Iodine and folate in the diet - 16 July, 2010 | Jean Hailes for Women's Health

Iodine and folate in the diet - 16 July, 2010

Just how much iodine and folate do we need, and where can we get it?

twif Adequate intake of iodine and folate during pregnancy and breastfeeding is crucial, and dependent on a high quality diet.

Population surveys, however, indicate a poor intake of iodine and folate, particularly in groups with increased requirements.

In September 2009, the Australian Government introduced mandatory fortification of all bread-making flour (except organic flour) with folic acid to help protect pregnant women from having babies with neural tube defects.

From October 2009, the Australian Government required that salt used to make bread, except organic bread, be replaced with iodised salt.

On January 2010, the NHMRC released an evidence-based public statement on iodine supplementation for pregnant and breastfeeding women.

Author

Dr Cate Lombard PhD, APD
Healthy Lifestyle Program Director,
A Helen MacPherson Smith Fellow
Jean Hailes Foundation for Women’s Health

Health impact

Like folate, iodine is essential for normal development of the brain and nervous system. In the developing foetus, baby and young child, the effects of iodine deficiency include diminished intelligence.

If preconception dietary intake of iodine is adequate there will be sufficient iodine to support mother and foetus at least for the first trimester.

If intake is deficient, the demands of later pregnancy may produce an iodine deficit. It is possible the maternal thyroid is able to adapt to poor intake although this needs to be confirmed in further studies.

How much do we need?

Folate

Folate, a B-group vitamin (also called folic acid) is found naturally in leafy green vegetables, legumes, seeds, liver, poultry, eggs and citrus fruits. All wheat bread other organic, in Australia is now required be fortified with folic acid, including breads unpackaged or without labels. Many breakfast cereals are fortified and other foods such as fruit juice may also have folic acid added. All are required to state fortification on labels or to have that information available in the case of unlabeled products.

Mandatory fortification cannot deliver sufficient amounts of folic acid and iodine to all pregnant and breastfeeding women without inadvertently causing large numbers of young children to exceed the upper level of intake. Therefore supplements will be required for some population groups to meet their needs.

The NHMRC recommend all adults consume 0.4mg/day folate, but this increases to 0.5mg/day for breastfeeding women and 0.6mg/day for pregnant women, (3 slices of fortified bread contains an average of 120 micrograms of folic acid). Women who are of child-bearing age are advised to take folic acid supplements for at least one month prior to conception and three months after conception to minimise the risk of neural tube defects.

Folic acid supplements are available in Australia over the counter but at varying doses. Supplements that contain at least 400 micrograms of folic acid will generally be supplements containing only folic acid or special pregnancy supplements. Trying to get folic acid needs from general multi-vitamins may result in intake of higher than recommended amounts of other vitamins and minerals.

The risk to public health and safety from the estimated increase in folic acid intakes due to mandatory fortification appears to be low. Mandatory folic acid fortification has been used safely in the United States and Canada for over 10 years.

Iodine

Iodine can be found in sea water, marine plants such as kelp and in soil. The amount of Iodine in food is dependent on season, soil, and processing. WHO in 2009 classified Australia as mildly iodine deficient. The main dietary sources are bread, dairy and seafood, but it is difficult to obtain adequate iodine through diet alone.

Iodine supplementation of 150 micrograms per day is recommended by the NHMRC for all women who are pregnant, breastfeeding or considering pregnancy. The recommended doses are not likely to lead to an iodine intake in excess of the upper limit of 1100micrograms. Supplementing intake at these levels even when dietary intake is sufficient is rarely going to exceed 1100 micrograms.

Supplements can vary in iodine content with one leading brand containing no iodine.

Kelp and seaweed based supplements should be avoided as the iodine content has been found to be highly variable and could exceed the upper limit. This was highlighted recently with the recall of a soy milk product that included seaweed extract leading to excessively high iodine levels in individuals.

Mandatory iodine fortification will increase iodine intakes by approximately 45-66 micrograms per day; an amount comparable to the iodine content of a large glass of milk (300ml).