The effect of consumption of selenium enriched rye/wheat sourdough bread on the body's selenium status.

The potential of selenium-enriched rye/wheat sourdough bread as a route for supplementing dietary selenium intakes is reported. In addition to their normal diets, 24 female volunteers (24 to 25 years old) were fed either selenium-enriched bread or non-enriched bread each day (68.02 and 0.84 microg selenium day(-1) respectively) for 4 weeks. The chemical form of the selenium in the bread had been characterised using HPLC-ICP-MS, which showed that 42% of the extractable selenium was present as selenomethionine. Plasma selenium levels and plasma platelet glutathione peroxidase (GPx1) activity were measured in the volunteers' blood over a 6-week period. A statistically significant difference (p = 0.001) was observed in the mean percentage change data, calculated from the plasma selenium level measurements for the enriched and control group, over the duration of the study. A comparable difference was not observed for the platelet GPx1 activity (p = 0.756), over the same period. Two weeks after cessation of the feeding stage, i.e., at t = 6 weeks, the mean percentage change value for the selenium plasma levels in the enriched group was still significantly elevated, suggesting that the absorbed selenium had been incorporated into the body's selenium reserves, and was then being slowly released back into the volunteers' blood.

Absorption of selenium from wheat, garlic, and cod intrinsically labeled with Se-77 and Se-82 stable isotopes.

There is limited information on the absorption of selenium from different foods in humans because of technical difficulties associated with isotopic labeling of dietary selenium. Wheat, garlic, and cod fish were intrinsically labeled with Se-77 or Se-82 stable isotopes. Labeled meals were fed in random order to 14 adults, with a minimum washout period of six weeks between each test meal. Apparent absorption was measured as luminal loss using a fecal monitoring technique over an 8-day period. Plasma appearance of the isotope was measured at 7, 24, and 48 hours post-ingestion. Selenium absorption (+/- SD) was significantly higher (p < 0.001) from wheat (81.0 +/- 3.0%) and garlic (78.4 +/- 13.7%) than from fish (56.1 +/- 4.3%). Lowest plasma concentration was observed after the fish meal at all three time points, with a peak at 24 hours, whereas wheat produced the highest plasma concentration at all three time points and peaked at 7 hours. Selenium absorption from wheat and garlic was higher than from fish, and inter-individual variation was low. Form of selenium and food constituents appear to be key determinants of post-absorptive metabolism.

Characterisation of selenium compounds in rye seedling biomass using 75Se-labelling/SDS-PAGE separation/gamma-scintillation counting, and HPLC-ICP-MS analysis of a range of enzymatic digests.

In the present study, selenium-enriched plant biomass was investigated to evaluate the ability of rye seedlings to take up, and assimilate, inorganic selenium. Two different analytical approaches were used. Electrophoretic separation (SDS-PAGE) of proteins extracted from 75Se-labelled biomass was used to investigate the biotransformation of selenite into organic forms of the element. Ion-pair chromatography coupled with ICP-MS detection was chosen for the analysis of selenium species, enzymatically extracted from the plant biomass. The results of three enzymatic hydrolysis procedures and three sequential enzymatic extractions procedures are compared. The most effective single extraction was proteolysis (using protease type XIV), giving an overall extraction efficiency of 48%. However, for combinations of enzymes, the most effective was cellulase (Trichoderma viride) followed by sequential extraction of the solid pellet using protease type XIV, giving an extraction efficiency of 70%. The complementary data from the electrophoretic fractionation of proteins, and the HPLC separation of Se-species in the proteolytic digests, reveal the existence of large number of selenium-containing compounds in the rye seedling plant biomass. The results showed the complete biotransformation of inorganic selenium into organic forms during germination of the rye seedlings. HPLC-ICP-MS analysis of extracts from the plant biomass did not show the presence of selenate or selenite. At the time of this study, the lack of suitable organic-MS facilities meant that it was not possible to characterise them fully. However, the data does show that a combination of different enzymes, rather than just the commonly-used protease, should be considered when developing an extraction strategy for selenium in different food types to those already reported in the literature.

Adaptive responses in men fed low- and high-copper diets.

The study of Cu metabolism is hampered by a lack of sensitive and specific biomarkers of status and suitable isotopic labels, but limited information suggests that Cu homeostasis is maintained through changes in absorption and endogenous loss. The aim of the present study was to employ stable-isotope techniques to measure Cu absorption and endogenous losses in adult men adapted to low, moderate and high Cu-supplemented diets. Twelve healthy men, aged 20-59 years, were given diets containing 0.7, 1.6 and 6.0 mg Cu/d for 8 weeks, with at least 4 weeks intervening washout periods. After 6 weeks adaptation, apparent and true absorption of Cu were determined by measuring luminal loss and endogenous excretion of Cu following oral administration of 3 mg highly enriched (65)Cu stable-isotope label. Apparent and true absorption (41 and 48 % respectively) on the low-Cu diet were not significantly different from the high-Cu diet (45 and 48 % respectively). Endogenous losses were significantly reduced on the low- (0.45 mg/d; P<0.001) and medium- (0.81 mg/d; P=0.001) compared with the high-Cu diet (2.46 mg/d). No biochemical changes resulting from the dietary intervention were observed. Cu homeostasis was maintained over a wide range of intake and more rapidly at the lower intake, mainly through changes in endogenous excretion.