In most cases, hypolactasia (lactase deficiency) appears during the early childhood stage, and gradually increases in intensity as age increases. Note that the lactase enzyme (lactase-phlorhizin hydrolase) is an enzyme enabling the digestion and absorption of lactose, a carbohydrate found in dairy products and other food sources, which include milk and cheese. As effect, individuals with lactase deficiency experience lactose maldigestion (or malabsorption) when eating food rich in lactose. This symptom is most commonly referred to as lactose intolerance.
A common characteristic of hypolactasia is that the condition first manifests as early as childhood. The condition can be diagnosed using various methods, such as the lactose tolerance test and small-intestinal biopsy. Eventually, scientists found the location within the human DNA that codes for lactase persistence/non-persistence. In various studies targeted within Finnish population, the trait has a perfect association with C/T-13910, a single nucleotide situated approximately 14kb from the 5' end of the lactase gene. Using this information, scientists developed another confirmatory test for lactose persistence/non-persistence, which is the determination of the C/T-13910 genotype. After the condition is diagnosed, the condition gradually intensifies until it results to primary hypolactasia. According to Seppo et al. (1082-1087), the age when hypolactasia first manifests varies based on ethnicity. However, despite the disparity between the age at manifestation depending on ethnicity, previous studies concluded that hypolactasia first manifests before reaching the age of 20 (Seppo et al. 1082). In this light, the researchers led by Seppo explored the possibility of hypolactasia appearing after 20 years of age.
The research was performed by conducting a confirmatory test for lactose persistence/non-persistence among individuals who had no hypolactasia during the first 20 years of age but reported gastrointestinal symptoms afterwards. The sample was selected from the epidemiological studies of the researchers. Moreover, the research compared the different confirmatory methods for the lactose persistence/non-persistence trait. The comparison between the confirmatory tests will be analyzed by taking the genotype determination of C/T-13910 as the most valid.
The subjects of the study were from the previous epidemiological studies of the researchers regarding lactose maldigestion among the Finnish populations. Needless to say, all of the subjects of the study have a Finnish origin, and all of the subjects of the study were diagnosed as lactose digesters. Note that the previous epidemiological studies mentioned were conducted 20 to 25 years ago. Therefore, this study seems to be a follow-up investigation from 20 to 25 years ago.
The research selected a total of 456 subjects from the previous epidemiological studies. During the previous studies, these 456 subjects were diagnosed as lactose digesters using the confirmatory test lactose tolerance test with ethanol (LTTE). According to Seppo et al. (1083), the researchers sent a questionnaire to each of the subjects discussing their gastrointestinal symptoms. Out of 456 subjects, only 322 (71%) responded, with 59 reporting that they had gastrointestinal symptoms after ingesting 20 grams or less of lactose. These 59 became the participants of the study but only 42 became the test subjects.
The subjects underwent the same LTTE performed two decades ago but with two minor changes: (1) the amount of ethanol was changed from 500 mg/kg to 300 mg/kg, and (2) the blood galactose analysis was performed using the peroxidase method rather than the oxidase method. Lactose maldigestion and hypolactasia would be implied if the results of the LTTE suggested a blood glucose level lower than 1.1 mmol/l and blood galactose level of 0.3 mmol/l. If the results of a subject showed inconsistency from the test two decades ago, the subject would be asked to undorge an upper gastrointestinal endoscopy to determine the status of disaccharidase activities in their small intestine.
Furthermore, the subjects were also given a questionnaire to subjectively describe the gastrointestinal symptoms, which include flatulence, abdominal pain and bloating, borborygmi, and diarrhea or loose stools. The subjects were to describe each symptoms prior to the intake of the lactose solution and after the intake, specifically every hour for four hours. The researchers would only consider the highest noted description (the scale for each symptom was 0 to 10 with 10 being the highest). As for the genotyping, the blood samples of 35 subjects underwent analysis (7 subjects declined for the DNA analysis). The DNA analysis was to determine and analyze the C/T-13910 gene.
The results of the study showed that 42 out of 59 subjects were diagnosed as lactose absorbers while 2 were considered to potentially have lactose maldigestion. Moreover, 13 subjects showed inconclusive results due to having a lower level of blood glucose rise than the limit but a higher rise of blood galactose level than the limit, or a higher rise of blood glucose level than the limit but a lower level of blood galactose level than the limit. Out of these 13, only 10 underwent the biopsy but none of them had a low lactase activity in the intestine. As for the genotyping, only 1 out of the 35 who gave blood samples had the C/C-13910 genotype. The subject who had the genotype is also one of the two who were diagnosed to potentially have lactose maldigestion from the LTTE. Therefore, only one of the subjects was diagnosed to have hypolactasia.
In the discussion part of their paper, Seppo et al. (1085-1086) stated that prior to the research, the subject who had the genotype and passed the confirmatory test had performed three lactose tolerance tests, all of which proclaimed that she was a lactose digester. She was asymptomatic at the age of 14 but the symptoms gradually appeared at the age of 25. She reported symptoms typical of lactose intolerance during the ages 22-24 years. Although the next lactose tolerance test was performed more than 20 years later, the researchers stated that they cannot verify whether the hypolactasia manifested after the age of 20 years since no data on the disaccharide activity of the subject was available.
Works Cited:
Larsen, Clark Spencer. Our Origins: Discovering Physical Anthropology. New York, NY: W. W. Norton & Company, Inc., 2014. Print.
Seppo, Leena. “Can primary hypolactasia manifest itself after the age of 20 years? A two-decade follow-up study.” Scandinavian Journal of Gastroenterology 43 (2008): 1082-1087. Print.
