Genetically defined adult-type hypolactasia and self-reported lactose intolerance as risk factors of osteoporosis in Finnish postmenopausal women

Association Between Self-Reported Lactose Intolerance, Additional Environmental Factors, and Bone Mineral Density in Young Adults

OBJECTIVES

This study examines the relationship between self-reported lactose intolerance (LI), environmental factors, and their effects on bone mineral density (BMD) in young adults from Slovakia.

METHODS

We assessed 985 adults aged 18-30 years, with an average age of 21.61 ± 2.32 years, who were enrolled in this pilot cross-sectional study during the period 2019-2023. Individual environmental factors (smoking status, alcohol consumption, physical activity, milk and milk product intake, and calcium intake) and self-reported LI were assessed using a detailed questionnaire. BMD was analyzed using the QUS device (Sunlight MiniOmni), and total weight was measured with the InBody 770 bioimpedance analyzer.

RESULTS

Linear regression analysis showed the independent influence of age, total weight, and the presence of LI on the speed of sound in meters per second (SOS; m/s) and Z-score parameters in women (p < 0.05), whereas in men, age and smoking status were significant predictors of SOS (p < 0.05), and age and LI status significantly influenced the Z-score (p < 0.05).

CONCLUSIONS

In the present study of young Slovak adults, the presence of self-reported LI and smoking had a negative effect on BMD, resulting in lower BMD in the radius.

[Food Intolerance]

The term food intolerance has been used non-specifically to define a wide range of disorders related to food intake. Recently, the use of the term "non-immunological adverse reactions to foods" (RANIAs) was recommended as a more correct clinical definition. The pathophysiological mechanisms can be diverse, sometimes unknown, and there are no validated diagnostic tests, making it difficult to obtain accurate data. The clinical manifestations of non-immunological adverse reactions to foods affect more than one organ or system; and gastrointestinal symptoms (pain, abdominal distension, flatulence, and diarrhea) are the most common. Non-immunological adverse reactions to foods are divided into independent and dependent on host factors. Foods may contain chemicals with pharmacological activity and be present naturally, such as vasoactive amines (histamine) and salicylates, or added for preservation, to improve appearance or flavor (monosodium glutamate, tartrazine, sulfites, and benzoates). In some cases, these types of reactions may be like to hypersensitivity reactions. Concomitant alcohol consumption may worsen symptoms by inhibiting histamine breakdown and increasing intestinal permeability. In patients diagnosed with non-immunological adverse reactions to foods, it is important to rule out some psychological problems: aversions or eating disorders.

[Differential diagnosis in food allergy]

It is important to establish the differential diagnosis of food allergy with other disorders, for example: toxic reactions that occur in any person exposed to a sufficient amount of some allergen, and non-toxic reactions that depend on individual susceptibility (food allergy or intolerance). The differential diagnosis is decisive to establish the appropriate treatment. Food intolerance involves adverse reactions to foods without any immunological response involved, and commonly manifests with gastrointestinal symptoms (malaise, abdominal pain or diarrhea). Food allergy is an exaggerated reaction of the immune system, often mediated by IgE, that can trigger serious symptoms (hives, inflammation, respiratory distress, even anaphylaxis). The complex thing is because the symptoms sometimes overlap. To establish an accurate diagnosis, exhaustive clinical evaluation, laboratory tests and, in some cases, controlled provocation tests are required. It is important to understand these distinctions, because treatment and management vary significantly. Food intolerance involves the elimination or reduction of the food that triggers the allergic reaction and requires rigorous measures (complete avoidance of the allergen and availability of epinephrine in cases of severe reactions).

Food Allergy and Intolerance: A Narrative Review on Nutritional Concerns

Adverse food reactions include immune-mediated food allergies and non-immune-mediated intolerances. However, this distinction and the involvement of different pathogenetic mechanisms are often confused. Furthermore, there is a discrepancy between the perceived vs. actual prevalence of immune-mediated food allergies and non-immune reactions to food that are extremely common. The risk of an inappropriate approach to their correct identification can lead to inappropriate diets with severe nutritional deficiencies. This narrative review provides an outline of the pathophysiologic and clinical features of immune and non-immune adverse reactions to food-along with general diagnostic and therapeutic strategies. Special emphasis is placed on specific nutritional concerns for each of these conditions from the combined point of view of gastroenterology and immunology, in an attempt to offer a useful tool to practicing physicians in discriminating these diverging disease entities and planning their correct management. We conclude that a correct diagnostic approach and dietary control of both immune- and non-immune-mediated food-induced diseases might minimize the nutritional gaps in these patients, thus helping to improve their quality of life and reduce the economic costs of their management.

Association of LCT -13910C>T polymorphism and hip fracture in a cohort of older adult population from Northern Spain

Hip fracture is a common health problem very frequent in the older adult population and is associated with significant morbidity, mortality, and societal costs. There are several factors that increase the risk of suffering a hip fracture, however, the effect of genetic lactase non-persistence is not clear-cut yet. For this reason, we investigated if the LCT -13910C>T polymorphism is a potential risk factor for osteoporotic hip fractures in older adult people from the Northern Spain population. A total of 740 individuals were included in this study. Of them, 364 belonged to the group of patients whit osteoporotic hip fracture while the control group consisted of 376 individuals without hip fracture. The genotypes for the LCT -13910C>T polymorphism were analyzed by using polymerase chain reaction and high resolution melting. The prevalence of the CC genotype, which is related to lactase non-persistence, did not differ significantly in both groups. Likewise, no differences were observed between groups when they were compared with regard to the C or the T allele, or when they were analyzed considering gender. Additionally, our results were compared with those obtained in a control group of 207 nonagenarian individuals originally from Northern Spain and no differences were observed. In conclusion, no significant association was observed between the LCT -13910C>T polymorphism and the risk for suffering hip fracture in the older adult population of Northern Spain.

Association of calcium intake, lactose intolerance and physical activity with bone health assessed via quantitative ultrasound among young adults of a Malaysian university

Lactose intolerance has been proposed to cause poor bone health. This study found the prevalence of lactose intolerance was high among Malaysian young adults, but not associated with bone health status, unlike calcium intake. This is the first study that investigated the association of lactose intolerance and bone health status in Malaysia.

PURPOSE

The aims of this study were to determine the prevalence of lactose intolerance, calcium intake and physical activity level and to investigate the association between these variables with bone health status among young adults.

METHODS

This cross-sectional study consisted of 300 Malay, Chinese and Indian students from Universiti Kebangsaan Malaysia with mean age of 22.5 ± 3.2 years. Determination of lactose tolerance status was performed using hydrogen breath test, lactose tolerance test and visual analogue scales. Calcium intake and physical activity level were evaluated using Food Frequency Questionnaire and International Physical Activity Questionnaire, respectively. Bone health status was assessed on calcaneal bone, using quantitative ultrasound.

RESULTS

Lactose intolerance was highly reported among the Malay subjects (72%) followed by Chinese (59%) and Indians (42%). The mean calcium intake was 542.9 ± 365.2 mg/day whilst the mean physical activity was 2757.6 ± 2007.2 MET-min/week. The bone assessment showed that 91% of the subjects had a low risk of developing osteoporosis. Only calcium intake showed a significant association with bone health status (β = 0.006; p = 0.033), whilst no association was shown for lactose intolerance and physical activity level.

CONCLUSIONS

Malaysian young adults showed a high prevalence of lactose intolerance. Calcium intake is associated with increased bone health status. In contrast, lactose intolerance and physical activity level did not directly influence bone health status. Nutrition education promoting adequate calcium intake should be implemented among young adults due to high lactose intolerance prevalence and low calcium intake among subjects.

Lactose intolerance in patients with inflammatory bowel diseases and dietary management in prevention of osteoporosis

Lactose intolerance affects 33% to 75% of the world population and may be associated with various genetic factors. Lactose in the diet can be found in milk and dairy products, which simultaneously constitute the primary sources of calcium. Gut microbiota also influences lactose tolerance. Patients with lactose intolerance often stop consuming milk and dairy products, which may lead to calcium and vitamin deficiency and osteoporosis. Insufficient production of lactase also occurs in patients with diseases of the gastrointestinal tract, such as inflammatory bowel diseases. Moreover, Crohn's disease and ulcerative colitis are risk factors for osteoporosis, and the intake of the proper amount of calcium is an essential element in preventing the decrease of bone mineral density. Diet may prevent the development of osteoporosis, thus, educating patients regarding proper diet should constitute a part of the treatment and prevention process. Patients should consume low-lactose, or lactose-free milk and bacterially fermented dairy products. Additionally, plant milk supplemented by calcium and vitamin D, mineral water with calcium, and certain vegetables also may be good sources of calcium.

Clinical Utility of LCT Genotyping in Children with Suspected Functional Gastrointestinal Disorder

Genetic testing is a good predictor of lactase persistence (LP) in specific populations but its clinical utility in children is less clear. We assessed the role of lactose malabsorption in functional gastrointestinal disorders (FGID) in children and the correlation between the lactase non-persistence (LNP) genotype and phenotype, based on exhaled hydrogen and gastrointestinal symptoms, during a hydrogen breath test (HBT). We also evaluate dairy consumption in this sample. We conducted a 10-year cross-sectional study in a cohort of 493 children with suspected FGID defined by Roma IV criteria. Distribution of the C/T-13910 genotype was as follows: CC, 46.0%; TT, 14.4% (LP allele frequency, 34.1%). The phenotype frequencies of lactose malabsorption and intolerance were 36.3% and 41.5%, respectively. We observed a strong correlation between genotype and both lactose malabsorption (Cramér’s V, 0.28) and intolerance (Cramér’s V, 0.54). The frequency of the LNP genotype (p = 0.002) and of malabsorption and intolerance increased with age (p = 0.001 and 0.002, respectively). In 61% of children, evaluated dairy consumption was less than recommended. No association was observed between dairy intake and diagnosis. In conclusion, we found a significant correlation between genotype and phenotype, greater in older children, suggesting that the clinical value of genetic testing increases with age.

Milk Consumption for the Prevention of Fragility Fractures

Results indicating that a high milk intake is associated with both higher and lower risks of fragility fractures, or that indicate no association, can all be presented in the same meta-analysis, depending on how it is performed. In this narrative review, we discuss the available studies examining milk intake in relation to fragility fractures, highlight potential problems with meta-analyses of such studies, and discuss potential mechanisms and biases underlying the different results. We conclude that studies examining milk and dairy intakes in relation to fragility fracture risk need to study the different milk products separately. Meta-analyses should consider the doses in the individual studies. Additional studies in populations with a large range of intake of fermented milk are warranted.

Adult lactose intolerance, calcium intake, bone metabolism and bone density in German-Turkish immigrants

INTRODUCTION

Adult lactose intolerance (ALI) significantly alters calcium intake and absorption, and thus may promote osteoporosis. ALI is a recessive condition with a geographical north-south gradient characterised by decreased levels of intestinal lactase. PCR-based genotyping of lactase (LCT) gene polymorphisms is a safe and easy way to diagnose ALI and may complement diagnostic procedures to identify individuals at risk for reduced calcium intake and subsequently osteoporosis due to lactose malabsorption. Therefore, we investigated the frequency of ALI and its influence on calcium intake, markers of bone metabolism and bone mineral density (BMD) in a cohort of Turkish immigrants living in Germany.

MATERIALS AND METHODS

We investigated single nucleotide polymorphisms of the LCT gene, calcium intake, markers of bone metabolism and BMD in 183 Turkish immigrants.

RESULTS

ALI was diagnosed in 154 out of 183 (81%) probands. ALI was significantly associated with self-reported lactose intolerance (p < 0.001) and dislike for dairy products (p < 0.01). Osteopenia was diagnosed in 59 out of 183 (32%) and osteoporosis in 15 out of 183 (8%) probands. Probands with reduced BMD had ALI in 86%. All probands had a decreased calcium intake [mg/week]. There was no significant association between ALI, calcium intake, markers of bone metabolism or BMD.

CONCLUSION

Turkish immigrants mostly have ALI and overall show a reduced calcium intake per week. However, ALI did not significantly influence calcium intake, markers of bone metabolism or BMD in this cohort. Therefore, ALI in Turkish immigrants does not seem to be a risk factor for osteoporosis.

Update on lactose malabsorption and intolerance: pathogenesis, diagnosis and clinical management

Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in populations that maintain the ability to digest this disaccharide in adulthood. Lactase deficiency (LD) is the failure to express the enzyme that hydrolyses lactose into galactose and glucose in the small intestine. The genetic mechanism of lactase persistence in adult Caucasians is mediated by a single C→T nucleotide polymorphism at the LCTbo -13'910 locus on chromosome-2. Lactose malabsorption (LM) refers to any cause of failure to digest and/or absorb lactose in the small intestine. This includes primary genetic and also secondary LD due to infection or other conditions that affect the mucosal integrity of the small bowel. Lactose intolerance (LI) is defined as the onset of abdominal symptoms such as abdominal pain, bloating and diarrhoea after lactose ingestion by an individual with LM. The likelihood of LI depends on the lactose dose, lactase expression and the intestinal microbiome. Independent of lactose digestion, patients with visceral hypersensitivity associated with anxiety or the Irritable Bowel Syndrome (IBS) are at increased risk of the condition. Diagnostic investigations available to diagnose LM and LI include genetic, endoscopic and physiological tests. The association between self-reported LI, objective findings and clinical outcome of dietary intervention is variable. Treatment of LI can include low-lactose diet, lactase supplementation and, potentially, colonic adaptation by prebiotics. The clinical outcome of these treatments is modest, because lactose is just one of a number of poorly absorbed carbohydrates which can cause symptoms by similar mechanisms.

Lactose Intolerance and Bone Health: The Challenge of Ensuring Adequate Calcium Intake

Calcium is an important nutrient with impact upon many biological systems, most notably bone. Ensuring adequate calcium intake throughout the lifespan is essential to building and maintaining bone. Lactose intolerance may predispose individuals to low calcium intake as the number of lactose-free, calcium-rich food sources is limited. In this review, we summarize data from human and animal studies on the influence of lactose and lactase deficiency on calcium absorption and bone health. Based on the available evidence, neither dietary lactose nor lactase deficiency have a significant impact on calcium absorption in adult humans. However, lactose intolerance may lead to reduced bone density and fragility fractures when accompanied by decreased intake or avoidance of dairy. Recently published human trials and meta-analyses suggest a weak but significant association between dairy consumption and bone health, particularly in children. Given the availability of simple dietary approaches to building lactose tolerance and the nutritional deficiencies associated with dairy avoidance, multiple public health organizations recommend that all individuals—including those that are lactose intolerant—consume three servings of dairy per day to ensure adequate nutrient intakes and optimal bone health.

Does primary lactase deficiency reduce bone mineral density in postmenopausal women? A systematic review and meta-analysis

Postmenopausal osteoporosis is a significant cause of morbidity and mortality. The role of primary lactase deficiency (PLD) in its development is not clear. This meta-analysis showed that PLD is a risk factor for osteoporosis in postmenopausal women. These women need special attention in terms of screening for osteoporosis and its prevention.

INTRODUCTION

Postmenopausal osteoporosis is an important predictor of bone fractures. The purpose of the study was to conduct a systematic review and meta-analysis of association of PLD and bone mineral density (BMD) in postmenopausal women.

METHODS

The electronic databases PubMed, Scopus, and Web of Science were searched over the course of July 2017 for any date of publication without language limitation. Studies were included in the meta-analysis if the diagnosis of PLD was made by genetic testing or H-2 breath tests and the diagnosis of osteoporosis was made by a modern reliable method for BMD measurement. Two investigators conducted a comprehensive, independent review of all the papers. Five of the studies initially identified met the inclusion criteria. We used MOOSE guidelines for abstracting data and assessing data quality and validity. Meta-analysis was performed using the random effects model.

RESULTS

Five case-control studies with 2223 participants and 763 lactase-deficient cases fulfilled the inclusion criteria. Meta-analysis showed a significantly higher bone density Z-score in absorbers (mean difference 0.20, CI (0.14-0.27), P = 0.000), with no significant heterogeneity among the studies. Moreover, the Z-score in the vast majority of the measured sites (femoral head, femoral neck, lumbar spine, radius, and Ward's triangle) was significantly higher in absorbers. There was no significant overall difference in BMD in g/cm² between absorbers and non-absorbers, but a significantly higher BMD using g/cm² was observed in absorbers in the total hip site.

CONCLUSIONS

Postmenopausal women with PLD had lower Z-scores at most anatomic sites compared to healthy controls.

Lactase persistence, milk intake, hip fracture and bone mineral density: a study of 97 811 Danish individuals and a meta-analysis

BACKGROUND

Whether a causal relationship exists between milk intake and reduced risk of fractures is unclear.

OBJECTIVES

We tested the hypothesis that genetically determined milk intake reduces the risk of fractures and increases bone mineral density (BMD).

METHODS

We investigated the association between milk intake, LCT-13910 C/T (rs4988235), which is associated with lactase persistence (TT/TC) in Northern Europeans, and hip fractures in three Danish prospective studies (N = 97 811, age ≥20 years). We added meta-analyses of LCT-13910 and fractures and BMD from five published Northern European population studies.

RESULTS

In the Danish studies, the adjusted hazard ratio (HR) for hip fracture per one glass per week higher milk intake was 1.00 (95% CI: 0.99-1.01). The per T-allele milk intake was 0.58 (0.49-0.68) glasses per week, but HR was 1.01 (0.94-1.09) for hip fracture. In meta-analyses of Danish studies with published Northern European population studies, the random effects odds ratio for any fracture was 0.86 (0.61-1.21; I² = 73%) for TT vs. CC and 0.90 (0.68-1.21; I² = 63%) for TC vs. CC. The standardized mean difference in femoral neck BMD was 0.10 (0.02-0.18; I² = 0%) g cm^-2 for TT vs. CC and 0.06 (-0.04 to 0.17; I² = 17%) g cm^-2 for TC vs. CC. There were no differences in lumbar spine or total hip BMD comparing TT or TC with CC.

CONCLUSION

Genetically lifelong lactase persistence with high milk intake was not associated with hip fracture in Danish population-based cohorts. A meta-analysis combining Danish studies with published Northern European population studies also showed that lactase persistence was not associated with fracture risk. Genetic lactase persistence was associated with a higher femoral neck BMD, but not lumbar spine or total hip BMD.

Gene-Dairy Food Interactions and Health Outcomes: A Review of Nutrigenetic Studies

Each person differs from the next by an average of over 3 million genetic variations in their DNA. This genetic diversity is responsible for many of the interindividual differences in food preferences, nutritional needs, and dietary responses between humans. The field of nutrigenetics aims to utilize this type of genetic information in order to personalize diets for optimal health. One of the most well-studied genetic variants affecting human dietary patterns and health is the lactase persistence mutation, which enables an individual to digest milk sugar into adulthood. Lactase persistence is one of the most influential Mendelian factors affecting human dietary patterns to occur since the beginning of the Neolithic Revolution. However, the lactase persistence mutation is only one of many mutations that can influence the relationship between dairy intake and disease risk. The purpose of this review is to summarize the available nutrigenetic literature investigating the relationships between genetics, dairy intake, and health outcomes. Nonetheless, the understanding of an individual’s nutrigenetic responses is just one component of personalized nutrition. In addition to nutrigenetic responses, future studies should also take into account nutrigenomic responses (epigenomic, transcriptomic, proteomic, metabolomic), and phenotypic/characteristic traits (age, gender, activity level, disease status, etc.), as these factors all interact with diet to influence health.

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

BACKGROUND & AIMS

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.

METHODS

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 50 g 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.

RESULTS

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).

CONCLUSIONS

The presence of diarrhoea and the symptom score after overload with 50 g 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.

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%.

Lactase non-persistence as a determinant of milk avoidance and calcium intake in children and adolescents

This study examines if lactase non-persistent (LNP) children and adolescents differ from those who are lactase persistent (LP) as regards milk avoidance and Ca intake. We also studied potential differences in anthropometric features related to obesity, and examined if milk avoidance is associated with lactase-persistence status. Additionally, we aimed to determine if heterozygous subjects showed an intermediary phenotype as regards Ca intake. Furthermore, we tested if LP and LNP influence vitamin D intake. The European Youth Heart Study is an ongoing international, multi-centre cohort study primarily designed to address CVD risk factors. 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. Mendelian randomisation was used. Milk avoidance was significantly more common in LNP adolescents (OR 3·2; 95% CI 1·5, 7·3). LP subjects had higher milk consumption (P < 0·001). Accordingly, energy consumption derived from milk and Ca intake was lower in LNP (P < 0·05 and P < 0·001, respectively). Heterozygous subjects did not show an intermediary phenotype concerning milk consumption. LP or LNP status did not affect vitamin D intake or anthropometric variables. LNP in children and adolescents is associated with reduced intake of milk and some milk-product-related nutritional components, in particular Ca. This reduced intake did not affect the studied anthropometric variables, indicators of body fat or estimated vitamin D intake. However, independently of genotype, age and sex, daily vitamin D intake was below the recommended intakes. Milk avoidance among adolescents but not children was associated with LNP.

Dairy intake, dietary adequacy, and lactose intolerance

Despite repeated emphasis in the Dietary Guidelines for Americans on the importance of calcium in the adult American diet and the recommendation to consume 3 dairy servings a day, dairy intake remains well below recommendations. Insufficient health professional awareness of the benefits of calcium and concern for lactose intolerance are among several possible reasons, This mini-review highlights both the role of calcium (and of dairy, its principal source in modern diets) in health maintenance and reviews the means for overcoming lactose intolerance (real or perceived).

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.

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.

Lactase gene c/t(-13910) polymorphism, calcium intake, and pQCT bone traits in Finnish adults

Genetic lactase nonpersistence may influence calcium intake and thereby bone health. We investigated in the Cardiovascular Risk in Young Finn Study whether young adults aged 31-46 years with the C/C(-13910) genotype are more susceptible to reduced bone phenotypes, low-energy fractures, and low calcium intake than subjects with other lactase genotypes. We also analyzed the gene-environment interactions on bone with calcium intake and physical activity. Peripheral quantitative computed tomography bone traits were measured from the distal and shaft sites of the radius and tibia. The total number of those subjects whose nondominant forearm was measured and the lactase genotype was defined was 1551. Information on diet, lifestyle factors, and fractures was collected with questionnaires. The mean intake of calcium was the lowest in men with the C/C(-13910) genotype (P = 0.001). Men with the T/T(-13910) genotype had ~3% higher trabecular density at the distal radius and distal tibia compared to other lactase genotypes (P = 0.03 and 0.02, respectively). In women, we found no evidence of the gene effect at the radius and tibia. No major interactions of the C/T(-13910) polymorphism with calcium intake or physical activity on bone phenotypes were found in either sex. In conclusion, the C/T(-13910) polymorphism was associated with trabecular density at the distal radius and tibia in men. These differences may be due to the differences in calcium intake between the lactase genotypes.

Multicomponent training program with weight-bearing exercises elicits favorable bone density, muscle strength, and balance adaptations in older women

Physical exercise is advised as a preventive and therapeutic strategy against aging-induced bone weakness. In this study we examined the effects of 8-month multicomponent training with weight-bearing exercises on different risk factors of falling, including muscle strength, balance, agility, and bone mineral density (BMD) in older women. Participants were randomly assigned to either an exercise-training group (ET, n = 30) or a control group (CON, n = 30). Twenty-seven subjects in the ET group and 22 in the CON group completed the study. Training was performed twice a week and was designed to load bones with intermittent and multidirectional compressive forces and to improve physical function. Outcome measures included lumbar spine and proximal femoral BMD (by dual X-ray absorptiometry), muscle strength, balance, handgrip strength, walking performance, fat mass, and anthropometric data. Potential confounding variables included dietary intake, accelerometer-based physical activity, and molecularly defined lactase nonpersistence. After 8 months, the ET group decreased percent fat mass and improved handgrip strength, postural sway, strength on knee flexion at 180°/s, and BMD at the femoral neck (+2.8%). Both groups decreased waist circumference and improved dynamic balance, chair stand performance, strength on knee extension for the right leg at 180°/s, and knee flexion for both legs at 60°/s. No associations were found between lactase nonpersistence and BMD changes. Data suggest that 8 months of moderate-impact weight-bearing and multicomponent exercises reduces the potential risk factors for falls and related fractures in older women.

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.

Impact of molecularly defined hypolactasia, self-perceived milk intolerance and milk consumption on bone mineral density in a population sample in Northern Europe

OBJECTIVE

Milk intake as a source of calcium is considered an important factor for bone mineral metabolism. Low lactase activity in adult-type hypolactasia (HL) and self-perceived lactose intolerance (LI) are the main limiting factors of milk intake. The aim of this study was to examine the relationship of HL, LI, individual milk consumption and bone mineral density in a population with high milk consumption and a prevalent vitamin D deficiency.

MATERIAL AND METHODS

A population-based study of 367 men and women aged 25-70 years was conducted in Estonia. HL was diagnosed by direct sequencing of the LCT gene, bone mineral density and body composition measured by dual energy X-ray absorptiometry (DXA). An original health questionnaire was used to collect data on milk and dairy consumption, self-perceived milk intolerance, supplement usage and fracture history.

RESULTS

Lactase genotype and phenotype had no effect on bone mineral density in this high milk consumption population with a prevalent vitamin D insufficiency. Milk consumption was a significant determinant of bone mineral density in Estonia. Self-perceived milk intolerance leads to self-imposed reductions in milk consumption, increases in bone turnover and an increased risk of fracture.

CONCLUSIONS

Self-perceived milk-intolerance rather than HL influences milk consumption and has deleterious effects on bone metabolism.

Associations of genetic lactase non-persistence and sex with bone loss in young adulthood

Some studies have reported that after attainment of peak bone mass (PBM), slow bone loss may occur in both men and women; however, findings are inconsistent. Genetic factors play a significant role in bone loss, but the available evidence is conflicting. Genetic lactase non-persistence (lactase C/C(-13910) genotype) is suggested to increase risk for inadequate calcium intake predisposing to poorer bone health. We investigated whether this genotype is associated with PBM and bone loss in young Finnish adults. Subjects belong to the Cardiovascular Risk in Young Finns Study that is an ongoing multi-centre follow-up of atherosclerosis risk factors. From the original cohort, randomly selected subjects aged 20-29 participated in baseline bone mineral density (BMD) measurements (n=358), and in follow-up measurements 12 years later (n=157). Bone mineral content (BMC) and BMD at lumbar spine (LS) and femoral neck (FN) were measured at baseline and follow-up with dual energy X-ray absorptiometry (DXA). Lactase C/T(-13910) polymorphism was determined by PCR and allele-specific fluorogenic probes. Information on lifestyle was elicited with questionnaires. During the follow-up, bone loss at both bone sites was greater in males (LS BMD: -1.1%, FN BMD: -5.2%) than in females (LS BMD: +2.1%, FN BMD: -0.7%) (both bone sites p=0.001). Younger age predicted greater loss of FN BMC and BMD in females (p=0.013 and p=0.001, respectively). Increased calcium intake predicted FN BMD gain in both sexes (in females B=0.007 g/cm(2)/mg, p=0.002; in males B=0.006, p=0.045), and increased physical activity LS BMD gain in females (B=0.091 g/cm(2)/physical activity point, p=0.023). PBM did not differ between the lactase genotypes, but males with the CC(-13910) genotype seemed to be prone to greater bone loss during the follow-up (LS BMD: C/C vs. T/T p=0.081). In conclusion, bone loss in young adulthood was more common in males than in females and seemed to occur mainly at the femoral neck. Young males with the lactase CC(-13910) genotype may be more susceptible to bone loss; however, calcium intake predicts changes in bone mass more than the lactase genotype.

LCT 13910 C/T polymorphism, serum calcium, and bone mineral density in postmenopausal women

SUMMARY

LCT 13910 CC genotype is associated with lactose intolerance, a condition often resulting in reduced milk intake. Women with the CC genotype were found to have decreased serum calcium and reduced bone mineral density.

INTRODUCTION

The CC genotype of the 13910 C/T polymorphism of the LCT gene is linked to lactose intolerance and low calcium intake.

METHODS

We studied 595 postmenopausal women, including 267 osteoporotic, 200 osteopenic, and 128 healthy subjects. Genotyping, osteodensitometry, and laboratory measurements were carried out.

RESULTS

Frequency of aversion to milk consumption was 20% for CC genotype and 10% for TT + TC genotypes (p = 0.03). The albumin-adjusted serum calcium was 2.325 +/- 0.09 mmol/L for CC genotype and 2.360 +/- 0.16 mmol/L for TT + TC genotypes (p = 0.031). Bone mineral density (BMD; Z score) was lower in the CC than TT + TC genotypes, respectively, at the radius (0.105 +/- 1.42 vs 0.406 +/- 1.32; p = 0.038), at the total hip (-0.471 +/- 1.08 vs -0.170 +/- 1.09; p = 0.041), and at the Ward's triangle (-0.334 +/- 0.87 vs -0.123 +/- 0.82; p = 0.044).

CONCLUSION

LCT 13910 C/T polymorphism is associated with decreased serum calcium level and lower BMD in postmenopausal women.

Genetic lactase non-persistence, consumption of milk products and intakes of milk nutrients in Finns from childhood to young adulthood

Previous evidence suggests that the lactase gene C/T- 13910 polymorphism (rs4988235) is associated with avoidance of milk products and lower Ca intake. We examined whether the consumption of milk and milk products and the intakes of milk nutrients differ between the lactase genotypes from childhood to young adulthood. Subjects belong to the Cardiovascular Risk in Young Finns Study where the first cross-sectional surveys were conducted in 1980 (n 3596), with follow-up studies in 1983, 1986, 1989, 1992 and 2001 (n 2620). The same dietary questionnaire was used throughout the follow-up to collect data on habitual consumption of milk and milk products in all subjects, and daily nutrient intakes were assessed with 48 h dietary recalls in 50 % of the subjects. Subjects with the lactase non-persistence (C/C- 13910) genotype consumed less milk since childhood, but the consumption of other milk products did not differ between the genotypes. In adult females, the lactose content of milk products consumed was lower (P = 0.003), and in both sexes low-lactose and milk-free diets were more common in the C/C- 13910 genotype than in the other genotypes. Inadequate Ca intake was most common in females with the C/C- 13910 genotype as early as in childhood (15-63 %), but in males only in adulthood (24 %). In adult females, preference for low-lactose milk and milk products equalised the differences in Ca intake between the genotypes. Thus, in those with the C/C- 13910 genotype, preference for low-lactose milk and milk products may decrease the risk for inadequate Ca intake.

Lactose digestion and the evolutionary genetics of lactase persistence

It has been known for some 40 years that lactase production persists into adult life in some people but not in others. However, the mechanism and evolutionary significance of this variation have proved more elusive, and continue to excite the interest of investigators from different disciplines. This genetically determined trait differs in frequency worldwide and is due to cis-acting polymorphism of regulation of lactase gene expression. A single nucleotide polymorphism located 13.9 kb upstream from the lactase gene (C-13910 > T) was proposed to be the cause, and the -13910*T allele, which is widespread in Europe was found to be located on a very extended haplotype of 500 kb or more. The long region of haplotype conservation reflects a recent origin, and this, together with high frequencies, is evidence of positive selection, but also means that -13910*T might be an associated marker, rather than being causal of lactase persistence itself. Doubt about function was increased when it was shown that the original SNP did not account for lactase persistence in most African populations. However, the recent discovery that there are several other SNPs associated with lactase persistence in close proximity (within 100 bp), and that they all reside in a piece of sequence that has enhancer function in vitro, does suggest that they may each be functional, and their occurrence on different haplotype backgrounds shows that several independent mutations led to lactase persistence. Here we provide access to a database of worldwide distributions of lactase persistence and of the C-13910*T allele, as well as reviewing lactase molecular and population genetics and the role of selection in determining present day distributions of the lactase persistence phenotype.

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.

Adult-type hypolactasia and calcium availability: decreased calcium intake or impaired calcium absorption?

Adult-type hypolactasia, as mediated by a widespread genetic predisposition, not only reduces calcium intake but also calcium absorption in the presence of high amounts of lactose and may, therefore, promote osteoporosis. A lactose-reduced diet and lactose-free calcium supplements may reverse this imbalance.

INTRODUCTION AND HYPOTHESIS

Adult-type hypolactasia (HL) defined by the LCT(-13910) polymorphism may reduce calcium intake by reducing dairy consumption and, therefore, promote osteoporosis. This study aimed to evaluate whether lactose also decreases intestinal calcium absorption in subjects with HL and whether lactose-reduced diet and lactose-free calcium supplementation as recommended could maintain bone mineral density (BMD).

METHODS

Based on LCT genotyping, 73 postmenopausal women with and without HL underwent a conventional H(2) breath test with a concomitant oral strontium absorption test lasting 150 minutes, which closely reflects intestinal calcium absorption. In addition, we compared bone-specific laboratory parameters, lumbar and femoral BMD, and spinal radiographs to a similar bone assessment 5 years earlier.

RESULTS

LCT genotyping and functional lactose malabsorption tests were highly correlated. Dairy product consumption was reduced by 80% in HL individuals. During concomitant lactose application, mean strontium absorption was blunted by 54% in HL subjects after 150 minutes (1272 +/- 629 microg/L vs. 2020 +/- 1130 microg/L in lactose tolerant subjects, p=0.001). Nevertheless, BMD in HL subjects remained stable with lactose-free calcium supplements during the observation period.

CONCLUSION

Both decreased calcium intake as well as lactose-associated impaired calcium absorption may predispose subjects with HL to osteoporosis. Lactose-free calcium supplementation may help to maintain BMD in HL subjects.

The effects of adult-type hypolactasia on body height growth and dietary calcium intake from childhood into young adulthood: a 21-year follow-up study--the Cardiovascular Risk in Young Finns Study

OBJECTIVE

The effect of adult-type hypolactasia, caused by the lactase-phlorizin hydrolase C/C-13910 genotype, on growth is unknown. We studied whether this polymorphism was associated with body height growth, the use of milk products, or dietary calcium intake.

METHODS

A prospective cohort study was performed among 3596 randomly selected Finnish children and adolescents (3-18 years of age) in 1980, with reexamination in 1983, 1986, and 2001 (after a 21-year follow-up period). Lactase-phlorizin hydrolase C/T-13910 polymorphism was determined for 2265 participants in 2002. Nutrient intakes were measured for 1137, 858, and 1031 subjects in 1980, 1986, and 2001, respectively.

RESULTS

The lactase-phlorizin hydrolase C/T-13910 polymorphism was not related to mean height growth speed for either boys or girls or to final mean body height in adulthood. The consumption of milk products, protein, and calcium was lowest for female subjects with the lactase-phlorizin hydrolase C/C-13910 genotype over the study years, but there were no genotype-related differences in the intake of vitamin D. For boys, significant differences were found in the consumption of milk products but not in the mean dietary intake of calcium, protein, or vitamin D.

CONCLUSIONS

The lactase-phlorizin hydrolase C/C-13910 genotype was not associated with mean growth speed or final mean body height for either boys or girls. However, it contributed significantly to milk product consumption and dietary calcium intake from childhood into young adulthood.

Genetics of Osteoporosis

Osteoporosis is a systemic skeletal disease comprising rarefaction of bone structure and loss of bone mass, finally leading to increased fracture risk. As a part of its multifactorial aetiology, twin and family studies have demonstrated an important genetic component of osteoporosis regarding many parameters of bone properties e. g. bone mineral density, with a heredity of 60-80 %. Whole genome screens, linkage analysis and candidate gene research have contributed to our current knowledge about genetic loci in osteoporosis. Genotyping of collagen alpha I, lactose intolerance or estrogen receptor alpha alleles are under investigation for their importance in individual and epidemiological practice, e. g. the European Union "GENOMOS" project with more than 50,000 subjects. In future, improved genotyping methods and design strategies as well as large scale epidemiological studies in the general population will bring the genetics of complex diseases such as osteoporosis to a point of success comparable to where mendelian genetics now firmly resides. Given the potential of these new techniques, a paradigm shift may occur both in diagnosis and prevention as well as in individualized treatment aspects of osteoporosis.