Iodine is perhaps, not as well known or considered as it should be. It’s something to do with your thyroid, it helps protect you from radiation sickness, and there’s lots in seaweed. Beyond that, most people know little about this vital element.

Why you need iodine

The thyroid gland is indeed an important consumer of iodine, where it is used to manufacture T3 and T4 hormones, which in turn control many processes throughout the body. If iodine levels fall too low, goiters (a large growth on the side of the neck) form as the thyroid enlarges in an attempt to produce more hormone. This has been long established, and as long ago as 1917, experiments demonstrated that

Iodine is also important for mental development , with iodine deficiencies in developing countries being a significant factor in intellectual disabilities and cognitive delays. Linked to this, it becomes most important for pregnant women to ensure they get sufficient iodine, as the developing fetus is entirely dependent on the mother to provide sufficient iodine for brain development. Iodine deficiencies may also be responsible for a deficit of up to 15 IQ points due to sub-optimal brain development.

Finally, there is a potential link (causation not proven) between iodine deficiencies and breast cancer. There is a demonstrated link between breast cancer mortality rates and endemic goiter areas, whilst Japan and Iceland – two countries with high levels of iodine intake, have both low goiter incidence and low breast cancer levels.

How much do you need

Somewhere between 70-200ug/day of iodine is considered optimal, with the WHO official level being 150ug/day. Depending on where you live and what you eat, this level may be generally attainable, or something you are likely to need to work on.

Perhaps surprisingly, the UK is right up there with much of the African continent in terms of iodine deficiency. Europe is generally ok, as is the US. Australia is improving.

Even within the countries that consider themselves to be ok, however, there is still an issue with pregnant and lactating mothers and young children getting sufficient iodine, even if the general population as a whole is receiving sufficient.

National Iodine Status. Taken from ICCIDD website.

Where to get iodine from

Ironically, and of interest to the current audience, iodine is an example of a vital nutrient that we have evolved to need, but that actually we now need to work really hard to get sufficient of, particularly if you follow a real food based diet.

One key reason for that is that iodine is in general not abundant in the Earth’s crust and tends to be concentrated in the oceans. This often leads to areas referred to as ‘Goitre belts’ – for example the Great Lakes areas of the US, where iodine deficiency was a particular problem.

The little that was in the top soil has gradually been eroded , and it has been suggested that iodine uptake by plants is therefore dwindling.

One of the big determining factors for iodine deficiency therefore is the availability of other sources of iodine, namely iodized salt.

Many countries have introduced either voluntary or mandatory regulations requiring the iodization of salt, either for use at the table, or within the food manufacturing industry.

The US for example, successfully introduced iodized salt and no longer has significant issues with Goiter belts. In the UK, iodized salt is not required (and is generally unavailable in high street stores), and thus iodine deficiency is a real issue, whilst much of the rest of Europe has introduced iodized salt at some level and again, significant iodine deficiency is not an issue. One interviewee told me:

We should all take [iodized salt] to ensure we get adequate levels [of iodine]

So, what are the options for ensuring sufficient iodine intake?

Option Comments
Depending on which country you live in, this may be freely available, or it may be very hard to get hold of! For those of a paleo persuasion however, the likely migration to sea salt will very probably remove iodized salt from your diet. The evaporation process used to manufacture sea salt effectively removes the iodine along with the water meaning sea salt has practically no iodine left in it. Some sea salt brands do have iodine added back in, but it is more likely than not, that no iodine is present. Also be aware that iodine can disappear over time (technically it sublimes) if the container is not air tight. The levels in t are intended to provide a good level of iodine without risking over-consumption
Bread and other processed food Again depending on country, iodine compounds may be used as preservatives in bread ( Try our Paleo Bread ). The unintentional consequence is iodine supplementation! Alternative preservatives are being used however so this is becoming a less viable source of iodine for the general population, never mind the grain free paleo folk who just wouldn’t go there!
Processed foods in some countries also have iodized salt added. Again, this varies enormously.
Milk Another unintended source of iodine supplementation. The disinfectant commonly used to clean milking equipment and the cow’s udder contained iodine and significant amounts got into the milk supply itself. Again depending on where you live, this is being used less now ( Australia being a particular example where iodine intake has dropped since iodine has stopped being used in dairy production). Also of relevance to paleo folk who do dairy but go organic, is this paper that reports that organic milk generally has lower levels of iodine present. It is also interesting to note that particularly in northern latitudes with harsher winter, cattle taken indoors will be provided with feed richer in iodine, so winter milk contains higher concentrations of iodine than summer milk.
Sea fish The sea itself is rich in iodine, and so the fish that live in it will be too. This won’t get you your RDA on its own, but can get you part way. Sardines typically provide 35ug/5oz, cod 99ug/3oz, shrimp 35ug/30z. It is felt likely that nations such as Iceland that have high levels of fish consumption receive adequate levels of iodine through this source (although it is recognised that as dietary habits change, fish consumption in Iceland is going down, which may lead to iodine issues). It was suggested by one interviewee that we could aim to achieve 50% of our requirements from fish.
Seaweed The blockbuster source! Seaweed is bursting with iodine, typically values are in the order of several thousand micrograms per serving. In fact, this level can be considered to be too high as excessive iodine can be as much of an issue as deficiencies, with thyroid autoimmunity and hypothyroidism the possible outcome . Both experts spoken to during the research for this post cautioned against the regular use of seaweed for iodide supplementation. Indeed, it was suggested that several groups are currently working on trying to get legislation requiring warning labels on seaweed regarding the levels of iodine and risks to toxicity.
Now clearly the Japanese consume large amounts, so why do they not have toxicity issues? It is likely to be due to adaptations in the Japanese population and also a history of high intake that has enabled them to tolerate such levels. Sudden high intakes however (ie running out to buy lots of seaweed tomorrow!) is likely to cause thyroid disorders
Supplements This is a viable option, with the levels being tightly regulated, and aimed at providing 150-200ug/day, sufficient for pregnant women whilst not being too much for the wider population.

So should we supplement?

As can be seen from above, if you follow a paleo diet (particularly if you exclude dairy), iodine sources are limited and even if your country in general is sufficient, unless you go out your way to get iodized salt (remembering sea salt generally doesn’t contain iodine), you too are likely to suffer some form of deficiency. This paper for example suggests that if you are in the US, your major sources of iodine are likely to be bread and milk.

For most developed countries (UK excluded), iodine is not a significant issue for the general population, but iodized salt won’t hurt, particularly if you’re paleo and potentially get lower levels in any case. Those in the UK should also consider whether they are likely to be getting enough or whether they should obtain salt or a supplement. Both interviewees suggested that using iodized salt is a good idea. Equally, both were concerned with the potential damage caused if people use seaweed as a regular iodine source.

Iodine Supplementation on Paleo

For pregnant or lactating women and small children, iodine supplementation appears to be a very important consideration. It has previously been estimated that up to 50% of women (UK and Ireland) could be significantly iodine deficient during gestation. Vitamin supplements aimed at pregnant women (e.g. Pregnacare) typically contain 140-150ug iodine, but it is worth checking.

Finally, selenium is another element linked to iodine function that it is important you get enough of. As Mark Sisson explains, selenium is also important for thyroid function so it is important you get enough in addition to your iodine. Brazil nuts, salmon , kidneys, lamb , egg yolks are all good sources of selenium.


My thanks to the following for providing insights and opinion for this article: Dr Maria Andersson (ETH Zurich, Switzerland), Prof Peter Smyth (UCD, Ireland)
About the author: Nigel Bailey is a blogger and paleo lifestyle coach seeking to help people improve their lives through adopting ancestral approaches to health and wellbeing. You can see more of his work on his blog , check out his services and .
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