Genetically defined adult-type hypolactasia and self-reported lactose intolerance as risk factors of osteoporosis in Finnish postmenopausal women.
OBJECTIVE
To study the relationships of molecularly defined lactose malabsorption (LM) and self-reported lactose intolerance (LI) to bone mineral density (BMD) and fractures among Finnish postmenopausal women.


METHODS
A cross-sectional study of two cohorts.


METHODS
Helsinki University Central Hospital.


METHODS
One cohort was population-based and comprised 453 women, aged 62-78 (mean 69) y. Another comprised 52 women, aged 69-85 (mean 75) y, with osteoporotic fractures and 59 control women, aged 69-83 (mean 74) y, without osteoporosis.


METHODS
A single nucleotide polymorphism of the lactase (LCT) gene at chromosome 2q21-22 was studied. It shows complete association with intestinal disaccharidase activity, with the genotype CC(-13 910) meaning adult-type hypolactasia (primary LM) and the genotypes CT(-13 910) and TT(-13 910) lactose absorption. BMD of the heel was measured by dual-energy X-ray absorptiometry (DXA).


RESULTS
In the population-based cohort, 16.0% of women had self-reported LI but only 15.3% of them had the CC(-13 910) genotype. Calcium intake from dairy products (P = 0.10) and BMD, adjusted for age, weight, height, exercise, smoking, and estrogen use (P = 0.71) were similar for the genotypes. Women with self-reported LI had reduced calcium intake from dairy products (P < 0.0001) but they were more frequent users of calcium supplements than lactose-tolerants (P < 0.0001). Adjusted BMD was similar for lactose intolerant and tolerant women (P = 0.60). Of 104 women with previous fracture in the population-based cohort, 13.5% had the CC(-13 910) genotype, which did not differ from the prevalence of 19.3% among 347 women without fractures (P = 0.29). The frequency of the CC(-13 910) genotype (23.1%) for 52 women with established osteoporosis was similar as for 59 control women (15.3%) (P = 0.19).


CONCLUSIONS
Molecularly defined LM and self-reported LI are not risk factors for osteoporosis, if calcium intake from diet and/or supplements remains sufficient. Our study confirms the poor correlation between self-reported LI and LM established by different techniques.
Enattah
N
N
Department of Medical Genetics, University of Helsinki, Helsinki, Finland.
Pekkarinen
T
T
Välimäki
M J
MJ
Löyttyniemi
E
E
Järvelä
I
I
D000368:Aged; D000369:Aged, 80 and over; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000378:metabolism; D016022:Case-Control Studies; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003611:Dairy Products; D005260:Female; D005387:Finland / Q000453:epidemiology; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D043322:Lactase / Q000172:deficiency / Q000235:genetics; D007785:Lactose / Q000378:metabolism*; D007787:Lactose Intolerance / Q000150:complications / Q000453:epidemiology / Q000235:genetics*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000453:epidemiology* / Q000209:etiology; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors
D002136:Calcium, Dietary; D043322:Lactase; D007785:Lactose