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

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.

Relation of the C/T-13910 LCT Polymorphism with Body Composition Measures and Their Modulation by Dairy Products in a Caucasian Men

The C/T-13910 LCT is closely associated with lactase persistence and LCT has emerged as a new candidate gene for obesity, in particular in northern Europeans. The aim of this research is to investigate to what degree sex determines the association between the LCT variant and anthropometric traits in a cohort of healthy individuals. We recruited 1000 (500 males and 500 females aged 18-65 years) healthy blood donors. The C/T-13910 LCT polymorphism was genotyped using TaqMan assays. All individuals were phenotyped with respect to anthropometric characteristics. Prevalence of genotypes was 22.7% CC (lactase non-persistent, LNP), 58.6% CT, and 18.7% TT. LNP genotype was present less frequently among men p = .0005; OR 0.582 [0.425-0.794]. Therefore, in addition statistical calculations were performed separately for men and women. Additional analysis demonstrated an association between the CC genotypes and higher chest (p = .03), waist (p = .005), and forearm circumference (p = .0004) or more lean body mass (p = .04), than T-allele carriers in males. In females, they were not significantly different. Men consumed more milk (p = .003), while women ate more yoghurt (p = .001). Pearson's correlation analysis showed that the higher intake of milk and dairy products was associated with higher fat body mass among men with lactase persistence. In Caucasian men, the LNP genotype is associated with reduced milk intake and dairy products, but more fat-free mass and higher forearm circumference, which may be relevant to dietary management for lactose intolerant.

Maternal Lactase Polymorphism (rs4988235) Is Associated with Neural Tube Defects in Offspring in the National Birth Defects Prevention Study

BACKGROUND

The risk of neural tube defect (NTD)-affected pregnancies is reduced with adequate folic acid intake during early pregnancy. However, NTDs have been observed among offspring of women with adequate folic acid intake. Some of these women are possibly not absorbing enough folic acid. Because lactase deficiency can lead to poor nutrient absorption, we hypothesized that lactase-deficient women will be at increased risk of having offspring with NTDs.

OBJECTIVE

We examined the association between maternal rs4988235 (a lactase deficiency genetic marker) and NTDs in offspring.

METHODS

We conducted a case-control study using data from the National Birth Defects Prevention Study, United States, 1997-2009, restricting to non-Hispanic white (NHW) and Hispanic women. Cases were women with an offspring with an NTD (n = 378 NHW, 207 Hispanic), and controls were women with an offspring without a birth defect (n = 461 NHW, 165 Hispanic). Analyses were conducted separately by race/ethnicity, using logistic regression. Women with the CC genotype were categorized as being lactase deficient. To assess potential effect modification, analyses were stratified by lactose intake, folic acid supplementation, dietary folate, and diet quality.

RESULTS

Among NHW women, the odds of being lactase deficient were greater among cases compared with controls (OR: 1.37; 95% CI: 1.02, 1.82). Among Hispanic women, the odds of being lactase deficient were significantly lower among cases compared with controls (OR: 0.50, 95% CI: 0.33, 0.77). The association differed when stratified by lactose intake in NHW women (higher odds among women who consumed ≥12 g lactose/1000 kcal) and by dietary folate in Hispanic women (opposite direction of associations). The association did not differ when stratified by folic acid supplementation or diet quality.

CONCLUSIONS

Our findings suggest that maternal lactase deficiency is associated with NTDs in offspring. However, we observed opposite directions of effect by race/ethnicity that could not be definitively explained.

Gender, Age, Race and Lactose Intolerance: Is There Evidence to Support a Differential Symptom Response? A Scoping Review

Research evaluating the relationship between lactose intolerance (LI) symptoms and age, gender and race is reviewed. An exhaustive search was conducted on the Google Scholar and PubMed databases. The evidence suggests that women, the elderly or specific racial groups are not more susceptible to LI, but rather dose, body size and genetic differences in lactase non-persistence (LNP) are the primary drivers of intolerance symptoms.

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.

Milk intake is not associated with ischaemic heart disease in observational or Mendelian randomization analyses in 98,529 Danish adults

BACKGROUND

Observationally, reports on the association between milk intake and risk of ischaemic heart disease (IHD) and myocardial infarction (MI) have produced conflicting results; and no previous large-scale study using the lactase persistent/non-persistent LCT-13910 C/T genotype as a largely unconfounded proxy for milk intake free of reverse causation has been conducted. We tested the hypothesis that milk intake observationally and genetically through the LCT-13910 C/T genotype is associated with risk of IHD and MI in a Mendelian randomization design.

METHODS

We included 98,529 White individuals of Danish descent, aged 20-100 years, from three studies of the general population. Information on IHD (N = 10,372) and MI (N = 4188) were obtained from national Danish registries. First, we investigated observational associations between milk intake and incident IHD and MI. Second, we confirmed the association between the rs4988235 genetic variant LCT-13910 C/T, associated with lactase persistence/non-persistence, and milk intake. Finally, we tested whether LCT-13910 C/T genotype was associated with risk of IHD and MI as well as with cardiovascular risk factors.

RESULTS

During a mean follow-up time of 5.4 years, the observational hazard ratio for a 1 glass/week higher milk intake was 1.00 [95% confidence interval (CI): 1.00,1.01] for both IHD and MI. Median milk intake was 3 glasses/week (interquartile range: 0-7) in lactase CC non-persistent individuals compared with 5 glasses/week (0-10) in lactase TC/TT persistent individuals (P = 3*10(-60)). In the dominant genetic model comparing lactase TC/TT persistent individuals with lactase CC non-persistent individuals, the odds ratio was 1.00 (0.92,1.09) for IHD and 0.96 (0.84,1.09) for MI. Finally, in the dominant genetic model genotype was not associated convincingly with plasma levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides or glucose, nor with blood pressure.

CONCLUSION

Milk intake was not associated with risk of IHD or MI, observationally or genetically.

Mitochondrial DNA genetic diversity and LCT-13910 and deltaF508 CFTR alleles typing in the medieval sample from Poland

We attempted to confirm the resemblance of a local medieval population and to reconstruct their contribution to the formation of the modern Polish population at the DNA level. The HVR I mtDNA sequence and two nuclear alleles, LCT-13910C/T SNP and deltaF508 CFTR, were chosen as markers since the distribution of selected nuclear alleles varies among ethnic groups. A total of 47 specimens were selected from a medieval cemetery in Cedynia (located in the western Polish lowland). Regarding the HVR I profile, the analyzed population differed from the present-day population (P = 0.045, F(st) = 0.0103), in contrast to lactase persistence (LP) based on the LCT-13910T allele, thus indicating the lack of notable frequency changes of this allele during the last millennium (P = 0.141). The sequence of the HVR I mtDNA fragment allowed to identify six major haplogroups including H, U5, T, K, and HV0 within the medieval population of Cedynia which are common in today's central Europe. An analysis of haplogroup frequency and its comparison with modern European populations shows that the studied medieval population is more closely related to Finno-Ugric populations than to the present Polish population. Identification of less common haplogroups, i.e., Z and U2, both atypical of the modern Polish population and of Asian origin, provides evidence for some kind of connections between the studied and foreign populations. Furthermore, a comparison of the available aDNA sequences from medieval Europe suggests that populations differed from one another and a number of data from other locations are required to find out more about the features of the medieval gene pool profile.

The lactase persistence genotype is associated with body mass index and dairy consumption in the D.E.S.I.R. study

OBJECTIVE

The T allele of a functional polymorphism (rs4988235: LCT-13910 C>T), close to the lactase gene, correlates with lactase persistence (LP) in adults. The LP genotype (TT+TC) has been associated with a higher BMI in European populations in cross-sectional studies. In the French D.E.S.I.R. cohort, a high consumption of dairy products was associated with a lower body weight gain over 9-years, and with a lower incidence of high plasma glucose levels and/or the metabolic syndrome. Our aim was to test in this study, the association of rs4988235 with BMI and related metabolic diseases, in interaction with dairy product consumption.

METHODS

Among 5212 subjects from D.E.S.I.R., 3575 Caucasians born in mainland France were genotyped and followed over 9years.

RESULTS

Those with the LP genotype (frequency: 78.5%) had a higher dairy product consumption, at inclusion and at year-9 (P<0.001). They also had a higher BMI at both time points (difference=0.3kg/m(2), P=0.05), but this effect was restricted to medium/high dairy product consumers (difference=0.5kg/m(2), P=0.006). This genotype was also associated with the metabolic syndrome (IDF definition), but this association disappeared after adjustment for BMI. In the whole population, the C allele was associated with a higher prevalence of impaired fasting glycemia and/or type 2 diabetes.

CONCLUSIONS

The lactase persistence genotype was shown to be associated with a higher BMI in a longitudinal study, mainly in those consuming high amounts of dairy products. The association of the C allele, responsible for lactase non-persistence, with the risk of hyperglycemia needs to be replicated.

Association between milk and milk product consumption and anthropometric measures in adult men and women in India: a cross-sectional study

BACKGROUND

The nutritional aetiology of obesity remains unclear, especially with regard to the role of dairy products in developing countries.

OBJECTIVE

To examine whether milk/milk product consumption is associated with obesity and high waist circumference among adult Indians.

METHODS

Information on plain milk, tea, curd and buttermilk/lassi consumption assessed using a Food Frequency Questionnaire was obtained from the cross-sectional sib-pair designed Indian Migration Study (3698 men and 2659 women), conducted at four factory locations across north, central and south India. The anthropometric measures included were Body Mass Index (BMI) and Waist Circumference (WC). Mixed-effect logistic regression models were conducted to accommodate sib-pair design and adjust for potential confounders.

RESULTS

After controlling for potential confounders, the risk of being obese (BMI ≥ 25 kg/m(2)) was lower among women (OR = 0.57;95%CI:0.43-0.76;p ≤ 0.0001) and men (OR = 0.67;95%CI: 0.51-0.87;p = 0.005), and the risk of a high WC (men: >90 cm; women: >80 cm) was lower among men (OR = 0.71;95%CI:0.54-0.93;p = 0.005) and women (OR = 0.79;95%CI:0.59-1.05;p>0.05) who consume ≥1 portions of plain milk daily than those who do not consume any milk. The inverse association between daily plain milk consumption and obesity was also confirmed in sibling-pair analyses. Daily tea consumption of ≥ 1 portion was associated with obesity (OR = 1.51;95%CI:1.00-2.25;p>0.050) and high WC (OR = 1.65;95%CI:1.08-2.51;p>0.019) among men but not among women but there was no strong evidence of association of curd and buttermilk/lassi consumption with obesity and high waist circumference among both men and women.

CONCLUSIONS

The independent, inverse association of daily plain milk consumption with the risk of being obese suggests that high plain milk intake may lower the risk of obesity in adult Indians. However, this is an observational finding and uncontrolled confounding cannot be excluded as an explanation for the association. Therefore, confirmatory studies are needed to clarify this relationship.

Optimization and shelf life of a low-lactose yogurt with Lactobacillus rhamnosus HN001

Lactose intolerance results in gastrointestinal discomfort and the malabsorption of certain nutrients, such as calcium. The replacement of milk with low-lactose and probiotic-enriched dairy products is an effective strategy of mitigating the symptoms of lactose intolerance. Lactobacillus rhamnosus HN001 (HN001) is a safe, immunity-stimulating probiotic. We have developed a process to increase the hydrolysis of lactose and HN001 growth in yogurt versus β-galactosidase (βG) concentration and enzymatic hydrolysis time (EHT) before bacterial fermentation. The objective of this study was to optimize the conditions by which yogurt is processed as a function of βG and EHT using a multifactorial design, with lactose content, HN001 growth, process time, and sensory quality as dependent variables. Further, the shelf life of the optimized yogurt was evaluated. In the optimization study, polynomials explained the dependent variables. Based on Pearson correlation coefficients, HN001 growth correlated positively with the hydrolysis of lactose. However, low lactose content and high HN001 count increased the fermentation time and lowered the sensory quality. The optimized conditions-using polynomials to obtain yogurt with >1 × 10(7) cfu of HN001/mL, <10 g of lactose/L, and a minimum overall sensory quality of 7 on the Karlsruhe scale-yielded a theoretical value of 910 neutral lactose units/kg for βG and 2.3h for EHT, which were validated in an industrial-scale assay. Based on a shelf-life study at 3 temperatures, the hydrolysis of lactose and the growth of HN001 continue during storage. Arrhenius equations were developed for the variables in the shelf-life study. Our results demonstrate that it is feasible to develop a low-lactose yogurt to which HN001 has been added for lactose-intolerant persons who wish to strengthen their immune system.

Correlation of G/A -22018 single-nucleotide polymorphism with lactase activity and its usefulness in improving the diagnosis of adult-type hypolactasia among North Indian children

Adult-type hypolactasia (AtH or lactase non-persistence) is the physiological decline in lactase activity that manifests in majority of the world's population after weaning. Recently, various single-nucleotide polymorphisms (SNPs) upstream of lactase gene (LCT) have been suggested to be associated with AtH or the lactase persistent trait in different human populations. C/T -13910 SNP was found be completely associated with AtH in Finnish population, and G/A -22018 SNP was found to be strongly, but not completely, associated with AtH. The aim of this study was to correlate G/A -22018 SNP with intestinal lactase activity in North Indian children. These children were also genotyped for C/T -13910 SNP. We also examined the differences in milk consumption and milk-related clinical symptoms in children with different genotypes of G/A -22018 and C/T -13910 SNPs. Intestinal biopsies were obtained from 231 children aged 2-16 years undergoing routine endoscopy for various abdominal complaints. The biopsies were assayed for lactase, sucrase, and maltase activities and genotyped for G/A -22018 and C/T -13910 SNPs using restriction fragment length polymorphism and DNA sequencing analysis. There was a significant correlation between lactase activity and different genotypes of G/A -22018 SNP. Children with G/G -22018 genotype had low lactase activity. With a reference value of <10 U/g protein (lactase activity) to be indicative of AtH, the sensitivity and specificity of genetic test based on G/A -22018 SNP was 94.4 and 94.1 %, respectively. Furthermore, the consumption of milk was lower in children with G/G -22018 genotype. Flatulence was the only symptom significantly more frequent among the children with G/G -22018 genotype compared to those with G/A and A/A -22018 genotypes. However, most of the children with G/G -22018 genotype seem to tolerate small amounts of milk without any significant difference in gastrointestinal symptoms from those with G/A and A/A -22018 genotypes.

Overweight in childhood and bone density and size in adulthood

We evaluated the adult bone structural traits in relation to childhood overweight in 832 men and women. Childhood overweight was associated with larger cross-sections at long bones in both sexes. Excess weight in childhood may also lead to higher trabecular density in females and somewhat lower cortical density in men.

INTRODUCTION

Excess body weight in childhood may impose more loading on growing skeleton and thus lead to more robust structure in adulthood.

METHODS

This prospective cohort study evaluated the adult bone structural traits in relation to childhood overweight in a subgroup of 456 women and 376 men from the population-based cohort of Cardiovascular Risks in Young Finns Study. Between-group differences were evaluated with analysis of covariance.

RESULTS

According to established body mass index (BMI) criterion at the age of 12 years, 31 women and 34 men were classified overweight in childhood. At the mean age (SD) of 36.1 (2.7) years, total cross-sectional (ToA) and cortical area (CoA) at the distal and shaft sites and cortical (shaft CoD) and trabecular (distal TrD) bone density of the nonweight-bearing radius and weight-bearing tibia were evaluated with pQCT. Despite being taller in adolescence, the adult body height of overweight children was similar. In both sexes, childhood overweight was consistently associated with 5-10% larger ToA at all bone sites measured in adulthood. CoA did not show such a consistent pattern. Women, who were overweight in childhood, had ~5% denser TrD with no difference in CoD. In contrast, TrD in men who were overweight in childhood was not different but their CoD was ~1% lower.

CONCLUSIONS

Childhood overweight was consistently associated with larger long bone cross-sections in both sexes. Excess weight in childhood may also lead to higher trabecular density in women and somewhat lower cortical density in men. Specific mechanisms underlying these associations are not known.

Association of the LCT-13910C>T polymorphism with obesity and its modulation by dairy products in a Mediterranean population

The -13910C>T polymorphism (rs4988235) upstream from the lactase (LCT) gene, strongly associated with lactase persistence (LP) in Europeans, is emerging as a new candidate for obesity. We aimed to analyze the association of this polymorphism with obesity-related variables and its modulation by dairy product intake in an elderly population. We studied 940 high-cardiovascular risk Spanish subjects (aged 67 ± 7 years). Dairy product consumption was assessed by a validated questionnaire. Anthropometric variables were directly measured, and metabolic syndrome-related variables were obtained. Prevalence of genotypes was: 38.0% CC (lactase nonpersistent (LNP)), 45.7% CT, and 16.3% TT. The CC genotype was not associated with lower milk or dairy product consumption in the whole population. Only in women was dairy intake significantly lower in CC subjects. The most important association was obtained with anthropometric measurements. CC individuals had lower weight (P = 0.032), lower BMI (29.7 ± 4.2 vs. 30.6 ± 4.2 kg/m(2); P = 0.003) and lower waist circumference (101.1 ± 11.8 vs. 103.5 ± 11.5 cm; P = 0.005) than T-allele carriers. Obesity risk was also significantly higher in T-allele carriers than in CC individuals (odds ratio (OR): 1.38; 95% confidence interval (CI): 1.05-1.81; P = 0.01), and remained significant even after adjustment for sex, age, diabetes, physical activity, and energy intake. However, in subgroup analysis, these associations were found to be significant only among those consuming moderate or high lactose intakes (>8 g/day). No significant associations with lipids, glucose, or blood pressure were obtained after adjustment for BMI. In conclusion, despite not finding marked differences in dairy product consumption, this polymorphism was strongly associated with BMI and obesity and modulated by lactose intake in this Mediterranean population.

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.

Frequency of lactose malabsorption among healthy southern and northern Indian populations by genetic analysis and lactose hydrogen breath and tolerance tests

BACKGROUND

Lactose malabsorption (LM), the inability to break down lactose into glucose and galactose, is due to a deficiency in the small intestinal lactase phlorizin hydrolase enzyme. Ethnic and geographic variations of LM are known.

OBJECTIVE

The aim of this study was to compare the frequency of LM in healthy southern and northern Indian populations.

DESIGN

A total of 153 healthy volunteers (76 from southern and 77 from northern India) were evaluated for LM by using a lactose tolerance test (LTT), a lactose hydrogen breath test (lactose HBT), and polymerase chain reaction-restriction fragment length polymorphism to identify the lactase gene C/T-13910 polymorphism (confirmed by sequencing).

RESULTS

Volunteers from southern and northern India were comparable in age and sex. The LTT result was abnormal in 88.2% of southern Indians and in 66.2% of northern Indians (P = 0.001). The lactose HBT result was abnormal in 78.9% of southern Indians and in 57.1% of northern Indians (P = 0.003). The CC genotype was present in 86.8% and 67.5% (P = 0.002), the CT genotype was present in 13.2% and 26.0% (P = 0.036), and the TT genotype was present in 0% and 6.5% (P = 0.03) of southern and northern Indians, respectively. The frequency of symptoms after the lactose load (47.4% compared with 15.6%; P < 0.001) and peak concentrations of breath hydrogen (88.5 +/- 71.9 compared with 55.4 +/- 61.9 ppm; P = 0.003), both of which might indicate the degree of lactase deficiency, were higher in southern than in northern Indians.

CONCLUSION

The frequency and degree of LM is higher in southern than in northern Indian healthy populations because of genetic differences in these populations.