Measurement of lactose consumption reliability and comparison of two methods

Dynamics of vitamin D in patients with mild or inactive inflammatory bowel disease and their families

BACKGROUND

25(OH) vitamin D levels may be low in patients with moderately or severely active inflammatory bowel diseases (IBD: Crohn's disease and Idiopathic Ulcerative Colitis) but this is less clear in patients with mild or inactive IBD. Furthermore there is limited information of any family influence on 25(OH) vitamin D levels in IBD. As a possible risk factor we hypothesize that vitamin D levels may also be low in families of IBD patients.

OBJECTIVES

To evaluate 25[OH] vitamin D levels in patients with IBD in remission or with mild activity. A second objective is to evaluate whether there are relationships within IBD family units of 25[OH] vitamin D and what are the influences associated with these levels.

METHODS

Participants underwent medical history, physical examination and a 114 item diet questionnaire. Serum 25[OH] vitamin D was measured, using a radioimmunoassay kit, (replete ≥ 75, insufficient 50-74, deficient < 25-50, or severely deficient < 25 nmol/L). Associations between 25[OH] vitamin D and twenty variables were evaluated using univariate regression. Multivariable analysis was also applied and intrafamilial dynamics were assessed.

RESULTS

55 patients and 48 controls with their respective families participated (N206). 25[OH] vitamin D levels between patients and controls were similar (71.2 ± 32.8 vs. 68.3 ±26.2 nmol/L). Vitamin D supplements significantly increased intake but correlation with serum 25[OH] vitamin D was significant only during non sunny months among patients. Within family units, patients' families had mean replete levels (82.3 ± 34.2 nmol/L) and a modest correlation emerged during sunny months between patients and family (r2 =0.209 p = 0.032). These relationships were less robust and non significant in controls and their families.

CONCLUSIONS

In patients with mild or inactive IBD 25[OH] vitamin D levels are less than ideal but are similar to controls. Taken together collectively, the results of this study suggest that patient family dynamics may be different in IBD units from that in control family units. However contrary to the hypothesis, intra familial vitamin D dynamics do not pose additional risks for development of IBD.

Lack of effect of lactose digestion status on baseline fecal micoflora

BACKGROUND

The genetics of intestinal lactase divide the world's population into two phenotypes: the ability (a dominant trait) or inability (a recessive trait) to digest lactose. A prebiotic effect of lactose may impact the colonic flora of these phenotypes differently.

OBJECTIVE

To detect and evaluate the effects of lactose on subjects divided according to their ability to digest lactose.

METHODS

A total of 57 healthy maldigesters (n=30) and digesters (n=27) completed diet questionnaires, genetic and breath hydrogen testing, and quantitative stool analysis for species of bacteria. Log10 transformation of bacterial counts was compared with lactose intake in both groups using multiple regression analysis.

RESULTS

There was a significant relationship between genetic and breath hydrogen tests. Daily lactose intake was marginally lower in lactose maldigesters (median [interquartile range] 12.2 g [31 g] versus 15 g [29.6 g], respectively). There was no relationship between lactose intake and breath hydrogen tests in either group. There were no differences in bacterial counts between the two groups, nor was there a relationship between bacterial counts and lactose intake in either group.

CONCLUSION

The differential bacterial effects of lactose were not quantitatively detected in stool samples taken in the present study.

Fructose malabsorption may be gender dependent and fails to show compensation by colonic adaptation

Fructose malabsorption is linked to gastrointestinal and other unusual symptoms. Polymers of fructose are also recognized prebiotics. While some prebiotics can self-adapt when consumed regularly (resulting in decreased breath hydrogen and symptoms), we wondered whether self-adaptation occurs with basic fructose. We evaluated 90 subjects (61 females). Each completed a diet questionnaire and underwent a fructose challenge. Breath hydrogen and quantified symptom scores were recorded. Group comparisons for sum of breath hydrogen and total symptom scores were evaluated with the Mann-Whitney U test. Spearman's correlation coefficient and chi(2) or Fisher's exact test were used as appropriate. Malabsorption occurred in 29 patients (32.2%) and low-grade symptoms without malabsorption in 30 (33%). Women complained of symptoms more frequently (p = 0.04) and exhibited more fructose malabsorption (p = 0.0527). Breath hydrogen correlated with symptoms (r = 0.516, p = 0.0037). Adaptation with increasing pretest fructose intake was absent. We conclude that gender may influence fructose malabsorption and there is no adaptation to regular consumption.

Comparison of a real-time polymerase chain reaction assay for lactase genetic polymorphism with standard indirect tests for lactose maldigestion

BACKGROUND & AIMS

There is a discrepancy in outcome between the lactose tolerance and breath hydrogen tests for lactose maldigestion. The availability of a validated genetic test for lactase polymorphism allows a reevaluation of these tests.

METHODS

Thirty healthy adults participated in a 50-g lactose challenge test at a university clinic. Blood was drawn for genetic and timed blood glucose testing (2 hours), and breath hydrogen was measured (4.5 hours). Lactase genetic polymorphism was assessed by a real-time polymerase chain reaction assay. Participants completed a diet questionnaire, and symptoms were recorded during the lactose challenge. Sensitivity and specificity were calculated for each indirect test. The 2-way kappa coefficient between these tests was evaluated. Student t test and Wilcoxon rank sum test were used to compare variables.

RESULTS

The lactose tolerance test as a standard had an 87.5% sensitivity and 92.7% specificity for genetic status. Only a moderate agreement between lactose tolerance test and breath hydrogen test was observed (2-way kappa coefficient, .53; 95% confidence interval, .22-.83). When genetic status was used as standard, symptoms had a moderate sensitivity and specificity. Lactose tolerance test had very good sensitivity, and the breath test had excellent specificity.

CONCLUSIONS

Both indirect tests independently have good to very good sensitivities and specificities for genetic lactase status. The noted disagreement likely reflects variables that affect the tests independently of intestinal lactase status. The value of these tests in the light of the availability of genetic testing is discussed.

Inverse dose effect of pretest dietary lactose intake on breath hydrogen results and symptoms in lactase nonpersistent subjects

The aim of this study was to determine a relationship between pretest intake of lactose and outcome of lactose breath hydrogen test. Patients presented at a testing laboratory participated in the study. A 3-hour breath hydrogen, 50-g lactose challenge was carried out. Results were tabulated and patients completed a 3-day recall diet questionnaire. Daily lactose intake was independently calculated and was associated with breath hydrogen and total symptom score. Statistical analysis used Spearman's correlation, Mann-Whitney U-test and chi2 or Fisher exact test. Of 118 patients, 50% were lactose maldigesters. In these patients, measured breath hydrogen and symptom scores were significantly higher in the lowest intake group (< 5 g/d) than in the highest intake group (> 20 g/d) (P < .05). In the presumed lactose digesters, 59% experienced some symptoms during testing for unclear reasons. Pretest dietary intake of lactose inversely affects results of breath hydrogen.

Development, validation and utilisation of food-frequency questionnaires - a review

OBJECTIVE

The purpose of this review is to provide guidance on the development, validation and use of food-frequency questionnaires (FFQs) for different study designs. It does not include any recommendations about the most appropriate method for dietary assessment (e.g. food-frequency questionnaire versus weighed record).

METHODS

A comprehensive search of electronic databases was carried out for publications from 1980 to 1999. Findings from the review were then commented upon and added to by a group of international experts.

RESULTS

Recommendations have been developed to aid in the design, validation and use of FFQs. Specific details of each of these areas are discussed in the text.

CONCLUSIONS

FFQs are being used in a variety of ways and different study designs. There is no gold standard for directly assessing the validity of FFQs. Nevertheless, the outcome of this review should help those wishing to develop or adapt an FFQ to validate it for its intended use.