Estimation of selenium intake in Switzerland in relation to selected food groups.

The selenium concentration in foods was analysed in order to identify principal sources of this trace element in Switzerland. Selenium intake estimations based on three different approaches were carried out. From the relationship between intake and serum/plasma concentration, the selenium intake was estimated to 66 µg day(-1). The second approach based on measured food groups combined with consumption statistics; and the third approach consisted of duplicate meal samples. With the last two methods, over 75% of the serum/plasma based intake was confirmed. Swiss pasta made of North American durum wheat was the food with the highest contribution to the dietary intake, followed by meat. The strong decrease in imports of selenium-rich North American wheat of the last years was not reflected in the present intake estimations. It appears that this intake loss was compensated by a consumption increase of other foods. Compared with former intake estimations, selenium intake seems to be in Switzerland nearly constant for the last 25 years.

Mechanisms of action of beta-glucan in postprandial glucose metabolism in healthy men.

OBJECTIVE: To assess whether beta-glucan (which is fermented in the colon) lowers postprandial glucose concentrations through mechanisms distinct from a delayed carbohydrate absorption and inhibits de novo lipogenesis. DESIGN: Administration of frequent small meals each hour over 9 h allows a rate of intestinal absorption to be reached which is independent of a delayed absorption. A group of 10 healthy men received either an isoenergetic diet containing 8.9 g/day beta-glucan or without beta-glucan for 3 days. On the third day, the diet was administered as fractioned meals ingested every hour for 9 h. SETTING: Laboratory for human metabolic investigations. SUBJECTS: Ten healthy male volunteers. MAIN OUTCOME MEASURES: Plasma glucose and insulin concentrations, glucose kinetics, glucose oxidation, de novo lipogenesis. RESULTS: On the third day, plasma glucose and free fatty acid concentrations, carbohydrate and lipid oxidation, and energy expenditure were identical with beta-glucan and cellulose. Plasma insulin concentrations were, however, 26% lower with beta-glucan during the last 2 h of the 9 h meal ingestion. Glucose rate of appearance at steady state was 12% lower with beta-glucan. This corresponded to a 21% reduction in the systemic appearance rate of exogenous carbohydrate with beta-glucan, while endogenous glucose production was similar with both diets. De novo lipogenesis was similar with and without beta-glucan. CONCLUSION: Administration of frequent meals with or without beta-glucan results in similar carbohydrate and lipid metabolism. This suggests that the lowered postprandial glucose concentrations which are observed after ingestion of a single meal containing beta-glucan are essentially due to a delayed and somewhat reduced carbohydrate absorption from the gut and do not result from the effects of fermentation products in the colon.

An evaluation of EDTA compounds for iron fortification of cereal-based foods.

Fe absorption was measured in adult human subjects consuming different cereal foods fortified with radiolabelled FeSO4, ferrous fumarate or NaFeEDTA, or with radiolabelled FeSO4 or ferric pyrophosphate in combination with different concentrations of Na2EDTA. Mean Fe absorption from wheat, wheat-soyabean and quinoa (Chenopodium quinoa) infant cereals fortified with FeSO4 or ferrous fumarate ranged from 0.6 to 2.2%. For each infant cereal, mean Fe absorption from ferrous fumarate was similar to that from FeSO4 (absorption ratio 0.91-1.28). Mean Fe absorption from FeSO4-fortified bread rolls was 1.0% when made from high-extraction wheat flour and 5.7% when made from low-extraction wheat flour. Fe absorption from infant cereals and bread rolls fortified with NaFeEDTA was 1.9-3.9 times greater than when the same product was fortified with FeSO4. Both high phytate content and consumption of tea decreased Fe absorption from the NaFeEDTA-fortified rolls. When Na2EDTA up to a 1:1 molar ratio (EDTA:Fe) was added to FeSO4-fortified wheat cereal and wheat-soyabean cereal mean Fe absorption from the wheat cereal increased from 1.0% to a maximum of 5.7% at a molar ratio of 0.67:1, and from the wheat-soyabean cereal from 0.7% to a maximum of 2.9% at a molar ratio of 1:1. Adding Na2EDTA to ferric pyrophosphate-fortified wheat cereal did not significantly increase absorption (P > 0.05). We conclude that Fe absorption is higher from cereal foods fortified with NaFeEDTA than when fortified with FeSO4 or ferrous fumarate, and that Na2EDTA can be added to cereal foods to enhance absorption of soluble Fe-fortification compounds such as FeSO4.

The influence of different cereal grains on iron absorption from infant cereal foods.

Iron absorption from various cereal grains was evaluated in the present study to identify possible preferences for the preparation of infant weaning foods. In six separate studies, four radioiron absorption tests were performed in each of 57 volunteer subjects by using a sequential double-isotopic method. Serum ferritin concentration was used to adjust for the effect of differences in the iron status of subjects participating in separate studies. Identical commercial processing and test meal composition were used to evaluate iron absorption from 50 g cooked cereal prepared from rice, wheat, maize, oats, millet, and sweet or bitter quinoa. In an initial evaluation of cereals fortified with 2.5 mg Fe as FeSO4, geometric mean absorption values were uniformly < 1% for all cereals and were not significantly different. In subsequent studies, percentage iron absorption was enhanced by either eliminating the fortifying iron or adding 50 mg ascorbic acid to the test meal. The effect was similar for most of the cereals tested with a composite mean increase in absorption of 37% when fortifying iron was removed and 270% when ascorbic acid was added. There was a strong inverse correlation between iron absorption and the phytate content of different cereals. Except for a modestly lower absorption of iron from quinoa and a remarkably higher absorption from one lot of maize, we conclude that the type of cereal grain has little influence on iron bioavailability of infant cereals. On the other hand, modification in the milling and processing methods for cereal grains that reduce their content of phytic acid is likely to improve iron availability significantly.

Iron fortification of infant cereals: a proposal for the use of ferrous fumarate or ferrous succinate.

Hemoglobin-repletion tests in rats, organoleptic studies, and iron-absorption studies in humans were used to search for Fe sources with high bioavailability that could be added to infant cereals as alternatives to the Fe compounds currently used for fortification. From rat and organoleptic studies on 11 alternative Fe sources, ferrous fumarate, ferrous succinate, and ferric saccharate were selected as the most suitable for infant-cereal fortification and, by use of radioactive labels, absorption of those compounds from fortified cereal was measured in adult human volunteers. There was no difference in absorption between ferrous fumarate and ferrous sulfate whereas the values for ferrous succinate, ferrous saccharate (10% Fe), and ferric pyrophosphate were 92%, 74%, and 39% of the ferrous sulfate values, respectively. We conclude that ferrous fumarate and ferrous succinate are highly available Fe sources in man that can be used to fortify infant cereals without causing fat oxidation or discoloration.