Progress in breeding for trace minerals in staple crops

Staples are not considered an important source of minerals in the diet. However, because of high staple consumption, any increase in mineral concentration might well have a significant effect on human nutrition and health. The nutritional quality of staple crops (rice, cassava, wheat, maize and beans) can be improved by breeding. Studies have shown the potential to exploit the genetic variation in seed concentration of iron and other minerals without the general negative effect on yield of adding new traits. The relationship between yield and mineral concentration may be positive, particularly in mineral-deficient soil. Initial evaluations have shown that some crop varieties have high Fe, Zn and carotene in their edible portions. The next step for conventional breeding will be to study the genetics of trace mineral inheritance to determine the best selection technique. Initial investigations of the genetics for high iron in rice have indicated a complex mode of inheritance, demonstrating additive and dominant gene and environmental effects. Breeding strategies have been developed based on these genetic findings. The use of biotechnological tools, such as molecular marker-assisted selection, will significantly increase the pace and prospects of success for breeding to improve the nutritional value of staple food crops.     

Effects of aqueous soaking on the phytate and mineral contents and phytate:mineral ratios of wholegrain normal sorghum and maize and low phytate sorghum

Soaking of cereal grains has been suggested as a method to reduce their phytate content and hence increase their mineral availability. Whole and milled wholegrain, normal and low phytate sorghum and normal maize were studied. Soaking of unmilled sorghum and maize did not result in substantial reductions in phytate or mineral contents. With milled grains, phytate solubilisation was somewhat greater in maize than in sorghum after a short (1?h) soaking period but not after 6–12?h of soaking when practically all phytate had been solubilised. Also, with milled, low phyate sorghums, phytate solubilisation was not substantially higher than in their null controls. Soaking milled grain substantially reduced mineral contents and Ca?×?phytate:zinc molar ratios. However, the loss in soluble minerals could have a greater negative effect on mineral availability, compared to the positive effect of the phytate reduction. Thus, soaking does not seem to be a viable household method to improve sorghum and maize mineral availability.     

Fecal phytate excretion varies with dietary phytate and age in women

OBJECTIVE: Information on the excretion of dietary phytate in humans under different conditions is limited. The purpose of this study was to investigate fecal excretion of dietary phytate and phosphorus in a group of young and elderly women consuming high and low phytate diets. METHODS: Fifteen young and fourteen elderly women were fed two experimental diets, high phytate and low phytate, for 10 days each with a washout period of 10 days between the two diet periods. Duplicate diet samples from two different menus and complete fecal samples were collected for 5 days during each diet period and analyzed for phytate and phosphorus contents. Mean daily excretions and percentages of dietary intakes of phytate and phosphorus were calculated. RESULTS: Dietary phytate level does impact phytate excretion, but the effect was observed only in young subjects. Fecal phytate excretion of young subjects during the high phytate diet (313 mg/d) was significantly higher than during the low phytate diet (176 mg/d), however, that of elderly subjects did not vary with dietary phytate levels. Phosphorus excretion, net absorption, and apparent absorption rate were affected by dietary phytate level but not by the age of the subjects. CONCLUSIONS: Results of this study indicate that phytate degradation in the gastrointestinal tract is substantial and more variable in young women than in elderly women. The high capacity of phytate degradation in elderly subjects may be related to long-term phytate intake but needs further clarification. Both beneficial and adverse health effects of phytate need to be studied considering the long-term phytate intake and age of subjects as well as dietary phytate levels.     

A low temperature cleanup procedure for triazine herbicides in root crops

Conclusions Crop extracts of the triazine herbicides, atrazine and simazine, were suitably cleaned up by low temperature precipitation for glc and nitrogen detection. The use of this technique as a multiresidue cleanup method for the glc screening of pesticides may be extended to include these and other similar triazine herbicides. The ec detector was found to be unsuitable for triazine analysis using the low temperature cleanup technique on the crops studied.     

High prevalence of low dietary calcium, high phytate consumption, and vitamin D deficiency in healthy south Indians

BACKGROUND: Data on the vitamin D status of the population in a tropical country such as India have seldom been documented. Vitamin D deficiency is presumed to be rare. OBJECTIVE: The objective was to document the dietary habits and concentrations of serum calcium, 25-hydroxyvitamin D [25(OH)D], and parathyroid hormone of Indian urban and rural populations. DESIGN: Healthy urban (n = 943) and rural (n = 205) subjects were studied for their dietary pattern and concentrations of serum calcium, phosphorus, alkaline phosphatase, 25(OH)D, and immunoreactive parathyroid hormone. RESULTS: The daily dietary calcium intake of both the urban and rural populations was low compared with the recommended dietary allowances issued by the Indian Council of Medical Research. Dietary calcium and phosphorous were significantly lower in rural adults than in urban adults (P < 0.0001). The dietary phytate-to-calcium ratio was higher in rural subjects than in urban subjects (P < 0.0001). The 25(OH)D concentrations of the rural subjects were higher than those of urban subjects (P < 0.001), both men and women. In the rural subjects, 25(OH)D-deficient (<20 ng/mL), -insufficient (20-30 ng/mL), and -sufficient (>30 ng/mL) states were observed in 44%, 39.5%, and 16.5% of the men and 70%, 29%, and 1% of the women, respectively. In the urban subjects, 25(OH)D-deficient, -insufficient, and -sufficient states were observed in 62%, 26%, and 12% of the men and 75%, 19%, and 6% of the women, respectively. CONCLUSIONS: Low dietary calcium intake and 25(OH)D concentrations were associated with deleterious effects on bone mineral homeostasis. Prospective longitudinal studies are required to assess the effect on bone mineral density, a surrogate marker for fracture risk and fracture rates.     

Effects of Mediterranean diets with low and high proportions of phytate-rich foods on the urinary phytate excretion

Background  

Important health benefits have been reported recently to phytate intake. This includes the prevention of pathological calcifications such as renal calculi, dental calculi and cardiovascular calcification, due its action as crystallization inhibitor of calcium salts, and as preventive of cancer.     

植酸磷的测定──离子交换法

介绍用离子交换法测定植酸磷的含量。对消化终点、最适的提取时间、离子交换树脂的分离效果进行了试验。黄豆粉、窝窝头、豆腐干植酸测得值的变异系数分别为２．１６％、４．９２％、１．７８％，回收率依次为１０３．３８％、１０２．８１％、１０３．４１％。植酸标准品的植酸含量理论值为５７．６４％，本法测定值为５５．２３％，相对误差为２．１４％。本法的精密度及准确度均符合要求。     

Absorption of monoferric phytate by dogs.

Recent studies have shown that the iron in wheat is predominantly in the form of monoferric phytate (MFP). Unlike phytate complexed with two or more iron atoms, MFP is soluble at pH 7.0 and above and may therefore be a relatively available form of dietary iron. To examine this point, we tested iron absorption in adult dogs using a double radioisotope method and total body counting. When given without food, MFP was about one-half as available as ferrous sulphate at an iron-equivalent dose of 1.5 mg and only about one-seventh as available at a dose of 15 mg iron. When administered with food, MFP underwent complete isotopic exchange with the nonheme pool of dietary iron. When added to meals of either high or low iron availability in amounts that might be used for iron fortification, the absorption was the same for MFP iron as for the major pool of dietary inorganic iron.     

The effects of low dietary levels of DDT on breeding performance in hybrid mice

A combination of breeding experiments was used to study the effects of various levels of dietary DDT on the reproductive efficiency in mammals. The results of feeding B6D2F₁ hybrid mice 5, 10, or 20 ppm of DDT in the first breeding experiment showed an increase in litter size and number weaned over controls. Ten ppm of DDT caused increases over controls in the number born and alive on day 1 (P<0.05). DDT caused decreases in the weight of pups at 5 ppm on days 15 and 30 (P<0.05 and 0.01, respectively), at 10 ppm on day 15 (P<0.005), and at 20 ppm on day 30 (P<0.05).A second breeding experiment using 30, 60, or 120 ppm of DDT showed a general detrimental effect on reproduction. Thirty ppm DDT-fed animals produced fewer pups than controls (P<0.01) at days 1, 15, and 30, and the pups weighed less than controls at 30 days of age (P<0.05). DDT at 120 ppm resulted in fewer mice at birth and at 30 days of age (P<0.01) than control diet.The third, fourth, and fifth breeding experiments involved diets with 0, 5, 10, and 20 ppm of DDT and with the addition of a 40-ppm level in the third and fourth studies. The data showed larger litter sizes on days 1, 15, and 30 for DDT-fed animals.This investigation indicates that 5, 10, 20, or 40 ppm of DDT in the diet often results in larger litter sizes and more pups weaned than controls. Animals fed levels of 30, 60, or 120 ppm of DDT generally produced fewer offspring than did control animals. DDT-fed mice often weighed less before weaning than control pups.Although variable responses were found, it appears from these studies that environmental levels of DDT are not detrimental to the reproductive efficiency of mice and may under certain circumstances be beneficial.This work was supported in part by the Illinois Agricultural Experiment Station.     

Comparison of four methods for phytate analysis in plant-based foods

Plant-based staple diets common in low-income countries (LICs) often contain high levels of phytic acid (myo-inositol hexaphosphate, IP6), an inhibitor of zinc absorption. Depending on food source, handling and preparation, varying amounts of IP6 may be broken down to less phosphorylated inositol phosphates such as inositol tetra- and pentaphosphates (IP4, IP5) which differ from IP6 in their impact on zinc absorption. IP4 has little impact, whereas IP5’s impact is moderately reduced as compared with IP6. Therefore to accurately estimate the risk of zinc deficiency, values both for phytic acid and IP5 may be required. High-Performance Liquid chromatography (HPLC) can separate and quantify IP6 and its breakdown products but requires specialized equipment and expertise and is relatively time-consuming and expensive. We compared HPLC and three low-tech and widely accessible alternative methods via an analysis of a sample of typical LIC staple foods. The “ferric precipitation” method and the much simpler “HL” colorimetric assay provide accurate data but they only assay total inositol phosphates. A Polyacrylamide Gel Electrophoresis (PAGE) method can separate IP5 and IP6 from IP4 and other breakdown products, and can provide valid quantitative data for these compounds. Therefore PAGE, alone or in combination with a simple colorimetric assay like the HL method, is an accessible, low-tech alternative to HPLC for estimating dietary total phytate, IP6 and IP5, and represents an appropriate technology for LIC laboratories.     

Soybean phytate content: effect on calcium absorption

Absorption of calcium from soybeans with low and high phytate contents, intrinsically labeled with 45Ca, was measured in 16 normal women and compared in 15 of these same subjects with absorption of calcium from labeled milk. The average test load of calcium for all three sources was 2.45 mmol. Fractional calcium absorption (+/- SD) from the high-phytate soybeans averaged 0.310 +/- 0.070; from the low phytate soybeans, 0.414 +/- 0.074; and from milk, 0.377 +/- 0.056. The mean difference (+/- SEM) in fractional calcium absorption for the two phytate levels was 0.104 +/- 0.014 (P less than 0.001).     

Effect of dietary phytate on bioavailability of iron

Experiments were carried out on iron-chelating capacity of phytic acid in fortified and unfortified diets of whole wheat, white flour and wheat bran using albino rats in a 10-day balance study. The results revealed that gross digestibility was highest in control diet (93.25%), least in the wheat brain diet with added ferrous sulfate (86.70%) and intermediate in other diets. Among the unfortified and fortified diets, the highest amount of phytate was present in the diet having wheat bran (2.69–4.99 mg/g). Phytate concentration of the rat faeces followed the pattern of dietary phytate content of test diets. The data indicated high values for iron (200.00–236.64 mg/g) in fortified diets while in the unfortified diets, the value was the same (16.67 mg/g) except the casein diet, which contained 69.99 mg/g of iron. Iron concentration of the fat faeces ranged 16.25–23.50 mg/g; the higher value being in the excreta of animals given fortified diets. The casein diet had iron 46.75 mg/g. The overall results showed that the phytate absorption was relatively higher in groups fed fortified diets. Iron absorption almost followed the pattern of phytate absorption. Correlation co-efficient analysis showed insignificant relationship between iron and phytate absorption indicating little effect of dietary phytate on the biovailability of iron.     

Phytate, zinc, and calcium contents of 30 East African foods and their calculated phytate:Zn, Ca:phytate, and [Ca][phytate]/[Zn] molar ratios

Representative samples of 30 staple Malawian foods, raw and prepared “as eaten,” were analyzed for phytate using an anion-exchange method, and for calcium and zinc by flame atomic absorption spectrophotometry. Phytic acid contents expressed on a fresh weight (FW) basis ranged from 211–1089 mg/100 g for cereals and 166–1297 mg/100 g for legumes, to 4–97 mg/100 g for leaves, 10–59 mg/100 g for roots, and 11–25 mg/100 g for fruits. In general, leaves had the highest calcium content (81–514 mg/100 g FW), followed by kidney beans (90 mg/100 g FW), and dry pigeon peas (112 mg/100 g FW). The calcium content of other foods analyzed was relatively low. The zinc content of wild blight, cassava leaves, and okra leaves was comparable to that for the less refined cereals and legumes (i.e., > 1.0 mg/100 g FW), but higher than that of highly refined cereals, pumpkin leaves, chinese cabbage, and other foods analysed (i.e., < 1.0 mg/100 g FW). Cooking had no effect on the phytate content of cereals, but milling and fermentation reduced both the phytate and zinc contents of maize flour. The phytate:Zn molar ratios calculated for all cereals and most legumes analyzed were greater than 20:1. Corresponding Ca:phytate molar ratios were low. Fruits, except for mangoes, vegetables, and roots, had low phytate: Zn molar ratios, but their Ca:phytate and [Ca][phytate]/[Zn] molar ratios were high. Mangoes had high phytate:Zn, Ca:phytate, and [Ca][phytate]/[Zn] molar ratios. These analytical results suggest that the bioavailability of zinc in the Malawian diet is probably low, due to the high phytic acid content of the staple foods.     

Phytate levels in diverse rat tissues: influence of dietary phytate

Phytate (inositol hexaphosphate; InsP6) was determined in rat tissues fed on diets with different phytate contents, using a GC-mass detection methodology that permitted the evaluation of the total amount of this substance present in such tissues. The highest InsP6 concentrations were found in brain 5.89 x 10(-2)(SE 5.7 x 10(-3)) mg/g DM), whereas the concentrations detected in kidneys, liver and bone were similar to each other 1.96 x 10(-3) (SE 0.20 x 10(-3), 3.11 x 10(-3) (SE 0.24 x 10(-3), 1.77 x 10(-3) (SE 0.17 x 10(-3)) mg/g DM respectively) and 10-fold less than those detected in brain. When rats were fed on a purified diet in which InsP6 was undetectable, the InsP6 levels of the organs mentioned earlier decreased dramatically (9.0 x 10(-4), 3.8 x 10(-5), 1.4 x 10(-5) mg/g DM in brain, kidneys and liver respectively) and in some cases became undetectable (bone). The addition of InsP6 to this purified diet led to the increase of InsP6 levels in these tissues. This clearly demonstrated that the majority of the InsP6 found in organs and tissues has a dietary origin and is not a consequence of endogenous synthesis. Consequently, considering that InsP6 could be involved in some important biological roles, the value of any diet on supplying this substance is noteworthy.     

Effect of tetracalcium dimagnesium phytate on bone characteristics in ovariectomized rats

The aim was to evaluate the influence of dietary Ca-Mg-phytate consumption on the bone characteristics of ovariectomized rats, an animal model for postmenopausal osteoporosis. Twenty ovariectomized female Wistar rats were randomly assigned to two groups fed, respectively, with a non-phytate diet (AIN-76A) or the same diet enriched with 1% phytate (as the calcium magnesium salt, phytin). After 12 weeks of feeding the rats were sacrificed, and both femoral bones and L4 vertebra were removed from each rat. Bone mass, length, width, volume, and mineral density were measured, and the phosphorus, calcium, magnesium, and zinc contents of bones were determined. Deoxypyridinoline (a bone resorption marker) was measured in urine, and osteocalcin (a bone formation marker) was measured in serum. The calcium and phosphorus contents and bone mineral density were significantly higher in both femoral bones and L4 vertebra for phytate-treated rats in comparison to rats in the non-phytate group. Deoxypyridinoline was significantly increased in rats in the non-phytate treatment group. Ca-Mg-phytate consumption reduces bone mineral density loss due to estrogen deficiency. Thus, phytate exhibits effects similar to those of bisphosphonates on bone resorption and may be of use in the primary prevention of osteoporosis if larger studies in humans confirm these findings.     

Chromium status of the rat as affected by phytate

Interactions involving phytate and trace element absorption have largely dealt with iron and zinc. The purpose of this study was to explore the interaction of phytate as found in soy protein with Cr status. Male weanling Sprague-Dawley rats were assigned to 5 groups, 10 rats per group. The 5 groups had either ground beef (GB), textured soy protein (TSP), a combination of GB and TSP (GB:TSP), Torula yeast (TY), or TY with added Cr (TY+CR) as the protein source. At wk 4, 7, and 10, an intravenous glucose tolerance test (IVGTT) was conducted, while at wk 13 or 15 lipoprotein lipase activity (LPL), total plasma cholesterol and insulin were determined. All 5 groups had a glucose removal rate (GRR) of 2.7%/min or lower during wk 7 of the experiment. By wk 10, the GRR improved in TSP fed rats (p<0.05) and tended to improve in the TY+Cr, GB:TSP and GB fed animals. The fasting plasma insulin of the TY+Cr fed animals was significantly greater than the GB, TSP, and GB:TSP fed animals (p<0.05). Concurrent plasma glucose was not significantly different. Total plasma cholesterol was not significantly different among the 5 groups. In all groups, the fed LPL activity was significantly greater than the fasted LPL activity (p<0.05). These results suggest that 0.35% phytate as found in the TSP diet is not detrimental to Cr status.