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Iodine, Thyroid Health and Modern Life: Could Our Iodine Reserves Be Lower Than We Think?
Iodine is needed in only tiny amounts, yet without it the thyroid cannot make its hormones properly. The thyroid uses iodine to produce T4 and T3 — hormones involved in energy production, temperature regulation, metabolism, growth and many other processes throughout the body.
For most adults, the usual recommended intake is around 150 micrograms (μg) per day. During pregnancy and breastfeeding, requirements rise considerably, with international recommendations generally around 220–250 μg during pregnancy and 250–290 μg during breastfeeding.
That may sound easy to achieve. However, iodine has one unusual characteristic: its natural availability varies enormously depending on where we live and where our food is produced.
Why geography matters
Prof. Ivan Turianica spent decades studying what he called environmental or biogeochemical iodine deficiency.
In his research with Milada Rothová, he described how goitre and iodine-deficiency disorders were historically more common in places where food contained little iodine because the soil itself was iodine poor, particularly in mountainous and inland regions.
Modern international research agrees with this basic principle.
The oceans contain the world's largest iodine reservoir. Over geological time, glaciation, heavy rain, snow, flooding and erosion can wash iodine out of soils and carry it toward rivers and ultimately the sea. As a result, inland, mountainous and heavily glaciated areas frequently have naturally low iodine concentrations in their soil and food chain.
This historically affected many parts of Europe, particularly the Alps and Carpathians and other inland areas.
Slovakia is a good example. It once had a significant problem with endemic goitre, and compulsory salt iodisation introduced in the 1950s dramatically changed the situation. Slovak research later found iodine prophylaxis to be successful, and Slovakia has reported to WHO that endemic goitre and cretinism have now practically disappeared. But this is just the bottom of the scale... the severe depletion is not obvious, but do we have optimal levels, is another question.
Similar historical problems have been recorded in southern Poland and the Carpathian region, where researchers measured low iodine in local water and foods.
Romanian Carpathian and sub-Carpathian regions have also remained areas of particular interest, including reports of mild iodine deficiency among pregnant women even after national salt-iodisation programmes were introduced.
This does not mean that everyone living in Slovakia, Poland, Romania, Hungary, Austria or another inland country is iodine deficient today. Modern diets, iodised salt, imported food and iodine supplementation have changed the picture enormously.
But it helps explain why iodine deficiency became such an important European public-health issue in the first place.
Your body also keeps an iodine reserve
An iodine-sufficient adult contains approximately 15–20 mg of iodine in total, with around 70–80% concentrated in the thyroid gland. The thyroid therefore represents our main long-term iodine reserve, but it is not the only tissue that uses or concentrates iodine. Iodine is also found throughout the body, and specialised tissues including the stomach, salivary glands, placenta and mammary glands can actively take it up. During breastfeeding, the breast becomes particularly important: it actively concentrates iodine from the mother's circulation into breast milk to supply the baby. Research suggests that when maternal iodine intake is low, this can occur partly at the expense of the mother's own iodine reserves. The liver and muscles also contain iodine, including iodine carried within thyroid hormones, but they are not considered major long-term iodine stores in the same way as the thyroid.
Think of it as a small reserve.
If iodine intake is consistently adequate, the thyroid has enough raw material to manufacture its hormones.
But if intake is marginal for a long time, that reserve can gradually become smaller.
At first, the thyroid tries to compensate. It becomes more efficient at trapping iodine from the bloodstream and may increase in size. This is one reason goitre is such a classic sign of long-term iodine deficiency.
If iodine availability becomes insufficient for thyroid-hormone production, people can eventually develop a pattern associated with an underactive thyroid.
Typical hypothyroid symptoms can include tiredness, feeling unusually cold, constipation, dry skin, hair changes, difficulty concentrating, low energy and weight gain. These symptoms are not specific to iodine deficiency, but iodine deficiency is one possible cause when the thyroid does not have enough iodine to manufacture normal amounts of hormone.
Pregnancy can dramatically increase the demand
Pregnancy is perhaps the clearest example of how someone who previously had "just enough" iodine might suddenly need considerably more.
During pregnancy, thyroid-hormone production rises by roughly 50%. At the same time, the kidneys remove more iodine from the circulation, and later in pregnancy iodine is transferred from the mother to the developing baby's thyroid.
If a woman begins pregnancy with good iodine stores, her body can usually adapt.
But if she begins with marginal stores, something different can happen.
Endotext describes how the thyroid initially tries to capture more iodine. If that isn't enough, it starts drawing on its stored iodine. Those stores can then become progressively depleted during pregnancy, particularly when dietary iodine remains low. If the adaptive mechanisms eventually cannot keep up, maternal T4 can fall, TSH can rise, and hypothyroidism or goitre may develop.
That makes the sequence fairly easy to understand:
small iodine reserve → pregnancy increases demand → more iodine is used and lost → stores fall further → thyroid has increasing difficulty meeting hormone requirements.
Prof. Turianica also specifically identified pregnancy as one of the circumstances in which iodine deficiency could develop or become more important.
Stress adds another piece to the thyroid puzzle
Turianica also discussed stress and physical overstrain alongside pregnancy as circumstances in which iodine deficiency or altered thyroid function could become relevant.
Modern research gives us a more detailed explanation on how chronic stress can influence the thyroid system.
Sustained cortisol signalling can reduce TRH and TSH signalling and alter the enzymes that convert the largely inactive thyroid hormone T4 into active T3. Under significant physiological stress, illness, inflammation or calorie restriction, conversion may shift toward less T3 and more inactive reverse T3.
So there can potentially be two separate pressures:
low iodine availability can limit how much thyroid hormone the gland can manufacture, while significant physiological stress can affect how those hormones are subsequently regulated and activated.
And breastfeeding continues the demand
Birth does not immediately return iodine requirements to normal.
During breastfeeding, the mammary gland actively takes iodine from the mother's blood and transfers it into breast milk. The baby needs that iodine for its own developing thyroid.
Around 100 μg of iodine per day can be transferred through breast milk, which is one reason breastfeeding women continue to have higher iodine requirements.
This becomes particularly interesting for women who have several children.
Research in moderately iodine-deficient areas has found a cumulative effect of successive pregnancies on thyroid enlargement. In one study, average thyroid volume progressively increased with the number of completed pregnancies, and researchers concluded that the effect of pregnancy was not completely reversible when iodine supply was inadequate.
This does not mean that having several children causes iodine deficiency. It means that repeated periods of pregnancy and breastfeeding create repeated periods of increased iodine demand.
If pregnancies are close together and iodine intake between pregnancies is also marginal, there may be less opportunity to rebuild depleted stores.
Why daily iodine intake matters
Prof. Turianica's work repeatedly returned to one basic idea: because iodine leaves the body, there must be a continuous dietary supply. His 2012 review describes iodine as indispensable for thyroid hormones and metabolism and discusses correcting iodine deficiency through food, iodised salt and iodine-containing preparations.
Mainstream guidance reaches essentially the same conclusion.
For adults, approximately 150 μg/day is normally required. Needs rise during pregnancy and lactation.
Where deficiency is present, restoring an adequate iodine supply can improve iodine status and deficiency-related thyroid changes. What it cannot do by itself is automatically correct every type of hypothyroidism.
Hashimoto's thyroiditis, for example, is an autoimmune disease and is now a major cause of hypothyroidism in iodine-sufficient countries. Excessive iodine can actually aggravate thyroid dysfunction in some susceptible people.
That distinction matters.
Why Prof. Turianica became interested in iodine bound to vegetable oils
One particularly interesting part of Turianica's research involved iodine organically associated with unsaturated fatty acids in vegetable oils, including pumpkin-seed oil.
This general idea is not unique to Fortuna Vitae.
For many years, international iodine-deficiency programmes used iodized oils, in which iodine was chemically associated with unsaturated fatty acids. Unlike ordinary soluble iodide, these preparations could provide iodine over an extended period.
The results were remarkable.
In one study, 104 iodine-deficient children aged 6–12 received a single oral dose containing 200 mg of iodine in iodized poppy-seed oil.
Remember: that is 200,000 μg, which is 1 000 times more than our daily dose in the Fortuna vitae oil!
Their iodine status remained significantly improved for an entire year, thyroid size fell substantially, and no child in that study developed iodine-induced hypo- or hyperthyroidism.
Another Romanian study followed 214 children after a single 200 mg iodized-oil dose. Iodine status remained improved for over a year, goitre prevalence fell from 29% to 9%, and thyroid-function tests and thyroid antibodies remained normal during follow-up.
A Cochrane review of iodine-supplementation studies also concluded that iodine supplementation — particularly iodized oil — generally reduced goitre and improved iodine status, although study quality varied and some minor/transient adverse effects were reported.
Why could an oil behave so differently?
Iodized oils can behave as a kind of iodine depot or reserve.
Instead of the whole iodine dose becoming freely available immediately, iodine associated with fatty acids can be retained and released over a much longer period as the lipid is processed.
The carrier oil itself may even matter.
In a human trial comparing iodized peanut oil with iodized poppy-seed oil, iodine retention from the peanut-oil preparation was estimated to be about three times greater, and protection against deficiency lasted roughly twice as long despite comparable iodine dosing.
That tells us something important: the oil is not necessarily just an inactive container. Its fatty-acid composition and the way iodine is incorporated can influence how long iodine remains available.
This provides a plausible scientific rationale for Turianica's interest in iodine associated with the unsaturated fatty acids of pumpkin-seed oil.
Is Iodine in Fortuna Vitae oil really impossible to overdose ...?
A.k.a.: How does Fortuna Vitae compare with those historical doses?
Fortuna Vitae currently provides approximately:
186 μg iodine per 10 mL daily serving.
That means a complete 250 mL bottle contains approximately 4,650 μg, or 4.65 mg, of iodine in total.
Now compare that with the children's iodized-oil trial mentioned above:
one Lipiodol dose = 200 mg iodine
versus
one entire 250 mL Fortuna Vitae bottle = 4.65 mg iodine.
The single 200 mg experimental dose therefore contained approximately 43 times more total iodine than the entire bottle of Fortuna Vitae.
Put another way, the 200 mg experimental iodized-oil dose contained as much total iodine as approximately 1,075 normal 10 mL Fortuna Vitae servings.
That comparison does not prove that Fortuna Vitae behaves identically to Lipiodol. They use different oils, different degrees of iodination and very different concentrations.
But the historical studies are valuable because they demonstrate an important biological principle: iodine incorporated into certain unsaturated-oil preparations can remain biologically available over long periods and has successfully been used to restore iodine status.
Is oil-bound iodine safer?
There is a promising safety argument. Historical iodized-oil studies demonstrate that very large depot doses could often be given successfully because iodine was available over a long period rather than behaving like the full dose of immediately available iodide.
That suggests a potential advantage of gradual delivery.
Organically bound iodine in an unsaturated oil may provide a more gradual, sustained iodine source, while the normal Fortuna Vitae serving supplies iodine at a nutritional — rather than pharmacological — amount.
For context, EFSA's current tolerable upper intake level for adults is 600 μg iodine per day from all sources. A 186 μg serving is therefore well below that level, although iodine from food and other supplements shall also be counted.
The bigger picture
The story of iodine is not simply "take more iodine."
It is about balance.
Some of us may begin with naturally lower iodine exposure because of geography, diet or food choices. Pregnancy can increase iodine requirements dramatically. Breastfeeding continues that increased demand. Repeated pregnancies may create repeated periods of higher iodine need. Heavy exercise and sweating can increase iodine losses. And chronic physiological stress can separately influence thyroid-hormone regulation and conversion.
In someone whose iodine intake is already marginal, these factors can gradually make a previously adequate supply insufficient.
That is why ensuring a regular, appropriate dietary supply of iodine matters.
And it is also why restoring iodine can be particularly helpful when thyroid dysfunction is genuinely related to iodine deficiency — while thyroid conditions such as Hashimoto's disease, Graves' disease or established hypothyroidism require individual medical assessment and other lifestyle changes rather than simply increasing iodine intake.
Prof. Turianica's central idea — that iodine availability depends both on our environment and on changing demands within the body — is therefore surprisingly consistent with much of what modern thyroid physiology now tells us. His work on iodine bound to vegetable-oil fatty acids adds another interesting idea: whether delivering small nutritional amounts of iodine in a lipid-bound form may provide a particularly gradual way of maintaining that supply.
The broader science behind iodine reserves, pregnancy-related depletion, environmental iodine deficiency and sustained iodine delivery through iodized oils is already well established.
If you would like a simple daily way to support your iodine intake and normal thyroid function, Fortuna Vitae provides iodine in a unique pumpkin-seed oil formulation designed for everyday use.
References:
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Turianica I, Rothová M. Symptoms and Prevention of the Iodine Deficiency. Journal of Microbiology, Biotechnology and Food Sciences. 2012;2(2):803–812. This is one of the most useful Turianica sources for the environmental-deficiency, pregnancy, physical activity and iodine-supplementation discussion.
Full article and PDF – Journal of Microbiology, Biotechnology and Food Sciences -
Turianica I, Rostoka L, Balint L, Hluchý S, Kulcicky O. Iodide Insufficiency – Consequences and Prophylaxis. Scientific Papers: Animal Science and Biotechnologies. 2009;42(1). The paper discusses environmental iodine deficiency, pregnancy, physical strain and stress, and presents Turianica's work with iodine-containing vegetable oils.
Full paper PDF -
Turianica I, Angelovičová M, Rostoka L, Kulčitský OK, Balint LI, Hluchý S, Toman R. Environmentálny jódový deficit a s ním spojené problémy / Environmental Iodine Deficit and Problems Connected With It. Nitra: Slovak University of Agriculture/Agrotár; 2007. 207 pages. ISBN 978-80-88943-24-2. The official Slovak Agricultural Library catalogues it under iodine deficiency, environmental burdens and thyroid diseases; the volume contains maps, graphs and tables.
Official Slovak Agricultural Library record -
Balint L, Rostoka L, Turianica I, Chlebo P, Cizmarova M, Kulcicky O. Impact of Iodine-Containing Pumpkin Oil on the Course of Cardiac Ischemia in the Residents of Zakarpattya Region. Scientific Papers: Animal Science and Biotechnologies. 2009;42(1). The study used 10 mL/day of Fortuna Vita described as containing 200 μg organically combined iodine and attributed part of the observed effect to normalization of iodine-thyroid status through iodine-containing fatty acids.
Journal article – Scientific Papers Animal Science and Biotechnologies -
NIH Office of Dietary Supplements. Iodine – Fact Sheet for Health Professionals. This is an important mainstream reference for iodine requirements, absorption, iodine deficiency, pregnancy/lactation requirements and safety; it states that an iodine-replete adult contains around 15–20 mg iodine, 70–80% of it in the thyroid.
NIH Iodine Fact Sheet for Health Professionals -
Pearce EN. Thyroid Regulation and Dysfunction in the Pregnant Patient. Endotext. Updated 6 July 2026. NCBI Bookshelf/NIH. Particularly valuable for the article: pregnancy increases thyroid-hormone production by approximately 50%, renal iodine clearance increases approximately 30–50%, iodine passes to the fetus, iodine stores can progressively decline when supply is inadequate, and lactation transfers iodine into breast milk.
NCBI Endotext – Thyroid Regulation and Dysfunction in Pregnancy -
Zimmermann MB, Adou P, Torresani T, Zeder C, Hurrell RF. Low dose oral iodized oil for control of iodine deficiency in children. British Journal of Nutrition. 2000;84(2):139–141. PMID 11029963. In 104 iodine-deficient children, a single 200 mg iodine dose in iodized poppy-seed oil improved iodine status for a year, reduced thyroid volume and produced no iodine-induced hypo- or hyperthyroidism in that study.
PubMed record – PMID 11029963 -
Simescu M, Varciu M, Nicolaescu E, Gnat D, Podoba J, Mihaescu M, Delange F. Iodized oil as a complement to iodized salt in schoolchildren in endemic goiter in Romania. Hormone Research. 2002;58(2):78–82. DOI 10.1159/000064657. PMID 12207166. Two hundred fourteen children received 200 mg iodine as iodized oil; iodine status remained improved for more than a year and goitre prevalence fell from 29% to 9% after one year.
PubMed record – PMID 12207166 -
Untoro J, Schultink W, West CE, Gross R, Hautvast JGAJ. Efficacy of oral iodized peanut oil is greater than that of iodized poppy seed oil among Indonesian schoolchildren. American Journal of Clinical Nutrition. 2006;84(5):1208–1214. DOI 10.1093/ajcn/84.5.1208. PMID 17093176. This randomized trial is important for the lipid-carrier argument: at equivalent 400 mg iodine doses, estimated iodine retention from the peanut-oil preparation was about three times greater, with approximately twice the duration of protection.
PubMed record – PMID 17093176 -
Rotondi M, Amato G, Biondi B, et al. Parity as a thyroid size-determining factor in areas with moderate iodine deficiency. Journal of Clinical Endocrinology & Metabolism. 2000;85(12):4534–4537. DOI 10.1210/jcem.85.12.7002. PMID 11134104. In 208 healthy women in a moderately iodine-deficient area, thyroid volume increased progressively with the number of previous pregnancies, supporting a cumulative effect of successive pregnancies when iodine supply is marginal.
PubMed record – PMID 11134104 -
Podoba J Jr, Hnilica P, Srbecký M, Podobová M. The effectiveness of iodine prophylaxis of endemic goiter in Slovakia from the viewpoint of physical and ultrasonographic examinations of the thyroid gland. Bratislavské lekárske listy. 1995;96(11):622–626. PMID 8624744. Examination of 2,946 Slovak children/adolescents found iodine prophylaxis had successfully brought thyroid measurements into ranges comparable with iodine-sufficient countries.
PubMed record – PMID 8624744 -
Lutyński R. Iodine deficiency in the Carpathian endemic region and iodine prophylaxis in Southern Poland. Przegląd Lekarski. 1996;53(11):816–819. PMID 9173446. Laboratory testing of food and water from the historically goitre-endemic Carpathian region demonstrated low environmental iodine, while interruptions in salt iodisation were followed by increases in goitre.
PubMed record – PMID 9173446 -
Dror DK, Allen LH. Iodine in Human Milk: A Systematic Review. Advances in Nutrition. 2018. PMID 29846524; PMCID PMC6008959. The review explains that the lactating mammary gland actively concentrates iodide, producing milk concentrations 20–50 times plasma concentrations, and notes that this can occur at the expense of maternal iodine reserves when maternal supply is inadequate.
Full article – PubMed Central -
Dohan O, De la Vieja A, Paroder V, et al. The sodium/iodide Symporter (NIS): characterization, regulation, and medical significance. Endocrine Reviews. 2003. DOI 10.1210/er.2001-0029. PMID 12588808. This major review establishes that NIS actively transports iodine not only into the thyroid but also into tissues including the salivary glands, gastric mucosa and lactating mammary gland.
PubMed record – PMID 12588808 -
ATSDR. Toxicological Profile for Iodine – Toxicokinetics/Distribution. NCBI Bookshelf. This government reference discusses iodine distribution throughout the body: thyroid as the dominant iodine reservoir, active iodide accumulation by breast, placenta, stomach and salivary glands, and uptake of iodine-containing thyroid hormones by liver and skeletal muscle.
NCBI Toxicological Profile for Iodine -
EFSA / Scientific Committee on Food. Tolerable Upper Intake Levels for Vitamins and Minerals – Iodine. The current EU summary retains an adult UL of 600 μg/day, including pregnancy and lactation; importantly, a UL is a chronic population-safety threshold, not an acute poisoning threshold.
EFSA Summary of Tolerable Upper Intake Levels