Prediction of dietary flavonol consumption from fasting plasma concentration or urinary excretion

OBJECTIVES: to predict flavonols content of the habitual diets of free-living subjects from urine and plasma concentrations of flavonols. DESIGN: Ten type 2 diabetic patients (five male, five female), mean age 60 (s.e.m. 7) y and BMI 30.2 (s.e.m. 3.5) kg/m2 were treated in a random crossover design for a 2 week period on either a low flavonoid diet or on the same diet supplemented at one of two high flavonols levels (total 77.3 or 110.4 mg/day) provided by supplements of 1500 ml tea daily and 400 g fried white onion in olive oil with and without tomato ketchup and herbs. SETTING: Glasgow Royal Infirmary, University of Glasgow, Scotland. MAIN OUTCOME MEASURES: Fasting plasma concentration, urine concentration and 24 h excretion of quercetin, isorhamnetin, kaempferol and myricetin. RESULTS: Plasma flavonol concentration (r=0.750, P=0.001), 24 h urine concentration (r=0.847, P=0.001) and 24 h urine excretion (r=0.728, P=<0.001) were all highly significantly related to dietary intake and gave similar estimates of intakes. Fasting plasma flavonols concentrations on habitual diets ranged from 0 to 43.7 ng/ml mean. Regression equations were constricted: total flavonols intake r=0.74, P<0.001 and quercetin intake r=0.744, P<0. 001. From these equations, flavonol intakes from habitual diets were estimated at 17-50, mean 35 mg/day. Of this, 91% was from quercetin. CONCLUSIONS: Dietary flavonols are absorbed and appear in plasma and urine as potential biomarkers in concentrations related quantitatively to intake. Estimation of dietary intake from plasma or urine concentrations appears possible. Sponsorship: Rank Prize Funds and Rank Foundation of the Department of Human Nutrition; Ministry of Health and Medical Education, IR Iran. European Journal of Clinical Nutrition (2000) 54, 143-149     

Validation of a phytoestrogen food frequency questionnaire with urinary concentrations of isoflavones and lignan metabolites in premenopausal women

OBJECTIVE: The purpose of this study was to examine the association between dietary intake of phytoestrogens estimated by a food frequency questionnaire (FFQ) with urinary metabolites. METHODS: Participants were 26 premenopausal, Caucasian women aged 25 to 42 years. Dietary intake of isoflavones (genistein and daidzein) and lignans (secoisolariciresinol and matairesinol) were estimated by a 53-item interviewer-administered FFQ on two occasions, reflecting 'habitual' (previous 2 months) and 'recent' (previous 2 days) dietary intake. Isoflavone (genistein, daidzein) and lignan (enterolactone, enterodiol and secoisolariciresinol) concentrations were measured in 24-hour urine samples by gas chromatography-mass spectrometry. Correlations between FFQ (habitual and recent, separately) and urinary metabolite values were assessed using Spearman correlation coefficients. RESULTS: Mean habitual isoflavone and lignan intakes were 13.7 mg/day and 13.8 mg/day, respectively. Mean urinary concentrations of isoflavones and lignans were 17.4 micromol/day and 20.6 micromol/day, respectively. Recent and habitual isoflavone intakes were correlated with urinary excretion of metabolites (r = 0.64, p < 0.001 and r = 0.54, p = 0.004, respectively). Urinary excretion of lignans was also modestly correlated with recent and habitual lignan intakes (r = 0.46, p = 0.02 and r = 0.40, p = 0.05, respectively). CONCLUSIONS: Our results support the use of this FFQ as a measure of dietary isoflavone and lignan intake in epidemiological studies.     

Dietary exposure to chlorpyrifos and levels of 3,5,6-trichloro-2-pyridinol in urine

Information on associations between chlorpyrifos residues in food and personal exposure to chlorpyrifos would be valuable for evaluating the relationship between personal exposure and possible health effects. We used food consumption records, chlorpyrifos levels in duplicate plates, and measures of 3,5,6-trichloro-2-pyridinol (TCPy) in urine obtained from human volunteers in the National Human Exposure Assessment Survey in Maryland (NHEXAS-MD) to evaluate a food consumption-chemical residue model for estimating dietary intake of chlorpyrifos. Model inputs were the NHEXAS-MD food consumption records and chlorpyrifos residues in specific foods measured in the U.S. Food and Drug Administration Total Diet Study (TDS) market baskets from 1993 to 1997. The estimated mean and standard deviation of chlorpyrifos concentration (microg/kg) in duplicate plates (n=203) were within 20% and 50%, respectively, of the corresponding parameters of measured chlorpyrifos levels. However, predicted and measured concentrations in the 78 duplicate plates with detectable levels of chlorpyrifos were not significantly associated according to Spearman correlation analysis (r=0.04, p=0.7667) and linear regression (p=0.2726). Measured and estimated chlorpyrifos intakes for observations with non-zero values for each intake measure (n=71) were moderately associated on a rank (Spearman's r=0.24, p=0.0462) and linear basis (regression r(2)=0.07, p=0.0242). Measured intakes of chlorpyrifos from food and urinary TCPy were significantly correlated in rank order (n=87, Spearman's r=0.30, p=0.0041) and linear (n=87, Pearson's r=0.22, p=0.0409) analyses. Correlation coefficients between estimated intake of chlorpyrifos from food and TCPy were significantly different from zero (n=87; Spearman's r=0.22, p=0.0393; Pearson's r=0.21, p=0.0479). Comparing mean measured chlorpyrifos intake from food (0.46 microg/day) to mean estimated TCPy excretion via urine (6.3 microg/day), dietary intake of chlorpyrifos accounted for approximately 7% of TCPy in this population. These findings suggest the food consumption-chemical residue model can yield reasonably accurate estimates of the population distribution of dietary chlorpyrifos intake, but has little ability to predict dietary exposure for individuals; and that intake of chlorpyrifos from food is a minor contributor to TCPy in urine.     

Dietary silicon intake and absorption

BACKGROUND: Increasing evidence suggests that silicon is important in bone formation. The main source of silicon for humans is the diet, but the bioavailability of silicon from solid foods is not well understood. OBJECTIVE: We estimated the dietary intake of silicon by adults, separately for men and women and for different age groups. Foods that were major contributors to silicon intake were identified. We then estimated the gastrointestinal uptake of silicon from major food sources and studied how uptake correlated with the silicon contents of the foods. DESIGN: Silicon intakes were determined in cohorts from the original Framingham Study and the Framingham Offspring Study by using a 126-item food-frequency questionnaire. Gastrointestinal uptake of silicon from foods was estimated in 3-8 healthy subjects by using urinary silicon excretion as a surrogate measure of silicon uptake. RESULTS: Mean silicon intakes in men (30 and 33 mg/d in the original Framingham and Framingham Offspring cohorts, respectively) were significantly higher than those in women (24 and 25 mg/d in the 2 cohorts, respectively; P = 0.0001). Silicon intake decreased with age (P < 0.001, adjusted for sex). The major food sources were beer and bananas in men and bananas and string beans in women. Silicon was readily available from foods; a mean of 41% of the ingested silicon was excreted in urine. The silicon content of the foods consumed was significantly correlated with urinary silicon excretion (P = 0.019). CONCLUSIONS: Solid foods are a major source of available silicon. The association between dietary silicon intake and bone health should now be investigated.     

Does dietary recall adequately assess sodium, potassium, and calcium intake in hypertensive patients?

OBJECTIVE: A diet low in sodium, high in potassium, and high in calcium is recommended to lower blood pressure. However, compliance with this diet is poor, probably because of dietary intake underestimation. Therefore, we compared electrolyte intake as estimated from dietary recall with a 24-h urinary excretion. METHODS: Thirty-six patients (26 men and 10 women) with a mean age of 46 +/- 8 y participated in the study. All participants had essential hypertension and were on no drug therapy (n = 20) or non-diuretic monotherapy (n = 16). Patients were instructed to consume a low-sodium (50 mmol/d), high-potassium (supplementation with 30 to 60 mmol/d), and high-calcium (1000 mg/d) diet. Compliance with the diet was assessed at baseline and then 1, 2, and 3 mo after starting the diet. Sodium, potassium, and calcium intakes were carefully estimated from patients' dietary recall and 24-h urinary collection. RESULTS: Estimated sodium intake significantly correlated with 24-h urinary excretion (R = 0.43 P < 0.001). However, estimated sodium intake was lower than urinary sodium excretion by 34% at baseline and by 47% after 3 mo of dieting (P < 0.05). Estimated potassium intake correlated with 24-h urinary excretion. Estimated calcium intake significantly increased from 933 +/- 83 mg/d to 1029 +/- 171 mg/d (P < 0.05). Calcium intake derived from patients' recall far exceeded and only slightly correlated with 24-h urinary excretion (R = 0.23, P < 0.01). CONCLUSIONS: Patients tend to underestimate their sodium intake by 30% to 50%; therefore, urinary sodium excretion is more accurate to assess sodium intake. Thus, 24-h urinary sodium excretion should be used in clinical practice and in clinical trials, especially when dietary non-compliance is suspected.     

Assessment of iodine intake in vegans: weighed dietary record vs duplicate portion technique

OBJECTIVE: To compare iodine intakes estimated from weighed dietary records with iodine intakes obtained by direct analysis of duplicate diets in a group of vegans. DESIGN: Cross-sectional study. SETTING: London and the south-east of England. SUBJECTS: Thirty-three vegans consuming their habitual diet were recruited through the UK Vegan Society; 26 subjects (11 males, 15 females), age 21-84 y, completed the study. INTERVENTIONS: Iodine intakes were estimated from 4 day weighed dietary records and compared with iodine intakes obtained by direct analysis of concurrent 4 day duplicate diets. RESULTS: There was wide variation in iodine intakes. Mean daily iodine intake in males was significantly lower (P<0.05) when estimated from dietary records (42 microg) compared with that analysed from duplicate diets (137 microg). Conversely, in females the mean daily iodine intake from dietary records (1448 microg) was higher (P=0.43) than from duplicate diets (216 microg). Variation in iodine intakes determined by the two different methods may be attributed to the absence of iodine content of some foods, in particular foods suitable for vegan consumption, in food composition tables and the variability in iodine content of seaweed. CONCLUSIONS: The use of current food tables to estimate iodine intake in vegans is limited. It is not always practical to determine iodine intake using the duplicate portion technique, therefore more reliable information on iodine content of foods, incorporating the variation within foods, is needed.     

Comparison of isoflavones among dietary intake, plasma concentration and urinary excretion for accurate estimation of phytoestrogen intake

Biological effects of dietary isoflavones, such as daidzein and genistein are of interest in preventive medicine. We estimated the dietary intake of isoflavones from dietary records and compared the values with the plasma concentrations and urinary excretions in Japanese middle-aged women. The dietary intake of daidzein and genistein was 64.6 and 111.6 mumol /day/capita (16.4 and 30.1 mg/day/capita), respectively. The isoflavones intake was mostly attributable to tofu, natto and miso. The median of plasma daidzein and genistein concentration was 72.46 and 206.09 nmol/L, respectively. The median of urinary excretion was 20.54 mumol /day for daidzein, 10.79 for genistein, 15.74 for equol and 1.64 for O-desmethylangolensin (O-DMA). Equol and O-DMA were excreted by 50% and 84% of all participants, respectively. Equol metabolizers were significantly lower the plasma and urinary daidzein and urinary O-DMA. The dietary intake of daidzein and genistein after the adjustment for total energy intake was significantly correlated with the urinary excretion (r = 0.365 for daidzein and r = 0.346 for genistein) and plasma concentration (r = 0.335 for daidzein and r = 0.429 for genistein). The plasma concentration of isoflavones was also significantly correlated with the urinary excretion. We conclude that in epidemiological studies measurements of plasma concentration or urinary excretion of these isoflavones are useful biomarkers of dietary intake and important for studies on their relation to human health.     

Methods and validity of dietary assessments in four Scandinavian populations

Average intakes of nonstarch polysaccharides (dietary fiber), foods, and nutrients were measured in representative samples of 30 men aged 50-59 in 4 Scandinavian populations with a 3-4 fold difference in risk for large bowel cancer. The assessment technique, a 4-day weighed record of food consumed and duplicate collections of all food eaten, was validated by chemical analysis of the duplicates, by measuring 24-hour urine and fecal nitrogen excretion, and by comparing the constituents of the urine samples collected during the survey with similar collections 1-2 weeks later. There were good agreements between estimates of fat and protein intake obtained by food-table calculations of the 4-day weighed record and the chemically analyzed duplicates. Urinary plus fecal nitrogen excretion was equal to estimated nitrogen intake during the survey, and no discernable changes in urinary output occurred after the survey, thereby implying that dietary habits had not changed as a result of the investigative technique. It is concluded that the dietary data are indicative of current patterns of food consumption and are sufficiently valid for comparison with data on cancer risk in the 4 areas.     

Three measures show high compliance in a soy intervention among premenopausal women

OBJECTIVE: To evaluate adherence to a soy-based diet among premenopausal women. DESIGN: First year of a 2-year, randomized dietary intervention. SUBJECTS: 220 healthy premenopausal women who reported low baseline soy intake. INTERVENTION: 5 counseling visits, 7 follow-up phone calls, and 12 group meetings. Main outcome measures Self-reported soy intake logs; food frequency questionnaires; repeated, randomly timed 24-hour recalls; and analysis of urinary isoflavone excretion by high-pressure liquid chromatography. Statistical analyses Frequency distributions, means, t tests, and mixed effects models. RESULTS: At baseline, the 2 groups did not differ in dietary soy intake (P=.51) or urinary isoflavone excretion (P=.16). According to the 24-hour recalls and the food frequency questionnaires, the intervention group's estimated isoflavone intake increased more than 10 times compared with baseline and with the control group (P<.0001). During follow-up, urinary isoflavone excretion results showed no change in the control group, but a 6-fold increase for intervention subjects (P<.0001). Intake logs showed a strong preference for soymilk and tofu over the other foods and indicated that intervention participants consumed at least 12 servings of soy foods per week during 84 out of 100 follow-up contacts. CONCLUSIONS: These data indicate a high level of compliance with the study regimen, which we attribute to the following strategies: repeated contact with the study subjects, personal relationships with the dietitians, wide choice of soy foods, easy access to soy foods at no cost, and recipes that allowed substitution of previously eaten foods with soy products.     

Estimation of salt intake by 24 h urinary sodium excretion in a representative sample of Spanish adults

The present study reports the Na intake of a representative sample of Spanish young and middle-aged adults aged 18-60 years (n 418, 53·1 % women, selected from the capitals of fifteen provinces and the surrounding semi-urban/rural area), measured with a 24 h urinary Na excretion method. To validate the paper collection of 24 h urine, the correlation between fat-free mass determined by electrical bioimpedance (50·8 (sd 11·3) kg) and that determined via urinary creatinine excretion (51·5 (sd 18·8) kg) was calculated (r 0·633, P < 0·001). Urinary Na excretion correlated with systolic and dyastolic blood pressure data (r 0·243 and 0·153, respectively). Assuming that all urinary Na (168·0 (sd 78·6) mmol/d) comes from the diet, Na excretion would correspond with a dietary salt intake of 9·8 (sd 4·6) g/d, and it would mean that 88·2 % of the subjects had salt intakes above the recommended 5 g/d. Logistic regression analysis, adjusted for sex, age and BMI, showed male sex (OR 3·678, 95 % CI 2·336, 5·791) and increasing BMI (OR 1·069, 95 % CI 1·009, 1·132) (P < 0·001) to be associated with excreting >200 mmol/d urinary Na--a consequence of the higher salt intake in men and in participants with higher BMI. The present results help us to know the baseline salt intake in the Spanish young and middle-aged adult population, and can be used as the baseline to design policies to reduce salt consumption.     

Effects of orange juice and proline betaine on glycine betaine and homocysteine in healthy male subjects

Background Proline betaine (PB), a glycine betaine (GB) analogue found in citrus foods, increases urinary GB loss and plasma total homocysteine (tHcy) concentrations in rats. Its presence in human plasma is associated with increased GB excretion. Aim To compare the effects of dietary levels of PB on GB excretion, and on plasma tHcy and GB concentrations in healthy volunteers. Methods In a randomized crossover study, eight healthy males (18–50 years) ingested either 750 mL orange juice (containing 0.545 g PB), a PB supplement (0.545 g PB dissolved in 750 mL apple juice), or 750 mL apple juice (control). Plasma PB, GB and tHcy, and urine PB, GB and creatinine concentrations were measured hourly for 6 h and at 24 h post-treatment. Results Plasma tHcy concentrations were not increased (relative to control) following ingestion of either orange juice or PB supplement. Both treatments produced a significant increase in plasma PB concentrations (P < 0.001), this effect being greater following orange juice compared with PB supplement (P < 0.05, 1–2 h). Urinary excretion of PB was greater than the control following both orange juice (P < 0.001) and PB supplement (P < 0.001), from 2 to 24 h post-treatment. This increase in PB excretion was significantly greater following orange juice compared with PB supplement with higher peak excretion (C _max difference, P = 0.008). GB excretion was significantly greater following ingestion of orange juice compared with PB in apple juice (P = 0.007) and apple juice control (P < 0.001) in the first 2 h post-ingestion. Conclusions PB administered in dietary doses had little effect on plasma tHcy concentrations in healthy humans. Ingestion of PB in orange juice compared with PB alone resulted in greater increases in the urinary excretion of PB and GB.     

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.     

Salt Intake of Lactating Women as Assessed by Modified Food Weighted Records

Objective: High salt intake among lactating women can increase the risk of hypertension and cardiovascular disease in infants/offspring. However, considering the limited salt intake data in lactating women, the aims of this study were to compare the salt intake assessed by modified food weighted records (FWR) with that estimated by 24-h urinary sodium excretion and to investigate the salt intake of lactating women.

Methods: In total, 30 lactating women aged 20–39 years who were 2 to 4 months postpartum were recruited from the cities of Tianjin and Luoyang in China. The household salt intakes of the lactating women were collected by modified FWR for 3 days. Information on the gender, age, eating behaviours and labour intensity of the family members and guests dining at home during the 3 days was recorded. Meanwhile, 24-h urine samples of lactating women were collected.

Results: The salt intakes of the lactating women estimated by modified FWR and 24-h urinary sodium excretion were 8.50 ± 5.32 g/d and 9.34±3.74 g/d (t=?1.29, P=0.207), respectively, which exceeded the WHO recommendation of 5 g/d. There was a significant correlation (r=0.628, P < 0.001) between the salt intakes assessed by the two methods. A Bland-Altman plot showed no significant mean difference between the two methods (salt intake measured by 24-h urinary sodium excretion-salt intake assessed by modified FWR=0.46 g/d, P=0.207).

Conclusions: The modified FWR is a reliable tool to assess the salt intake of lactating women. The salt intake of lactating women in China remains higher than the WHO recommendation and should be restricted through further efforts.     

A comparison of methods of assessment of dietary selenium intakes in Otago, New Zealand

The aims of the present study were (1) to compare three methods of assessment of dietary Se intake, i.e. chemical analysis of duplicate diets, diet records and a food-frequency questionnaire (FFQ) designed specifically for Se, and (2) to determine dietary Se intakes of residents of Otago, New Zealand. The FFQ was completed by 110 free-living adults. Diet records (3 d) and duplicate diet collections were carried out by forty-three of these subjects chosen on the basis of low blood Se concentration, and during a period when consumption of the high-Se foods fish, kidney, liver and Brazil nuts was discouraged. Mean Se intakes were similar for duplicate diet analysis (29 (SD 13) micrograms/d) and diet record assessments (28 (SD 15) micrograms/d). Estimates of intakes from the FFQ for the subgroup of forty-three subjects were higher (51 (SD 26) micrograms/d) than those from duplicate diets and diet records. Values from duplicate diet analysis and diet record assessments were strongly correlated (r 0.7, P = 0.0001), but difference plots indicated a lack of agreement between the two methods. Thus, diet record assessment was not adequate for predicting dietary Se intakes of individuals. Significant correlations were found for relationships between Se intake from duplicate diets (microgram/kg body weight per d) and plasma Se, Se intake from diet records (microgram/d and microgram/kg body weight per d) and plasma Se; and Se intake from the FFQ and whole-blood Se. Se intakes from duplicate diets and diet records were similar to those reported previously for New Zealanders, but lower than the recommended intakes in the USA (National Research Council, 1989), Australia (Truswell et al. 1990) and the UK (Department of Health, 1991) and the World Health Organization/Food and Agriculture Organization/International Atomic Energy Agency (1996) normative requirement.     

Does degree of obesity influence the validity of reported energy and protein intake? Results from the SOS Dietary Questionnaire. Swedish Obese Subjects.

OBJECTIVE: To test the validity of a dietary questionnaire which was developed with the particular goal of measuring dietary intake in obese subjects. DESIGN: Reported energy intake was compared with 24 h energy expenditure measured in a chamber for indirect calorimetry (24 EE) and reported nitrogen intake with nitrogen in urine collected during the 24 h in the chamber. SUBJECTS: Twenty-nine overweight men and women, body mass index (BMI) ranging from 25.5 49.5 kg/m2. RESULTS: Reported energy intake correlated significantly with 24 EE (r = 0.50, P = 0.006) and reported urinary nitrogen correlated significantly with urinary nitrogen excretion (r=0.56, P=0.0015). Mean reported energy intake+/-s.d. was 10.2+/-3.6 MJ and mean 24 EEi s.d. was 10.3+/-1.9 MJ. Although this difference was small and non significant, it indicates some underreporting if one can assume that these overweight subjects are less physically active in the chamber than in free-living conditions. Reported nitrogen intake also suggested underreporting at the group level. However, when the data were analysed at the individual level it was clear that the underreporting errors did not increase with increasing degree of obesity. CONCLUSIONS: Previous studies with the SOS dietary questionnaire have demonstrated that it is possible to obtain plausible energy intakes from both obese and nonobese subjects. This present analysis further demonstrates that the questionnaire discriminates overweight subjects with high and low intakes of energy and protein, using unbiased biomarkers to judge validity. These data provide additional support for the usefulness of the SOS dietary questionnaire.     

Zinc and vitamin A intake and status in a national sample of British young people aged 4-18 y

OBJECTIVE: To examine zinc and vitamin A intake and status and associated dietary, socio-demographic, lifestyle and physiological factors in British young people. DESIGN: National Diet and Nutrition Survey of young people aged 4-18 y. SETTING: Great Britain, 1997. SUBJECTS: Complete 7-day weighed dietary records were provided by 1520 participants, while 1193 provided blood samples. RESULTS: A total of 13 and 11% of participants respectively reported low dietary intakes of zinc and vitamin A (retinol equivalents), relative to the UK lower reference nutrient intake. These percentages were not altered significantly by including contributions to intake from supplements, mainly containing vitamin A (as retinol). Likelihood of low zinc and/or vitamin A intake was more often associated with age, sex and likely under-reporting of food consumption than with other socio-demographic and lifestyle factors. Low zinc and vitamin A intakes were generally less likely in those with higher consumption of dairy foods (mainly milk). Zinc and vitamin A status (assessed by plasma zinc and retinol concentrations) were adequate in almost all participants. Plasma zinc concentration was not significantly associated with zinc intake. Plasma retinol concentration was correlated with vitamin A intake (overall r=0.17, P<0.001; adjusted for age and plasma alpha(1)-antichymotrypsin concentration) and increased significantly with age (P<0.001) in both sexes. A significant association was found between plasma zinc and retinol concentrations in boys only (r=0.17, P=0.001). CONCLUSION: Zinc and vitamin A intakes and status were generally adequate in this national sample of British young people.     

Peer Reviewed: Assessing Calcium Intake in Postmenopausal Women

Introduction

Because foods fortified with calcium are increasingly available, the calcium content of calcium-fortified foods may not be adequately captured in traditional assessments of dietary intake, such as dietary records analyzed with commercially available software. The primary objective of our study was to design and test a calcium-focused food frequency questionnaire (CFFFQ) including foods naturally rich in calcium and calcium-fortified foods. Secondary objectives were to review calcium sources and adequacy of intake in black and in white postmenopausal women.

Methods

We studied a convenience sample of 46 black and 139 white postmenopausal women (mean [SD] age 69.4 [5.8] years). Subjects completed a multiple-pass interview for 24-hour recall of foods eaten and the 46-item CFFFQ.

Results

The correlation between measures for total daily calcium intake was moderately strong (r = 0.53, P < .001). The CFFFQ estimated greater total daily calcium intake than did the 24-hour recall (mean [SD], 1,021 [624] mg/d vs 800 [433] mg/d, P < .001). As daily calcium intake increased, the 24-hour recall increasingly underreported calcium (r = 0.41, P < .001) compared with the CFFFQ. Cross-tabulation and Χ² analyses found that the CFFFQ had greater specificity for lower calcium intakes. For calcium classified by food groups, there was moderate correlation for dairy (r = 0.56, P < .001) and fruits (r = 0.43, P < .001). The CFFFQ overestimated mean total calcium compared with the 24-hour recall by 221 mg/d (P < .001), including within racial groups (195 mg/d for black women, P = .04, and 229 mg/d for white women, P < .001). Dairy was the primary calcium source for both groups (55% of intake for black women and 57% of intake for white women).

Conclusion

The CFFFQ can be used to identify postmenopausal women with inadequate calcium intakes (<800 mg/d) and to identify key sources of dietary calcium. Older black women consume less daily calcium than do older white women.     

Primary school children from northeast Thailand are not at risk of selenium deficiency

Selenium has important roles as an antioxidant, in thyroid hormone metabolism, redox reactions, reproduction and immune function, but information on the selenium status of Thai children is limited. We have assessed the selenium status of 515 northeast Thai children (259 males; 256 females) aged 6 to 13 years from 10 rural schools in Ubon Ratchthani province. Serum selenium (n=515) was analyzed by Graphite Furnace Atomic Absorption Spectrophotometry and dietary selenium intake by Hydride Generation Absorption Spectrophotometry from one-day duplicate diet composites, from 80 (40 females; 40 males) randomly selected children. Inter-relationships between serum selenium and selenium intakes, and other biochemical micronutrient indices were also examined. Mean (SD) serum selenium was 1.46 (0.24) micro mol/L. Concentrations were not affected by infection or haemoglobinopathies, but were dependent on school (P< 0.001), sex (P=0.038), and age group (P=0.003), with serum zinc as a significant covariate. None of the children had serum selenium concentrations indicative of clinical selenium deficiency (i.e. <0.1 micro mol/L). Significant correlations existed between serum selenium and serum zinc (r= 0.216; P < 0.001), serum retinol (r = 0.273; P < 0.001), urinary iodine (r = -0.110; P = 0.014), haemoglobin (r = 0.298; P <0.001), and haematocrit (r = 0.303; P< 0.001). Mean (SD) dietary selenium intake was 46 (22) micro g/d. Children with low serum selenium concentrations had a lower mean selenium intake than those with high serum selenium concentrations (38 +/- 17 vs.51 +/- 24 micro g/d; P< 0.010). In conclusion, there appears to be no risk of selenium deficiency among these northeast Thai children.     

Validity and reproducibility of an iodine‐specific food frequency questionnaire to estimate dietary iodine intake in older Australians

Aim: Iodine deficiency, which has adverse effects on health has re‐emerged in Australia. The present study aimed to develop and validate a novel iodine‐specific food frequency questionnaire for use in older Australians. Methods: A 49‐item food frequency questionnaire that included iodine‐rich foods was constructed and administered in 84 men and women aged 60–95 years with normal cognitive function. Dietary iodine intake assessed by the food frequency questionnaire was validated against three repeated 24‐hour dietary recalls. Urinary spot iodine concentrations were selected as iodine intake biomarker. Agreement between the two dietary methods was determined using a Bland–Altman plot and intra‐class coefficients. Correlations between dietary and urinary iodine were assessed. Forty‐three participants repeated the questionnaire after 9 months for reproducibility. Results: Mean iodine intake measured by the food frequency questionnaire and 24‐hour dietary recalls did not differ significantly (P= 0.870). The two methods were moderately correlated (r = 0.377; P < 0.05) and the Bland–Altman plots demonstrated an acceptable level of agreement (P= 0.870). Despite an association (r = 0.230; P < 0.05) between urinary iodine concentrations and 24‐hour dietary recalls, the food frequency questionnaire was not associated with urinary iodine concentration (r = 0.094; P= 0.40). The method of triads showed coefficients of 0.238 (urinary iodine), 0.953(food frequency questionnaire), 0.396 (24‐hour dietary recall) with the unknown true value. Conclusion: A short food frequency questionnaire to assess habitual dietary iodine intake in older Australians has been shown to be valid at the group level with regard to categorising individuals according to their habitual iodine intake. Reproducibility of the food frequency questionnaire remains to be demonstrated.     

Riboflavin status: Dietary intake,urinary excretion,and erythrocyte glutathione reductase coefficient activity of female university students

The riboflavin status of 58 healthy, non-pregnant female university students was investigated. Riboflavin nutriture was assessed by using dietary intake and biochemical data. Riboflavin intakes were calculated from three-day diet records using a computer program based on nutrient values from Agriculture Handbook No. 8. Urinary riboflavin (24 hr) was determined by fluorometric analysis. Erythrocyte glutathione reductase activity coefficients (EGRACs) were obtained using the automated flavin adenine dinucleotide-dependent glutathione reductase assay. The mean riboflavin intake was 1.39±0.49 mg/day (mean±SD). The mean urinary riboflavin was 0.44±0.32 mg/day, and the mean EGRAC was 1.21±0.12. There was a significant positive correlation between dietary riboflavin intake with energy intake (r=0.581, p<0.001) and protein intake (r=0.749, p<0.001). Riboflavin excretion was found to have significant positive correlation with riboflavin, protein, and energy intakes. A negative correlation between riboflavin excretion and EGRAC was also observed (r=−0.305, p<0.05). The riboflavin status of most of the subjects (90%) of the study appears to have been adequate as assessed by dietary intakes, urinary excretions, and EGRAC values.