Evolutionary Association, Chapter 9: Iodine

The Dietary Change

Since the 1980s, restricting salt intake has found its way into the dietary guidelines - and in quite a few people I have met, what I saw came close to a fear of salt. The main reason given is avoiding high blood pressure, but other cardiovascular and organ diseases (the kidneys in particular) are cited as well.

At the same time, our exposure to other halogens went up: toothpaste contains fluoride; furniture, cars and electronics contain bromine in flame retardants. And the dietary guidelines recommend an ever more plant-based diet - an approach that, crudely simplified, comes down to “more plants == more good”.

Iodine is an important trace element, and its main sources are iodised table salt, sea fish, seafood, milk, dairy products and other animal foods⁽¹⁾: sea fish and seafood take their iodine from their surroundings, and in animal feed it is often added, because it turned out that animal health is better served that way. (We could take that as a hint for human nutrition - last time I checked, there were some rather large parallels between humans and animals…)

What all of these iodine sources have in common is that the current dietary guidelines either cap them or go as far as recommending we minimise them - and the iodine gets run over along with them.

The Phenomenon

Since this dietary shift, we have been seeing a marked rise in thyroid disease

functional disorders, nodules and Hashimoto’s.

And noncommunicable diseases⁽²⁾ outside the thyroid, none of them exactly unheard of - cardiac arrhythmia, heart failure, osteoporosis, cognitive impairment in older people and even adverse pregnancy outcomes - are linked to a lack of iodine, and have been on the rise since⁽³⁾.

The Biochemical Association

Let us start with one of the important uses of iodine in the body: the hormones T3 and T4 contain iodine as a key building block - as many atoms each as the number in their name suggests. If there is not enough iodine in the body, these hormones get scarce.

Iodine belongs to the chemical group of the halogens. In an iodine deficiency in particular, the body may end up building in bromine instead - all the more so when bromine is abundant at the same time.

The immune system recognises these “wrong hormones” as foreign bodies and starts attacking the tissue where it finds them: the thyroid. That is an autoimmune reaction against the thyroid⁽⁴⁾ - better known as Hashimoto’s.

Fluoride (or fluorine) is a halogen as well, but here I found nothing about it being built into hormones. What I did find is an English observational study: Doctors in areas with fluoridated drinking water report a nearly twice as high rate of underactive thyroids as their colleagues in non-fluoridated areas⁽⁵⁾. The study explicitly names fluoride as a factor alongside iodine deficiency, not in its place. And let us not forget that those areas differ in other respects too - given that this series is explicitly about associations, the study fits in here nicely.

But halogens are not all that can displace iodine - they are just the usual first suspects, and probably not even the most important ones. From my reading, other substances seem to be more effective: perchlorate⁽⁶⁾ (fair enough, that contains the halogen chlorine too, but chlorine is something the body itself copes with very well), thiocyanate⁽⁷⁾ (not a halogen, but a so-called pseudohalide) and nitrate - unlike bromine, though, these do not end up in the finished hormone. They push in on the way there: they either inhibit the incorporation of iodine before it happens, or stop it from getting into the thyroid in the first place. That way it is enough for a local iodine shortage to exist exactly where these hormones are built. Which makes the effect of these substances very different from triggering an autoimmune reaction⁽⁴⁾.

And on top of that: because of their oestrogen metabolism, women are more sensitive when it comes to thyroid function, which is considered one explanation for why this kind of problem shows up more often in them. That has “always” been the case, but it stands out all the more as the cases pile up. At the moment the ratio of thyroid disease between women and men sits at roughly 8:1.

Fancy a Halogen Salad?

butterbei.de would not be butterbei.de if there were not another angle to this - and especially when it makes it this easy to have another go at the dietary guidelines:

I mentioned at the start that the dietary guidelines steer us towards an ever more plant-based, low-salt diet, and that this pushes the main sources of iodine further and further into the background. In every set of statistics I have seen, women follow the guidelines far more “exemplarily” than men do. And “milk alternatives”, as far as I can tell, are more popular with women than with men - the guidelines say nothing about them, while society is busy normalising them. At the same time they seem to have enough of an effect on health to be named explicitly in the subtitle of a WHO article⁽²⁾ on iodine deficiency in Europe.

Why does that matter? Anyone who has been reading here for a while may remember goitrogens⁽⁸⁾ coming up - “goitre-forming substances” that occur in some plants, and the perchlorate and thiocyanate mentioned above are goitrogens.

For perchlorate there are, according to Wikipedia, even maximum levels in food (in the EU), and thiocyanate is formed among other things in the breakdown of cyanides, which we have already come across in connection with almonds.

Articles where goitrogens have already been covered

A prepared dish with rice, beans and other ingredients in a wooden bowl

Superfood or Antinutrient?

Foods praised for their ingredients often bring the antidote along too. How do antinutrients work? Can they be rendered harmless? A selection.

Colourful breakfast things in a bowl and scattered across the table. Probably not healthy, but fitting for the rainbow theme

"Eat the Rainbow", Part 2

There’s a second aspect that can be read as a motive for ’eat the rainbow’. Because the rainbow also influences what you don’t eat.

Now, broccoli as a goitrogen-containing plant is certainly not the biggest problem, but in various parts of the world cassava and millet are staple foods. If those are not prepared properly, they cause serious trouble - they contain goitrogens in an entirely different order of magnitude, and those have to be rendered harmless before they are eaten.

Conclusion

An increased susceptibility to iodine-related problems, combined with a reduced intake of iodine and a potentially increased share of goitrogens in the diet through guideline-compliant plant consumption. To me, that looks like a perfect storm for thyroid problems and other iodine-dependent symptoms. I cannot and will not single out any one of these points as the cause. But when all of these aspects point in the same direction, it does not surprise me if their combination can account for the rise in problems.

Personally, it strikes me as questionable - at least where an iodine deficiency has been established or is suspected - to keep avoiding every main source of iodine, and to eat foods instead that make it even harder for the body to use what little iodine is there.

Supplementation or fortification (adding iodine to foods) are ways out. In the article mentioned above, the WHO proposes fortification: if the natural sources are not being eaten any more, we will just tip some into the industrially produced replacements. 🤷

But when my bathtub is draining too fast, I check whether the plug still seals before I turn the tap up any further.