A HPLC method was developed for separation and quantitative determination of inositol tri-, tetra-, penta-, and hexaphosphates. The method included extraction of inositol phosphates with HCI, separation of the inositol phosphates from the crude extract by ion-exchange chromatography, and ion-pair C18 reverse phase HPLC analysis using formic acid/methanol and tetrabutylammonium hydroxide in the mobile phase. The inositol 3–6 phosphates of raw and extruded bran, soy flour, and intestinal contents were determined by HPLC and compared to phytate determinations by two iron precipitation methods. Inositol 3–5 phosphates were found in extruded products and intestinal contents. The HPLC method was rapid and gave reproducible values, which differed from those obtained by the precipitation methods in some samples.

HPLC Method for Determination of inositol Tri-, Tetra-, Penta-, and Hexaphosphates in Foods and Intestinal Contents

The effect of leavening of bread containing bran on the phytic acid content and on zinc absorption in man was studied. Twenty breads with leavening times varying from 0 to 120 h were prepared. The breads contained 250 g wheat bran/kg flour. The phytic acid content was determined after baking. The phytic acid content of bread containing bran was reduced to about 40% after 2 h of leavening and to 15% after 2 d. No further decrease was observed. Zn absorption from single meals was determined using a radioisotope technique. Forty-two students volunteered for these studies. They were served a breakfast of milk, butter, bread and 10, 16 or 30 g bran served either raw or baked into the bread with fermentation times of 15 min, 45 min, 3 h or 16 h. One meal contained no bran, but phytate and Zn were added in amounts equivalent to the content of 10 g bran. The amount and percentage of Zn absorbed increased at each bran level as fermentation was prolonged. The percentage of Zn absorbed was reduced by increased bran content in the meal. It is concluded that the fermentation of bread containing bran reduces the phytic acid content and increases Zn absorption from such bread. This may be of importance to people subjected to diets with a high cereal content, especially in combination with a low animal-protein intake.

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Reduction of the phytate content of bran by leavening in bread and its effect on zinc absorption in man

Besides being important in the fermentation of foods and beverages, yeasts have shown numerous beneficial effects on human health. Among these, probiotic effects are the most well known health effects including prevention and treatment of intestinal diseases and immunomodulatory effects. Other beneficial functions of yeasts are improvement of bioavailability of minerals through the hydrolysis of phytate, folate biofortification and detoxification of mycotoxins due to surface binding to the yeast cell wall.

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Beneficial effects of probiotic and food borne yeasts on human health

Few data are available on bone density in late adolescence. We studied factors affecting peak bone density in females. Forty-three white girls, aged 13-20 yr, were studied. Integrated estrogen exposure over the pubertal years was obtained by a score based on physiological events known to reflect circulation estrogen levels. The subjects were selected to provide great variation in estrogen exposure. Bone mineral density (BMD) was measured by single photon absorptiometry (midradius) and dual photon absorptiometry (spine and first metatarsal of the foot). Weight, estrogen score, and testosterone levels were highly correlated with BMD of the spine, wrist, and foot (P less than 0.05). Age correlated positively only with the BMD of the wrist. Twenty-four girls reaching ages 18-20 yr in the 2 yr of observation were divided into groups reflecting low (less than 24), medium (25-48), and high (greater than or equal to 49) estrogen exposure. The lowest scoring groups had the lowest spine and wrist BMD (P less than 0.05). This group weighed less and had lower weight to height ratio (P less than 0.05), the lowest weight (P less than 0.05) during adolescence, the highest age of menarche, and the highest amount of fiber in the diet (P less than 0.05). These subjects were separated into low and high BMD groups. Those subjects with the lowest values for spine, wrist, and foot were found to have significantly lower estrogen exposure scores and lower weight/height ratios; in addition, low BMD of the foot was associated with higher activity levels. Thus, wrist and spine BMD are affected by estrogen exposure during adolescence and weight; foot BMD, in addition, was negatively affected by activity, suggesting that bone mass in the active adolescent is affected by the absence of estrogen exposure.

Effects of hormonal status on bone density in adolescent girls.

The effect of increasing levels of various protein sources on zinc absorption from a legume-based meal was studied in humans with the use of a radionuclide technique. The meals were extrinsically labelled with 65Zn and absorption was determined from measurements of the whole-body retention of the isotope. The mean fractional zinc absorption for the 13 meals was 24.7 +/- 6.9% and was only influenced by the protein content of the meal to a limited extent (r = 0.45). However, the amount of zinc absorbed from the meals was strongly correlated with both the protein (r = 0.85) and zinc content (r = 0.86): 5.9 +/- 1.7 mumol of zinc was absorbed from the basal bean meal which had the lowest protein content; the addition of low zinc chicken doubled the protein content and increased zinc absorption to 10.3 +/- 2.0 mumol; the addition of zinc-rich beef also doubled the protein content, however, zinc absorption was increased to 15.9 +/- 4.7 mumol. It is concluded that the zinc content of the main protein source of the diet determines the amount of zinc absorbed to a large extent. However, relatively small amounts of animal protein can significantly improve the value of a legume-based meal as a source of zinc.

Effect of Protein Level and Protein Source on Zinc Absorption in Humans

1. Studies on mineral absorption were carried out in ileostomy patients using the metabolic balance technique. The effect of wheat bran on the absorption of phosphorus, calcium, magnesium, zinc and iron was studied. The extent of digestion of bran phytate in the stomach and small intestine was also investigated. 2. Eight patients with well established conventional ileostomies were studied during two periods while on a constant low-fibre diet. In the second period, 16 g wheat bran/d (American Association of Cereal Chemists) was added to the diet. The amount of phytate-P, non-phytate-P, Ca, Mg, Zn and Fe was determined in the ileostomy contents and in duplicate portions of the diet. 3. Of the added bran phytate-P 24-61% was recovered in the ileostomy contents. In the bran period a significantly decreased amount of Zn was absorbed, while the apparent absorption of Fe and phytate-P increased and that of non-phytate-P, Ca and Mg remained constant. Due to the mineral content of bran, the relative absorption differed in some respects from the absolute absorption, being decreased for Zn, Mg and phytate-P but unchanged for Ca, Fe and non-phytate-P. 4. It is concluded that phytate is partly digested in the stomach and small intestine or possibly absorbed. Addition of 16 g bran/d to the diet does not seem to impair the mineral absorption from the small intestine except that of Zn.

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The effect of wheat bran on the absorption of minerals in the small intestine.

1. The absorption of zinc in humans from composite meals, was determined by extrinsic labelling of the meals with 65Zn and measurement of the whole-body retention of the radioisotope. 2. Low-Zn (mean 25 mumol) chicken meals with 150 g white bread or 225 g potatoes, carrots, turnips, cabbage or green peas were studied. The effect of a beet-pulp-fibre preparation used as a breakfast cereal, in bread and as a meat extender on Zn absorption was also studied. 3. The mean percentage absorption from the chicken meals with white bread, carrots and cabbage was significantly different from the meals with potatoes, turnips and green peas. When the amount of Zn in the meals was taken into account a slightly higher absorption was observed from the white-bread meal compared with the meals with potatoes and cabbage, while no differences were seen between the vegetable meals. 4. The beet-pulp-fibre preparation did not affect the extent of Zn absorption when used as a meat extender. The absorption of Zn was higher when the beet fibre was included in bread than when used as muesli. 5. The results obtained suggest that, besides the low-Zn content in vegetables, a large intake of vegetables or a pure-vegetable-fibre preparation has no significant effect on Zn availability from animal-protein-based meals.

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Claes Hasselblad

Papers

The effect of wheat bran on the absorption of minerals in the small intestine.

The effect of vegetables and beet fibre on the absorption of zinc in humans from composite meals.