Elsevier

Journal of Functional Foods

Volume 14, April 2015, Pages 479-486
Journal of Functional Foods

Effect of lettuce biofortified with iodine by soil fertilization on iodine concentration in various tissues and selected biochemical parameters in serum of Wistar rats

https://doi.org/10.1016/j.jff.2015.02.027Get rights and content

Highlights

  • The effect of lettuce biofortified with iodine was evaluated in rats.

  • Iodine from lettuce is bioavailable for rodents.

  • Content of iodine increased in various tissues of rats fed biofortified lettuce.

  • Biofortified lettuce can be a good source of iodine in daily diets.

Abstract

In this study, for the first time, we evaluated the effect of lettuce biofortified with iodine on iodine content in various tissues and selected biochemical parameters in the serum of Wistar rats. Significantly higher concentrations of iodine were measured in urine, faeces, hearts, and kidneys of rats fed the control diet (C diet) and the diet containing biofortified lettuce (BFL) compared to rats fed a diet containing non fortified-control lettuce or a diet with a lower level of iodine (equal to the content in control lettuce). Significantly higher concentrations of iodine were measured in the liver and femoral muscle of rats fed the BFL diet compared to the other experimental groups. Thyroid hormones, thyroid stimulating hormone, aspartate aminotransferase, alanine aminotransferase and selected genes' mRNA activities were not affected by the presence of biofortified lettuce in the diet compared to the control group. Biofortified lettuce may be considered as a potential source of iodine in the prevention of deficiency of this trace element.

Introduction

Iodine is a trace element which is essential for health and the development of humans and animals, particularly mammals (Dong et al, 2009, WHO, 2014). This trace element is necessary for the biosynthesis of thyroid hormones: thyroxin (T4) and triiodothyronine (T3). Iodine deficiency contributes to a wide spectrum of diseases: from endemic goiter to impaired memory and cognitive function/mental disorder (Dong et al, 2009, Melse-Boonstra, Jaiswal, 2010). Developing fetuses are most susceptible to the lack of iodine which leads to numerous neurological disorders beginning with lowered intelligence quotient scores to severe mental retardation (cretinism). Children are particularly liable to iodine deficiency in every stage of development (Melse-Boonstra, Jaiswal, 2010, Skeaff, 2011, Walker et al, 2007).

According to the current World Health Organization (WHO) data, the deficiency of iodine was ascertained in 1993 in 110 countries around the World. In 2013 this number decreased to 31 countries. Deficiency of iodine is still common in Asia, Africa and Eastern Europe. It has been estimated that about 1.88 billion people suffer from it (WHO/UNICEF, 2007, WHO, 2014). Fortification of salt with iodine has been a major reason for the reduction of iodine deficiency in many countries in Europe (i.e. Austria, Finland, Poland, Switzerland, Norway), Asia (i.e. China, Indonesia, India), and Latin America (i.e. Ecuador, Peru, Venezuela) mainly due to relatively high levels of salt intake in daily diets (7.9–16.0 g NaCl/day), (Andersson et al, 2010, WHO, 2008, WHO, 2014). However, this level of salt consumption exceeds the amount recommended by WHO (5 g NaCl/day). Excessive salt intake is one of the major causes of cardiovascular diseases (i.e. hypertension, stroke, atherosclerosis) and other diseases such as stomach cancer (WHO, 2008, Maillot, Drewnowski, 2012). Global economic and social effects of these disorders are enormous. For that reason WHO established the “2008–2013 Action Plan for the Global Strategy for the Prevention and Control of Noncommunicable Diseases”. This particular programme included guidelines for reducing table salt consumption as well as the development/identification of alternative ways of iodine reduction in the human daily diet (WHO, 2008, WHO, 2014). One of these methods (apart from iodized mineral water, milk, flour, bread etc.) can be plant fortification-biofortification with iodine trace element during plant cultivation (Blasco et al, 2008, Caffagni et al, 2011, Smoleń et al, 2011, Strzetelski et al, 2010, Ujowundu et al, 2010, Voogt et al, 2010).

The objective of this study was to evaluate the effect of the addition of lettuce biofortified with iodine in KI form, on iodine content in selected tissues, lipid profile, thyroid hormone concentration and mRNA expression of selected genes involved in iodine metabolism in Wistar rats.

Section snippets

Plant material

Lettuce ‘Melodion’ cv. was cultivated in the spring season of 2012 in a field experiment on heavy soil (24% sand, 23% dust and 53% loam) characterized by: pH(H2O) 6.02, pH(KCl) 4.97, EC (electrical conductivity) 0.10 mS cm−1 and the content of: organic matter −2.33%, N as a ammonium nitrate (NH4NO3; NO3 and NH4+ in proportion 1:1) −13.4 mg, P-32.7 mg, K-168.6 mg, Mg-194.2 mg, Ca-2089.3 mg and S-41.4 mg in 1 dm3 of soil. One day before plant seedling into the field, mineral fertilizers:

Results

Biofortification of lettuce with iodine did not affect basic chemical composition when compared to the control lettuce (Table 2). Iodine content significantly increased in the biofortified lettuce when compared to the control lettuce.

The body weight gain, feed efficiency ratio (FER), heart and kidney weights were not affected by various dietary treatments. Liver weight was significantly higher (P ≤ 0.05) in the rats fed the control diet when compared to the liver of the rats fed the BFL diet as

Discussion

Basic chemical composition of the biofortified lettuce was not affected by soil fertilization with iodine. The biofortified lettuce had a higher content of iodine in comparison to the control lettuce (Table 2). According to the current dietary recommendations we should consume 5 portions of vegetables and fruits per day (WHO/FAO, 2003). Our results shows that a 100 g of dried, biofortified lettuce will deliver about 500 µg of iodine, and only 30 g will deliver the Recommended Nutrient Intake

Acknowledgement

This work was financed by the 2012–2015 Polish National Science Center – grant no. DEC-2011/03/D/NZ9/05560 “I and Se biofortification of selected vegetables, including the influence of these microelements on yield quality as well as evaluation of iodine absorption and selected biochemical parameters in rats fed with vegetables biofortified with iodine”.

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