Leaflet 14. Avoiding salt and getting enough iodine
Iodised salt may have been a good idea when everybody was eating salt, but salt skippers can prevent and treat iodine deficiency in other ways. Even goitre patients can obtain all the iodine they need from other sources.
Original problem areas
Iodine deficiency has been seen in most Australian States except WA:
Queensland: the Atherton Tableland, the mountains behind the city of Mackay and the granite belt in the south-west.
New South Wales and ACT: large areas in the valleys of the great Dividing Range, the Hunter Valley, the high plains of the Southern Alps, Canberra District, Wyalong plains.
Victoria: the Southern Alps and Eastern Gippsland.
Tasmania: the whole island.
South Australia: the hills to the east of Adelaide.
At first the problem went away
In the developed countries regional iodine deficiency went away without government intervention. The reasons usually given are:
By the 1980s iodised salt was no longer considered necessary in the United States (American Heart Journal 1982; 103:1084–5), and in New Zealand a survey of urinary iodine excretion in a former goitre district in the South Island showed that people could avoid salt and still get an adequate intake of iodine (NZ Medical Journal 1986; 97:890–3).
Now it seems to be coming back
Although goitre as a result of iodine deficiency is still very rare in Australia, a Sydney survey found in 1999 that about 25% of participants had an iodine excretion rate below the standard set by WHO (Medical Journal of Australia 1999; 171:467–70). Similar results are coming in from several other developed countries.
This is potentially serious. Goitre itself is a fairly trivial complaint and easily treated, but the big worry now is the effect of mild iodine deficiency on brain development and the intelligence of the growing child. This is of great national and international importance because iodine deficient regions tend to be intellectually retarded and economically backward. An association is also suspected between iodine deficiency and cancer of the thyroid, but the effect on brain development and mental health is well established and has been universally accepted for over a decade. In 1990 the UN Declaration for the Survival, Protection and Development of Children stated that ‘every child has the right to an adequate supply of iodine to ensure its normal development’.
Australian residents at the greatest risk would be inhabitants of former goitre districts where the soil still lacks iodine, especially the few isolated families who live well inland, seldom eat seafood, depend mainly on home-grown produce and livestock and milk their own cow, fed only on local pasture.
What has gone wrong?
Iodine intake may be declining now for several reasons. Dairies sterilise equipment now by other methods and over half the people surveyed in Hobart recently said they ‘never or rarely’ cooked with salt or added salt at the table. Only table salt is iodised, so these people get no iodine supplement, even if they have a very high—and grossly unhealthy—salt intake coming from bacon, pizzas, olives, etc. Also supermarket shelf space shows that less than half the salt on sale in Sydney and Hobart is now iodised.
1. Patients who need iodine
To correct serious iodine deficiency doctors can prescribe Lugol’s iodine (it is also sold over the counter without a prescription). The recommended dietary intake (RDI) for iodine is 120 micrograms (mcg) daily for women and 150 mcg for men. One drop of Lugol’s iodine contains roughly 2000 mcg, which is the male RDI for about two weeks.
The usual prescription for iodine deficiency is one drop daily in milk or skim milk for a limited time such as one month. On porridge Lugol’s iodine makes a dark blue stain with an unpleasant taste, but stewed plums or rhubarb will conceal it. If you add it to the water before making the porridge you will probably agree that it cannot be seen or tasted.
After the initial course to correct the deficiency it was previously a common practice to recommend the daily use of iodised salt. That of course would be extremely bad advice at any time, and even more so since May 2000, when the entire population of the United States was recommended by the US government to adhere to a ceiling sodium intake of 1500 mg per day (www.nhlbi.nih.gov/new/press/may17-00.htm). That is even a little lower than the Pritikin Program’s ceiling of 1600 mg/day. Naturally a ceiling of 1500 mg (65 mmol) makes iodised salt obsolete, and we are lucky that we have so many good alternatives.
2. Routine supplements for everybody
The multivitamin capsules and tablets with minerals and trace elements often include iodine. The Australian Prescription Products Guide names the following brands, with iodine content in micrograms (mcg) per tablet or capsule:
Also there is a meal replacement on the market for weight loss called Vitatrim (made by VitaGlow), which has 100 mcg per 80g serving (2 scoops of powder).
Of course people who take the trouble to eat a good diet shouldn’t need a vitamin supplement. It is true that the long-term use of multivitamin supplements was recently found to reduce the risk of colon cancer in a follow-up study of 88 756 nurses from 1980 to 1994 (Archives of Internal Medicine 1998;129:517–24), but the authors suggested that this effect may have been solely due to the inclusion of folic acid, implying that the numerous other ingredients in the multivitamin tablets or capsules may have been a waste of money. Folate deficiency (from the Latin folium, a leaf) comes from not eating enough leafy vegetables and salad greens.
Some patients take multivitamins on medical advice for special reasons such as macular degeneration of the retina, or to compensate for restricted diets (due for example to irritable bowel syndrome). If they want iodine they can just look at the above list and choose one of the brands that supplies iodine as well.
2.2 Kelp tablets
One brand of kelp tablet (Blackmores) states the iodine content on the label (150–240 mcg per tablet). Tablets that don’t give the iodine content are not recommended. You don’t need a tablet every day. If you assume that you are getting at least half the RDI for iodine daily from other sources, a supplement of 150 mcg is enough for two days.
There was no goitre in Tasmania before white settlement. Eating seafood protected the Aboriginal population.
There is as much iodine in canned seafood as in fresh seafood, and a meal of seafood once or twice a week should give the consumer enough iodine. In any case nutrition experts recommend 2–3 fish meals a week for other reasons—marine fish oils will help to prevent heart disease (Australian Journal of Nutrition & Dietetics 1992;49:74–5).
Sea fish (fresh or canned without salt), eaten 2–3 times a week for the oil content, should prevent iodine deficiency at the same time.
2.4 Using iodine in a bread machine
Bread has two advantages—it is a more universal food than milk, and iodine can become a standard ingredient of commercial dough improvers, which are always measured very accurately when making up the dough. With a bread machine you can do it yourself.
You can buy Lugol’s iodine from a pharmacy over the counter (without a prescription). It is often supplied in a bottle of 30 mL. You will need a dropper, which is sometimes built into the cap of the bottle.
If you add just one drop of Lugol’s iodine to a whole loaf baked in your bread machine it will give you plenty of iodine.
Arithmetic. Lugol’s iodine provides 50 mg in 1 mL, which is 50 000 micrograms. Droppers vary, giving about 15–25 drops/mL, so you can assume that one single drop will supply at least 2000 mcg, equivalent to the RDI for about two weeks. The whole 30 mL bottle supplies 150 mcg/day for about 27 years.
If a slice of bread weighs 34g (20 hand cut slices from a small loaf weighing 680g) you will get about 100–170 mcg of iodine from each slice of bread
3. Other issues
3.1 Objection to sea salt
Most of the iodine in the ocean is in marine plants and animals. Seawater itself—and sea salt—are very poor sources of iodine.
3.2 Iodine overdose
A form of goitre due to too much iodine occurs in Japan in people who are too fond of edible seaweed. It also used to occur when large doses of potassium iodide were taken in cough mixtures for long periods for chronic lung conditions such as bronchiectasis.
The margin of safety is wide, and various authorities put the maximum safe intake for a healthy adult at 1000 to 2000 mcg/day.
3.3 Iodine sensitivity
Minute traces of pure iodine are present in the air we breathe, and the additional traces that are essential to life have not been known to cause any adverse reaction when present in the diet.
True allergy (an antibody reaction) has not been reported, but some people are sensitive to large doses of iodine if they are applied to the skin or given by injection. The possible adverse reactions are:
3.4 Misinformation about salt and iodine
Please write to us at the Salt Skip Program if you disagree with anything in this leaflet, or if you have any questions, comments, or suggestions for improving the leaflet.
Salt Skip Program, Queensland Hypertension Association, PO Box 193, Holland Park, QLD 4121. Phone (07) 3899 1659, FAX 3394 7815. Leaflet 14, updated July 2001.