oligosaccharides. This mechanical and enzymatic activity prepares carbohydrates for further processing in the gastrointestinal tract.
After being swallowed, the partially digested carbohydrates mix with gastric secretions in the stomach. However, the acidic environment...
After being swallowed, the partially digested carbohydrates mix with gastric secretions in the stomach. However, the acidic environment...
01:16Methods for Studying Drug Absorption: In vitro
In vitro experiments are crucial for understanding the transport and absorption of drugs through biological materials. These studies employ varied methods such as the diffusion cell method, the everted sac technique, and the everted ring technique.
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...
01:09Methods for Studying Drug Absorption: In situ
In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...