Urinary sugars biomarker relates better to extrinsic than to intrinsic sugars intake in a metabolic study with volunteers consuming their normal diet.

BACKGROUND/OBJECTIVES: Sugars in diet are very difficult to measure because of the unreliability of self-reported dietary intake. Sucrose and fructose excreted in urine have been recently suggested as a biomarker for total sugars intake. To further characterize the use of this biomarker, we investigated whether urinary sugars correlated better to extrinsic compared to intrinsic sugars in the diet. SUBJECTS/METHODS: Seven male and six female healthy participants were living for 30 days in a metabolic suite under strictly controlled conditions consuming their usual diet as assessed beforehand from four consecutive 7-day food diaries kept at home. During the 30-day study, all 24 h urine specimens were collected, validated for their completeness and analysed for sucrose and fructose. RESULTS: The mean total sugars intake in the group was 202+/-69 g day(-1). Daily intake of extrinsic, intrinsic and milk sugars contributed 60.1, 34.4 and 5.5%, to the total sugars intake, respectively. The individuals' 30-day mean sugars excretion levels were significantly correlated with the 30-day means of extrinsic sugars (r=0.84; P<0.001) but not with the intrinsic sugars intake (r=0.43; P=0.144). In the regression, only extrinsic sugars intake explained a significant proportion of the variability in sugars excretion (adjusted R(2)=0.64; P=0.001); daily excretion of 100 mg sucrose and fructose in urine predicted 124 g of extrinsic total sugars in the diet. Using fewer urinary and dietary measurements in the analysis did not change the overall trend of the findings. CONCLUSIONS: In this group of volunteers, sucrose and fructose in urine better correlated to extrinsic than to intrinsic sugars intake.

Urinary sucrose and fructose as biomarkers of sugar consumption: comparison of normal weight and obese volunteers.

Using urinary sugars as a biomarker of consumption, we have previously shown that obese people consume significantly more sugars than individuals of normal weight. However, there is concern that recovery of this biomarker may differ between normal weight and obese individuals. A total of 19 subjects, divided into two groups according to their body mass index (BMI) (normal weight BMI < or = 25 kg/m(2), n=10; obese BMI > or = 30 kg/m(2), n=9), participated in a randomized crossover dietary intervention study of three diets providing 13, 30 and 50% of energy from sugars for 4 days each while living in a volunteer suite. The mean urinary sucrose and fructose excretions in 24-h urine increased with increasing sugar consumption over the three dietary periods in both BMI groups and were significantly different between the diets (P < 0.01). There was no significant interaction effect of BMI class on the mean urinary excretions of these sugars with different sugar intakes, either as absolute values or expressed as a percentage of total sugar intake. In conclusion, BMI does not affect the validity of sucrose and fructose excretions in 24-h urine collections used as biomarkers to estimate total sugar consumption.

Twenty-four-hour urinary thiamine as a biomarker for the assessment of thiamine intake.

OBJECTIVE: To investigate 24-h urinary thiamine as a potential biomarker for thiamine intake for use in validation studies to assess the validity of dietary intake data collected by self-reporting dietary methods. SUBJECTS: Seven male and six female healthy participants living for 30 days in a metabolic suite under strictly controlled conditions consuming their usual diet as assessed beforehand from four consecutive 7-day food diaries kept at home. During the 30-day study, all 24-h urine specimens were collected, validated for their completeness and analysed for thiamine. RESULTS: Thirty-day mean (+/-s.d.) calculated thiamine intake was 2.22+/-0.55 mg/day. Thirty-day mean (+/-s.d.) urinary excretion of thiamine was 526.5+/-193.0 microg/day (24.7+/-8.10% of intake). There was a highly significant correlation between individuals' 30-day means of thiamine intake and their mean excretion level (r=0.720; P=0.006), where 1 mg of thiamine intake predicted 268.2 microg of thiamine in urine. The correlations between intake and excretion remained significant when measurement from a single 24-h urine collection was used (r=0.56). CONCLUSION: Twenty-four-hour urinary thiamine can be used as a concentration biomarker for thiamine intake in dietary validation studies.

Use of biological markers to validate self-reported dietary intake in a random sample of the European Prospective Investigation into Cancer United Kingdom Norfolk cohort.

BACKGROUND: The validity of dietary assessment methods should be established before diet-disease associations are reported. OBJECTIVE: Our objective was to validate a 7-d food diary and a food-frequency questionnaire (FFQ) against independent biomarkers of intake in urine (nitrogen, potassium, and sodium) and blood (plasma ascorbic acid). DESIGN: A total of 146 healthy middle-aged men and women were recruited from the European Prospective Investigation into Cancer UK Norfolk cohort, a free-living cohort of approximately 25000 persons. Over a 9-mo period, urinary nitrogen, potassium, and sodium were estimated from 2-6 complete 24-h urine collections in 134 subjects and plasma ascorbic acid was estimated from 2-3 fasting blood samples in 118 subjects. Subjects completed 2 FFQs and two 7-d food diaries. RESULTS: In men and women combined, correlations between 24-h urinary nitrogen excretion and dietary intake from the 7-d food diary were high (r = 0.57-0.67) compared with those for the FFQ (r = 0.21-0.29). Similarly, correlations between urinary potassium and dietary potassium were higher for the 7-d food diary (r = 0.51-0.55) than for the FFQ (r = 0.32-0.34). There was no overall difference in correlations between plasma ascorbic acid and dietary vitamin C between the 7-d food diary (r = 0.40-0.52) and the FFQ (r = 0.44-0.45). CONCLUSIONS: These data indicate that, despite increased subject burden, the 7-d food diary provided a better estimate of nitrogen and potassium intakes than did the FFQ in this study population. However, with respect to plasma ascorbic acid, both the FFQ and 7-d food diary provided a similar ranking of subjects according to vitamin C intake.

Nutritional methods in the European Prospective Investigation of Cancer in Norfolk.

OBJECTIVE: To describe methods and dietary habits of a large population cohort. DESIGN: Prospective assessment of diet using diet diaries and food-frequency questionnaires, and biomarkers of diet in 24-h urine collections and blood samples. SETTING: Free living individuals aged 45 to 75 years living in Norfolk, UK. SUBJECTS: Food and nutrient intake from a food-frequency questionnaire on 23 003 men and women, and from a 7-day diet diary from 2117 men and women. Nitrogen, sodium and potassium excretion was obtained from single 24-h urine samples from 300 individuals in the EPIC cohort. Plasma vitamin C was measured for 20 846 men and women. RESULTS: The food-frequency questionnaire (FFQ) and the food diary were able to determine differences in foods and nutrients between the sexes and were reliable as judged by repeated administrations of each method. Plasma vitamin C was significantly higher in women than men. There were significant differences in mean intake of all nutrients measured by the two different methods in women but less so in men. The questionnaire overestimated dairy products and vegetables in both men and women when compared with intakes derived from the diary, but underestimated cereal and meat intake in men. There were some consistent trends with age in food and nutrient intakes assessed by both methods, particularly in men. Correlation coefficients between dietary intake assessed from the diary and excretion of nitrogen and potassium in a single 24-h urine sample ranged from 0.36 to 0.47. Those comparing urine excretion and intake assessed from the FFQ were 0.09 to 0.26. The correlations between plasma vitamin C and dietary intake from the first FFQ, 24-h recall or diary were 0.28, 0.35 and 0.40. CONCLUSIONS: EPIC Norfolk is one of the largest epidemiological studies of nutrition in the UK and the largest on which plasma vitamin C has been obtained. Methods for obtaining food and nutrient intake are described in detail. The results shown here for food and nutrient intakes can be compared with results from other population studies utilising different methods of assessing dietary intake. The utility of different methods used in different settings within the main EPIC cohort is described. The FFQ is to be used particularly in pooled analyses of risk from diet in relation to cancer incidence within the larger European EPIC study, where measurement error is more likely to be overcome by large dietary heterogeneity on an international basis. Findings in the UK, where dietary variation between individuals is smaller and hence the need to use a more accurate individual method greater, will be derived from the 7-day diary information on a nested case-control basis. 24-h recalls can be used in the event that diary information should not be forthcoming from some eventual cases. Combinations of results utilising all dietary methods and biomarkers may also be possible.

Apolipoprotein E and methylenetetrahydrofolate reductase genetic polymorphisms in relation to other risk factors for cardiovascular disease in UK Caucasians and Black South Africans.

Genetic polymorphisms for apolipoprotein E (apo E) and methylenetetrahydrofolate reductase (MTHFR) are believed to modulate risk of coronary heart disease (CHD) acting through regulation of lipid and homocysteine metabolism, respectively. The distributions of apo E and MTHFR alleles in Black South Africans, a population with a low CHD incidence, and UK Caucasians from the Cambridge area, with a higher CHD incidence, were therefore compared. Clinically healthy volunteers (207), including 107 UK Caucasians from the Cambridge area and 100 Black South Africans, participated in the study. Apo E and MTHFR genotypes were determined in all of them. Analyses for serum total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and plasma fibrinogen were carried out in 65 UK Caucasians and 60 Black South Africans. The apo E epsilon4 allele, which is associated with elevated CHD risk, was present in 48% of Black South Africans compared to 20.8% of Caucasians (P < 0.0001); however, both total and LDL cholesterol levels in Black South Africans were 18-32% lower than in Caucasians with similar apo E genotypes. Hyperhomocysteinemia-causing MTHFR 677T variant was detected in only 20% of Black South Africans (no homozygotes) versus 56% of Caucasians with 12% homozygotes (P<0.0001). Our findings suggest that the potentially unfavourable pattern of apo E allele distribution in Black South Africans does not result in increased CHD incidence due to protection by dietary and/or other life style related factors. The exceptionally low frequency of MTHFR mutant homozygotes in this population suggests that this polymorphism should not be regarded as an important CHD risk factor among Black South Africans.

Apolipoprotein E genotype modulates the effect of black tea drinking on blood lipids and blood coagulation factors: a pilot study.

Apolipoprotein E (ApoE) genotype was determined in sixty-five subjects who had taken part in a 4-week randomized crossover trial to compare the effect of six mugs of black tea per day v. placebo on blood lipids and blood coagulation factors. Four ApoE genotype variants (seven E2/E3, forty-five E3/E3, twelve E3/E4 and one E4/E4) were found. ApoE allele frequency was within the range typical for Caucasian populations (ApoE-E2 5.4%; ApoE-E3 83.8%; ApoE-E4 10.8%). Individuals bearing at least one E4 allele had substantially higher levels of serum total cholesterol, LDL cholesterol and triacylglycerols. Mean plasminogen activator inhibitor (PAI-1) activity was higher in ApoE-E4 allele-bearing individuals (E3/E4 + E4/E4, 11.89 (SE 1.27) U/ml; E3/E3, 9.19 (SE 0.80) U/ml; E2/E3, 7.21 (SE 1.04) U/ml, P values of E4-group v. E3 and E2 being respectively 0.093 and 0.030). These unexpected findings imply that elevated PAI-1 activity may be a hitherto unrecognized additional factor involved in the increased cardiovascular disease risk associated with apoE-E4 allele. The interactions between tea drinking and genotype were also examined. In the E3/E3 homozygotes, HDL-cholesterol was significantly reduced in the tea period (mean placebo 1.54 mmol/l v. mean tea 1.50 mmol/l, P = 0.027). In the E2/E3 group, triacylglycerol concentration was significantly reduced (mean placebo 1.18 mmol/l v. mean tea 1.09 mmol/l, P = 0.039). Tea also caused a significant decrease of PAI-1 activity in the subjects with E2/E3 genotype (mean placebo 7.21 U/ml v. mean tea 5.88 U/ml, P = 0.007). In the other two genotype groups, there was no significant effect of tea. The results indicate that tea drinking has a beneficial effect on some cardiovascular disease risk-associated factors, especially in E2 allele-bearing individuals. Dietary intervention may be particularly effective in population groups with certain genetic characteristics.

Effect of black tea drinking on blood lipids, blood pressure and aspects of bowel habit.

Thirty-one men (47 (SD 14) years) and thirty-four women (35 (SD 13) years) took part in a 4-week randomized cross-over trial to compare the effect of six mugs of black tea daily v. placebo (water, caffeine, milk and sugar) on blood lipids, bowel habit and blood pressure, measured during a run-in period and at the end of weeks 2, 3 and 4 of the test periods. Compliance was established by adding a known amount of p-aminobenzoic acid (PABA) to selected tea bags, and then measuring its excretion in urine. Mean serum cholesterol values during run-in, placebo and on tea drinking were 5.67 (SD 1.05), 5.76 (SD 1.11) and 5.69 (SD 1.09) mmol/l (P = 0.16). There were also no significant changes in diet, LDL-cholesterol, HDL-cholesterol, triacylglycerols, and blood pressure in the tea intervention period compared with placebo. Compared with placebo, stool consistency was softened with tea (P = 0.04), and no other differences were found in bowel habit. Results were unchanged when fifteen 'non-compliers', whose PABA excretion indicated that fewer than six tea bags had been used, were excluded from the analysis, and when differences between run-in and tea periods were considered separately for those who were given tea first or second.

Validation of dietary assessment methods in the UK arm of EPIC using weighed records, and 24-hour urinary nitrogen and potassium and serum vitamin C and carotenoids as biomarkers.

BACKGROUND: In the UK EPIC validation studies, the accuracy of several methods was assessed by comparison with to-day weighed records and the biomarkers, 24-hour urine nitrogen (N) and potassium (K), plasma carotenoids and plasma vitamin C. METHODS: Comparisons between methods were made on 156 women, studied over 1 year at 3-monthly intervals at home. On each of four occasions, volunteers completed 4 days of weighed records and provided two 24-hour urine collections and a fasting blood sample. RESULTS: In comparison with the 16 days of weighed records, a food frequency questionnaire (FFQ) yielded higher values mainly due to greater reported consumption of milk and of vegetables. A 24-hour recall was as good as the FFQ in placing individuals in the distribution of habitual diet from weighed records. Results obtained from a 7-day estimated record were closest to those obtained from the weighed record. Correlations between 24-hour urine excretion and dietary N intake from weighed records were high (0.78-0.87) as were those with estimated food diaries (0.60-0.70). Correlations between urine N and the FFQ and 24-hour recall were lower (0.10 to 0.27), but improved by energy adjustment using residuals for N and K which are correlated with total energy intake. Comparisons between dietary estimates and urinary K and serum carotenoids and vitamin C showed broadly similar results. Limited biomarker information amongst 200 UK EPIC participants supported the findings of the validation study. CONCLUSIONS: UK EPIC uses three methods (the 7-day diary, an improved FFQ, and the 24-hour recall) to assess diet. 93% of first food diaries are returned completed by participants. Repeated diaries are the main dietary assessment method for nested case-control analyses.

Validation of weighed records and other methods of dietary assessment using the 24 h urine nitrogen technique and other biological markers.

Results from analysis of 24 h urine collections, verified for completeness with para-amino benzoic acid, and blood samples collected over 1 year were compared with 16 d weighed records of all food consumed collected over the year, and with results from 24 h recalls, food-frequency questionnaires and estimated food records in 160 women. Using the weighed records, individuals were sorted into quintiles of the distribution of the urine N excretion:dietary N intake ratio (UN:DN). UN exceeded DN in the top quintile of this ratio; mean ratio UN:DN = 1.13. Individuals in this top quintile were heavier, had significantly greater body mass indices, were reportedly more restrained eaters, had significantly lower energy intake:basal metabolic rate ratios (EI:BMR), and had correlated ratios of UN:DN and EI:BMR (r -0.62). Those in the top quintile reported lower intakes of energy and energy-yielding nutrients, Ca, fats, cakes, breakfast cereals, milk and sugars than individuals in the other quintiles but not lower intakes of non-starch polysaccharides, vitamin C, vegetables, potatoes or meat. Correlations between dietary intake from weighed records and 24 h urine K were 0.74 and 0.82, and between dietary vitamin C and beta-carotene and plasma vitamin C and beta-carotene 0.86 and 0.48. Correlations between dietary N intake from weighed records and 24 h urine excretion were high (0.78-0.87). Those between N from estimated food records and urine N were r 0.60-0.70. Correlations between urine N and 24 h recalls and food-frequency questionnaires were in the order of 0.01 to 0.5. Despite problems of underreporting in overweight individuals in 20% of this sample, weighed records remained the most accurate method of dietary assessment, and only an estimated 7 d diary was able to approach this accuracy.

para-amino benzoic acid in the assessment of completeness of 24-hour urine collections from hospital outpatients and the effect of impaired renal function.

Eighteen (29%) of 24-h urine collections made by 63 hospital outpatients attending a gastroenterology clinic were incomplete, as judged by 24 h urine recovery of an oral marker, para-amino benzoic acid (PABA), despite more than the usual efforts to obtain complete collections. Incomplete collections contained significantly less sodium, urea and total nitrogen than full collections. Average outputs were 134 mmol and 103 mmol per day for sodium (P less than 0.02); 301 mmol and 223 mmol for urea (P less than 0.001); and 10.1 g and 8.3 g nitrogen (P less than 0.01) in the complete and incomplete collections respectively. In renal outpatients with a plasma creatinine in excess of 125 mumol per litre, urine recoveries of PABA were reduced, but within the expected range in renal patients whose plasma creatinine was normal.