Approaches used to estimate bioavailability when deriving dietary reference values for iron and zinc in adults

This review aims to describe approaches used to estimate bioavailability when deriving dietary reference values (DRV) for iron and zinc using the factorial approach. Various values have been applied by different expert bodies to convert absorbed iron or zinc into dietary intakes, and these are summarised in this review. The European Food Safety Authority (EFSA) derived zinc requirements from a trivariate saturation response model describing the relationship between zinc absorption and dietary zinc and phytate. The average requirement for men and women was determined as the intercept of the total absorbed zinc needed to meet physiological requirements, calculated according to body weight, with phytate intake levels of 300, 600, 900 and 1200 mg/d, which are representative of mean/median intakes observed in European populations. For iron, the method employed by EFSA was to use whole body iron losses, determined from radioisotope dilution studies, to calculate the quantity of absorbed iron required to maintain null balance. Absorption from the diet was estimated from a probability model based on measures of iron intake and status and physiological requirements for absorbed iron. Average dietary requirements were derived for men and pre- and post-menopausal women. Taking into consideration the complexity of deriving DRV for iron and zinc, mainly due to the limited knowledge on dietary bioavailability, it appears that EFSA has made maximum use of the most relevant up-to-date data to develop novel and transparent DRV for these nutrients

Modeling tool for calculating dietary iron bioavailability in iron-sufficient adults

Background: Values for dietary iron bioavailability are required for setting dietary reference values. These are estimated from predictive algorithms, nonheme iron absorption from meals, and models of iron intake, serum ferritin concentration, and iron requirements. Objective: We developed a new interactive tool to predict dietary iron bioavailability. Design: Iron intake and serum ferritin, a quantitative marker of body iron stores, from 2 nationally representative studies of adults in the United Kingdom and Ireland and a trial in elderly people in Norfolk, United Kingdom, were used to develop a model to predict dietary iron absorption at different serum ferritin concentrations. Individuals who had raised inflammatory markers or were taking iron-containing supplements were excluded. Results: Mean iron intakes were 13.6, 10.3, and 10.9 mg/d and mean serum ferritin concentrations were 140.7, 49.4, and 96.7 mg/L in men, premenopausal women, and postmenopausal women, respectively. The model predicted that at serum ferritin concentrations of 15, 30, and 60 mg/L, mean dietary iron absorption would be 22.3%, 16.3%, and 11.6%, respectively, in men; 27.2%, 17.2%, and 10.6%, respectively, in premenopausal women; and 18.4%, 12.7%, and 10.5%, respectively, in postmenopausal women. Conclusions: An interactive program for calculating dietary iron absorption at any concentration of serum ferritin is presented. Differences in iron status are partly explained by age but also by diet, with meat being a key determinant. The effect of the diet is more marked at lower serum ferritin concentrations. The model can be applied to any adult population in whom representative, good-quality data on iron intake and iron status have been collected. Values for dietary iron bioavailability can be derived for any target concentration of serum ferritin, thereby giving risk managers and public health professionals a flexible and transparent basis on which to base their dietary recommendations. This trial was registered at clinicaltrials.gov as NCT01754012

Iron bioavailability: UK Food Standards Agency workshop report

The UK Food Standards Agency convened a group of expert scientists to review current research investigating factors affecting iron status and the bioavailability of dietary iron. Results presented at the workshop show menstrual blood loss to be the major determinant of body iron stores in premenopausal women. In the presence of abundant and varied food supplies, the health consequences of lower iron bioavailability are unclear and require further investigatio

Lead exposure in an Italian population: Food content, dietary intake and risk assessment

Background and aim: Lead is a highly toxic heavy metal released into the environment after natural and anthropogenic activities. Excluding populations in occupations where there is possible lead contamination, food is the major source of human exposure. In this study, we determined lead contamination in food and beverages consumed in a Northern Italy community and performed a health risk assessment. Methods: We collected a total of 908 food samples and measured lead levels using inductively coupled plasma mass spectrometry. Using a validated food frequency questionnaire, we assessed the dietary habits and estimated daily lead dietary intakes in a sample of 719 adult individuals. We performed risk assessment using a benchmark dose and margin of exposure approach, based on exposure levels for both adverse effect of systolic blood pressure and chronic kidney disease. Results: Foods with the highest lead levels include non-chocolate confectionery (48.7 µg/kg), leafy (39.0 µg/kg) and other vegetables (42.2 µg/kg), and crustaceans and molluscs (39.0 µg/kg). The estimated mean lead intake was 0.155 µg/kg bw-day in all subjects, with little lower intakes in men (0.151 µg/kg bw-day) compared to women (0.157 µg/kg bw-day). Top food contributors were vegetables, cereals, and beverages, particularly wine. In relation to risk assessment, the estimated dietary intake was lower than levels associated with cardiovascular risk and nephrotoxicity. Conclusions: Our study provides an updated assessment of lead food contamination and dietary exposure in a Northern Italian community. The margin of exposure risk assessment approach suggests that risk of detrimental effects due to dietary lead intake is low in the investigated population. Nonetheless, these exposure levels for adverse effects are not reference health standards, and no safety threshold value can be established for lead. As a consequence, other and more subtle adverse effects may still occur in vulnerable and occupationally exposed individuals, particularly in relation to the nervous system

Sodium and potassium content of foods consumed in an Italian population and the impact of adherence to a Mediterranean diet on their intake

High sodium and low potassium intakes are associated with increased levels of blood pressure and risk of cardiovascular diseases. Assessment of habitual dietary habits are helpful to evaluate their intake and adherence to healthy dietary recommendations. In this study, we determined sodium and potassium food-specific content and intake in a Northern Italy community, focusing on the role and contribution of adherence to Mediterranean diet patterns. We collected a total of 908 food samples and measured sodium and potassium content using inductively coupled plasma mass spectrometry. Using a validated semi-quantitative food frequency questionnaire, we assessed habitual dietary intake of 719 adult individuals of the Emilia-Romagna region. We then estimated sodium and potassium daily intake for each food based on their relative contribution to the overall diet, and their link to Mediterranean diet patterns. The estimated mean sodium intake was 2.15 g/day, while potassium mean intake was 3.37 g/day. The foods contributing most to sodium intake were cereals (33.2%), meat products (24.5%, especially processed meat), and dairy products (13.6%), and for potassium they were meat (17.1%, especially red and white meat), fresh fruits (15.7%), and vegetables (15.1%). Adherence to a Mediterranean diet had little influence on sodium intake, whereas potassium intake was greatly increased in subjects with higher scores, resulting in a lower sodium/potassium ratio. Although we may have underestimated dietary sodium intake by not including discretionary salt use and there may be some degree of exposure misclassification as a result of changes in food sodium content and dietary habits over time, our study provides an overview of the contribution of a wide range of foods to the sodium and potassium intake in a Northern Italy community and of the impact of a Mediterranean diet on intake. The mean sodium intake was above the dietary recommendations for adults of 1.5–2 g/day, whilst potassium intake was only slightly lower than the recommended 3.5 g/day. Our findings suggest that higher adherence to Mediterranean diet patterns has limited effect on restricting sodium intake, but may facilitate a higher potassium intake, thereby aiding the achievement of healthy dietary recommendations