Nutritional Value of the Duckweed Species of the Genus Wolffia (Lemnaceae) as Human Food.

Species of the genus Wolffia are traditionally used as human food in some of the Asian countries. Therefore, all 11 species of this genus, identified by molecular barcoding, were investigated for ingredients relevant to human nutrition. The total protein content varied between 20 and 30% of the freeze-dry weight, the starch content between 10 and 20%, the fat content between 1 and 5%, and the fiber content was ~25%. The essential amino acid content was higher or close to the requirements of preschool-aged children according to standards of the World Health Organization. The fat content was low, but the fraction of polyunsaturated fatty acids was above 60% of total fat and the content of n-3 polyunsaturated fatty acids was higher than that of n-6 polyunsaturated fatty acids in most species. The content of macro- and microelements (minerals) not only depended on the cultivation conditions but also on the genetic background of the species. This holds true also for the content of tocopherols, several carotenoids and phytosterols in different species and even intraspecific, clonal differences were detected in Wolffia globosa and Wolffia arrhiza. Thus, the selection of suitable clones for further applications is important. Due to the very fast growth and the highest yield in most of the nutrients, Wolffia microscopica has a high potential for practical applications in human nutrition.

Interlaboratory variability of urinary iodine measurements.

BACKGROUND: The iodine status of populations is usually assessed by median urinary iodine concentrations (UIC) in population-based studies, but it is unclear to which extent UIC are comparable across different laboratories. The aim of our study was to investigate the variability of UIC measurements across three well-established German laboratories with long-term clinical-chemical expertise in iodine measurements and to compare these results to the gold standard inductively coupled plasma mass spectrometry (ICP-MS). METHODS: UIC levels were measured from 303 urine samples derived from the "Dortmund Nutritional and Anthropometric Longitudinally Designed Study" and from volunteers of the University Medicine Greifswald at four different German laboratories. Three of these laboratories used Sandell-Kolthoff reaction with different digestion methods for UIC measurement (Lab1-Lab3), whereas one laboratory used ICP-MS as gold standard. RESULTS: Median UIC levels were significantly different across the four laboratories (ICP-MS: 77 µg/L; Lab1: 69 µg/L; Lab2: 73 µg/L; Lab3: 111 µg/L). Linear regressions associating UIC levels of Lab1-Lab3 with UIC levels of ICP-MS showed intercepts significantly different from 0 and slopes significantly different from 1. Intraclass correlations (ICC) in comparison to ICP-MS were 0.91 for Lab1, 0.98 for Lab2, and 0.69 for Lab3. Using the digestion method of Lab2 in Lab3 improved the comparison of UIC levels of Lab3 with those from the ICP-MS (ICC=0.89). CONCLUSIONS: We have demonstrated larger interlaboratory variations across high-quality laboratories with long-lasting experience in iodine measurements indicating a relevant non-comparability of UIC measurements in iodine monitoring studies. Therefore, standardization of UIC measurements has to be expedited.

Iodine in the feed of cows and in the milk with a view to the consumer's iodine supply.

Milk may be an iodine source for humans, but its magnitude depends on the iodine content of cow feed. The present investigation focused on the iodine level of feed and milk in German feeding practice in comparison with the results of previous milk monitoring and dose-response experiments with dairy cows. In 73 samples of straight feedstuffs (41 concentrates, 32 silages prepared from grass or green maize) and a total of 83 vitamin mineral premixes and compound feeds, respectively, the iodine content was determined and along with the expected daily iodine intake of cows. In six Thuringian cow herds, the total cow diets (51 total mixed rations, TMR) as well as the bulk milk (n=77) were analysed for iodine. Cereal and legume grains and extracted meals from oilseeds had very low native iodine contents at<9-43µg iodine/kg dry matter (DM). Silages showed higher contents than the concentrates. In grass silage, the median amounted to 173µg iodine/kg DM. The significant relationship between the silages' ash and iodine content indicates contamination of grass during harvesting by soil. With regard to supplements, dairy cows received via premixes a mean of 1.2mg iodine/kg diet DM and this was in the magnitude of 0.8mg iodine/kg DM determined in TMR on farm. However, the resulting mean milk concentration of 105µg iodine/kg, median 100µg/kg, is only a half of that in dose-response experiments with 200µg iodine/kg milk at 1mg iodine/kg cow feed DM. The decrease of iodine transfer into the mammary gland and milk is caused by rapeseed meal (RSM) with the glucosinolates and their degradation compounds, e.g. isothiocyanates. By compensating for the iodine antagonist effects of diets containing RSM, more iodine should be added. Twice the current mean feed iodine supplement would optimize the contribution of animal-source food to the human iodine supply in Germany.

Nutritional value of duckweeds (Lemnaceae) as human food.

Duckweeds have been consumed as human food since long. Species of the duckweed genera, Spirodela, Landoltia, Lemna, Wolffiella and Wolffia were analysed for protein, fat, and starch contents as well as their amino acid and fatty acid distribution. Protein content spanned from 20% to 35%, fat from 4% to 7%, and starch from 4% to 10% per dry weight. Interestingly, the amino acid distributions are close to the WHO recommendations, having e.g. 4.8% Lys, 2.7% Met+Cys, and 7.7% Phe+Tyr. The content of polyunsaturated fatty acids was between 48 and 71% and the high content of n3 fatty acids resulted in a favourable n6/n3 ratio of 0.5 or less. The phytosterol content in the fastest growing angiosperm, W. microscopica, was 50mgg(-1) lipid. However, the content of trace elements can be adjusted by cultivation conditions. Accordingly, W. hyalina and W. microscopica are recommended for human nutrition.

Effect of calcium phosphate and vitamin D3 supplementation on bone remodelling and metabolism of calcium, phosphorus, magnesium and iron.

BACKGROUND: The aim of the present study was to determine the effect of calcium phosphate and/or vitamin D3 on bone and mineral metabolism. METHODS: Sixty omnivorous healthy subjects participated in the double-blind, placebo-controlled parallel designed study. Supplements were tricalcium phosphate (CaP) and cholecalciferol (vitamin D3). At the beginning of the study (baseline), all subjects documented their normal nutritional habits in a dietary record for three successive days. After baseline, subjects were allocated to three intervention groups: CaP (additional 1 g calcium/d), vitamin D3 (additional 10 µg/d) and CaP + vitamin D3. In the first two weeks, all groups consumed placebo bread, and afterwards, for eight weeks, the test bread according to the intervention group. In the last week of each study period (baseline, placebo, after four and eight weeks of intervention), a faecal (three days) and a urine (24 h) collection and a fasting blood sampling took place. Calcium, phosphorus, magnesium and iron were determined in faeces, urine and blood. Bone formation and resorption markers were analysed in blood and urine. RESULTS: After four and eight weeks, CaP and CaP + vitamin D3 supplementations increased faecal excretion of calcium and phosphorus significantly compared to placebo. Due to the vitamin D3 supplementations (vitamin D3, CaP + vitamin D3), the plasma 25-(OH)D concentration significantly increased after eight weeks compared to placebo. The additional application of CaP led to a significant increase of the 25-(OH)D concentration already after four weeks. Bone resorption and bone formation markers were not influenced by any intervention. CONCLUSIONS: Supplementation with daily 10 µg vitamin D3 significantly increases plasma 25-(OH)D concentration. The combination with daily 1 g calcium (as CaP) has a further increasing effect on the 25-(OH)D concentration. Both CaP alone and in combination with vitamin D3 have no beneficial effect on bone remodelling markers and on the metabolism of calcium, phosphorus, magnesium and iron. TRIAL REGISTRATION: NCT01297023.

Influencing factors on iodine content of cow milk.

PURPOSE: Iodine is an essential trace element for humans and animals, and it is incorporated into the thyroid hormones such as thyroxine and triiodothyronine, which have multiple functions in energy metabolism and growth, but also as transmitter of nervous stimuli and as an important factor for brain development. Because of the small range between iodine requirements and the upper level for humans (between 1:2.5 and 3), the requirements should be met, but excesses should be avoided. One of the most important iodine sources for humans is milk of ruminants. Therefore, various influencing factors on the iodine content of milk of ruminants should be analyzed in the paper. RESULTS: The iodine content of milk depends on many factors, such as iodine content and level of iodine supplementation of feed, iodine source, iodine antagonists such as glucosinolates in the feed, farm management, teat dipping with iodine-containing substances, and milk processing in the dairy. The effects of some factors on the iodine content of milk are demonstrated and discussed. Feed iodine supplementation has the main effect on milk iodine. However, the iodine content of milk may vary considerably depending on many other influencing factors. CONCLUSIONS: As a consequence of preventive consumer protection, the European Food Safety Authority proposed a reduction in the iodine upper level for lactating ruminants from 5 to 2 mg/kg complete feed.

Iodine concentration of milk in a dose-response study with dairy cows and implications for consumer iodine intake.

Most feed is poor in iodine and iodine supplementation of cow's diets must guarantee milk iodine concentrations for humans that contribute to prevention of the deficiency and minimize the risk of exceeding an upper limit of iodine intake. Five Holstein cows were fed four iodine doses (via Ca(Iota O(3))(2).6H(2)O). In four sequential 14-d periods, doses of 0.2 (basal diet), 1.3, 5.1, and 10.1 mg iodine kg(-1) diet dry matter (DM) were administered. Samples of milk were collected during each period; blood was also sampled from each cow for each iodine dosage. In an 18-d depletion period, a non-supplemented diet was provided. Iodine was determined by inductively coupled plasma-mass spectrometry. The iodine content of milk and serum reflected the iodine dosages in feed significantly. The levels for the four doses tested in milk were 101+/-32, 343+/-109, 1215+/-222, and 2762+/-852 microg iodine kg(-1). The total amount of iodine in milk per day was 30-40% of ingested supplemental iodine. Omitting additional iodine resulted in a short-term reduction of serum and milk iodine following an exponential decay function. The iodine supplementation of 0.5-1.5 mg kg(-1) diet DM represents the requirement of the cow, resulting in 100-300 microg iodine L(-1) milk, which optimally contributes to human supply. The maximum dietary levels of former and present EU legislations (10 and 5 mg iodine kg(-1) cow feed) increase the risk of iodine excess in humans.

Influence of dietary iodine on the iodine content of pork and the distribution of the trace element in the body.

BACKGROUND: Millions of people worldwide still suffer from iodine deficiency disorders. Besides salt iodination, iodine is added to animal feed to concentrate it in food of animal origin (milk, eggs, meat). Otherwise possible adverse effects of high supplementation should be avoided. AIM OF THE STUDY: The objective of the study was to evaluate the iodine content of pork at various feed iodine concentrations to estimate its contribution to human iodine supply. Furthermore the handling of low and high iodine dosages by the organism should be investigated using the pig as a model for the human. METHODS: Seventy pigs (live weight period 27-115 kg), divided into five groups, were fed diets supplemented with 0 (group 1), 0.5 (group 2), 1 (group 3), 2 (group 4) and 5 (group 5) mg iodine per kg diet. Iodine was determined in the thyroid and in the fractions innards/blood, bones and muscle/fat of four pigs of each group by ICP-MS. RESULTS: Rising iodine supplementation of feed significantly increased (P < 0.05) the iodine content of the muscle/fat fraction [3.9 (group 1), 6.0 (group 2), 8.5 (group 3), 10.8 (group 4) and 17.1 (group 5) microg I/kg]. Carry over (of supplemented iodine) into muscle/fat varied between 0.10 and 0.24%. The highest tested iodine dosage (5 mg I/kg diet) caused a 3.6-fold iodine concentration of the total body (calculated from the contents of the fractions), and a significantly increased thyroid weight compared to the group without supplementary iodine. Iodine supplementation increased iodine content in thyroid and bones significantly (P < 0.05) but not in innards/blood. On an average of the groups, the thyroid contained 80% of the body's iodine, innards/blood 14%, muscle/fat 5% and bones 1%. CONCLUSIONS: The iodine content of pork, and consequently its contribution to human iodine supply ( approximately 1%), is very low, even at high supplementation of feed. The total body iodine content (empty body) is determined by the iodine intake. Irrespective of the iodine dosage, the thyroid contains about 4/5 of the body iodine. Bones represent a very low iodine concentration, even at a strongly increased iodine intake. The increase of the thyroid weight as an adverse effect of iodine supplementation requires further research with high dietary iodine.

Nutritional and toxicological importance of macro, trace, and ultra-trace elements in algae food products.

The content of 5 macro elements (Na, K, Ca, Mg, and P), 6 trace elements (Fe, Mn, Zn, Cu, Se, and I), and 4 ultra-trace elements (As, Pb, Cd, and Hg) in 34 edible dried seaweed products of brown algae (Laminaria sp., Undaria pinnatifida, and Hizikia fusiforme) and red algae (Porphyra sp.) originated from China, Japan, and Korea and bought by retail in Germany was determined. The content of these elements was analyzed by spectrometric methods (ICP-AES, ICP-MS, HGAAS, and CVAAS). Assuming a daily intake with 5 g FM of algae, the contribution of the essential elements to the diet is low, with the exception of I. Brown algae contained as much as 1316 +/- 1669 mg of I/kg FM. More than 4000 mg of I/kg FM were found in several Laminaria sp. Moreover, some brown algae, such as Hizikia fusiforme, had high contents of total As (87.7 +/- 8.2 mg/kg FM).