Iodine continues to be a controversial issue with some suggesting supplementation is always inappropriate while others proclaim massive doses.
For a change, this paper looks at a range of iodine intakes, and not as a supplement but in the water supply.
Open Access
Published: 31 August 2021
The Effects of Long-Term High Water Iodine Levels in the External Environment on the Carotid Artery
Ji Bian, Man Zhang, Feng Li, Jie Gao, Zhexue Wei, Zijing Liu, Xiaoming Wang, Wen Jiang & Jianchao Bian
Biological Trace Element Research (2021)
Abstract
Iodine excess typically affects thyroid function in the human body and may damage carotid artery. Four investigation plots with different water iodine levels were selected in Shandong Province, China. These included a low, medium, and high iodine group and an iodine excess group whose water iodine content was<10, 50–150, 150–300, and>300 μg/L, respectively. Residents aged 20–65 years answered a questionnaire and underwent carotid artery ultrasonography, and their height, weight, and urinary iodine concentrations were measured. A total of 2026 individuals participated in the study. Urinary iodine concentration increased with increased water iodine levels. The medial thickening rate and intimal roughness rate in the iodine excess group were significantly higher than in the other three groups. After controlling for factors such as gender, age, and BMI, iodine excess remained as a risk factor for carotid intima-media thickening. Excess water iodine in the external environment is a risk factor for intima-media thickening of the carotid artery, suggesting that iodine excess may cause vascular injury and promote atherosclerosis.
Well, strictly speaking it doesn’t but I know what you’re getting at.
The difference is, levothyroxine is usually taken by people who can’t produce enough thyroid hormone for some reason. Whereas iodine in the water supply is something that people with and without thyroid problems can’t avoid. Excess iodine for people who don’t need it is a problem.
The article isn’t talking about purposely added iodine. It’s talking about iodine that’s either naturally in the water supply or is there because of the drugs/food the local indigenous people consume.
I don’t think I wish that iodine was added to the U.K. water supply.
It isn't added to the water supplies in the places discussed.
It is very common for discussions of iodine to entirely miss the effect of iodine/iodine compounds on rain (and other precipitation) and the iodine content of the precipitation. It is even suggested that iodine is a significant factor in causing rain to fall.
The parliamentary report is a bit odd as it veers from stating 6ppm is required to questioning how much is needed.
The map I posted a link to shows large areas of the UK (at least, England and Wales) have adequate (i.e. over 6ppm to high iodine). Most of Wales except a few small areas looks fine.
And the lack of historical data makes depletion a question. Much iodine comes in rain - over which we have little control either in quantity or in iodine content.
Thanks, helvella for the map, As our area's level is 14.99 in topsoil, firstly, it's clear that we should not have moved, and confirmation that the liquid seaweed I use on my home-grown is not necessary. In fact, perhaps we would be better off buying imported fruit and veg, hmm.
so everyone should be starved of iodine for the sake of people with hashimotos ?
what about pregnant women around the world with iodine deficiency giving birth to babies born with congenital hypothyroidism aka cretinism - a debilitating condition that could so easily be avoided ?
Lizzo30, I’m really not sure why you’re directing replies at me. I didn’t post the article although I found it very interesting.
I am aware that deficiency of iodine can be a problem. Equally, I am aware that it’s common for people to assume that if their thyroids don’t seem to be working properly that maybe they should take iodine / Kelp—when actually that can be the worst thing they could have done because it can make failing thyroids fail faster. Iodine should never be supplemented without testing being done to find out whether a deficiency actually exists.
I really don’t have anything else to say about this.
People with Hashimoto's don't have to totally avoid all iodine. They simply need to avoid the levels that typically come with supplementation.
And discussing iodine in soil in the UK has little to do with iodine deficiency around the world. Though in countries which have introduced things like universal iodised salt have tended to see increases in autoimmune thyroid disease. Which in my view emphasises the need to manage supplementation carefully.
On a side note—because this discussion made me do some Googling —the author of that evidence submitted to Parliament is a dairy farmer trying to do what she can to avoid her cattle being slaughtered due to Bovine TB…. The iodine aspect was almost incidental.
However, there does seem to be plenty of evidence of concern about falling iodine intake in the U.K.—it would seem many folk are chronically deficient. But when chronically deficient people suddenly supplement with iodine, their thyroids don’t cope too well. I happened across a snippet about how they’d introduced mandatory iodisation of salt in Denmark in 1998 which then increased levels of hypothyroidism.
One of the suggested reasons for the UK was the combination of a switch away from iodophor teat disinfectant in the dairy industry and a reduced milk intake (whether as fresh milk, or cheese, cream, butter, or other dairy products.)
Iodised salt is also problematic in an era of the health lobbies insisting we reduce salt intake.
Similarly, the problem of fortifying wheat flour with folic acid. Not much good for those who avoid wheat.
Yes indeed. As someone who has to be gluten free because otherwise—well, let’s not get into detail —it took me a while to realise that was the reason my folate levels kept tanking.
Don’t get me started on salt. The way it’s been vilified is quite astonishing.
I never cease to be amazed by what info I pick up here. 😀 Thanks for the iodine map.
So, extrapolating, if there is fluoride in Birmingham’s water, is that why the topsoil iodine content in the Birmingham area is so low? It’s been a while since I did A level chemistry but a dim recollection makes me wonder if it’s got something to do with it.
And do bear in mind that a sizeable amount of water in Birmingham comes from Wales (Elan valley reservoirs).
Oh doh, yes I suppose it does!
I now know a lot more about both iodine in the soil and fluoridation. Not what I was expecting to learn this evening, but every day’s a school day. Thanks!
I think I used to have—it came with the house when we bought it—but there were no instructions about how to look after it and Google didn’t really exist back then. So it got all furred up and when we eventually had a new kitchen was taken out!
However, UK, models are much more compact (as a rule).
If all water goes through the softener, it does increase the amount of sodium in the water - which can affect taste and is not advised for those who need low sodium intake.
We have got a 3 way tap at the kitchen sink which provides hard (cold) water for drinking and softened water for washing up (hot and cold). It was here when we bought the house in June and I'm so glad it was because they cost about £600. Ouch.
The actual water softener is a small unit in the garage and our mains water comes through it.
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—it took me a while to realise that was the reason my folate levels kept tanking. 
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