This algorithm has several applications. It can be used to predict iron absorption from various diets, to estimate the effects expected by dietary modification, and to translate physiologic into dietary iron requirements from different types of diets.

Objective: To relate meal pattern of Swedish adolescents to food choice, nutrient intake and other lifestyle factors. Design: Cross-sectional study including diet history and interview about smoking, ethnicity, social factors and retrospectively collected data of menarche and growth. Setting: School setting, Göteborg, Sweden. Subjects: A total of 611 boys and 634 girls in grade 9 (15-16 y). Results: The majority of the students, 65% of the boys and 52% of the girls, consumed three main meals daily. The in-between meals, however, contributed the major part of the energy intake. The energy intake was 12.973.5 MJ (mean7s.d.) for boys and 9.072.5 MJ for girls. Irregular breakfast eating, 12% of the boys and 24% of the girls, was related to negative lifestyle factors where smoking was the strongest, odds ratio 3.8 (95% CI: 2.6-5.4) and to irregular intake of lunch and dinner. These boys and girls had a food choice including a higher percentage of energy from snack food (26% vs 20% and 19% in boys and girls respectively, all Po0.001), mostly consumed between the main meals. These groups had significantly lower intakes of micronutrients, but higher intakes of sucrose and alcohol compared to the groups with regular breakfast intake. Girls omitting breakfasts and lunches (8%) also had a less healthy food choice and the poorest nutrient intake. These girls had matured earlier, with menarche age of 12.271.1 y vs 12.971.0 y (Po0.001) in girls with regular main meal intake. Conclusions: Meal pattern with omission of breakfast or breakfast and lunch was related to a clustering of less healthy lifestyle factors and food choice leading to a poorer nutrient intake.

The dose-dependent inhibitory effect of sodium phytate on iron absorption was studied in man by serving wheat rolls containing no phytates and rolls to which various amounts (seven dose levels between 2 and 250 mg expressed as phytate phosphorus) were added just before serving. Fe in the two kinds of rolls was labeled with two radioisotopes of Fe (55Fe, 59Fe) and the rolls were served on alternate days. The inhibition of Fe absorption was strongly related to the amount of phytate added; 2 mg inhibited absorption by 18%, (p less than 0.001), 25 mg by 64% (p less than 0.001), and 250 mg by 82% (p less than 0.001). The addition of ascorbic acid significantly counteracted the inhibition whereas the corresponding effect of meat was less well defined and only seen at the highest phytate level. The marked inhibition of Fe absorption by phytates and the significant counteracting effect of ascorbic acid have wide nutritional implications.

Dietary iron requirements are dependent on the amount and availability of food iron ingested. On the basis of recent studies of food iron absorption employing extrinsic tag techniques, the availability of heme iron has been defined and estimates of the availability of nonheme iron based on the amounts of enhancing substances appear possible. A model has been developed whereby the availability of iron in a given meal may be estimated. Calculations are made on a meal basis of 1) the amount of heme iron and its availability, and 2) the amount of nonheme iron and its availability as influenced by the meal's content of enhancing factors. Examples of these calculations are provided.

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