Prevalence and trends in adult-type hypolactasia in different age cohorts in Central Sweden diagnosed by genotyping for the adult-type hypolactasia-linked LCT -13910C > T mutation

Development of Personalized Nutrition: Applications in Lactose Intolerance Diagnosis and Management

Recent discoveries in the “omics” field and the growing focus on preventive health have opened new avenues for personalized nutrition (PN), which is becoming an important theme in the strategic plans of organizations that are active in healthcare, food, and nutrition research. PN holds great potential for individual health optimization, disease management, public health interventions, and product innovation. However, there are still multiple challenges to overcome before PN can be truly embraced by the public and healthcare stakeholders. The diagnosis and management of lactose intolerance (LI), a common condition with a strong inter-individual component, is explored as an interesting example for the potential role of these technologies and the challenges of PN. From the development of genetic and metabolomic LI diagnostic tests that can be carried out in the home, to advances in the understanding of LI pathology and individualized treatment optimization, PN in LI care has shown substantial progress. However, there are still many research gaps to address, including the understanding of epigenetic regulation of lactase expression and how lactose is metabolized by the gut microbiota, in order to achieve better LI detection and effective therapeutic interventions to reverse the potential health consequences of LI.

Do adults and older people follow current guidelines for milk consumption?

OBJECTIVE

To estimate the prevalence of frequent milk consumption (≥five times/week), the consumption of low-fat/skimmed milk and associated factors in adults and older people, evaluating adherence to current Brazilian guideline.

DESIGN

Population-based cross-sectional study involving the analysis of data from the 2015 Campinas Food Intake and Nutritional Status and 2015 Campinas Health Survey. The prevalence of milk consumption was analysed according to socio-economic characteristics, morbidities and health-related behaviours.

SETTING

City of Campinas, state of São Paulo, Brazil.

PARTICIPANTS

A sample of 1710 participants of the 2015 Campinas Nutritional and Health Surveys.

RESULTS

A total of 73·8 % of the population consumed milk, but the prevalence of frequent consumption was only 44·0 %. Frequent milk consumption was higher among women, older people and individuals with better diet quality. A total of 18·4 % of the individuals who consumed milk reported consuming low-fat/skimmed milk; this prevalence was higher among women, individuals with a higher socio-economic status, those with better diet quality and those with chronic diseases.

CONCLUSION

Despite the high nutritional quality of milk and the different types available on the market, adults and older people do not follow current recommendations regarding its consumption. Information on the nutritional quality of milk and current recommendations should be disseminated more at healthcare services.

Use of genetic testing for hypolactasia trait in the North Denmark Region

OBJECTIVE

Lactose intolerance (LI) may be considered in patients with unspecific gastrointestinal symptoms, but there is no clear consensus on when and how to diagnose the disorder. The LCT-13910 CC genotype is associated with acquired primary lactase deficiency (adult-type hypolactasia; ATH). We aimed to describe the number of tests and test results in the North Denmark Region considering patient age, geographical origin and repeated testing.

METHODS

Retrospective evaluation of the polymerase chain reaction-based LCT-13910 genotype tests registered in the clinical laboratory information system (LABKA II) with data linkage to Danish nationwide registers.

RESULTS

Between 18 May 2007 and 31 December 2018, a total of 23,560 individuals were tested. There was a sevenfold increase in the number of tests performed during the study period. About 9.8% of the tests performed in 2018 were repeated testing in the same individuals. Overall, 8.8% of tested individuals were younger than 5 years, 90.7% were of Danish origin and 5.5% originated from outside of Europe. The LCT-13910 CC genotype was identified in 13.3% of all tested individuals, in 16.0% of children younger than 5 years, in 6.8% of Danish individuals and in 90.9% originating from outside of Europe.

CONCLUSIONS

In the North Denmark Region, a marked increase in the use of genetic testing for hypolactasia was observed and repeated testing was frequent. Furthermore, the use of the test and the test results were dependent on patient age and geographical origin. Results inform the debate on when and how to use genetic testing in the diagnosing of LI.

Prospective Study of Lactose Intolerance as a Potential Cause of Gas Bloat Syndrome in Patients Treated Surgically for Gastroesophageal Reflux

Introduction. The high incidence of lactose intolerance leads us to consider that many of our patients could suffer from this alteration. Therefore, as its main sign (even when asymptomatic) is increased intestinal gas, patients recovering from a Nissen fundoplication have a significant probability of suffering from gas bloat syndrome. Materials and Methods. This prospective study was conducted from November 2012 to January 2017, we included all the patients who had been treated by the Nissen technique for gastroesophageal reflux disease with gas bloat syndrome detected during follow-up and tested positive for lactose intolerance. The study participants were then prescribed a lactose-poor diet to be followed for 3 months. The patients were asked to complete quality of life and symptomatology questionnaires before and after diet. The pre- and post-diet results were then compared. Results. The pre- and post-diet results showed statistically significant improvements in both questionnaires. Conclusion. Lactose intolerance may account for the symptoms presented by a significant number of patients with gas bloat syndrome following antireflux surgery; these patients could benefit from consuming a lactose-free diet, which we expect to alleviate or, in some cases, eliminate the above symptoms.

Prevalence of food hypersensitivity in relation to IgE sensitisation to common food allergens among the general adult population in West Sweden

Background

The prevalence of self-experienced adverse reactions to foods seems to have an increasing trend in both adults and children. However, it is unclear if the prevalence of food hypersensitivity in the Swedish adult population is still rising, what symptoms are caused by different foods and which are the most common foods to which adults are more frequently IgE-sensitised.

Methods

In a cross-sectional study based on questionnaire responses, interviews and clinical examinations as part of the West Sweden Asthma Study, 1042 subjects from the general population, 17–78 years of age, living in Västra Götaland, Sweden, were included. The subjects reported symptoms for 56 specified foods and blood samples were taken to examine the IgE-sensitisation pattern for 9 common foods.

Results

Approximately 32% of adults reported food hypersensitivity, affecting mostly women and subjects less than 61 years old. The foods most often reported to cause adverse reactions were hazelnut (8.9%), apple (8.4%), milk (7.4%) and kiwi (7.3%). Less than one percent (0.9%) reported symptoms from ingestion of meat. Symptoms mostly affected the gastrointestinal tract (15%) and the skin (2.7%). Sixteen per cent were IgE-sensitised to common foods, most often to hazelnut (13.3%), peanut (4.9%) and almond (3.0%), while 5.9% reported symptoms and were IgE-sensitised to the same food, mainly to hazelnut (5.3%).

Conclusions

The prevalence of self-reported food hypersensitivity in West Sweden indicates a rising trend. The correspondence between self-reported symptoms and IgE-sensitisation to foods is generally poor, except for hazelnut and almond which exhibit moderate or fair correlation.

Hypolactasia is associated with insulin resistance in nonalcoholic steatohepatitis

AIM

To assess lactase gene (LCT)-13910C>T polymorphisms in Brazilian non-alcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) patients in comparison with healthy controls.

METHODS

This was a transverse observational clinical study with NAFLD patients who were followed at the Hepatology Outpatient Unit of the Hospital das Clínicas, São Paulo, Brazil. The polymorphism of lactase non-persistence/lactase persistence (LCT-13910C>T) was examined by PCR-restriction fragment length polymorphism technique in 102 liver biopsy-proven NAFLD patients (steatosis in 9 and NASH in 93) and compared to those of 501 unrelated healthy volunteers. Anthropometric, clinical, biochemical and liver histology data were analyzed. Continuous variables were compared using the t or Mann-Whitney tests, and categorical data were compared with the Fisher’s exact test. Univariate logistic regression and multivariate logistic regression adjusted for gender and age were performed.

RESULTS

No differences in the LCT-13910 genotype frequencies were noted between the NAFLD patients (66.67% of the patients with steatosis were CC, 33.33% were CT, and none were TT; 55.91% of the patients with NASH were CC, 39.78% were CT, and 4.3% were TT; P = 0.941) and the healthy controls (59.12% were CC, 35.67% were CT, and 5.21% were TT) or between the steatosis and NASH patients. That is, the distribution of the lactase non-persistence/lactase persistence polymorphism (LCT-13910C>T) in the patients with NAFLD was equal to that in the general population. In the NASH patients, the univariate analysis revealed that the lactase non-persistence (low lactase activity or hypolactasia) phenotype was associated with higher insulin levels (23.47 ± 15.94 μU/mL vs 15.8 ± 8.33 μU/mL, P = 0.027) and a higher frequency of insulin resistance (91.84% vs 72.22%, P = 0.02) compared with the lactase persistence phenotype. There were no associations between the LCT genotypes and diabetes (P = 0.651), dyslipidaemia (P = 0.328), hypertension (P = 0.507) or liver histology in these patients. Moreover, in the NASH patients, hypolactasia was an independent risk factor for insulin resistance even after adjusting for gender and age [OR = 5.0 (95%CI: 1.35-20; P = 0.017)].

CONCLUSION

The LCT-13910 genotype distribution in Brazilian NAFLD patients was the same as that of the general population, but hypolactasia increased the risk of insulin resistance in the NASH patients.

Milk allergy is a minor cause of milk avoidance due to perceived hypersensitivity among schoolchildren in Northern Sweden

AIM

We investigated phenotypes of milk hypersensitivity among schoolchildren aged 11-12 in Northern Sweden.

METHODS

In a population-based cohort, 1824 (98%) children aged 11-12 participated in a questionnaire survey, skin prick testing, interviews on food hypersensitivity and assessment of body mass index (BMI). Of the 265 children reporting milk hypersensitivity, milk avoidance and no coeliac disease, 236 (89%) participated in a structured interview and blood samples for analyses of milk-specific Immunoglobulin E. The children were then categorised into milk hypersensitivity phenotypes according to preset criteria.

RESULTS

In all, 14.5% reported milk hypersensitivity. Of these, 3% were categorised as current milk allergy, 23% as outgrown milk allergy, 40% as probable lactose intolerance and 11% as nondefinable. Furthermore, 23% had discontinued their elimination diet. Milk allergy was associated with other atopic disorders and lower BMI, with an odds ratio of 0.82 and 95% confidence interval of 0.80-0.98. Only 2% had previously undergone an oral challenge.

CONCLUSION

The most common symptom phenotypes among Swedish children aged 11-12 with self-reported milk hypersensitivity and milk avoidance were probable intolerance and outgrown milk allergy, while current milk allergy was uncommon. Children with milk allergy had a lower BMI and most lacked a challenge-proven diagnosis.

Lactase persistence versus lactose intolerance: Is there an intermediate phenotype?

BACKGROUND

According to the prevailing theory about the genetic background to lactose intolerance, there are three genotypes but only two adult physiological phenotypes: lactase persistence in individuals with the CT and TT genotypes and lactase non-persistence in individuals with the CC genotype. However, analysis of lactase activity from intestinal biopsies has revealed three distinct levels of activity, suggesting that an intermediate physiological phenotype may exist.

AIM

To assess possible disparities between different genotypes with regard to biomarkers of lactase activity and physical symptoms during an oral lactose load test.

METHODS

A retrospective study using an oral lactose load test (n=487). Concentrations of hydrogen in exhaled air and blood glucose were measured. Afterwards, subjects were asked to provide oral mucosa samples for genotyping and answer a questionnaire (participation rate 56%, n=274).

RESULTS

Mean hydrogen levels in exhaled air at 120min were significantly higher in the CT genotype than in the TT genotype. There was no significant difference in blood glucose levels between the two groups. Reported symptoms, with the possible exception of abdominal pain, were equally prevalent in both groups.

CONCLUSIONS

Subjects with the CT and TT genotypes, hitherto classified as lactase-persistent, differ in their physiological response to lactose intake, indicating differences in phenotype which could have clinical significance.

The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds

Humans learned to exploit ruminants as a source of milk about 10,000 years ago. Since then, the use of domesticated ruminants as a source of milk and dairy products has expanded until today when the dairy industry has become one of the largest sectors in the modern food industry, including the spread at the present time to countries such as China and Japan. This review analyzes the reasons for this expansion and flourishing. As reviewed in detail, milk has numerous nutritional advantages, most important being almost an irreplaceable source of dietary calcium, hence justifying the effort required to increase its consumption. On the other hand, widespread lactose intolerance among the adult population is a considerable drawback to dairy-based foods consumption. Over the centuries, three factors allowed humans to overcome limitations imposed by lactose intolerance: (i) mutations, which occurred in particular populations, most notably in the north European Celtic societies and African nomads, in which carriers of the lactose intolerance gene converted from being lactose intolerant to lactose tolerant; (ii) the ability to develop low-lactose products such as cheese and yogurt; and (iii) colon microbiome adaptation, which allow lactose intolerant individuals to overcome its intolerance. However, in a few examples in the last decade, modern dairy products, such as the popular and widespread bio-cultured yogurts, were suspected to be unsuitable for lactose intolerant peoples. In addition, the use of lactose and milk-derived products containing lactose in non-dairy products has become widespread. For these reasons, it is concluded that it might be important and helpful to label food that may contain lactose because such information will allow lactose intolerant groups to control lactose intake within the physiological limitations of ~12 g per a single meal.

Assessment of Allergy to Milk, Egg, Cod, and Wheat in Swedish Schoolchildren: A Population Based Cohort Study

Objectives

Knowledge about the prevalence of allergies to foods in childhood and adolescence is incomplete. The purpose of this study was to investigate the prevalence of allergies to milk, egg, cod, and wheat using reported data, clinical examinations, and double-blind placebo-controlled food challenges, and to describe the phenotypes of reported food hypersensitivity in a cohort of Swedish schoolchildren.

Methods

In a population-based cohort of 12-year-old children, the parents of 2612 (96% of invited) completed a questionnaire. Specific IgE antibodies to foods were analyzed in a random sample (n=695). Children reporting complete avoidance of milk, egg, cod, or wheat due to perceived hypersensitivity and without physician-diagnosed celiac disease were invited to undergo clinical examination that included specific IgE testing, a celiac screening test, and categorization into phenotypes of food hypersensitivity according to preset criteria. Children with possible food allergy were further evaluated with double-blind challenges.

Results

In this cohort, the prevalence of reported food allergy to milk, egg, cod, or wheat was 4.8%. Food allergy was diagnosed in 1.4% of the children after clinical evaluation and in 0.6% following double-blind placebo-controlled food challenge. After clinical examination, children who completely avoided one or more essential foods due to perceived food hypersensitivity were categorized with the following phenotypes: allergy (29%), outgrown allergy (19%), lactose intolerance (40%), and unclear (12%).

Conclusions

There was a high discrepancy in the prevalence of allergy to milk, egg, cod and wheat as assessed by reported data, clinical evaluation, and double-blind food challenges. Food hypersensitivity phenotyping according to preset criteria was helpful for identifying children with food allergy.

Food hypersensitivity is common in Swedish schoolchildren, especially oral reactions to fruit and gastrointestinal reactions to milk

AIM

This study examined the prevalence, symptom expression and risk factors for food hypersensitivity among Swedish schoolchildren.

METHODS

Parents of 2585 (96% of invited) children aged 7-8 years completed a questionnaire regarding food hypersensitivity and allergic diseases. A random sample of 1700 children (90% of invited) also participated in skin prick testing with ten airborne allergens.

RESULTS

The overall prevalence of reported food hypersensitivity to milk, egg, fish, wheat, soya, fruits and, or, nuts was 21%, with symptoms caused by milk (9%) being the most common. The most frequently reported symptoms were oral symptoms (47.4%), mainly caused by fruit, and gastrointestinal symptoms (45.7%), mainly caused by milk. Factors associated with any food hypersensitivity were female sex, allergic heredity and a positive skin prick test. Eczema was consistently associated with symptoms caused by milk, egg, fish, wheat, soya, fruits and nuts. Rhinitis was associated to the same foods, except milk.

CONCLUSION

Reported food hypersensitivity was common among Swedish schoolchildren. The most frequent symptom expressions were oral symptoms triggered by fruits and gastrointestinal symptoms triggered by milk. The high prevalence of reported symptoms should be validated by clinical examinations to provide a diagnosis.

Frequency of LCT-13910C/T and LCT-22018G/A single nucleotide polymorphisms associated with adult-type hypolactasia/lactase persistence among Israelis of different ethnic groups

Primary lactase deficiency (PLD), the physiological decline of lactase, is associated with the LCT-13910C/T and LCT-22018G/A polymorphisms. PLD is the most common phenotype in humans and varies widely as a function of ethnicity. Israel is a multiethnic country. We analyzed the genetic frequencies of PLD in different Israeli ethnicities. Ethnicity-related frequencies were analyzed in 439 Israelis: Ashkenazi (n=96), Iraqi (n=96), Moroccan (n=96) Jews and Bedouin-Arabs (n=151). DNA was extracted from leukocytes; LCT-13910C/T, -22018G/A and -13915T/G (in Bedouin-Arabs) polymorphisms were analyzed by PCR-restriction fragment length polymorphism analysis. There was a significant association between ethnicity and genotype in both polymorphic LCT SNPs (-13910C/T and -22018). Prevalence of the CC (LCT-13910C/T) genotype associated with adult hypolactasia was 97%, 93%, 83% and 82% among Bedouin-Arabs and Iraqi, Ashkenazi and Moroccan Jews, respectively. The prevalence of the GG (LCT-22018G/A) adult hypolactasia genotype among those groups was identical to that of the CC genotype in each group, except for Iraqi-Jews, of which only 83% carried the GG genotype. The prevalence of heterozygous and homozygous genotypes associated with lactase persistence (CT, TT for -13910C/T and GA, AA for -22018G/A) was 3%, 7%, 17% and 18% and 3%, 17%, 17% and 18% for Bedouin-Arabs, Ashkenazi, Iraqi and Moroccan Jews, respectively. A significant correlation between SNPs was found. PLD prevalence is high among different ethnic groups in Israel and varies between ethnicities. The prevalence of the -13915*G allele, indicative of lactose persistence in African and Arab populations, was 41% in the Bedouin-Arabs group. Lactase persistence genotype prevalence was found to vary between Israeli ethnicities (4-18%). SNPs (-13910C/T and -22018) showed significant correlation in detecting genotype prevalence in Israeli Jews. We suggest adjusting nutritional recommendations accordingly.

Lactose intolerance: diagnosis, genetic, and clinical factors

Most people are born with the ability to digest lactose, the major carbohydrate in milk and the main source of nutrition until weaning. Approximately 75% of the world’s population loses this ability at some point, while others can digest lactose into adulthood. This review discusses the lactase-persistence alleles that have arisen in different populations around the world, diagnosis of lactose intolerance, and its symptomatology and management.

Lactase non-persistent genotype influences milk consumption and gastrointestinal symptoms in Northern Russians

BACKGROUND

Milk is an important source of nutrients. The consumption of milk, however, may cause abdominal complaints in lactose intolerant individuals. The frequency of -13910C/C genotype is known to be high among Northern Russians, exceeding the prevalence in northern Europe. In our study we tested two hypotheses: 1) subjects with lactase non-persistent genotype (-13910C/C) have more gastrointestinal (GI) symptoms associated with milk 2) subjects with lactase non-persistence avoid using milk.

METHODS

In total, 518 students aged 17 to 26 years were randomly selected from different departments in the Northern State Medical University (NSMU) for genotyping the lactase activity-defining -13910C/T variant. All subjects filled in a questionnaire covering their personal data, self-reported GI symptoms and milk consumption habits.

RESULTS

Northern Russians consume very small amounts of milk daily. Among carriers of the lactase non-persistent (LNP) genotype there were 10 percentage units of milk-consumers fewer than among lactase-persistent (LP) subjects (p = 0.03). Complaints of GI disorders caused by milk were different between the genotypes (p = 0.02). Among all types of food analyzed only milk was associated with increased GI symptoms among subjects with the LNP genotype (OR = 1.95, CI 1.03-3.69)

CONCLUSIONS

Subjects with -13910C/C have more GI symptoms from milk. Subjects with lactase non-persistent genotype avoid using milk. In the case of increasing milk consumption symptoms may increase the need for medical consultation. It is thus important either for people themselves or for health care staff to be aware of lactase persistence/non-persistence.

Lactase persistence and milk consumption are associated with body height in Swedish preadolescents and adolescents

BACKGROUND

Body height is a classic polygenic trait. About 80%-90% of height is inherited and 10%-20% owed to environmental factors, of which the most important ones are nutrition and diseases in preadolescents and adolescents.

OBJECTIVE

The aim of this study was to explore potential relations between the LCT (lactase) C>T-13910 polymorphism, milk consumption, and body height in a sample of Swedish preadolescents and adolescents.

DESIGN

In a cross-sectional study, using a random sample of preadolescents and adolescents (n = 597), dietary intakes were determined. Anthropometric measurements including sexual maturity (Tanner stage) and birth weight were assessed. Parental body height and socio-economic status (SES) were obtained by questionnaires. Genotyping for the LCT C>T-13910 polymorphism that renders individuals lactase persistent (LP) or lactase non-persistent (LNP) was performed by DNA sequencing. Stepwise backward multivariate linear regression was used.

RESULTS

Milk consumption was significantly and positively associated with body height (β = 0.45; 95% CI: 0.040, 0.87, p = 0.032). Adjustments were performed for sex, parental height, birth weight, body mass index (BMI), SES, and Tanner stage. This model explains 90% of the observed variance of body height (adjusted R(2) = 0.89). The presence of the -13910 T allele was positively associated with body height (β = 2.05; 95% CI: 0.18, 3.92, p = 0.032).

CONCLUSIONS

Milk consumption is positively associated with body height in preadolescents and adolescents. We show for the first time that a nutrigenetic variant might be able to explain in part phenotypic variation of body height in preadolescents and adolescents. Due to the small sample size further studies are needed.

The European lactase persistence genotype determines the lactase persistence state and correlates with gastrointestinal symptoms in the Hispanic and Amerindian Chilean population: a case-control and population-based study

BACKGROUND

The lactase persistent (LP) or lactase non-persistent (LNP) state in European adults is genetically determined by a single nucleotide polymorphism (SNP) located 13.9 kb upstream of the lactase (LCT) gene, known as LCT C>T(-13910) (rs4988235). The LNP condition leads to an inability to digest the milk sugar lactose leading to gastrointestinal symptoms and can affect nutrient and calcium intake in certain populations.

OBJECTIVES

The authors studied a group of 51 Chilean patients to assess whether this SNP influences the LP/LNP state in this population, and determined the prevalence of LCT C>T(-13910) genotypes in a representative sample of 216 Hispanics and 43 Amerindians with correlation to digestive symptoms.

DESIGN

Case-control study done in Chilean patients with clinical suspicion of LNP that were assessed using clinical survey, hydrogen breath test (HBT) and SNP genotyping. The population sample of Hispanics and Amerindians was assessed by clinical survey and SNP genotyping.

RESULTS

Of the 51 patients with clinical suspicion of LNP, 29 were HBT-positive. The CC genotype (LNP) was present in 89.7% of the patients with positive HBT and in only 4.7% of those with negative HBT. The prevalence of the CC genotype was 56.9% in the Hispanic population and 88.3% in Amerindians, and was associated with a higher self-reported clinical intolerance to ingestion of dairy products.

CONCLUSION

The LP/LNP state is determined by the LCT C>T(-13910) variant in Chileans. This variant predicts digestive symptoms associated with the ingestion of lactose and is a good tool for the diagnosis of primary adult hypolactasia. The LCT T(-13910) allele is rare in the Amerindian population and is suggestive of European ancestry in this contemporary population.

Analysis of three functional polymorphisms in relation to osteoporosis phenotypes: replication in a Spanish cohort

Osteoporosis is a complex disease involving many putative genetic factors. Association analysis of functional SNPs in candidate genes is an important tool for their identification. However, this approach is affected by limited power, population stratification, and other drawbacks that lead to discordant results. Replication in independent cohorts is essential. We performed association analyses of three functional polymorphisms previously associated with bone phenotypes--namely, Ala222Val in MTHFR, Ile1062Val in LRP6, and -13910C>T in LCT--in a cohort of 944 postmenopausal Spanish women, all of them with lumbar spine (LS) bone mineral density (BMD) data and most with femoral neck (FN) BMD and fracture data. We found significant differences between genotypes only for the MTHFR polymorphism and vertebral factures, with an OR of 2.27 (95% CI 1.17-4.38) for the TT vs. CC/CT genotypes, P = 0.018. We present genotype and allele frequency data for LCT -13910C>T for a Spanish population, where the T allele (conferring lactase persistence) has a frequency of 38.6%. Genotype frequencies were consistent with observed clines in Europe and with the prevalence of lactase nonpersistence. The LCT -13910C>T polymorphism was significantly associated with height and weight, such that T allele carriers were 0.88 cm taller (95% CI 0.08-1.59 cm, P = 0.032, adjusted by age) than CC individuals and TT homozygotes were 1.91 kg heavier than CC/CT individuals (95% CI 0.11-3.71 kg, P = 0.038, adjusted by age). In conclusion, no significant association was observed between the studied polymorphisms and LS BMD or FN BMD in postmenopausal Spanish women, and only MTHFR Ala222Val was associated with vertebral fractures.

Body fat and dairy product intake in lactase persistent and non-persistent children and adolescents

Background

Lactase non-persistent (LNP) individuals may be lactose intolerant and therefore on a more restricted diet concerning milk and milk products compared to lactase persistent (LP) individuals. This may have an impact on body fat mass.

Objective

This study examines if LP and LNP children and adolescents, defined by genotyping for the LCT-13910 C > T polymorphism, differ from each other with regard to milk and milk product intake, and measures of body fat mass.

Design

Children (n=298, mean age 9.6 years) and adolescents (n=386, mean age 15.6 years), belonging to the Swedish part of the European Youth Heart Study, were genotyped for the LCT-13910 C > T polymorphism. Dietary intakes of reduced and full-fat dairy varieties were determined.

Results

LNP (CC genotype) subjects consumed less milk, soured milk and yoghurt compared to LP (CT/TT genotype) subjects (p<0.001). Subsequent partitioning for age group attenuated this observation (p=0.002 for children and p=0.023 in adolescents). Six subjects were reported by parents to be ‘lactose intolerant’, none of whom were LNP. LNP children and adolescents consumed significantly less reduced fat milk and milk products than LP children and adolescents (p=0.009 for children and p=0.001 for adolescents).

Conclusions

We conclude that LP is linked to an overall higher milk and dairy intake, but is not linked to higher body fat mass in children and adolescents.

A worldwide correlation of lactase persistence phenotype and genotypes

BACKGROUND

The ability of adult humans to digest the milk sugar lactose - lactase persistence - is a dominant Mendelian trait that has been a subject of extensive genetic, medical and evolutionary research. Lactase persistence is common in people of European ancestry as well as some African, Middle Eastern and Southern Asian groups, but is rare or absent elsewhere in the world. The recent identification of independent nucleotide changes that are strongly associated with lactase persistence in different populations worldwide has led to the possibility of genetic tests for the trait. However, it is highly unlikely that all lactase persistence-associated variants are known. Using an extensive database of lactase persistence phenotype frequencies, together with information on how those data were collected and data on the frequencies of lactase persistence variants, we present a global summary of the extent to which current genetic knowledge can explain lactase persistence phenotype frequency.

RESULTS

We used surface interpolation of Old World lactase persistence genotype and phenotype frequency estimates obtained from all available literature and perform a comparison between predicted and observed trait frequencies in continuous space. By accommodating additional data on sample numbers and known false negative and false positive rates for the various lactase persistence phenotype tests (blood glucose and breath hydrogen), we also apply a Monte Carlo method to estimate the probability that known lactase persistence-associated allele frequencies can explain observed trait frequencies in different regions.

CONCLUSION

Lactase persistence genotype data is currently insufficient to explain lactase persistence phenotype frequency in much of western and southern Africa, southeastern Europe, the Middle East and parts of central and southern Asia. We suggest that further studies of genetic variation in these regions should reveal additional nucleotide variants that are associated with lactase persistence.

A comparison of diagnostic tests for lactose malabsorption--which one is the best?

Background

Perceived milk intolerance is a common complaint, and tests for lactose malabsorption (LM) are unreliable. This study assesses the agreement between diagnostic tests for LM and describes the diagnostic properties of the tests.

Methods

Patients above 18 years of age with suspected LM were included. After oral intake of 25 g lactose, a combined test with measurement of serum glucose (s-glucose) and hydrogen (H2) and methane (CH4) in expired air was performed and symptoms were recorded. In patients with discrepancies between the results, the combined test was repeated and a gene test for lactose non-persistence was added. The diagnosis of LM was based on an evaluation of all tests. The following tests were compared: Increase in H2, CH4, H2+CH4 and H2+CH4x2 in expired air, increase in s-glucose, and symptoms. The agreement was calculated and the diagnostic properties described.

Results

Sixty patients were included, seven (12%) had LM. The agreement (kappa-values) between the methods varied from 0.25 to 0.91. The best test was the lactose breath test with measurement of the increase in H2 + CH4x2 in expired air. With a cut-off level < 18 ppm, the area under the ROC-curve was 0.967 and sensitivity was 100%. This shows that measurement of CH4 in addition to H2 improves the diagnostic properties of the breath test.

Conclusion

The agreement between commonly used methods for the diagnosis of LM was unsatisfactory. A lactose breath test with measurement of H2 + CH4x2 in expired air had the best diagnostic properties.

Associations between lactase persistence and the metabolic syndrome in a cross-sectional study in the Canary Islands

BACKGROUND

The single nucleotide polymorphism (SNP) LCT -13910 C>T, associated with genetically determined phenotypes of lactase persistence (LP) or non-persistence (LNP), was studied in relation to the metabolic syndrome (MS).

AIM OF THE STUDY

The aim was to determine if milk intake and MS are associated. We applied Mendelian randomization (MR). The SNP, LCT -13910 C>T, with the genotypes LP (TT/CT) and LNP (CC), was taken as a proxy for milk consumption.

METHODS

A representative sample of adults belonging to the Canary Islands Nutrition Survey (ENCA) in Spain aged 18-75 years (n = 551) was genotyped for the LCT -13910 C>T polymorphism. We used the International Diabetes Federation (IDF) criteria to define MS.

RESULTS

60% of the population was LP and 40% LNP. One hundred seven LP subjects (35.0%) and 53 LNP subjects (25.6%) showed MS (chi (2) = 5.04, p = 0.025). LP subjects showed a significantly higher odds ratio (OR) for MS than LNP subjects computed for the whole population: both the crude OR (1.56; 95% CI 1.06-2.31) and adjusted OR for sex, age, daily energy intake, physical activity and educational level (1.57; 95% CI 1.02-2.43). Adjusted OR for women with LP was 1.93; 95% CI 1.06-3.52.

CONCLUSIONS

The T allele of the SNP might constitute a nutrigenetic factor increasing the susceptibility of LP subjects, especially women, to develop MS in the Canary Islands.

Simultaneous genotyping of the three lactose tolerance-linked polymorphisms LCT -13907C>G, LCT -13910C>T and LCT -13915T>G with Pyrosequencing technology

BACKGROUND

We required a new genotyping method for the diagnosis of adult hypolactasia, which would allow the simultaneous genotyping of three known polymorphic loci linked to lactose tolerance (LCT -13907C>G, LCT -13910C>T and LCT -13915T>G) in a single PCR/pyrosequencing test run.

METHOD

We utilized Pyrosequencing technology, a DNA-sequence-by-synthesis technique.

RESULTS

The developed Pyrosequencing method allowed genotyping of the three loci LCT -13907C>G, LCT -13910C>T and LCT -13915T>G in a single PCR/pyrosequencing test run. A separate Pyrosequencing assay was developed for genotyping of the LCT -14010G>C mutation. The methods were evaluated in 116 clinical samples from patients of non-European descent, sent to the laboratory for diagnosis of adult hypolactasia. The "African" mutations LCT -13907C>G and LCT -13915T>G were found in subjects originating not only from Somalia, Ethiopia and Eritrea but also in Arabs and Iranians. Several compound heterozygotes LCT -13907CG/-13915TG were found among Ethiopian, Eritrean and Somalian subjects. No subject with the LCT -14010G>C mutation was found among the studied subjects. Advantages compared to the other genotyping methods are less staff hands-on time than, e.g., restriction fragment length polymorphism (RFLP) analyses, avoiding radioactivity as in the originally described isotope-minisequencing and in addition, Pyrosequencing is a direct DNA sequencing technique which gives unambiguous genotyping results as well as some redundant sequence information beyond the single nucleotide polymorphism (SNP) position, which serves as a valuable internal control obtained for each sample.

CONCLUSIONS

Pyrosequencing is a robust genotyping modality suitable for clinical genotyping of patients not only of European, but also of African or Middle Eastern descent, who may harbor any combination of the three LCT mutations, LCT -13907C>G, LCT -13910C>T, LCT -13915T>G.