Exp Clin Endocrinol Diabetes 2007; 115 - OR04_6
DOI: 10.1055/s-2007-972226

Genetically defined adult-type hypolactasia and calcium balance: high amounts of lactose decrease calcium absorption

B Obermayer-Pietsch 1, M Gugatschka 1, A Groselj-Strele 2, W Goessler 3, H Dobnig 1, C Högenauer 4, A Fahrleitner-Pammer 1, W Renner 5
  • 1Univ. Klinik f. Innere Medizin, Endokrinologie/Nuklearmedizin, Graz, Austria
  • 2Zentrum für Medizinische Grundlagenforschung, Statistik und Dokumentation, Graz, Austria
  • 3Karl-Franzens-Universität, Institut für Chemie – Analytische Chemie, Graz, Austria
  • 4Univ. Klinik f. Innere Medizin, Gastroenterologie und Hepatologie, Graz, Austria
  • 5Medizinische Universität, Klinisches Institut für medizinisch-chemische Labordiagnostik, Graz, Austria

Background: Adult-type hypolactasia (HL), affecting more than half of the world's population, reduces calcium supply by reducing dairy consumption and may contribute to decreased calcium balance, hence promoting low bone mineral density and bone fractures. We have shown that concomitant lactose administration in high amounts may reduce the intestinal absorption of calcium equivalents (Obermayer-Pietsch et al., Osteoporosis International in press). Our study aimed to evaluate whether smaller amounts of lactose also decrease intestinal calcium absorption in subjects with HL as defined by the LCT(-13910) polymorphism.

Methods: Based on LCT genotyping, 26 premenopausal women (14 with genotype CC, associated with HL; 12 with genotype TT, with lactase persistence) underwent at four time-points a conventional H2 breath test with a concomitant oral strontium absorption test (closely related to intestinal calcium absorption) including 50g, 10g, 2g or no lactose. Clinical data and strontium serum levels were determined at baseline, 150, 240 and 300min thereafter.

Results: LCT genotyping and functional HL tests were highly correlated. Dairy product consumption was reduced by 80% in CC individuals. As shown recently, 50g lactose administered orally again blunted mean calcium equivalent absorption by more than 50% in CC subjects as compared to the TT group up to 300 minutes after ingestion. However, lower amounts of lactose showed no decrease of calcium equivalent absorption.

Conclusions: Decreased calcium supply by dairy products, but also impaired calcium absorption in the presence of high amounts of lactose may predispose subjects with HL to decreased calcium balance and osteoporosis. Amounts below 2g of lactose might be better tolerable. However, the widespread use of lactose in foods and drinks, often inadequately labelled, could further reduce the ability of the intestine to absorb calcium from nutritional sources and warrants public dietary information and health care.