Päivi Ekholm

Effects of nationwide addition of selenium to fertilizers on foods, and animal and human health in Finland: From deficiency to optimal selenium status of the population

Despite different geological features the Nordic countries are generally selenium-poor areas. In each country various factors such as food importation and life-style determine the selenium (Se) intake. Due to an extremely low Se intake in the 1970s in Finland, 0.025 mg/day, an official decision was made in 1984 to supplement multinutrient fertilizers with Se in the chemical form of sodium selenate. Almost all fertilizers used in Finland since 1985 have contained Se. Currently all crop fertilizers contain 15 mg Se/kg. Finland is still the only country to take this country-wide measure. In a national monitoring programme, sampling of cereals, basic foodstuffs, feeds, fertilizers, soils, and human tissues has been carried out annually since 1985 by four governmental research organizations. Sampling of foods has been done four times per year and human blood has been obtained annually from the same (n=60) adults. The accuracy of analyses has been verified by annual interlaboratory quality control. During this programme the selenium concentration of spring cereals has increased on average 15-fold compared with the level before the Se fertilization. The mean increase in the Se concentration in beef, pork and milk was 6-, 2- and 3-fold. In terms of Se, organically grown foods of plant origin are generally comparable to products produced before the Se supplementation of fertilizers. Milk from organically fed cows is 50% lower in Se than the usual milk. The average dietary human intake increased from 0.04 mg Se/day/10 MJ in 1985 to a present plateau of 0.08 mg Se/day/10 MJ, which is well above the current nutrition recommendations. Foods of animal origin contribute over 70% of the total daily Se intake. The mean human plasma Se concentration increased from 0.89 μmol/L to a general level of 1.40 μmol/L that can be considered to be an optimal status. The absence of Se deficiency diseases and a reference population have made conclusions on the impact on human health difficult. However, the rates of cardiovascular diseases and cancers have remained similar during the pre- and post-supplementation indicating medical and life-style factors to be much stronger determinants than Se. The nationwide supplementation of fertilizers with sodium selenate is shown to be effective and safe in increasing the Se intake of the whole population. Also, the health of animals has improved.

Structural characterization of water soluble β-glucan of oat bran

β-glucan was isolated from oat bran in a highly purified form. The bran was characterized for its contents of dietary fiber, β-glucan, fat and protein. The isolated β-glucan was free of protein and contained only glucose in GC sugar analysis. Two types of β-glucan were obtained with different solubilities. Their molar masses were 1.6 million for the less soluble and 1.1 million for the more readily soluble type. No structural differences were found. The two-dimensional correlation NMR spectrum of the isolated β-glucan showed that the glucose units are joined with 1,3- and 1,4-linkages only. The oligosaccharides produced by the action of a specific enzyme, lichenase, were analyzed by HPLC and capillary zone electrophoresis. The major products are 32-β-d-glucosyl cellobiose (trisaccharide) and 33-β-d-glucosyl cellotriose (tetrasaccharide), which account for 95% of the whole. Also, 34-β-d-glucosyl cellotetraose (pentasaccharide) and other oligosaccharides with degree of polymerization (DP) higher than 5 were detected as minor components.

The effect of phytic acid and some natural chelating agents on the solubility of mineral elements in oat bran

The effect of phytic acid on the solubility of mineral elements in oat bran was studied by digesting phytic acid with phytase enzyme. The combined effect of phytase treatment and the addition of three chelating agents common in food were also tested. Starch and proteins were digested enzymatically. The sample was dialysed, using an equilibrium dialysis method, and the soluble mineral elements were analysed from the dialyzate. The minerals studied were calcium, magnesium, iron, manganese, zinc, potassium and phosphorus. The chelating agents used were citric and malic acids and glucose. The phytase treatment increased the solubility of minerals less than expected. Citric acid was the most efficient chelating agent. The effect of malic acid was small. The results confirmed that the minerals were tightly bound to the dietary fibre of oat bran and were only partially released when the influence of phytic acid was reduced by degradation.

Effects of Selenium Fertilization on the Selenium Content of Selected Finnish Fruits and Vegetables

Abstract In order to raise the selenium (Se) content of Finnish foods all agricultural and horticultural multinutrient fertilizers have been supplemented with sodium selenate since autumn 1984. This intervention has affected practically all agricultural products in Finland. The Se content of 16 fruits and vegetables was determined by electrothermal atomic absorption spectrophotometry. The selenate supplemented fertilization has clearly increased the Se content of most vegetables, with onion and the cruciferous vegetables (cabbages, broccoli and swede) showing the highest increments; fruits are still low in Se. The mean Se values (mg/kg dry matter) were potato 0.07, carrot 0.07, swede 0.18, white cabbage 0.23, chinese cabbage 0.35, broccoli 0.75, lettuce 0.03, spinach 0.11, rhubarb 0.05, onion 0.25, pea 0.23, tomato 0.03, cucumber 0.13, apple 0.01, strawberry 0.02 and black currant 0.04. The Se levels for a single food type varied considerably, perhaps reflecting differences in fertilization practices. The...

The intake of inorganic arsenic from long grain rice and rice-based baby food in Finland – Low safety margin warrants follow up

We evaluated total and inorganic arsenic levels in long grain rice and rice based baby foods on Finnish market. Inorganic arsenic was analysed with an HPLC-ICP-MS system. The total arsenic concentration was determined with an ICP-MS method. In this study, the inorganic arsenic levels in long grain rice varied from 0.09 to 0.28mg/kg (n=8) and the total arsenic levels from 0.11 to 0.65mg/kg. There was a good correlation between the total and inorganic arsenic levels in long grain rice at a confidence level of 95%. The total arsenic levels of rice-based baby foods were in the range 0.02 - 0.29mg/kg (n=10), however, the level of inorganic arsenic could only be quantitated in four samples, on average they were 0.11mg/kg. Our estimation of inorganic arsenic intake from long grain rice and rice-based baby food in Finland indicate that in every age group the intake is close to the lowest BMDL0.1 value 0.3μg/kg bw/day set by EFSA. According to our data, the intake of inorganic arsenic should be more extensively evaluated.

Effects of Natural Chelating Agents on the Solubility of Some Physiologically Important Mineral Elements in Oat Bran and Oat Flakes

ABSTRACT The solubility of mineral elements from oat bran and flake samples was studied by a method using equilibrium dialysis after enzymatic digestion of starch and proteins. The effects of six potential chelating agents common in food were tested on the solubility of mineral elements. The minerals studied were calcium, magnesium, iron, manganese, zinc and potassium, and the chelating agents were citric, lactic, malic, and ascorbic acids, glucose and xylitol. The mineral elements were tightly bound to the dietary fiber of the samples. Bran fiber bound even the zinc and calcium contributed through the enzymes used. Adding citric, malic, or lactic acids increased the solubility of the mineral elements studied, except for potassium which was easily dialyzable as such. Iron was insoluble in all situations. Citric acid was the most efficient chelating agent in solubilizing the mineral elements. The effect of malic and lactic acids on the solubility of minerals was small. No effect was found with glucose, asc...

Transport of feed selenium to different tissues of bulls.

The effects of different types of Se supplementation on the selenium concentration of beef, bovine internal organs and some other tissues were studied. The animals (thirty-two bulls) were kept in four dietary groups from birth until to the age of 13-14 months, and fed on rations containing either 0.03 mg Se/kg (basic level in local feeds), 0.25 mg inorganic Se supplemented as sodium selenite, or 0.25 or 0.4 mg/kg plant Se in dry matter from feed produced by spraying with sodium selenite. Samples of four muscles and ten other tissues and organs were taken at slaughter. Se was determined by an electrothermal atomic absorption method. Se supplementation significantly increased the Se concentration of all tissue samples. The maximum response was caused by the diet containing 0.40 mg/kg plant Se. In muscles, this diet raised the Se concentration by a factor of 10-12. In other samples, the increment was 1.5-7.5 fold, depending on the type of tissue. In general, plant Se raised the Se level more effectively than inorganic Se. Se supplementation did not affect the vitamin E status of muscle tissue.

Sediment resuspension: rescue or downfall of a thermally stratified eutrophic lake?

The aim of this study was to estimate the effect of sediment resuspension, a common phenomenon in many lakes, on the phosphorus budget of a eutrophicated lake. We used two different approaches, mass balance calculations and spatially comprehensive resuspension measurements, to determine the level of phosphorus loading from which rehabilitation action is started in a dimictic north temperate lake. The effect of resuspension was assumed to be significant, since it often is a governing process for cycling of material in lakes. Internal loading was multifold to that of external loading as determined by the budget calculation. Spatially comprehensive sedimentation and resuspension measurements were necessary, since deep site versus spatially comprehensive measurements had a marked difference in their results. Resuspension of P slightly exceeded the internal loading assessed by budget calculations and thereby proved its significance as a governing in-lake process that influences P cycling strongly. The shallow areas were of importance, since most of the total P load originated from there. The fate of P after resuspension depends on the retention capacity of resuspended particles in addition to prevailing biological and physico-chemical conditions. Therefore, sediment resuspension can either strengthen or diminish internal nutrient load and the processes of the shallow zones are of importance.