Effects of high potassium iodate intake on iodine metabolism and antioxidant capacity in rats.

BACKGROUND: KIO3 and KI are the most common salt iodization agents. Coincidentally, iodine exists naturally in high-iodine drinking water in the form of iodide (I-) or iodate (IO3-). As an oxidizing substance, IO3- should be reduced to I- before it can be effectively used by the thyroid. However, there is a lack of systematic studies on the metabolic process of high dose KIO3in vivo. METHODS: The iodine metabolism processes in the thyroid and serum of rats after high KIO3 intake were determined using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC/ICP-MS) and arsenic cerium catalytic spectrophotometry. The changes of redox activity in the serum, thyroid, liver, and kidneys were observed by detecting total antioxidative activity (TAA). RESULTS: High doses of IO3- were completely reduced to I-in vivo within 0.5 h. The level of organic bound iodine in the serum was stable, while the organic bound iodine in the thyroid increased to a plateau after intake of high-dose KIO3. The levels of total iodine and I- in serum and thyroid increased quickly, then all decreased after reaching the maximum absorption peak, and I- had two absorption peaks in serum. The thyroid blocking dose of I- was 0.5 mg/kg in rat. Additionally, high KIO3 intake did not influence the TAA in serum and other tissues. CONCLUSION: The body is able to reduce and utilize high doses of KIO3 ingested through the digestive tract. The metabolism of high KIO3in vivo is characterized by two absorption process of I- in serum and the thyroid blocking effect. Moreover, a single intake of high-dose KIO3 does not affect TAA in vivo. The results suggest that such excess IO3- may have be reduced in the digestive tract before I- enters the blood.

Biofortification of lettuce (Lactuca sativa L.) with iodine: the effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce grown in water culture.

BACKGROUND: Iodine is an essential trace element for humans. Two billion individuals have insufficient iodine intake. Biofortification of vegetables with iodine offers an excellent opportunity to increase iodine intake by humans. The main aim was to study the effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce, grown in water culture. RESULTS: In both a winter and summer trial, dose rates of 0, 13, 39, 65, and 90 or 129 microg iodine L(-1), applied as iodate (IO(3)(-)) or iodide (I(-)), did not affect plant biomass, produce quality or water uptake. Increases in iodine concentration significantly enhanced iodine content in the plant. Iodine contents in plant tissue were up to five times higher with I(-) than with IO(3)(-). Iodine was mainly distributed to the outer leaves. The highest iodide dose rates in both trials resulted in 653 and 764 microg iodine kg(-1) total leaf fresh weight. CONCLUSION: Biofortification of lettuce with iodine is easily applicable in a hydroponic growing system, both with I(-) and IO(3)(-). I(-) was more effective than IO(3)(-). Fifty grams of iodine-biofortified lettuce would provide, respectively, 22% and 25% of the recommended daily allowance of iodine for adolescents and adults.

Iodate and iodide effects on iodine uptake and partitioning in rice (Oryza sativa L.) grown in solution culture.

In the Xinjiang province of western China, conventional methods of iodine (I) supplementation (i.e, goiter pills and iodinated salt) used to mitigate I deficiencies were ineffectual. However, the recent addition of KIO3 to irrigation waters has proven effective. This study was conducted to determine the effects of I form and concentration on rice (Oryza sativa L.) growth, I partitioning within the plant, and ultimately to assist in establishing guidelines for incorporating I into the human food chain. We compared IO3- vs. I- in order to determine how these chemical species differ in their biological effects. Rice was grown in 48 L aerated tubs containing nutrient solution and IO3- or I- at 0, 1, 10, or 100 micromoles concentrations (approximately 0, 0.1, 1, and 10 mg kg-1 I). The IO3- at 1 and 10 micromoles had no effect on biomass yields, and the 100 micromole treatment had a small negative effect. The I- at 10 and 100 micromoles was detrimental to biomass yields. The IO3- treatments had more I partitioning to the roots (56%) on average than did the I- treatments (36%), suggesting differences in uptake or translocation between I forms. The data support the theory that IO3- is electrochemically or biologically reduced to I- prior to plant uptake. None of the treatments provided sufficient I in the seed to meet human dietary requirements. The I concentration found in straw at 100 micromoles IO3- was several times greater than seed, and could provide an indirect source of dietary I via livestock feeding on the straw.