Iodine Revisited: Is There Something There?

Iodine Overview

I will risk losing a few followers with this post.

“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.” – Mark Twain

Iodine is one of the most hated and most loved nutrients depending who you ask. Even my favorite nutrition group, the Ray Peat-arians, are typically against iodine supplementation, and for good reason when first examining the facts.  I certainly don’t want to say they’re “wrong” because I really don’t know. I can only tell you what I feel from it, and try to come up with reasons why. And I definitely don’t want to throw stones at the physiological giant Ray Peat. But, we need to remember that Ray Peat does recommend consuming foods with iodine such as shellfish, milk, cheese and potatoes.  I’m not recommending mega-dosing iodine because I believe in balance, but I am advocating paying attention to iodine consumption versus other halogen consumption.

I used iodine heavily prior to finding the work of Ray Peat. This was around the time I was regularly sucking down blended chia seeds, hemp seeds, pumpkin seeds and the worst tasting of all, sesame seeds. Hey, they’ve got lots of calcium.  I still had good results from iodine at that time. I sometimes think that my initial outstanding results with Peatarianism (see my Eat as Much as Possible post) were at least partially from the iodine I had built up in my system.

The RDA for iodine is 150 micrograms. That means .000150 grams. A tiny amount, right – so why would we need to take more? Typically we can get this much from potatoes, eggs and milk, depending on the source of aforementioned foods. Animals grazing near or in the goiter (goitre) zones are likely to have less iodine in their products than animals that graze elsewhere.  See the goiter zones in Alexander Keith Johnston’s 1856 map of North American disease patterns.  This is likely a result of the climate, erosion from glaciers and the topographic features of the northern part of the US and Canada.  Glaciers likely melted and took a lot of the iodine (and other trace minerals) to the Gulf of Mexico via the Missouri and Mississippi river systems.


Turns out that the RDA was really only calculated to be the bare minimum necessary for preventing goiter.  In theory, some goiters occur because the thyroid tissue expands to absorb additional iodine. Of course, that is not enough of a justification for you to begin guzzling the gross metallic tasting brown stuff. I aim to provide some real research and math to justify considering iodine supplementation.  As always, you’re the master of your own ship so you need to find what works for you.

I weigh about 200 lbs or 90 kgs.  Based on numbers I’ve found on the internet, the body’s daily requirement is 1.7 mcg / kg of thyroid hormone T4, and .5 mcg / kg of thyroid hormone T3.  This means I need about 153 mcg T4 and 46 mcg T3 (30% of the T4 number) on a daily basis.  These numbers should also be used for accurate thyroid dosing to ensure you’re getting enough thyroid for your body.  I will post more about my theories on this later.

A T4 molecule contains four atoms of iodine, or about 65.34% of the mass.  This is 153 mcg * 65.34% = 99.9 mcg of iodine (1)

A T3 molecule contains three atoms of iodine, or about 59.73% of the mass.  This is 46 mcg * 59.73% = 27.4 mcg of iodine (2)

This is a total of 127.4 mcg of iodine needed for production of thyroid hormone only.  This actually lines up quite well with the RDA value of 150 mcg to prevent goiter.  However, the problem, as always, gets more complex.

Why People May Need More than the RDA of 150 micrograms

Environmental toxins

The halogen elements fluoride and bromide are abundant in our “modern” environment.  These fill iodine receptors and displace iodine in the body.  “Fluoride, the negative ion of the element fluorine, easily displaces iodine in the body because it is much lighter and therefore more reactive. In fact the activity of any one of the halogens is inversely proportion to its atomic weight (14). Iodine has the highest atomic mass and is therefore more easily displaced by the smaller halogens. Here are examples of where you come in contact with them, and typically how much.

Bromide – In Food, Pesticides, Laundry Detergent, Furniture

An American typically consumes or absorbs 2 to 8mg on a daily basis (3) – which is 13 to 53 times more than the RDA (150 mcg) for iodine.  Bromide is found in pesticides (methyl bromide), bread products (potassium bromate in “brominated flour”), and brominated vegetable oil that may be added to citrus-flavored drinks like Mountain Dew or Gatorade, hot tub cleansers, prescription drugs, plastics and some fabric dyes (4).

In thyroid cancer patients, Malenchenk found bromide levels are 50 times higher than normal thyroid tissue (5).  Rats fed the minimal amount of bromine expected from the environment for 16 and 66 days underwent goiter-like changes (6),  a potential case of bromide dominance.  Rats exposed to the brominated flame retardant compound (in furniture), bromocyclodecane, showed consistent effects on the thyroid hormone axis, including decreased T4.  Thyroid gland cells increased in size and had larger nuclei, indicating increased synthetic bromide activity. (7) With more than environmentally expected intake of bromide, fully one-third of the iodine content in the thyroids of rats was replaced by bromide. (8,9)

Beyond the thyroid, bromide has detrimental effects on the brain. Bromide toxicity has been implicated in mental conditions such as transitory schizophrenia (10).  Additionally, “Psychiatric symptoms (of bromism) may include, in the earlier stages, disinhibition, self-neglect, fatigue, sluggishness, impairment of memory and concentration, irritability or emotional instability, and depression” (11). Often, psychiatric drugs are prescribed to deal with these symptoms which may actually worsen bromism.  Some contain bromide (Celexa) and all SSRIs contain fluoride (Paxil, Prozac, Luvox, Lexapro) except Zoloft.

Prevously, bromide (Neurosine pharmaceutical) was used to suppress women’s sex drive in the 1950s (12).

The UK banned bromate in bread in 1990.  Canada banned bromate in bread in 1994. The U.S. has not banned bromate in spite of a petition submitted in 1999 by the Center for Science in the Public Interest.  The center claimed that the FDA has known for years that bromate causes cancer in lab animals (13)

You can best reduce your chance of getting bromism by avoiding bromide/bromate/bromine.  Otherwise, ensuring your iodine levels are sufficient (on par with bromide consumption) may be a decent defense from this environmental toxin crowding out iodine in your thyroid and other tissues.

Fluoride – In Water, In Food: Time to Get out the Tinfoil hat, right?  Well, let’s look at the facts.

“Fluoride is a universal G-protein activator/inhibitor. The stimulation of certain G-proteins occurs due to the toxic effects of fluoride, which has the effects of switching off the uptake into the cell of the active thyroid hormone (14).”  TSH is commonly used to estimate the activity of the thyroid.  A high TSH means the thyroid isn’t adequately responding to the TSH so the pituitary gland “tries” harder.  “The TSH output from pituitary gland is inhibited by fluoride, thus reducing thyroid output from thyroid glands. Fluoride competes for the receptor sites on the thyroid gland which respond to TSH; so that less of this hormone reaches the thyroid gland and fewer hormones are manufactured (Wilson and DeEds 1940; Susheela et al. 2005).” (14)

A study in India was conducted on 60 children examining fluoride intake’s effects. They were broken into subgroups – those that have dental fluorosis and those that don’t – subgroups 1A and 1B. Group 1A where 15 children were selected in India with fluoride levels in water up to 2.6 mg / L, and Group 1B where 15 children had water levels were up to 5.1 mg / L.  The group 2 (ten) children were of similar socio-economic status, but had “safe” (<1mg / L) levels of fluoride in their water.  Group 1 had 43 children of 60 (71%) with derangement of thyroid hormones – FT3, FT4 and TSH.  Group 2 had 1 child of 10 with derangement (14).

The US government previously recommended that the fluoridated water supply to contained .7 mg / L to 1.2 mg / L.  Now, they are recommending no more than .7 mg / L after about 41% of adolescents are suffering from fluorosis – a condition affecting the appearance of tooth enamel (8).  Most “health” experts recommend consuming 8 cups of water in a day.  This is approximately two liters, and therefore 2 mg of fluoride.  Which, again, is 13 times more fluoride than the RDA of iodide.

Indeed, data has shown that fluoride can also affect fertility and sex drive similar to bromide.  “The annual total fertility rate (TFR) for women in the age range 10-49 yr was calculated for the period 1970-1988. For each region separately, the annual TFR was regressed on the fluoride measure and sociodemographic covariables. Most regions showed an association of decreasing TFR with increasing fluoride levels. Meta-analysis of the region-specific results confirmed that the combined result was a negative TFR/fluoride association with a consensus combined p value of .0002-.0004, depending on the analytical scenario” (17).

Black tea is also a fairly significant source (<2 mg / L) of fluoride.  Higher quality black teas typically have less fluoride.  Green and white teas also typically have less fluoride than black tea.  (9) Toothpaste is another potentially significant source of fluoride intake.  Many commercial baked goods are made with tap-water.  Same with a lot of sports drinks.  When making baked goods such as bread, hamburger buns or cupcakes, flour is made with water.  When the temperature rises, water becomes steam and leaves behind the minerals fluoride and bromide in a very digestible form without excess liquid.

In one study, rats with insufficient iodine status were fed fluoride at 10 mg a day.  They gained weight and their thyroids gained weight (18).

Again, either avoid fluoride by using steam distilled water / spring water in everything you do, and managing tea intake, or consider defending yourself by establishing iodine sufficiency status on par with your expected consumption of fluoride.

Chlorate, Perchlorate – In Water, In Fertilizer and Food Prepared with Tap Water

“Perchlorate inhibits thyroidal iodine uptake and subsequently decreases thyroid hormone production.” (25). The Health Reference Level for chlorate in tap water is 210 mcg / L.  This isn’t very much, but it’s still greater than the RDA of iodine.  In addition, 35% of locations sampled in the US had levels higher than that, including a few with values in the 700 mcg / L to 1000 mcg / L (26).

Along the Mississippi river valley, sodium chlorate is heavily used as a fertilizer for soybeans, corn, cotton and rice.  Most of Mississippi, Iowa and the northern part of Louisiana use greater than 2.57 lbs of this fertilizer per acre (26).  This will accumulate in the water supply everywhere downstream of this use.

Even the EPA identifies that “Chlorate, similar to perchlorate, is a goitrogen and can decrease iodide uptake through competitive inhibition leading to the formation of goiters (enlargement of the thyroid). The USEPA cited the interference of perchlorate with iodine transport into the thyroid gland and low iodine uptake in general as the major health concern requiring a perchlorate MCL (USEPA 2011b), and thus might be 22 another factor EPA considers in regulating chlorate.” (26)

Polyunsaturated fats – In Food, In Everything


Using iodine is one of the methods for determining how unsaturated an oil is.  The number of grams of iodine absorbed by 100 grams of a given oil is called the iodine value.  You can read about it more on Wikipedia here. The more unsaturated the more iodine it absorbs – some very unsaturated oils actually absorb more grams of iodine than their own mass.

Unsaturated fatty acids are the those containing carbon-carbon double bonds.  Iodine atoms react across the carbon-carbon bonds. The iodine will attach itself over a double bond to make a single bond where an iodine atom is now attached to each carbon atom. Higher iodine numbers do not refer to the amount of iodine in the oil, but rather the amount of iodine needed to “saturate” the oil, or break all the double bonds (23).  Therefore, the more unsaturated, the more iodine it takes to break all the double bonds.

Most Peat-arians know the value of Saturated oils – those without double-bonds that resist becoming peroxides or hydrogenated at high temperatures.  They are also are well-versed in the dangers associated with high polyunsaturated fat intake due to their effects on the thyroid gland, inflammation, and blood sugar metabolism. Every gram of our favorite soybean oil absorbs between 1.2 and 1.36 grams of iodine.  Yes, you read that right.  1.36 GRAMS! (19)

Linoleic Acid Becomes Similar to Stearic Acid

Linoleic Acid Becomes Similar to Stearic Acid

This means if my body is 20% body fat (18 kilograms), let’s be generous and say that it is 40% fully saturated (similar to cocoa butter – see table here), my body fat is capable of absorbing 18,000 grams * .40  = 7200 grams of iodine.  If I were fully made up of our good friend coconut oil, my body fat would only absorb 18,000 *.12 = 2160 grams of iodine.  This example may be a red herring, but it goes to show that essentially the more fat you eat, especially the more unsaturated fat you eat, the more iodine you may need in your diet.

How to Properly Use Iodine – According to the Iodine megadosers

Companion nutrients: Magnesium, vitamin C, Selenium, Vitamin B2 Riboflavin, Vitamin B3 Niacinamide, and salt.
The iodine workshop of 2007 developed this list of companion nutrients to help protect from any potential negative side effects associated with iodine’s use.

Iodine – some people use Kelp as their iodine source – it is okay as long as the water has not been polluted or irradiated.  This is few and far between nowadays.  Here are a few options for Lugol’s 2% or Lugol’s 5% the latter being mined iodine crystals mixed with water. Most iodine therapy programs use one of these “inorganic” options instead of plants or foods.  Or some even just recommend straight SSKI – or super-saturated potassium iodide.  This is the form supposedly with the least amount of side-effects.

Magnesium – I like getting magnesium from food, body spray mag chloride or magnesium bicarbonate made like this with Gerolsteiner water, which is already high in easy to digest minerals like magnesium and calcium, and Milk of Magnesia without bleach.

Vitamin C – I like using acerola powder and other high vitamin C foods such as oranges.  I do not like synthetic ascorbic acid as sustained intake of of ascorbic acid are toxic and immunosuppressive for human T cells.  Ascorbic acid also frequently comes GMO corn.

Selenium – I don’t recommend supplements for this.  I like getting selenium from my diet (oysters, liver, tuna or Brazil nuts if you can handle phytic acid) even though every “iodine protocol” out there recommends getting between 200mcg and 400mcg of selenomethionine daily.  For me, the commonly used selenomethionine instantly causes toxicity in me and my hair and nails become brittle.  These are common symptoms of selenium toxicity (20). Perhaps this is because the amino acid methionine is known to be somewhat thyroid antagonistic. Sodium selenite is supposedly a less reactive and less toxic form, but I haven’t been able to find a good source of it.

Vitamins B2 and B3:  Riboflavin / Niacinamide – “Autoimmune” disorders are mislabeled according to Haidut over at Ray Peat Forums.  According to him, what’s really going on is the immune system is building antibodies against cells with deranged metabolisms (low NAD/NADH ratios).  Vitamins B2 and B3 can support the NAD/NADH ratio by increasing cellular ATP and keeping cells in a fully oxidized state preventing an “autoimmune” reaction from iodine and increasing the organification of iodine (21).  People commonly use ATP Cofactors,or you can buy B2 and B3 powders individually to avoid excipients.

Salt can help with your body’s removal of fluoride, heavy metals, and bromide.  I recommend this Celtic Sea salt.  It isn’t pink, but that’s a good thing.  Iron is a heavy metal that when consumed in excess is toxic.  Additionally, where there is iron, there are other heavy metals.

Iodine interacts with the following minerals:  Hg (mercury), F (Fluorine), Co (Cobalt), As (Arsenic).  These all have antagonistic effect on Iodine.  Concurrent deficiencies in selenium, iron, or vitamin A may exacerbate the effects of iodine deficiency (24).

Why is Iodine so rare yet so needed?  Where did it all go?  Because iodine has a heavy atomic mass, a lot of it will naturally fall towards the lower parts of the earth (the ocean).  From a more historical perspective, if there was a Great Flood (see – Epic of Gilgamesh or Noah’s Ark) on the earth, it is quite likely that as water receded from the soil, it took a lot of the iodine with it back into the ocean.  And really, iodine deficiency may not be such a problem if it were not for the competitive toxins listed above.

Potential negatives of using iodine

The doctors of the last three generations are all taught the Wolff-Chaikoff effect.  That it is a well-known law of physiology that iodine “shuts down the thyroid gland.”  Now, that would be strange considering iodine is one of the two building blocks of thyroid hormone.  But, let’s examine why that became a well-known law of physiology.

Since the hypothalamus has overall control of thyroid hormone output, it releases TRH which stimulates the pituitary to release TSH which instructs the healthy thyroid to take up iodine and produce thyroid hormone which should provide negative feedback reducing the need for TRH and TSH.

When iodine is administered, TSH goes way up. “Oh my god! Iodine causes hypothyroidism!”  This patient now has now been diagnosed with subclinical hypothyroidism because their thyroid is seemingly not responding or is no longer sensitive to TSH, and especially if the patient also exhibits low T3 or T4 blood levels even though Ray Peat has written about the inaccuracy of protein bound iodine tests.

In fact, if you want to be officially be diagnosed as hypothyroid, take a few milligrams of iodine a day or two before your test, and your doctor will surely come away with a diagnosis that you’re hypothyroid.  This happened to me.  That said, it is definitely a sign of problems if your TSH goes up and never comes back down as your T4 and T3 levels rise.  This is likely where a lot of the anti-TSH movement started.

It actually makes sense to me that upon sensing more raw materials (read: iodine) are available to the body, that the hypothalamus would ramp up production of TRH.  Would it not?

This is a very simple explanation for why iodine seems to be the cause of hypothyroidism.  Unfortunately, it throws out analysis of the symptoms which are typically better for diagnosing hypothyroidism such as low body temperature.

The table produced by this study where iodine worsened thyroid function all had patients with some sort of thyroid disorder prior to administering iodine: Graves, Hashimoto’s, prior Iodine deficiency then exposed to > 2mg, elderly with subclinical hypothyroidism, and individuals with family history of goiters or thyroiditis (27).  This infers that something else is going on.  Either low NAD+ / NADH ratio, damaged or mutated sodium iodide symporter gene or lack of selenium.

Potential Benefits

“Nobel laureate Dr. Albert Szent Györgi (1893—1986), the physician who discovered vitamin C, writes: “When I was a medical student, iodine in the form of KI was the universal medicine. Nobody knew what it did, but it did something and did something good. We students used to sum up the situation in this little rhyme:

‘If ye don’t know where, what, and why Prescribe ye then K and I.’  The standard dose of potassium iodide given was 1 gram, which contains 770 mg of iodine, an insane amount of iodine.  It’s weird how much science and medicine has changed in regards to iodine over the last 100 years.

Indeed, there is something magical that happens with iodine, if you can handle it.  I’m not sure the effect is entirely related to the endocrine system – especially as the transient effects show subclinical hypothyroidism.  The benefit may be due to iodine being a universal electron donor – allowing better electrical current throughout the body, and binding with positively charged oxidants.

Well, what do we know is actually does do since we don’t seem to fully understand its interactions with the thyroid.

Iodine & Diabetes Type 1:

“The incidence of type 1 diabetes in control BB rats was 68% at the age of 19 weeks. Sodium Iodide and T3 reduced the incidence, whereas TSH had no effect” (28).

Iodine & Diabetes Type 2:

(Low) “Urinary iodine is associated with insulin resistance in subjects with diabetes mellitus type 2.”  The concentration of urine iodine was significantly lower in Type 2 Diabetes Patients than in healthy control subjects (84.6±2.3 vs. 119.4±3.4, p<0.001), which remained significant after creatinine correction and controlling for age (p=0.01).

Furthermore, people with low urinary iodine had larger waist and hips, are prone to SAD, and high glucose, insulin, HOMA-IR triglyceride, resistin, angiotensin II (Ang II), and CRP.  High urinary iodine was correlated with higher TSH as expected (29).

Iodine & Heart Disease –

The lower salt movement has removed some iodine from Americans’ diets.  These changes “have led to a general decline in iodine intake in many developed countries. For example, a United States national health survey conducted in the early 1970s observed that 1 in 40 individuals had urinary iodine levels suggestive of moderate or greater iodine deficiency; twenty years later, moderate to severe iodine deficiency was observed in 1 in 9 participants.”

“Iodine and iodine-rich foods have long been used as a treatment for hypertension and cardiovascular disease; yet, modern randomized studies examining the effects of iodine on cardiovascular disease have not been carried out.”  (30)

Iodine & Estrogen –

“The protective effects of iodine on breast cancer have been postulated from epidemiologic evidence and described in animal models. The molecular mechanisms responsible have not been identified but laboratory evidence suggests that iodine may inhibit cancer promotion through modulation of the estrogen pathway.” (32)

Although the mechanism is not understood and may not be iodine, kelp reduces estrogen levels significantly.  “They did a simple experiment in which female rats received 175 or 350 mg of seaweed per kg of bodyweight each day. The highest dose was the most effective and reduced the concentration of estradiol in the rats by almost 40 percent. [Human equivalent of the high dose: 3000-5000 mg/day.] The graph below shows this.” (33).

The reduction may be due to total reduction of sex hormones although the article claims progesterone production rose slightly.

Iodine as an antioxidant –

“Several tissues share with the thyroid gland the capacity to actively accumulate iodine; these include the salivary glands, gastric mucosa, lactating mammary gland, the choroid plexus, ciliary body of the eye, lacrimal gland, thymus, skin, placenta, ovary, uterus, prostate, and pancreas, and they may either maintain or lose this ability under pathological conditions. “

“Iodine in comparison with ascorbic acid, using the in vitro ferric reducing/antioxidant power assay; it shows that I2 exerts a 10- or 50-fold greater antioxidant action than ascorbic acid or KI, respectively.”

“Iodine also has well-known anti-inflammatory effects. It is well established that povidone–iodine, besides its excellent antibacterial effect, also exerts an anti-inflammatory action by neutralizing radical oxygen species. Moreover, I2 inhibits the generation of nitric oxide in murine macrophages and tumor necrosis factor-α expression in human monocytes/macrophages.” (31).

Mysterious Effects on me:

I feel the following changes when I use iodine: less brain fog – words come more quickly, I fear less about the future, I fear less about food, I become less neurotic or concerned someone is getting something over on me, a bit more energy, less thyroid medicine required.  It may just all be related to higher TSH.  Who knows?  Before you get into it, do your-own research and don’t dive-in head first.  You may end up doing more harm than good.

If you would like to read more about the iodine advocates, seek out work by Lynne Farrow, Dr. Jorge Flechas, Dr Guy E. Abraham, or Dr. David Brownstein.  If you’d like read about the problems with iodine just google “iodine excess” or “iodine toxicity. “

In summary, iodine seems to help some thyroid patients come off of thyroid medication.  For others, it worsens their symptoms.  What about you?  Have you tried iodine?  Please comment about your results.






(5) Malenchenko AF et al., The Content and Distribution of Iodine, Chlorine and Bromide in the Normal and Pathologically Changed Thyroid Tissue, Med Radiol 1984.

(6) Velicky J et al., Potassium Bromide and the Thyroid Gland of the Rat: Morphology and Immunochemistry, RIA and INAA Analysis, Ann Anat 1997.

(7) Issue 6, July 2006


(9) Vobecky M et al., Interaction of Bromine with Iodine in the Rat Thyroid Gland at Enhanced Bromide Intake, Biol Trace Elem Res 1996.



(12) Nymphomania:  A History


(14) A comparative study of fluoride ingestion levels, serum thyroid hormone & TSH level derangements, dental fluorosis status among school children from endemic and non-endemic fluorosis areas


(16) Prevalence and Severity of Dental Fluorosis in the United States, 1999-2004

(17) Exposure to high fluoride concentrations in drinking water is associated with decreased birth rates.

(18) Summary of Effects of Fluoride Exposure for Rats with Different Amounts of Iodine Intake (Means ± SD)

(19) Iodine value





(24) Hess SY. The impact of common micronutrient deficiencies on iodine and thyroid metabolism: the evidence from human studies. Best Pract Res Clin Endocrinol Metab. 2010;24(1):117-132.



(27) Iodine, Iodine metabolism and Iodine deficiency disorders revisited

(28) Iodine and tri-iodo-thyronine reduce the incidence of type 1 diabetes mellitus in the autoimmune prone BB rats.

(29) Urinary iodine is associated with insulin resistance in subjects with diabetes mellitus type 2

(30) Hypothesis: dietary iodine intake in the etiology of cardiovascular disease.

(31) The Extrathyronine Actions of Iodine as Antioxidant, Apoptotic, and Differentiation Factor in Various Tissues

(32) Iodine Alters Gene Expression in the MCF7 Breast Cancer Cell Line: Evidence for an Anti-Estrogen Effect of Iodine

(33) Kelp has anti-estrogenic effect.