Lena Davidsson

A micronised, dispersible ferric pyrophosphate with high relative bioavailability in man.

Ferric pyrophosphate is a water-insoluble Fe compound used to fortify infant cereals and chocolate-drink powders as it causes no organoleptic changes to the food vehicle. However, it is only of low absorption in man. Recently, an innovative ferric pyrophosphate has been developed (Sunactive Fe trade mark ) based on small-particle-size ferric pyrophosphate (average size 0.3 microm) mixed with emulsifiers, so that it remains in suspension in liquid products. The aim of the present studies was to compare Fe absorption of micronised, dispersible ferric pyrophosphate (Sunactive Fe trade mark ) with that of ferrous sulfate in an infant cereal and a yoghurt drink. Two separate Fe absorption studies were made in adult women (ten women/study). Fe absorption was based on the erythrocyte incorporation of stable isotopes ((57)Fe and (58)Fe) 14 d after the intake of labelled test meals of infant cereal (study 1) or yoghurt drink (study 2). Each test meal was fortified with 5 mg Fe as ferrous sulfate or micronised, dispersible ferric pyrophosphate. Results are presented as geometric means. There was no statistically significant difference between Fe absorption from micronised, dispersible ferric pyrophosphate- and ferrous sulfate-fortified infant cereal (3.4 and 4.1 % respectively; P=0.24) and yoghurt drink (3.9 and 4.2 % respectively; P=0.72). The results of the present studies show that micronised, dispersible ferric pyrophosphate is as well absorbed as ferrous sulfate in adults. The high relative Fe bioavailability of micronised, dispersible ferric pyrophosphate indicates the potential usefulness of this compound for food fortification.

Approaches to Improve Iron Bioavailability from Complementary Foods

The importance of trace element bioavailability in the etiology of nutritional deficiencies, for example in the etiology of iron deficiency and iron deficiency anemia, can be expected to be most pronounced in individuals with high requirements. Of special concern is the situation in poor communities where infants and young children are consuming monotonous, cereal-based diets. Traditionally, cereal-based gruels are often one of the first semisolid foods to be introduced into the infants diet. These foods can be expected to have low energy and nutrient density as well as low bioavailability of iron due to the presence of phytic acid. Ascorbic acid is a potent enhancer of non-heme iron absorption that can overcome the inhibiting effect of phytic acid when present in high enough quantities. However, home prepared complementary foods based on cereals and legumes contain negligible amounts of ascorbic acid unless ascorbic acid-rich foods are mixed with the cereal or consumed at the same time. Different approaches to improve iron bioavailability from plant-based complementary foods, e.g., by enzymatic degradation of phytic acid and/or by increased consumption of ascorbic acid-rich foods, should be explored and adapted to local conditions. In addition, there is a need to evaluate efficacy and effectiveness of strategies to increase the dietary intake of bioavailable iron by dietary diversification and food fortification under realistic conditions.

Iron absorption from ferrous fumarate in adult women is influenced by ascorbic acid but not by Na2EDTA.

Ascorbic acid and Na2EDTA enhance Fe absorption from the water-soluble Fe compound FeSO4 but their effect on poorly water-soluble Fe compounds such as ferrous fumarate is less well established. In the present study, the effects of ascorbic acid and Na2EDTA on Fe absorption from ferrous fumarate were evaluated in adult women (ten women/study) from the erythrocyte incorporation of Fe stable isotopes ((57)Fe or (58)Fe) 14 d after administration. Two separate studies were made with test meals of Fe-fortified infant cereal (5 mg Fe/meal). Data were evaluated by paired t tests and the results are presented as geometric means. In study 1a, the comparison between Fe absorption from ferrous fumarate- and FeSO4-fortified cereal showed that adult women absorb Fe as well from ferrous fumarate as from FeSO4 (3.0 and 3.1 % respectively, P=0.85). After addition of Na2EDTA (Na2EDTA:fortification Fe molar ratio of 1:1), Fe absorption from FeSO4 was significantly higher than from ferrous fumarate (5.3 v. 3.3 % respectively, P<0.01; study 1b). In study 2, Fe absorption was compared from ferrous fumarate-fortified meals with and without ascorbic acid added at a 4:1 molar ratio (relative to fortification Fe) and the results showed that ascorbic acid increased Fe absorption from ferrous fumarate significantly (6.3 v. 10.4 %, P=0.02). The results of the present studies show that Fe absorption from ferrous fumarate is enhanced by ascorbic acid but not by Na2EDTA, thus emphasising that not all findings from Fe absorption studies made with FeSO4 can be extrapolated to Fe compounds with different solubility properties.

Iron absorption from experimental infant formulas based on pea (Pisum sativum)-protein isolate : the effect of phytic acid and ascorbic acid

Infant formula based on pea (Pisum sativum)-protein isolate has been suggested as an alternative to soybean formula in countries where soybean is not a native crop, or when soybean protein cannot be used due to allergic reactions or intolerances. In the present study, Fe absorption from experimental infant formulas based on pea-protein isolate was measured in healthy non-anaemic young women. The influence of phytic acid and ascorbic acid on Fe absorption was evaluated, using a stable-isotope technique based on incorporation of Fe stable-isotope labels into erythrocytes 14 d after administration. Geometric mean Fe absorption increased from 20.7 (+1 SD 41.6, -1 SD 10.3) % to 33.1 (+1 SD 58.6, -1 SD 18.7) %; (P < 0.0001; n 10) after enzymic degradation of virtually all phytic acid. Doubling the molar ratio Fe:ascorbic acid from 1:2.1 to 1:4.2 in the infant formula with native phytic acid content also increased Fe absorption significantly (P < 0.0001; n 10); geometric mean Fe absorption increased from 14.8 (+1 SD 32.1, -1 SD 6.8) % to 22.1 (+1 SD 47.2, -1 SD 10.4) %. These results confirm the inhibitory and enhancing effects of phytic acid and ascorbic acid respectively on Fe absorption, but also indicate relatively high fractional Fe absorption from the pea-protein-based formulas. After adjusting for differences in Fe status, our data indicate that Fe absorption from dephytinised pea protein might be less inhibitory than dephytinised soybean protein as measured in a previous study (Hurrell et al. 1998).

Dephytinisation of soyabean protein isolate with low native phytic acid content has limited impact on mineral and trace element absorption in healthy infants

Infant formulas based on soyabean protein isolate are often used as an alternative to cows-based formulas. However, the presence of phytic acid in soya formulas has raised concern about the absorption of trace elements and minerals from these products. The aim of the present study was to evaluate mineral and trace element absorption from regular and dephytinised soya formula in healthy infants. Soyabean protein isolate with a relatively low native content of phytic acid was used for production of a regular soya formula (300 mg phytic acid/kg liquid formula) and an experimental formula was based on dephytinised soya protein isolate (<6 mg phytic acid/kg liquid formula). Using a crossover study design, apparent mineral and trace element absorptions were measured by a stable isotope technique based on 72 h faecal excretion of non-absorbed stable isotopes (Zn, Fe, Cu and Ca) and by the chemical balance technique (Mn, Zn, Cu and Ca) in nine infants (69-191 d old). Fe absorption was also measured by erythrocyte incorporation 14 d after intake. The results from the present study demonstrated that Zn absorption, measured by a stable isotope technique, was significantly greater after dephytinisation (mean value 16.7 v. 22.6 %; P=0.03). No other statistically significant differences between the two formulas were observed. The nutritional benefit of dephytinisation was marginal in the present study. Based on these results, the use of soyabean protein isolate with low native content of phytic acid should be promoted for production of soya formulas and adequate addition of ascorbic acid to enhance Fe absorption should be ensured in the products.

Comparison of urinary monitoring, faecal monitoring and erythrocyte analysis of stable isotope labels to determine magnesium absorption in human subjects

We have evaluated urinary monitoring and erythrocyte analysis to determine Mg absorption in human subjects as alternatives to the conventional technique of faecal monitoring by stable-isotope techniques. Ten healthy adults received 2.2 mmol (25)Mg in water, together with wheat bread, followed 15 min later by intravenous injection of 0.6 mmol (26)Mg (day 1). Brilliant blue and Yb (given on day 0 and day 1 respectively) served as qualitative and quantitative faecal markers. Urine was collected for 6 d after test meal intake. Complete collections of faeces were made until excretion of the second brilliant blue marker (given on day 7). Mg isotope ratios were determined by thermal ionisation-MS in urine and faeces and by inductively coupled plasma-MS in erythrocytes. Absorption was determined based on: (1) 6 d urine pools; (2) 24 h urine pools (collected 22-46 h after test meal intake); (3) erythrocytes from a blood sample drawn on day 14; (4) complete 6 d faecal pools; (5) faecal pools based on the first three consecutive stools after excretion of the first brilliant blue marker. Differences in mean Mg absorption (42 44 %) were statistically insignificant between techniques, except when based on 6 d urine pools for which the value was significantly lower (33 (sd 7) %, P=0.0003, ANOVA). The results indicate that Mg absorption can be determined from 24 h urine pools or erythrocytes obtained 14 d after test meal intake, an alternative method to the more time-consuming and labour-intense faecal monitoring. The choice of technique depends on practical and financial considerations.

The effect of retinyl palmitate added to iron-fortified maize porridge on erythrocyte incorporation of iron in African children with vitamin A deficiency.

Retinyl palmitate added to Fe-fortified maize bread has been reported to enhance Fe absorption in adult Venezuelan subjects but not in Western Europeans. It is not known to what extent these results were influenced by differences in vitamin A status of the study subjects. The objective of the present study was to evaluate the influence of retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe in children with vitamin A deficiency, before and after vitamin A supplementation. Erythrocyte incorporation of Fe-stable isotopes was measured 14 d after intake of maize porridge (2.0 mg Fe added as ferrous sulfate) with and without added retinyl palmitate (3.5 micromol; 3300 IU). The study was repeated 3 weeks after vitamin A supplementation (intake of a single dose of 210 micromol retinyl palmitate; vitamin A capsule). Vitamin A status was evaluated by the modified relative dose-response (MRDR) technique. Retinyl palmitate added to the test meal reduced the geometric mean erythrocyte incorporation of Fe at baseline from 4.0 to 2.6 % (P=0.008, n 13; paired t test). At 3 weeks after vitamin A supplementation, geometric mean erythrocyte incorporation was 1.9 and 2.3 % respectively from the test meal with and without added retinyl palmitate (P=0.283). Mean dehydroretinol:retinol molar ratios were 0.156 and 0.125 before and after intake of the single dose of 210 micromol retinyl palmitate; vitamin A capsule (P=0.15). In conclusion, retinyl palmitate added to the labelled test meals significantly decreased erythrocyte incorporation of Fe in children with vitamin A deficiency at baseline but had no statistically significant effect 3 weeks after vitamin A supplementation. The difference in response to retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe before and after intake of the vitamin A capsule indicates, indirectly, changes in vitamin A status not measurable by the MRDR technique. The lack of conclusive data on the effect of retinyl palmitate on Fe absorption indicates the complexity of the interactions between vitamin A status, dietary vitamin A and Fe metabolism.