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Iodine, the Thyroid, and Radiation Protection

Posted by on March 17, 2011 86 comments

We have friends in Japan, living both north and south of the damaged reactors, and Shou-Ching asked me to do a post about how to protect against radiation.

The Concern

The radioactive substances released by the Chernobyl nuclear power plant meltdown are represented in this chart:

(Source. If you’re wondering what the other radioactive elements are, or why radioactive iodine is a byproduct of uranium fission, a possible place to start is Wikipedia, “Fission products by element” ).

Note first of all that the chart presents percentages of radioactive substances, not amounts. The amounts are highest on the first day and then decline rapidly. The great danger comes in the first few days.

During these dangerous first days, iodine-131 is, along with tellurium-132 and its decay product iodine-132, the dominant source of radioactivity. These radioactive iodine species account for over 50% of the radiation.

Not only its abundance, but also its effectiveness at causing biological damage make iodine far and away the greatest danger. Iodine radiation is highly effective at causing cellular damage:

Due to its mode of beta decay, iodine-131 is notable for causing mutation and death in cells which it penetrates, and other cells up to several millimeters away. [Source: Wikipedia, Iodine-131]

Worse, iodine is an important biological molecule that gets concentrated in the thyroid. So the dose of radiation becomes very high in the thyroid, and this leads to DNA damage producing a high risk for thyroid cancer.

Thyroid cancer is “the only unequivocal radiological effect of the Chernobyl accident on human health.” [1] Since Chernobyl released a great deal more radiation than the Japanese reactor meltdowns are likely to do, it’s likely that this will be the case in Japan also.

The rate of thyroid cancer after Chernobyl was higher the younger the age at time of exposure. Children and infants are at greatest risk:

It is now well documented that children and adolescents exposed to radioiodines from Chernobyl fallout have a sizeable dose-related increase in thyroid cancer, with the risk greatest in those youngest at exposure and with a suggestion that deficiency in stable iodine may increase the risk. [2]

The last point is crucial – iodine deficiency increases the risk.

Iodine deficiency and radiation risk

In iodine deficiency, the thyroid gland has difficulty generating enough thyroid hormone. T4 thyroid hormone, manufactured in the thyroid and so named because it has 4 iodine atoms, is 65.4% iodine by weight, so iodine is the key ingredient in thyroid hormone.

To compensate for an iodine deficiency, the body does two things:

  • The thyroid gland grows, so that it can more aggressively scan the blood for iodine. An enlarged thyroid is called a goiter.
  • The pituitary gland issues thyroid stimulating hormone (TSH), which induces the thyroid to aggressively scavenge iodine from the blood and turn it into thyroid hormone.

So in iodine deficiency the thyroid is aggressively scavenging all available iodine. This means that when a large dose of iodine-131 or iodine-132 arrives during radiation fallout, these radioactive iodine atoms are quickly picked up by the thyroid. There, they release their radiation and damage the thyroid.

On the other hand, in thyroid replete persons, the thyroid has all the iodine it needs and takes up little iodine from the blood. In this case, iodine that enters the body is distributed throughout the body, or excreted. Doses in any single cell are much lower. The danger to the thyroid is not much greater than that to other organs – which, the Chernobyl experience tells us, is not detectable to epidemiology. (There is even a theory that low-level radiation may be beneficial through hormesis.)

How can the thyroid be made replete with iodine?

The best way, which we recommend in our book, is to supplement with iodine and gradually build up the dose over a four to six month period. Start below 1 mg/day, take that for a month, then double the dose. After a month, double the dose again. Continue doubling until you reach your desired maintenance dose; we recommend at least 3 mg/day (a quarter Iodoral tablet), with 12.5 mg/day a reasonable dose. Some people taking as much as 50 mg/day.

At 12.5 mg/day, it can take a year or more to become replete with iodine in all tissues and to fully drive out other halogens, such as bromine, from the body. This has great benefits for immune function. So, it is best to get started!

Risks of high-dose iodine supplementation

If a person’s thyroid gland is adapted for iodine scarcity and the person takes a large dose of (non-radioactive) iodine, the likely course of events is:

1.      Hyperthyroidism. The thyroid, aggressively scavenging for iodine to repair a deficiency of thyroid hormone, scoops up all the iodine and makes a large amount of thyroid hormone. The person develops symptoms of hyperthyroidism (too much thyroid hormone): anxiety, intolerance of heat, muscle aches, hyperactivity, irritability, hypoglycemia, elevated body temperature, palpitations, hair loss, difficulty sleeping.

2.      Wolff-Chaikoff effect. As thyroid hormone levels become too high, the body induces mechanisms for suppressing thyroid hormone production. Simply reducing TSH output is not effective to suppress thyroid hormone production if a very large iodine influx is received. Fortunately there is another mechanism for suppressing thyroid hormone formation, mediated by iodine itself: the formation of iodine-rich proteins (iodopeptides) in the thyroid that inhibt synthesis of the thyroid peroxidase (TPO) enzyme. Normally, this mechanism operates for a few days and wears off, restoring normal thyroid function. [3]

3.      Reactive hypothyroidism? Usually, everything will normally return to normal after a few days. But sometimes in previously iodine-deficient adults and more commonly in newborns and fetuses and some diseased persons, after very high doses of iodine the Wolff-Chaikoff effect can persist. In this case the early hyperthyroidism is followed by a period of hypothyroidism (too little thyroid hormone). This “hypothyroidism is transient and thyroid function returns to normal in 2 to 3 weeks after iodide withdrawal, but transient T4 replacement therapy may be required in some patients.” [3]

4.      Risk for lasting hypothyroidism. People who develop a reactive hypothyroidism following a large dose of iodine are at high risk for later development of persistent hypothyroidism. [3]

So most people will experience transient hyperthyroid symptoms for a few days and then do fine. Some will develop a reactive hypothyroidism lasting a few weeks and then be OK, save for an elevated risk of hypothyroidism later which may or may not be due to the reactive episode.

Advice of the authorities to fallout victims

The advice from public health authorities is a compromise between the protective effects of high-dose iodine and the risk of messing up the thyroid.

A US Center for Disease Control (CDC) fact sheet explains the recommendations. A single large dose of iodine offers protection for about 24 hours. Recommended intakes are:

  • Adults should take 130 mg/day while exposure persists.
  • Children older than 3 and smaller than adults should take 65 mg/day while exposure persists.
  • Infants and toddlers aged 1 month to 3 years should take 32 mg/day.
  • Newborns should take 16 mg/day.

Our advice

The CDC dosage advice strikes us as very reasonable.

If you are not currently exposed to fallout, but think you may be exposed in the near future, you should consider beginning with small doses of iodine now – say, 3 mg/day. If that does not produce any symptoms, then try 6 mg/day; if it does, back off to half that dose. This will begin the adaptation process for your thyroid gland and help minimize hyperthyroid or hypothyroid reactions if you do have to take high doses.

Also, obtain your iodine tablets in advance. If fallout does occur, it may be hard to find iodine pills. NukePills.com says they are out of stock and have a large order backlog. I saw a story the other day that a 14-dose packet of potassium iodide was being sold at one site for $200, up from the normal $10 list price.

We recommend Iodoral 12.5 mg tablets. This is a good size for supplemental use; to reduce it to a 3 mg dose, cut the tablet in quarters with a razor blade. If fallout arrives, you can use ten Iodoral tablets to get a 125 mg adult dose.

For doses below 3 mg, smaller iodine tablets or liquid iodine solutions may be best; you can dilute liquid solutions to your desired dose. Some brands were recommended by readers in comments on our Supplement Recommendations page.

Conclusion

Outside of Japan, the risk is minimal, and even in Japan those who are replete with iodine are unlikely to develop thyroid cancer from exposure. After Chernobyl, thyroid cancer rates were high in Russia, the Ukraine, and Belarus which did not distribute iodine, but low in Poland which did. Fortunately, Japan has one of the highest iodine intakes in the world thanks to its high seaweed consumption. With that preparation plus proactive distribution of iodine tablets, we can expect and hope that the health effects of the reactor meltdowns will be minimal.

References

[1] Thomas GA et al. Integrating Research on Thyroid Cancer after Chernobyl-The Chernobyl Tissue Bank. Clin Oncol (R Coll Radiol). 2011 Feb 22. [Epub ahead of print] http://pmid.us/21345659.

[2] Cardis E, Hatch M. The Chernobyl Accident-An Epidemiological Perspective. Clin Oncol (R Coll Radiol). 2011 Mar 9. [Epub ahead of print] http://pmid.us/21396807.

[3] Markou K et al. Iodine-Induced hypothyroidism. Thyroid. 2001 May;11(5):501-10. http://pmid.us/11396709.

Around the Web; Eating Disorders and Hypothyroidism

Posted by on February 19, 2011 37 comments

Items that caught my eye this week:

(1) Would You Be My Meatheart?: I wasn’t clever enough to give this to Shou-Ching for Valentine’s Day, but would have known to use genuine hearts from the Asian market. Wait till next year honey!

(2) By the way: Who knew Manolo has a food blog?

(3) Ronaldo Forced Out of Soccer for Lack of Thyroid Hormone. Famed soccer star Ronaldo is retiring because he has hypothyroidism and he says soccer authorities consider treatment to be doping – so he has to retire to fix his health.

Absurd! Mary Shomon agrees.

(4) Ronaldo may play the “beautiful game,” but we Americans play the crazy game. This running back plays football like I used to:

(5) Startling if True: Paleo Pepper abridges a talk by Dr. Flechas at iodine4health.com claiming that thyroid hormone replacement may actually increase risk of breast cancer among hypothyroid women – what is needed is high-dose iodine:

A women with hypothyroidism has a 6% chance of developing breast cancer. Once she starts taking thyroid hormone, it doubles her chances. Once she’s been on thyroid hormone replacement for 15 years, it more than triples it – she now has a 19.6% chance of developing breast cancer.

I have not seen such statistics before and would have to check these claims. We recommend iodine and selenium as the first steps in dealing with hypothyroidism, but generally support thyroid hormone replacement.

(6) Burying the Lede: Is “strengthens pelvic floor muscles” really the number one benefit?

(7) Another Perfect Health breakfast idea: Emily suggests cream of rice with cream, butter, and apricot applesauce.

(8) Paleolithic Dairy?: Ravi at Daia Sol Gaia argues that dogs may have been domesticated and goats tamed and used for milk as early as 35,000 years ago – the start of the Upper Paleolithic. Is goat milk a Paleo food?

(9) The authentic way to drink Paleo goat milk: Paleolithic settlers at Gough Cave in England, c. 13,000 to 10,000 BC, ate human bone marrow and brain and used the skulls as drinking chalices:

Via Dienekes. Apparently drinking from human skulls is a widely attested practice, both in Paleolithic and historical times – see e.g. the Krum and Herodotus’s Scythians.

Reference: Bello SM et al. Earliest Directly-Dated Human Skull-Cups. PLoS ONE 6(2): e17026. doi:10.1371/journal.pone.0017026. Link.

(10) Avoid vegetable oils if you want a baby: Chris Highcock found a paper showing that infertile women eat 23% more polyunsaturated fat, and 17% less saturated fat, than fertile women. Infertile men eat 20% more polyunsaturated fat than fertile men.

Reference: Revonta M et al. Health and life style among infertile men and women. Sex Reprod Healthc. 2010 Aug;1(3):91-8. http://pmid.us/21122604.

(11) Never give up:

“I had the head doctor of surgical I.C.U. say, ‘Miracles happen.’“

(Via Craig Newmark)

(12) Which Machine for the Hippo? I thought this was a cool picture:

(From NPR via John Durant)

(13) Finally, our video: We’ve had a bit of discussion of eating disorders this week, in the comments to the “Therapy AND Life” post. That reminded me of this CBS News interview of a “Biggest Loser” contestant who said she developed an eating disorder during the show:

Micronutrient Deficiencies: An Underappreciated Cause of Hypothyroidism

Posted by on December 3, 2010 72 comments

A significant number of our readers have hypothyroidism with normal T4 but low T3. For instance, Kratos:

I followed a strict low carb diet with around 50g of carb per day for over 1 year and I think I have developed hypothyroidism …

TSH 3.4 (0.3-4.0)

FT3 2.2 (2.1-4.9)

FT4 11.4 (6.8-18.0)

This situation can have many causes. Our last post discussed how shift work and disrupted circadian rhythms can cause hypothyroidism. Another often-overlooked cause of hypothyroidism is nutrient deficiencies.

As noted in the book, selenium and iodine deficiencies are classic causes of hypothyroidism. Here I want to look at a few other possiblities.

Copper and Iron Deficiency

Copper deficiency, iron deficiency, and iodine deficiency during pregnancy or infancy generate similar neurological defects, and during adulthood generate similar hypothyroid symptoms:

Cu, Fe, and iodine/TH deficiencies result in similar defects in rodent brain development, including hypomyelination of axons, aberrant hippocampal structure and function, altered brain energy metabolism, and altered neuronal signaling (8–13). In addition, the behavioral and neurochemical abnormalities associated with perinatal Cu, Fe, and iodine/TH deficiencies are irreversible and persist into adulthood (14–16). These similarities suggest that there may be a common underlying mechanism associated with all three deficiencies contributing to the observed neurodevelopmental defects.

Several studies in postweanling rodents show that Cuand Fe deficiencies impair thyroid metabolism. Fe deficiency reduces circulating thyroxine (T4) and triiodothyronine (T3) concentrations (17–20), peripheral conversion of T4 to T3 (18, 19), TSH response to TRH (19), and thyroid peroxidase (TPO) activity (20). Cu deficiency also reduces circulating T4 andT3 concentrations and peripheral conversion of T4 to T3  (21, 22). In addition, Cu deficiency reduces serum and brain Fe levels, which may contribute to the Cu-dependent effect on thyroidal status (23). [1]

In infant rats, deficiencies of either copper or iron cause hypothyroidism:

Cu deficiency reduced serum total T(3) by 48%, serum total T(4) by 21%, and whole-brain T(3) by 10% at P12. Fe deficiency reduced serum total T(3) by 43%, serum total T(4) by 67%, and whole-brain T(3) by 25% at P12. [1]

Note that copper deficiency hypothyroidism reduces serum T3 levels more strongly than T4 levels, the same pattern that Kratos displays.

While We’re On the Topic of Micronutrients and Hypothyroidism …

Hypothyroidism induces the symptoms of riboflavin deficiency. This is because thyroid hormone is needed for production of the enzyme flavin kinase, which is in turn needed to generate flavin adenine dinucleotide (FAD). Riboflavin deficiency and thyroid hormone deficiency lead to the same low FAD levels in both rats and humans. [2]

This suggests that hypothyroid persons may wish to supplement with riboflavin, so that extra riboflavin may help make up for deficient flavin kinase.

Conclusion

I believe that those with health problems should strive to “overnourish” themselves. Micronutrient deficiencies can have insidious disabling effects, yet be impossible to diagnose. In disease conditions, needs for many micronutrients are increased. Many micronutrients are non-toxic up to fairly large doses and can be safely supplemented.

An effort to eat micronutritious foods and supplement micronutrients into their “plateau ranges” to eliminate deficiencies might generate startling health improvements.

Minerals like copper, selenium, and iodine are among the most important nutrients – they are among our eight essential supplements – yet also among the most widely deficient. Most supplementers neglect key minerals; but optimizing their intake can pay large health dividends.

References

[1] Bastian TW et al. Perinatal iron and copper deficiencies alter neonatal rat circulating and brain thyroid hormone concentrations. Endocrinology. 2010 Aug;151(8):4055-65. http://pmid.us/20573724.

[2] Cimino JA et al. Riboflavin metabolism in the hypothyroid newborn. Am J Clin Nutr. 1988 Mar;47(3):481-3. http://pmid.us/3348160.

Intermittent Fasting as a Therapy for Hypothyroidism

Posted by on December 1, 2010 128 comments

Reader Adam Kadela has begun intermittent fasting and wonders how it might affect his hypothyroidism:

I have a question pertaining to the section at the end of the book covering extended fasts. I regularly practice the 16-8 fast/feast protocol (breakfast at noon, last meal before eight), and plan to throw in a 36 hour fast once a month per your book. However, I am hypothyroid (hashimoto’s) and take synthetic T4 and T3 (unithroid and cytomel), so I’m wondering if an extended fast could affect my thyroid function negatively.

This is a great question. I think the daily 16-hour fast should be therapeutic for hypothyroidism, but I’m not sure about the 36-hour fast.

In today’s post I want to talk about why daily intermittent fasting may be therapeutic for Hashimoto’s, which is an autoimmune hypothyroidism.

Food Sets The Circadian Clock

The circadian clock is strongly influenced by diet: indeed, food intake dominates light in setting the circadian clock. If you regularly eat at night and fast during the day, the body will start treating night as day and day as night. [1]

(Alcohol consumption at night will also tend to reset the clock, which may explain why college students are often night owls!)

This suggests that controlling the timing of food consumption can help to maintain circadian rhythms.

The Circadian Clock and Hypothyroidism

The thyroid follows circadian rhythms. There is a circadian pattern to TSH levels:  high at night, low during the day.

The thyroid’s circadian pattern is diminished in autoimmune hypothyroidism. In a study of hypothyroid children, the night-time surge of TSH averaged 22%, compared to 124% in normal children. Only one of 13 hypothyroid children had a night-time TSH surge in the normal range. [2]

The study authors concluded:

We suggest that the nocturnal surge of TSH is important for maintenance of thyroid function and conclude that the nocturnal TSH surge is a much more sensitive test than the TSH response to TRH for the diagnosis of central hypothyroidism. [2]

Shift Work and Hypothyroidism

If circadian rhythms are important for thyroid function, we would expect shift workers to have high rates of hypothyroidism. Shift workers sleep during the day and eat at night, which disrupts circadian rhythms.

It turns out that shift work doubles the risk of autoimmune hypothyroidism:

Stress induces autoimmune disorders by affecting the immune response modulation. Recent studies have shown that shift work stress may enhance the onset of the autoimmune Graves hyperthyroidism. On the other hand, the possible association between occupational stress and autoimmune hypothyroidism has not yet been investigated…. Subclinical autoimmune hypothyroidism was diagnosed in 7.7 percent shift workers and in 3.8 percent day-time workers with a statistically significant difference: Odds Ratio (OR) 2.12, 95 percent Confidence Interval (CI) 1.05 to 4.29; p=0.03…. Our data show a significant association between shift work and autoimmune hypothyroidism. This finding may have implications in the health surveillance programs. [3]

Shift Work Affected Adam Too

In a follow up email, Adam told me that night shift work may have helped cause his hypothyroidism:

[T]he paper about thyroid and fasting … is particularly interesting to me due to my experience with night shift work for 10 months last year. My circadian rhythm was all out of whack due to experimenting with different sleep schedules and trying to workout around midnight before going into work at two a.m. I also played around with different diet strategies (grazing method w/ small meals, warrior diet, and ultimately settling on the 16-8, which is by far superior imo). My thyroid, along with other hormones, did not enjoy these trials.

Intermittent Fasting May Be Therapeutic

Since the circadian rhythm is affected by both food and light exposure, lifestyle practices can enhance natural circadian rhythms. These practices should optimize the circadian cycle:

  • Light entrainment:  Get daytime sun exposure, and sleep in a totally darkened room.
  • Daytime feeding: Eat during daylight hours, so that food rhythms and light rhythms are in synch.
  • Intermittent fasting: Concentrate food intake during an 8-hour window during daylight hours, preferably the afternoon. A 16-hour fast leading to lower blood sugar and insulin levels, and the more intense hormonal response to food that results from concentration of daily calories into a short 8-hour time window, will accentuate the diurnal rhythm.
  • Adequate carb intake:  Eat at least 400 “safe starch” carbohydrate calories daily during the afternoon feeding window. Relative to a very low-carb diet, this will increase daytime insulin release and, by increasing insulin sensitivity, may reduce fasting insulin levels. It will thus enhance diurnal insulin rhythm.

Adam tells me that intermittent fasting seems to be improving his hypothyroidism:

I think you’re correct in that I’ve experienced some curative effects. However, with the improved nutrient absorption and gut health from healthier eating and fasting, I think I fluctuate a lot b/w slightly hypo, normal, and hyper, since my medication is constant. I’m still in the process of finding a balance, but it’s a bigger improvement than my past state.

Conclusion

Many doctors mistakenly assume that little can be done to cure autoimmune disorders. In fact, however, autoimmune conditions commonly disappear once the chronic infections, food toxins, or poor health practices that cause them are eliminated.

Circadian rhythms have powerful influences on many biological processes, and disrupted circadian rhythms are a common feature of disease. Without clinical trials it’s impossible to be sure, but efforts to enhance circadian rhythms may be therapeutic for diseases such as hypothyroidism.

Intermittent fasting, daytime light exposure, excluding light from the bedroom, night fasting and daytime feeding are simple practices. But they may be underappreciated keys to good health.

References

[1] Fuller PM et al. Differential rescue of light- and food-entrainable circadian rhythms. Science. 2008 May 23;320(5879):1074-7. http://pmid.us/18497298.

[2] Rose SR et al. Hypothyroidism and deficiency of the nocturnal thyrotropin surge in children with hypothalamic-pituitary disorders. J Clin Endocrinol Metab. 1990 Jun;70(6):1750-5. http://pmid.us/2112153.

[3] Magrini A et al. Shift work and autoimmune thyroid disorders. Int J Immunopathol Pharmacol. 2006 Oct-Dec;19(4 Suppl):31-6. http://pmid.us/17291404.