Iodineinitiative: learning from tanzania Teacher Guide

overview

According to recent reports, up to 70% of British young people do not take in enough iodine. Iodine deficiency causes goitre and brain damage, and may reduce IQ. In this activity students discover how a Tanzanian initiative reduced iodine deficiency diseases, and look at lessons the UK can learn from the example of this African nation.

LEARNING OBJECTIVES

In this lesson students will:

  • Recognise the symptoms of iodine deficiency
  • Apply knowledge about elements and compounds
  • Evaluate evidence to decide whether UK salt should be iodised
Curriculum LINKs

England National Curriculum KS3:

  • Working Scientifically: Analysis and evaluation – evaluate data
  • Biology: Nutrition and digestion – the consequences of imbalances in the diet, includingobesity, starvation anddeficiency diseases
  • Chemistry:Atoms, elements and compounds– differences between atoms,elements and compounds

In this activity, you can choose to focus on chemistry, biology, or both. See theRunning notes below for guidance.

TEACHING MATERIALS

The Presentation PowerPoint outlines the lesson structure. Three student sheets are included to print out. These include scientific evidence to evaluate, a role play, and a practical activity.

You will need
  • One copy of each of student sheets 1 and 2 per student
  • One copy of student sheet 3 per group of 6 students, cut into role cards and laminated if possible
  • To introduce the lesson – iodine crystals to show students (harmful) See CLEAPSS Hazcard 54A or Student Safety Sheet 56 (first web link) For the practical, per group:
  • 6 test tubes in a test tube rack
  • 1 spatula
  • Distilled water, up to 100 cm3
  • Solid potassium iodide, half small spatula measure (low hazard)
  • Solid sodium chloride, half small spatula measure (low hazard)
  • 0.1 mol/dm3 silver nitrate solution, up to 5 cm3(low hazard)
  • Sample of sodium chloride, labelled X (low hazard)
  • Second sample of sodium chloride, labelled Y (low hazard)
  • Sample of sodium chloride mixed with an equal volume of potassium chloride, labelled Z (low hazard)

STAGE/PURPOSE RUNNING NOTES

Starter
(15min)Discover the consequences of iodine deficiency. / Display slide 3 and, if possible, show students a sample of iodine (Please take care – iodine is harmful. Students must not touch the iodine.)
Display slide 4 and point out that studies have shown that iodine deficiency in pregnancy can result in children with lower IQ values than normal, as well as causing more serious brain damage and goitre. Iodine is a constituent element of two important hormones, which are made in the thyroid gland.
Display slide 5(or give students a print out of this slide) and ask students to estimate their daily iodine intake. Emphasise that the foods include iodine that is in the food as part of a compound. Iodine is not present as the element on its own.
Display slide 6 to introduce the big question. Should the UK add iodine compounds to salt? Point out that salt is the food to which iodine compounds are usually added, which is why this is the focus of the activity.
Core task 1
(30min) Evaluate a Tanzanian study about the impact on health of salt iodisation / Display slide 7. Students read student sheet 1 which describes a study to evaluate the effectiveness of a Tanzanian initiative to reduce the incidence of iodine deficiency diseases by adding an iodine compound to table salt, sodium chloride. The study is described in a 2009 research article in BMC Public Health by Vincent Assey et al (see web links.)
Students then tackle the task on student sheet 1, which asks them to evaluate the Tanzanian study. They are likely to conclude that salt iodisation improved health since the incidence of goitre decreased. More sophisticated scientists might point out that the correlation observed does not necessarily indicate a causal relationship.
Discuss the impact of salt iodisation on the health of Tanzanians. Do students feel the initiative was worthwhile?
Core task 2 (30-45 mins)Evaluate evidence to decide whether UK salt should be iodised. / This activity focuses mainly on the biological implications of iodising salt. Organise groups of 6. Within each group, give each student one card cut from student sheet 2. If you wish, give students time to research further information in support of their role. This preparation task could be tackled for homework. Student sheet 3 outlines the preparation task and provides suitable web links.
Then allow time for students in role to discuss the question Should the UK introduce salt iodisation?
During this activity you might like to emphasise that excessive salt consumption – and excessive iodine consumption – can both be harmful to health. Emphasise, too, the importance of considering diet before making a decision – a typical Tanzanian diet is less rich in iodine than a typical dairy-rich UK diet. Of course those Tanzanians who consume large quantities of fish or dairy products are unlikely to suffer the consequences of iodine deficiency. Students might also like to consider who should be responsible for health – the individual or the government?
Plenary
(15min) Make a decision on whether the UK should add iodine to food. / Explain to students that at present there is no compulsory salt iodisation in the UK; current advice is that a balanced diet provides sufficient iodine.However there is already a law that iron, calcium carbonate and vitamin B1 must be added to bread. In some areas fluoride compounds are added to water.
Ask the students, out of role, to write two lists:
• the benefits of salt iodisation in the UK
• the disadvantages of adding iodine compounds to salt
Students then make and justify a decision:Should the UK introduce salt iodisation?
Extension
(25 min)Use a practical test to work out which salt has been iodised. / This is an optional chemistry practical activity. Adding silver nitrate to a solution of a chloride salt makes a white precipitate of silver chloride. Adding silver nitrate to a solution of an iodide salt makes a yellow precipitate of silver iodide. Students can find out which salt has been iodised by observing which sample produces a yellow precipitate on the addition of silver nitrate. Point out that the scientists in the study used a more sophisticated test to identify the relatively small amounts of iodine compounds that are added to salt in the iodisation programme.
Web links
Iodine student safety sheet

Simple Q and A on iodine deficiency

Simple advice on iodine consumption

An evaluation of research on the impact of iodine deficiency during pregnancy on a child’s IQ – suitable for fluent readers

Detailed background information about iodine from the USA National Institutes of Health – suitable for fluent readers

Report of the Tanzanian research (for teacher reference)

Abstract of the Chinese study referred to on student sheet 3 (for teacher reference)

Acknowledgments

This activity was produced by the Association for Science Education in partnership with Practical Action as part of the Global Learning Programme (GLP).

The GLP is a ground-breaking new programme which will create a national network of like-minded schools, committed to equipping their students to succeed in a globalised world by helping them to deliver effective teaching and learning about international development and global issues at Key Stages 2 and 3.

ASE is providing the science education support for the Global Learning Programme which is funded by the Department for International Development. This activity can be found on the Global Learning Programme ASE Primary upd8 and Practical Action Schools websites.