Assessment of Lactose-Free Diet on the Phalangeal Bone Mineral Status in Italian Adolescents Affected by Adult-Type Hypolactasia.

Adult-type hypolactasia (ATH) is a clinical syndrome of primary lactase deficiency. A lactose-free diet is advisable to avoid the symptoms linked to the condition, but this potentially creates problems for optimal bone mineralization due to reduced calcium intake. To evaluate the effect of the lactose-free diet on the bone mineral status (BMS), we compared the phalangeal BMS of adolescents with ATH to that of peers on a normal diet. Also, we analyzed the correlations between BMS and dietary behavior, physical exercise, and calcium and vitamin D intake. A total of 102 cases and 102 healthy controls filled out a diet record and underwent phalangeal Quantitative Ultrasound (QUS). No difference in BMS was observed. The time spent on lactose-free diet (4.8 ± 3.1 years) was inversely correlated to the BMS. More than 98% of cases consumed lactose-free milk, but calcium and vitamin D intake were significantly lower. Calcium intake was correlated to physical exercise but not to BMS. Our results suggest that a lactose-free diet does not affect the phalangeal BMS of adolescents with primary lactase deficiency when their diet includes lactose-free cow’s milk. However, there is still a significantly lower calcium intake than in the population reference. The inverse correlation observed between the BMS and the time spent on a lactose-free diet suggests that a long-term follow-up is advisable.

Genetic testing for adult-type hypolactasia in Italian families.

BACKGROUND: Adult-type hypolactasia is characterized by the inability to digest lactose during adulthood, due to lactase (LCT) deficiency. It is usually diagnosed by the measurement of breath hydrogen increase after a lactose load (breath hydrogen test, BHT). A substitution of C to T at position -13910 bp upstream the LCT gene (rs4988235), in a regulatory region, was found to be strongly associated with the lactase persistence phenotype in North-European populations. METHODS: We investigated the -13910 C/T polymorphism to determine LCT genotype distribution and to validate genetic testing for adult-type hypolactasia in a Southern European population. A total of 43 children referred for suspected lactose malabsorption were enrolled in the study, their parents and siblings (whole sample=112 individuals) also took the breath test, and all were enrolled for clinical monitoring and genotype determination. In addition, 125 unrelated blood donors from the same geographic area were genotyped for the calculation of allelic frequencies. The frequency of C/C genotypes was 70%. RESULTS: The correlation between the C/C genotype (which should correspond to lactose non-digesters) and positive BHT in unrelated family founders was significant (chi(2)=16.7, p<0.002). The genetic test compared to the BHT had a sensitivity of 95% and 91% and a specificity of 48% and 55% in adults and children, respectively. CONCLUSIONS: Low specificity might be due to intrinsic limitations of the standard BHT or to other possible mutations, although no sequence variation was found upon sequencing a 253 bp fragment of the LCT regulatory region in asymptomatic individuals.