Warning
Although genetic testing can provide important information for the diagnosis, treatment and prevention of health conditions, there are limitations. For example, if you are a healthy person, a positive genetic test result does not mean that you will develop a different health status than you currently have. On the other hand, in some situations, a negative result does not guarantee that you will not have a certain disorder. Test results are intended for educational purposes only and not for diagnostic use. Any findings from the analysis of genome sequence information that might be deemed medically relevant should be confirmed using alternative tests. If you have questions or concerns about what you learn from these informative genome sequence tests, you should contact a genetic counselor.
Lactose intolerance
At the basis of the symptoms of lactose intolerance there is a defect in the lactase enzyme in the intestinal microvilli which leads to the lack of hydrolysis of lactose into glucose and galactose and a consequent malabsorption syndrome. Patients suffering from primary lactose intolerance develop generic enteropathy symptoms such as abdominal distension, bloating, colic, diarrhea, nausea and vomiting after the intake of milk and dairy products, as well as all products containing lactose.
The functionality of the lactase enzyme is compromised by a mutation at position –13910 which is in the regulatory region of the gene that encodes lactase (hence the negative sign in front of the number meaning that the sequence change is 13910 nucleotides upstream of the start of the lactase gene). The persistent lactase phenotype is highly variable throughout the world. In Europe there is a North-South gradient. In Scandinavian countries, 90% of the adult population can digest lactose, while in Mediterranean populations less than 50% of adults are tolerant. In Italy the genotype (C/C), meaning the individual is intolerant to lactose, represents a frequency of 62.3%. In Southern Italy, the frequency is equal to 67.1%. Studies performed on Italian, Finnish, German and Korean patients with biochemically demonstrated lactase deficiency have shown a complete correlation with the –13910 CC genetic variant. The frequency of lactose intolerance is very different depending on the population studied. The T to C mutation means that at this position a Thymine (T) is changed to Cytosine (C). This results in a quantitatively lower activity of the lactase enzyme. As we well know, DNA is a double helix, which contains two copies of the genome, one that comes from the mother and is contained in her oocytes, and the other from the father in his sperm. At the time of conception, the two copies unite in the maternal oocyte, after the sperm has injected its copy into the oocyte itself to give life to a new organism.
The test analyzes both copies of DNA which can both be changed, and which therefore give three possibilities of genetic configuration, the TT configuration, or wild type, i.e. normal non-intolerant, the CT configuration, heterozygous for the polymorphism and the CC configuration, homozygous and lactose intolerant. In the case of lactose intolerance, if we have both copies of the DNA changed to cytosine, we will have a primary manifestation of lactose intolerance.
The importance of a precise diagnosis is clear if we consider the fact that the therapy for lactose intolerance consists in changing the patient's eating habits by moving from a diet with the presence of lactose to another with the absence of lactose. The genetic test correlates with 88.6% congruence with the Breath Test.
Scientific literature
Congruency of genetic predisposition to lactase persistence and lactose breath test (2019). Enza Coluccia, Patrizia Iardino, Diego Pappalardo, Anna Lisa Brigida, Vincenzo Formicola, Bruna De Felice, Claudia Guerra, Alessia Pucciarelli, Maria Rosaria Amato, Gabriele Riegler and Laura De Magistris. Nutrients 2019, 11, 1383; doi:10.3390/nu11
