Primary Hypolactasia Research Articles

Частота генотипа гиполактазии взрослых (первичной лактазной недостаточности) у больных хроническим полипозным риносинуситом

An assumption has been made about the role of lactase deficiency in the pathogenesis of polypous rhinosinusitis in the domestic literature. Objective. A pilot study of the frequency of carriage of the genetic marker of adult hypolactasia of the C/C(-13910) polymorphism of the MCM6 gene in patients with chronic polypous rhinosinusitis; analysis of modern literature data on the prevalence of C/T(-13910) polymorphism of the MCM6 gene in the population of the European part of Russia. Patients and methods. 16 Caucasian patients with chronic rhinosinusitis with nasal polyps (CRSwNP) were examined. The prevalence of the nasal polyposis was assessed on the basis of computed tomography of the paranasal sinuses, the determination of the genetic marker of the C/T(-13910) polymorphism of the MCM6 gene was determined by real-time PCR. Results. Severe course of CRSwNP based on CT data of the paranasal sinuses was established in 69% of cases. Concomitant pathology of the respiratory tract was detected in 75% of patients: a combination of CRSwNP, bronchial asthma (BA), and allergic rhinitis (AR) 31%; CRSwNP and BA 19%; CRSwNP and AR 25% of cases. The CC genotype associated with primary hypolactasia was detected in 37.5% of cases. The genotypes associated with lactase persistence were established: CT in 56.25%, TT in 6.25% of patients. Allele frequency C 0.65, T 0.34. The distribution of genotype frequencies corresponds to the Hardy–Weinberg equilibrium distribution (χ2 test 0.97, Hardy–Weinberg exact equilibrium test p = 0.43). 67% of carriers of the CC genotype in patients with CRSwNP did not have any clinical signs of lactase deficiency. Among 3 patients with CRSwNP who noted intestinal discomfort after eating dairy products, CC genotype was in 2 people (33% of genotype carriers), CT in 1 patient (11% of heterozygotes). Conclusion. The frequency of carriage of the CC genotype of the single nucleotide polymorphism C/T (-13910) of the MCM6 gene associated with low lactase activity in patients with CRSwNP (Saint Petersburg residents) was detected at the level of 37.5%, which does not exceed the prevalence of the primary hypolactasia genotype in the general population of the European part of Russia.

The incidence of adult type hypolactasia in patients with irritable bowel syndrome

The incidence of lactose intolerance in irritable bowel syndrome (IBS) varies in the literature (27-72%). Primary adult lactase deficiency (adult type hypolactasia) is the most common type of primary enzyme deficiency. Complaints related to lactose intolerance may overlap with the symptoms of IBS. To assess the prevalence of primary hypolactasia in patients with IBS. The study included 56 patients with IBS diagnosed based on the Rome III criteria and 23 healthy people. All study participants completed a questionnaire on IBS symptoms and lactose intolerance, and they underwent a hydrogen breath test (HBT) with lactose. In the group of patients with positive results of HBT, the polymorphism C/T -13910 and G/A -22018 in the promoter of the LCT gene encoding lactase was determined. Lactase deficiency was diagnosed in HBT in 34 (60.7%) patients with IBS and in the control group - in 10 (43.5%). Primary adult type hypolactasia was confirmed in 78.9% (n = 30; 79.3% in the study group; 77.8% in the control group). There were no statistically significant differences in the occurrence of LCT gene polymorphisms in particular IBS subtypes. Adult type hypolactasia was significantly more common in patients with severe than moderate and mild enzyme deficiency in HBT (p < 0.05). The incidence of lactase deficiency in IBS patients is not different from that found in healthy subjects. Nevertheless, irrespective of the IBS subtype, lactose intolerance may pose additional issues in patients with IBS and requires the targeted treatment.

Prospects of fermented milk products in children with primary hypolactasia of the adult type

Lactose (β-galactosyl-1,4 glucose) is milk sugar, the main disaccharide of human and other mammalian breast milk. Lactase is intestinal disaccharidase that catalyzes the lactose hydrolysis. The lactase gene LCT controls biological function of the enzyme. The age-related genetically determined feature of disaccharide expression, epigenetic factors, and natural selection with persistent tolerance to milk sugar throughout lifetime has divided the human population according to the LCT gene into two phenotypes: lactase persistent and lactase non-persistent. There is conflicting evidence that the latter phenotype is associated with low calcium absorption and the development of osteoporosis. The regular use of fermented probiotic dairy products by individuals with the lactase non-persistence phenotype ensures the accumulation of peak bone mineralization and prevents osteoporosis.

Real-time PCR based detection of the lactase non-persistence associated genetic variant LCT-13910C>T directly from whole blood.

Primary hypolactasia is the main cause of lactose intolerance in adults. It is strongly associated with the single genetic variant LCT-13910C>T, located upstream of the lactase encoding gene. Consequently, analysis of LCT-13910C>T has been recommended as a direct genetic test for the trait. The aim of our study was to develop a TaqMan probe based real-time PCR protocol for the detection of the LCT-13910C>T variant directly from whole blood, circumventing DNA isolation. The LCT-13910C>T variant was determined using the DirectBlood Genotyping PCR Kit (myPOLS Biotec, Konstanz, Germany) together with an in-house TaqMan primer-probe assay. Validity and specificity of the assay was evaluated using EDTA anti-coagulated whole blood samples and corresponding DNA samples. Results from real-time PCR were compared with results obtained by Sanger sequencing from 105 blinded whole blood samples. Validity and specificity of the assay using whole blood were comparable to those using purified genomic DNA as substrate in PCR. Genetic analysis of blood samples were in complete agreement with results obtained by Sanger sequencing. In conclusion, we present a reliable real-time PCR protocol for the detection of the LCT-13910C>T variant directly from whole blood further facilitating diagnosis of primary hypolactasia in symptomatic patients.

Yogurt and dietary recommendations for lactose intolerance

Malabsorption to lactose is caused by the inability to digest sugar due to the decrease in the activity of intestinal lactase. Malabsorption may be due to a primary or secondary disorder. Adult type primary hypolactasia is an autosomal recessive disorder, characterized by the progressive loss of lactase after weaning. The secondary hypolactasia is a transitory disorder, which will be corrected after the cure of the basic pathology. For lactose malabsorption diagnosis, the hydrogen and methane exhaled tests after lactose overload stand out and, in the case of the primary adult type, the molecular test of the simple nucleotide polymorphism (SNP C / T-13910). However, the diagnosis of lactose intolerance requires the presence of symptoms after consumption. The treatment of primary adult-type hypolactasia consists in decreasing the lactose in the diet below the trigger dose. A significant percentage of individuals with malabsorption tolerate habitual amounts of consumption. Practically 99% of them tolerate yogurt or fermented dairy products, thus allowing to cover the daily recommendations of calcium and vitamin D intake. In addition, nutritional strategies that reduce the lactose load, gastric emptying time and / or intestinal transit time or increase lactic activity and colonic compensation, will allow a greater tolerance.

Primary hypolactasia diagnosis: Comparison between the gaxilose test, shortened lactose tolerance test, and clinical parameters corresponding to the C/T-13910 polymorphism

There is no consensus on the most accurate method to diagnose primary hypolactasia. We aimed to compare the diagnostic accuracy of the new gaxilose test with 2 traditional tests (lactose tolerance test and clinical criteria) for the diagnosis of primary hypolactasia using the C/T-13910 polymorphism as a reference standard. Patients with a clinical suspicion of lactose intolerance were subjected to gaxilose tests, shortened lactose tolerance tests, and symptom questionnaires before and after overload with 50g lactose and after a lactose-free diet. The diagnostic accuracy and degree of agreement and correlation were assessed using a genetic test (C/T-13910 polymorphism) as a reference standard and their respective 95% confidence intervals. Thirty consecutive patients (70% women) participated in the study. The genetic test confirmed the C/T-13910 polymorphism in 11 patients (36.8%). The presence of diarrhoea and the symptom score after lactose overload, along with the tolerance test, were the variables with the highest degree of agreement (κ>0.60). Area under the ROC curve was >0.82 (p<0.05), with sensitivity and specificity values of >0.80. However, the gaxilose test obtained lower values: κ, 0.47; area under curve, 0.75 (0.57-0.94); sensitivity, 0.82 (0.55-1); and specificity, 0.68 (0.45-0.92). The multivariate analysis showed an association between the post-overload symptom questionnaire and the results of the genetic test (odds ratio: 1.17; 1.04-1.31; p<0.01). The presence of diarrhoea and the symptom score after overload with 50g lactose showed a higher degree of agreement and diagnostic accuracy for primary hypolactasia than the gaxilose test when the genetic test is used as a reference standard.

Genetic Aspects of Adult-Type Hypolactasia

Background and Objective: Lactose is a disaccharide sugar and is found in mammals milk and derivatives. Lactose intolerance is the inability to metabolize lactose, because of a lack of the required enzyme lactase in the digestive system. Genetically the physiological hypolactasia (primary LM) is associated with the LCT-13910 C/T and LCT-22018 G/A polymorphisms. The aim of this study focused on the diagnosis and treatment intolerance or malabsorption of lactose in a cohort of 983 patients for the appearance of non-specific symptoms suggestive of a lactose intolerance. Methods: The work was divided into the following phases: diagnosis of lactose intolerance or malabsorption; Check the incidence of primary lactase deficiency in the population Lucana (Italy); Evaluate the improvement of post-diagnosis symptoms and impact on quality of life (Q.O.L: Quality Of Life) as a result of enzymatic and/or food therapy in intolerant subjects. Evaluate the correlation genotype/phenotype studying variants -13910 C>T and -22018 A>G in LPH gene. Results: Of the 983 participants, 668 subjects (67.95%) had a positive homozygous mutation (associated to-13910CC hypolactasic phenotype), 314 subjects (31.94%) had a positive heterozygous mutation (associated to -13910CT lactase persistent phenotype) and only in 1 subject (0,1%) the 2 alleles were not mutated (-13910TT dominant homozygous). The present work reveals a 67.95% of participant with a positive homozygous mutation (-13910CC). Conclusions: The lactose malabsorption is a condition widespread in Italy, but much less frequently is the syndrome of intolerance. Embarking on a diet that a priori excludes milk and derivatives, in the absence of a definitive diagnosis, it can have a negative impact on the welfare of the organism The genetic test is really simple and noninvasive, confirms or excludes a malabsorption and in particular circumstances provides a predictive test to detect primary hypolactasia long before of her clinical manifestation.

Prevalence of Lactose Intolerance in Chile: A Double-Blind Placebo Study

Background and Study Aims: Lactase non-persistence (LNP), or primary hypolactasia, is a genetic condition that mediates lactose malabsorption and can cause lactose intolerance. Here we report the prevalence of lactose intolerance in a double-blind placebo study. Methods: The LCT C>T_-13910 variant was genotyped by RT-PCR in 121 volunteers and lactose malabsorption was assessed using the hydrogen breath test (HBT) after consuming 25 g of lactose. Lactose intolerance was assessed by scoring symptoms (SS) using a standardized questionnaire following challenge with a lactose solution or saccharose placebo. Results: The LNP genotype was observed in 57% of the volunteers, among whom 87% were HBT(+). In the HBT(+) group the median SS was 9 and in the HBT(-) group the median SS was 3 (p < 0.001). No difference was observed in the SS when both groups were challenged with the placebo. The most common symptoms included audible bowel sounds, abdominal pain and meteorism. In the ROC curve analysis, an SS ≥6 demonstrated 72% sensitivity and 81% specificity for predicting a positive HBT. To estimate prevalence, lactose intolerance was defined as the presence of an SS ≥6 points after subtracting the placebo effect and 34% of the study population met this definition. Conclusions: The LNP genotype was present in more than half of subjects evaluated and the observed prevalence of lactose intolerance was 34%.

Evaluation of a genetic test for diagnose of primary hypolactasia in northeast of iran (khorasan).

Primary or adult type hypolactasia, the most common enzyme deficiency in the world, is due to reduced lactase activity in the intestinal cell after weaning. Lactase non-persistence is inherited as an autosomal recessive trait. A DNA variant, single nucleotide polymorphism C/T-13910 which is located on 13910 base pairs (bp) upstream of the lactase gene (LCT) at chromosome 2 has been show to associate with the lactase persistence/non-persistence. The prevalence of the C/T-13910 variant is different for hypolactasia in European, Asian, African-American and Northern African populations. In this study, we investigated, for the first time the allele frequent of the single nucleotide polymorphism C/T-13910 in the Iranian population in khorasan province with hypolactasia. Peripheral blood was collected from 100 subjecs with primary hypolactasia and 100 healthy individuals as a control group. Genomic DNA was extracted. The genotype was analyzed with the PCR-RFLP method. A statistical analysis was performed by chi-square test using SPSS software. A P-value of <0.05 was considered statistically significant. In case group allelic frequency for SNP T-13910C (C, T) was respectively 95%, 5% vs. control group 86% and 14%. Genotype frequency (CC, CT, TT) in patient group was 90%, 10%, 0% vs. control group 74%, 24% and 2%. So according to our findings, there were significant differences between allelic frequencies (P=0.03), and in genotype frequency between case and control groups (P=0.006). Based on our results, analysis of C\T-13910 polymorphism can be used as a simple genetic test for diagnosis of primary type hypolactasia in the Iranian population.

Molecular analysis of LCT gene in association with primary hypolactasia in the random population of Mashhad, Iran

Molecular analysis of LCT gene in association with primary hypolactasia in the random population of Mashhad, Iran

Single nucleotide polymorphism C/T -13910, located upstream of the lactase gene, associated with adult-type hypolactasia: Validation for clinical practice

Objectives To validate C/T -13910 polymorphism associated with primary hypolactasia for clinical practice. Design and methods Lactose breath test and PCR-RFLP for the C/T -13910 polymorphism were performed. Results Twenty-seven of 28 patients with genotype CC had positive breath tests; all twenty-two patients with genotypes CT or TT had negative breath tests. Agreement of tests was high ( p < 0.0001; Kappa Index 0.96). Conclusion C/T -13910 polymorphism detection may be a new tool for primary hypolactasia diagnosis.

Can primary hypolactasia manifest itself after the age of 20 years? A two-decade follow-up study

Objective. The age at manifestation of primary hypolactasia varies between ethnic groups. Many people report experiencing the first symptoms of lactose intolerance at adult age. The purpose of this study was to investigate whether primary hypolactasia can appear after the age of 20 among the Finnish population and to investigate the outcome of different diagnostic methods of lactose maldigestion. Material and methods. Lactose digestion status was assessed by the lactose tolerance test with ethanol (LTTE) in 42 subjects (38–71 years) who reported having gastrointestinal symptoms after the ingestion of 20 g or less of lactose and who were diagnosed as lactose digesters in earlier studies. Thirteen of the study subjects underwent upper gastrointestinal endoscopy, and 35 gave a blood sample for DNA analysis. Results. Only one of the 42 subjects studied had the genotype C/C−13910 indicating hypolactasia. Lactase activity was higher in those with the genotype T/T (69.2 U/g protein) than in those with the heterozygous genotype C/T (36.3 U/g protein) (p=0.017). Conclusions. Although primary hypolactasia normally appears before the age of 20 years, the decline in lactase activity may on rare occasions continue after that age. Genotyping of the C/T−13910 variant was found to be a reliable diagnostic approach in defining the lactase persistence/non-persistence status of the study subjects.

Correlation between lactose absorption and the C/T-13910 and G/A-22018 mutations of the lactase-phlorizin hydrolase (LCT) gene in adult-type hypolactasia

The C/T-13910 mutation is the major factor responsible for the persistence of the lactase-phlorizin hydrolase (LCT) gene expression. Mutation G/A-22018 appears to be only in co-segregation with C/T-13910. The objective of the present study was to assess the presence of these two mutations in Brazilian individuals with and without lactose malabsorption diagnosed by the hydrogen breath test (HBT). Ten milk-tolerant and 10 milk-intolerant individuals underwent the HBT after oral ingestion of 50 g lactose (equivalent to 1 L of milk). Analyses for C/T-13910 and G/A-22018 mutations were performed using a PCR-based method. Primers were designed for this study based on the GenBank sequence. The CT/GA, CT/AA, and TT/AA genotypes (lactase persistence) were found in 10 individuals with negative HBT. The CC/GG genotype (lactase non-persistence) was found in 10 individuals, 9 of them with positive HBT results. There was a significant agreement between the presence of mutations in the LCT gene promoter and HBT results (kappa = -0.9, P < 0.001). The CT/AA genotype has not been described previously and seems to be related to lactase persistence. The present study showed a significant agreement between the occurrence of mutations G/A-22018 and C/T-13910 and lactose absorption in Brazilian subjects, suggesting that the molecular test used here could be proposed for the laboratory diagnosis of adult-type primary hypolactasia.

Polymorphism C/T-13910 of the LCT gene regulatory region and lactase deficiency in Eurasian populations

Genetically determined deficiency of the lactase enzyme in adults (primary hypolactasia) is a recessive trait. As shown earlier, in some European populations primary hypolactasia is determined by carrying the CC genotype at the single-nucleotide polymorphism (SNP) LCT*С/T-13910. In this work allele and genotype frequencies were estimated for the single-nucleotide polymorphism (SNP) LCT*C/ T-13910 in 7 samples (346 individuals in total), representing Eurasian populations (Saami, Mari, Russians from the Volga-Ural Area, Kazakhs, Uyghurs, Buriats, Arabs). For part of these groups and for some of the earlier studied groups the frequencies of the CC genotype are similar to the epidemiological-clinical data on hypolactasia frequency reported for respective or closely located populations (in Russians, Ukrainians, Byelorussians, Kola Saami, Mari, Komi-Permyaks, Udmurts, Pamir Mountain dwellers, and in Chukchi, Iranians and Arabs). For the Asian populations, the data are contradictory, and evaluation of genetic determination of hypolactasia in these populations requires further studies of larger samples. Considering association of primary hypolactasia with CC genotype in the Russian sample found by us earlier, the obtained results point that the CC genotype at SNP LCT*C/ T-13910 is the main genetic determinant of primary hypolactasia for populations of the European part of Russia.

Molecular diagnosis and frequencies of primary hypolactasia in populations of Russia and neighboring countries

Molecular diagnosis and frequencies of primary hypolactasia in populations of Russia and neighboring countries

Genotyping of the Lactase-Phlorizin Hydrolase −13910 Polymorphism by LightCycler PCR and Implications for the Diagnosis of Lactose Intolerance

Hypolactasia and lactose intolerance are common conditions worldwide. Hypolactasia seems to be strongly correlated with genotype C/C of the genetic variant C-->T(-13910) upstream of the lactase phlorizin hydrolase (LPH) gene. We developed a rapid genotyping assay for LPH C-->T(-13910) and investigated the relationship of positive lactose breath hydrogen test (LBHT) results suggesting lactose intolerance with LPH C-->T(-13910) genotype. Using automated DNA purification on the MagNA Pure LC and real-time PCR on the LightCycler, we examined samples from 220 individuals to estimate genotype frequencies; we then determined LPH C-->T(-13910) genotype in samples from 54 Caucasian patients with a positive LBHT result and symptoms of lactose intolerance. Genotyping of 220 individuals revealed frequencies of 21.4%, 41.8%, and 36.8% for genotypes C/C, C/T, and T/T. Of the patients with positive LBHT results, only 50% had the C/C genotype suggestive of primary adult hypolactasia in our study population. The other patients had various degrees of secondary hypolactasia or symptoms of lactose intolerance. Patients with C/C genotype had a mean (SD) peak H2 increase in the LBHT [108 (58) ppm] that was significantly higher than in patients with the C/T [65 (54) ppm] and T/T [44 (34) ppm] genotypes. The new real-time PCR assay provides a rapid, labor-saving means for the genotyping of LPH C-->T(-13910). Use of the assay may assist in differentiating patients with primary hypolactasia from those with secondary hypolactasia and lactose intolerance, who may need further clinical examinations to diagnose their underlying primary diseases.

GENETIC PREDISPOSITION FOR PRIMARY HYPOLACTASIA OF THE ADULT TYPE IN CHILDREN AND ADOLESCENTS WITH RECURRENT ABDOMINAL PAIN

Aim: Primary hypolactasia of the adult type (HL) presents clinically as lactose intolerance (LI), a frequent cause of recurrent abdominal pain (RAP). It bears the risk of impaired bone growth due to avoidance of dairy products and thus inadequate calcium intake. Using a molecular genetic assay, genetic predisposition for HL was found in 24% of female adults in our region. There are only few data on this predisposition in children and adolescents as assessed by this method. We used it to determine genetic HL predisposition in children and adolescents with RAP to identify individuals at risk for LI and impaired bone growth. Methods: From VII-XII'04 65/220 patients with self reported RAP fulfilled the ROME II criteria for RAP (f: 38; m: 27; 25/65 < 8 yrs. 40/65 > 8 yrs.) and presented clinically with LI. The LCT genotypes CC, TC and TT were determined by an allele specific PCR-based assay (defining the LCT-[13910]-polymorphism near the lactase phlorizin hydrolyse gene), using 150 microliters of capillary blood or saliva. For compliance reasons lactose H2 breath tests were performed in the elder patients only (17/65). Results: 36/65 patients with RAP and clinical LI were CC homozygote (55.4%; f: 24, m: 12). 23/65 (35.4%; f: 12, m: 11) were TC heterozygote and 6/65 (9.2%; f: 3, m: 3) TT homozygote. 9/17 patients undergoing H2 breath tests had positive results: 7/9 had the CC-, and 2/9 the TC-genotype. Genotypes of the 8 patients with negative results were as follows: CC = 3, TC = 2, TT = 3. Summary: 90.8% of patients with RAP and clinically suspected LI had the CC or TC genotype for HL. Because these genotypes are both associated with a higher risk for osteoporosis, these patients and those with positive H2 breath tests are warranting close observation. An explanation for the negative functional test results in the 3 CC patients might be a higher individual threshold to the oral lactose load. Conclusion: The PCR-based genotyping for lactose gene polymorphisms presented might serve as a valuable screening method for paediatric patients with RAP and at risk for LI and osteoporosis that needs to be performed only once, is unexpensive, easy and feasible from minute blood and saliva volumes respectively.

Lactase enzyme, detected immunohistochemically, is lost in active celiac disease, but unaffected by oats challenge.

The loss of lactase activity that occurs in active celiac disease resolves on adherence to a gluten-free diet that excludes the cereals wheat, barley, rye, and oats. Recently, an immunohistochemical technique has been described to evaluate lactase expression in primary hypolactasia. We have adapted this method to study lactase activity in adult celiac patients and to assess its value as a diagnostic tool. In addition, given the results of two recent studies suggesting the safety of reintroducing oats cereal into the celiac diet, we have also evaluated the response of lactase expression to oats exposure. Duodenal biopsies from 26 patients were stained for lactase expression using an indirect immunoperoxidase method. Eleven disease control patients had normal architecture and nine had features of active celiac disease. Ten patients, who had celiac disease in clinical and histological remission, underwent oats challenge for 12 wk. Confluent expression of lactase was observed in the 11 control patients with normal histology, whereas staining was absent in the nine patients with active celiac disease. All 10 patients with treated celiac disease had normal lactase expression after exposure to oats. The immunohistochemical technique used in this study provides an easy, reliable method of assessing lactase enzyme and confirms the value of this index as a marker of celiac disease activity. The results of two recent studies demonstrating the lack of oats toxicity in adult celiac patients have been further corroborated by our findings, which show the preservation of lactase enzyme after oats challenge.

Lactase enzyme, detected immunohistochemically, is lost in active celiac disease, but unaffected by oats challenge

OBJECTIVES: The loss of lactase activity that occurs in active celiac disease resolves on adherence to a gluten-free diet that excludes the cereals wheat, barley, rye, and oats. Recently, an immunohistochemical technique has been described to evaluate lactase expression in primary hypolactasia. We have adapted this method to study lactase activity in adult celiac patients and to assess its value as a diagnostic tool. In addition, given the results of two recent studies suggesting the safety of reintroducing oats cereal into the celiac diet, we have also evaluated the response of lactase expression to oats exposure. METHODS: Duodenal biopsies from 26 patients were stained for lactase expression using an indirect immunoperoxidase method. Eleven disease control patients had normal architecture and nine had features of active celiac disease. Ten patients, who had celiac disease in clinical and histological remission, underwent oats challenge for 12 wk. RESULTS: Confluent expression of lactase was observed in the 11 control patients with normal histology, whereas staining was absent in the nine patients with active celiac disease. All 10 patients with treated celiac disease had normal lactase expression after exposure to oats. CONCLUSIONS: The immunohistochemical technique used in this study provides an easy, reliable method of assessing lactase enzyme and confirms the value of this index as a marker of celiac disease activity. The results of two recent studies demonstrating the lack of oats toxicity in adult celiac patients have been further corroborated by our findings, which show the preservation of lactase enzyme after oats challenge.

Hypolactasia in Saami subpopulations of Russia and Finland

Primary hypolactasia is a gene attributed condition of the inability of adult individuals to consume whole milk. Subpopulations of the Russia (Kildin) and Finland Saami are characterized by a large variability of the LAC*R (lactase restriction) gene frequencies (0.50-0.77). The distribution of primary hypolactasia among the Saami is ranging from 25% to 60%. The intensive reindeer breeding was developed by the Saami only 300-400 years ago. Reindeer milk is poor in lactose (2.4%) and is consumed by the Saami in small amounts. Thus, "milk behaviour" connected with reindeer breeding could not have influenced the trait evolution too much. The large between-group differences of the LAC*R gene frequencies in the Saami seem to reflect the level of genetic influence of neighbouring non-Saami populations. The role of gene inflow in reducing the level of primary hypolactasia in various Saami subpopulations is confirmed by historic data of various ethnoterritorial groups as well as by the reduction of the number of traditional family name bearers and the change of the AB0 blood group gene frequencies among the Kildin Saami in the last 30 years.