Original Communication
European Journal of Clinical Nutrition (2005) 59, 1105–1111. doi:10.1038/sj.ejcn.1602219; published online 6 July 2005
Genetically defined adult-type hypolactasia and self-reported lactose intolerance as risk factors of osteoporosis in Finnish postmenopausal women
Guarantor: MJ Välimäki.
Contributors: All investigators contributed to the study design and writing of the paper. NE performed the genotyping. TP performed medical examinations and was responsible for data collection. MJV is the guarantor and finalized the manuscript. EL was responsible for statistical analyses. IJ was responsible for the DNA analyses and supervised the lab work.
N Enattah1,6, T Pekkarinen2,6, M J Välimäki3, E Löyttyniemi4 and I Järvelä1,5
- 1Department of Medical Genetics, University of Helsinki, Helsinki, Finland
- 2Department of Medicine, Peijas Hospital, Vantaa
- 3Division of Endocrinology, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland
- 4Department of Statistics, University of Turku, Turku, Finland
- 5HUCH Laboratory Diagnostics, Laboratory of Molecular Genetics, Helsinki University Central Hospital, Helsinki, Finland
Correspondence: MJ Välimäki, Division of Endocrinology, Department of Medicine, Helsinki University Central Hospital, FI-00029 HUS, Helsinki, Finland. E-mail: matti.valimaki@hus.fi
6These authors equally contributed to the study.
Received 8 November 2004; Revised 14 April 2005; Accepted 13 May 2005; Published online 6 July 2005.
Abstract
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.
Design:
A cross-sectional study of two cohorts.
Setting:
Helsinki University Central Hospital.
Subjects:
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).
Conclusion:
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.
Sponsorhip:
Supported by the Research Funding from Helsinki University Central Hospital (Erityisvaltionosuus) and by the Miina Sillanpää Foundation, Helsinki, Finland.
Keywords:
lactase, lactose intolerance, lactose malabsorption, genotype, bone mineral density, fractures, osteoporosis
