Iodine: Absorbing Is Not the Same as Using

Iodine: Absorbing Is Not the Same as Using

by Laurent Glatz – for Athletic Carnivore

Iodine is often presented as a simple nutrient: you consume it, absorb it, and the thyroid uses it. The biological reality is far more complex. It is possible to absorb over 90% of ingested iodine and still exhibit slowed thyroid function. Because the real challenge is not digestive absorption. It lies in cellular uptake, organification, hormonal conversion, and the overall endocrine environment.

Where Do We Actually Stock Up on Iodine?

Daily requirements are precise.

- 150 micrograms per day for adults.
- 200 to 250 micrograms during pregnancy and breastfeeding.

Consuming less than 100 micrograms daily over several weeks can reduce hormone synthesis. Conversely, chronic intake above 1,000 micrograms may trigger inhibitory mechanisms.

The main dietary sources are concentrated.

Marine products are the richest: sea fish, crustaceans, shellfish. Cod can contain between 100 and 300 micrograms per 100 grams. Seaweed sometimes exceeds several thousand micrograms per gram, with extreme variations depending on the species.

Eggs provide on average 20 to 30 micrograms each.

Dairy products contain variable amounts depending on animal feed.

Land meat is relatively poor, often less than 10 micrograms per 100 grams.

In a carnivore diet based solely on red meat without marine products or eggs, iodine intake can become insufficient.

Intestinal absorption, however, poses almost no problem. Iodide is absorbed at over 90% in the jejunum and ileum, then enters the bloodstream.

But this is where true biological selection begins.

Thyroid Uptake: A Mechanism Under Influence

The thyroid captures iodine via the NIS transporter (sodium-iodide symporter). This transporter depends on the sodium gradient and stimulation by TSH.

Any disruption of this transporter reduces effective iodine utilization.

First factor: halogen competition.

Fluoride, bromide, and perchlorate share chemical similarities with iodine. They can interfere with uptake through NIS. Fluoride is present in some water supplies and dental products. Bromide can be found in certain food additives and flame retardants. Perchlorate is detected in some contaminated waters.

Thus, iodine can be properly absorbed but poorly taken up by the thyroid.

Second factor: excess estrogens.

Estrogens increase the synthesis of TBG (thyroid-binding globulin). This raises the bound fraction of thyroid hormones and can reduce the free active fraction. Moreover, a chronic hyperestrogenic environment is linked to a higher risk of autoimmune thyroid diseases.

Excess estrogens can also influence NIS expression and alter thyroid sensitivity to TSH. This does not block iodine in the intestine but can impair its functional effectiveness.

Third factor: selenium.

Deiodinase enzymes that convert T4 into active T3 are selenium-dependent. Insufficient selenium intake reduces peripheral conversion, even if iodine is adequate. This can result in normal T4 but low T3 levels.

Fourth factor: iron.

Thyroperoxidase, the key enzyme for iodine organification in the thyroid, depends on iron. Iron deficiency can therefore impair iodine incorporation into hormones.

Fifth factor: the Wolff-Chaikoff effect.

In cases of massive iodine intake, the thyroid can temporarily block its use to prevent hormone overproduction. In some individuals, this inhibition persists and may lead to iodine-induced hypothyroidism.

What the Body Actually Uses

Once taken up, iodine is incorporated into thyroglobulin to form T4 and T3. T4 contains four iodine atoms; T3 contains three. Each thyroid hormone molecule is literally an iodinated structure.

The average daily production of T4 is about 80 to 100 micrograms. Circulating T3 is mostly produced by peripheral conversion.

Basal metabolism, body temperature, heart rate, lipolysis, protein synthesis, and mitochondrial function depend on these hormones.

Insufficient intake slows the entire system.

Poorly regulated excess can disrupt it.

The Modern Paradox

We live in an environment where:

- Exposure to competing halogens is increasing,
- Consumption of marine products is decreasing,
- Hormonal imbalances, notably hyperestrogenism, are rising,
- Selenium and iron deficiencies persist in some populations.

In this context, iodine can be absorbed but poorly utilized.

The distinction between “intake,” “absorption,” and “hormonal efficacy” becomes central.

One can consume 150 micrograms of iodine, absorb 90%, and still show symptoms of metabolic slowdown if thyroid uptake, organification, or peripheral conversion are impaired.

Iodine is not just a micronutrient. It is an endocrine lever.

And the essential question may not be: do you consume enough iodine?

But rather: does your hormonal and mineral environment truly allow this iodine to be used?

To analyze your overall terrain, not just an isolated nutrient, you can [take the free questionnaire](/en/questionnaire-neuroprofil.html).

FAQ

Is iodine always well absorbed?

Why does selenium matter?

Can too much iodine be harmful?

Does red meat provide much iodine?

The real issue is therefore not just iodine intake. It is the thyroid’s capacity to transform this intake into usable hormones.

#Iodine #Thyroid #T3 #T4 #TSH #Selenium #Iron #Hormones #Carnivore #AthleticCarnivore