genetic analysis and lactose hydrogen.pdfVIP

Frequency of lactose malabsorption among healthy southern and northern Indian populations by genetic analysis and lactose hydrogen breath and tolerance tests1–3 Janaki Babu, Sunil Kumar, P Babu, Jaishri H Prasad, and Uday C Ghoshal ABSTRACT 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 geo- graphic 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 compa- rable 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 concen- trations of breath hydrogen (88.5 6 71.9 compared with 55.4 6 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 dif- ferences in these populations. Am J Clin Nutr 2010;91:140–6. INTRODUCTION Lactose malabsor