Are Cruciferous Vegetables Goitrogenic? And What You Should Know About Iodine

Haven’t you heard from the world wide web that cruciferous vegetables and soy might damage your thyroid health and even cause goiters?

When I was battling hypothyroidism I heard my share of scary stories. The list of foods that I “should” or “should not” eat piled high quickly. It was disconcerting to me that I might have to give up my most beloved vegetables: radishes, cabbage, kale, bok choy and others from the Brassica family. I was not ready to “sacrifice” that much for my health…so, I rebelled, and asked questions.

It made no sense to me that such nutrient dense, whole foods would be bad for me. How is it possible?

So, in spite of everything I read online, I threw caution to the wind and kept enjoying my cruciferous vegetables while reversing hypothyroidism.

The good news? I reversed hypothyroidism! AND…

I did not get a goiter!

I still enjoy my cabbage, kale, soy and occasional tofu.

If you are battling any thyroid disorders, such as hypothyroidism, hyperthyroidism, Grave’s disease, Hashimoto’s or any other hormone imbalances, you are probably in the same boat – confused about what you can and cannot ingest.

So, I want to help you set yourself free.

In today’s article I will tell you why cruciferous vegetables should be enjoyed, instead of being demonized, why they do not cause hypothyroidism or make it worse, and what truly causes goiters.

I am going to show you why the theory of goitrogenic foods is nothing but poorly interpreted conclusions of those who have taken research on cruciferous vegetables out of context and spread it to the unsuspecting masses.



Goiter is an enlargement of the thyroid gland that often produces a noticeable swelling in the front of the neck.

Goitrogens – simply defined, are any substances that induce the formation of a goiter.

Cruciferous vegetables – not goitrogens – a group of delightful, nutrient dense vegetables, known for its ability to prevent, halt, and fight cancers, improve hormone health, improve cognitive abilities and slow aging process. These vegetables are rich in fiber, protein and Omega-3 fats, are very affordable and delicious.

What Causes Goiters?

Goiters can be caused by iodine deficiency, inability of the body to use iodine correctly, or a variety of thyroid disorders, including infection, tumors, and autoimmune disease, and use of certain medications. Much like iodine deficiency, iodine excess can be a cause for goiter formation and lead to hyperthyroidism. (3, 4)

Many drugs, such as lithium, phenylbutazone, birth control medications, etc., are goitrogens because they interfere with iodine metabolism. In effect, these and many other drugs, cause hypothyroidism in some and hyperthyroidism in others.

Environmental pollutants and heavy metal poisonings can contribute to goiter formation.

A large number of agents in the environment and some medications are known to interfere with thyroid gland function, posing the danger of thyroid disease. Pollutants that cause goiter are known as environmental goitrogens which may cause the condition by acting directly on the thyroid gland but also indirectly by altering its regulatory mechanisms and the peripheral metabolism and excretion of thyroid hormones. However, the mechanism that induces the trophic changes leading to goiter formation, and in some instances with hypothyroidism, is not well understood. Anti-thyroid compounds may enter into the water, air and food exposure pathways, becoming an important environmental goiterogenic factor in man and other animals. Naturally-occurring and anthropogenic agents may act as goitrogens, as well as some drugs, which in the presence of dietary iodine deficiency may exaggerate the goiter and associated disorders. In iodine-sufficient areas, these compounds may be responsible for the development of some “sporadic’ goiters or the persistence of the goiter endemia with its associated disorders. (1)

High levels of man-manufactured minerals such as calcium and magnesium, and certain bacteria in drinking water, have shown to be goitrogenic.

Nutrient deficiencies, including zinc, manganese, and vitamin A, and severe protein malnutrition contribute to an inability to use iodine well and to aid goiter development. So, poor farming practices, as we see them today, deplete soil of natural minerals. In addition to this problem, chemicals used in growing conventional crops lead not only to soil demineralization, but act as goitrogens as well.

Epidemiological studies in Russia comparing populations consuming water with varying amounts of minerals suggest that low-mineral water may be a risk factor for goiters, among other health risks. (2)

Bromine exposure is another factor to consider. Bromine, which can be found in baked goods, processed flour (especially white and non-organic), plastics, soft drinks, medications, pesticides and other substances, interferes with iodine absorption, which would lead not only to goiter formation, but to other health issues such as increased risk for breast, thyroid gland, ovary and prostate cancers.

Flouridated drinking water is a contributing factor as well, since chemical grade (not naturally occurring) fluoride, which is used in a most municipal water purification systems, interferes with thyroid function.


Both iodine deficiency and inability to use iodine make the thyroid gland unable to produce thyroid hormone, which induces the state of hypothyroidism, as well as goiters in some.


Iodine-deficiency goiters more commonly occur in regions where the soil and foods have insufficient iodine. While iodine deficiency (not our lovely vegetables!) is the leading cause of goiters worldwide, it is a rare cause of goiter in the developed world. If you live in the developed countries and have a goiter, you should be evaluated by a skilled healthcare provider to determine a true case of it, if possible, to avoid unnecessary treatments or be scared from consuming some of the healthiest foods on this planet.

Goitrogenic Foods | The History

So, where and how did the goitrogenic foods myth begin?

In 1928 Chesney and his co-workers, Clawson and Webster, announced the production of large goiters in rabbits being used to study experimental syphilis. Since they used a lot of cabbage to feed the poor animals during these experiments, they assumed that it was cabbage that caused goiters.

Later experiments could not replicate these findings.

What was discovered, however, is that cabbage grown in different regions and parts of the world had different nutrition profiles when it came to compounds, found in some of the Brassica plants, considered to have goitrogenic effect.

In 1936, in New Zealand, Hercus and Purves, could not replicate the results—the cabbage they used did not produce the same goitrogenic effects as the other scientists thought they discovered. So, these two guys used seeds of cabbage, rape and mustard in order to achieve the same results. They also noted that additional iodine prevented goiters from forming.

By 1940s and late 1950s more scientists tried to replicate the results of the original study. In 1956 Greer found that a compound, thought to be a goitrin present in the seeds and roots of some of the cruciferous vegetables, was an inactive precursor, which require enzymic action for conversion to the active form, can be deactivated (destroyed) by simply cooking seeds and roots. So even with this premise (not that many humans ever eat cabbage seeds or roots(!), the plants were safe to eat.

In 1957 the same scientist discovered that the progoitrin content of these seeds varied not only from season to season, but from batch to batch!

By 1959 Altamura, Long and Hesselstrom showed that even if present the concentration of the considered goitrin compound was only one part in eight million in cabbage“a quantity which is negligible in practical nutrition” they said.

Other tests were also observations on animals (livestock) and results varied from region to region. (5)

Based on this research one cannot be convinced that cruciferous vegetables or soy are the cause of goiters or are harmful in those with hypothyroidism.

Is there anything in the present day research that could convince us otherwise?

Present Day Research

I am going to show you some of the research the anti-cruciferous veg crowd is using to confuse not only themselves but the masses. Some of them point to information which, when read and interpreted correctly, will lead us to derive a sound conclusion, while others link to short abstracts from studies which are insufficient to make a sound conclusion based on the information provided (in such cases the entire study needs to be seen to draw conclusions).

You will see one thing all of these studies have in common—they used isolated compounds which, when used in studies are used in highly concentrated amounts not similar to those we would normally consume in a daily diet.

In 1995 two different phytochemicals present in cruciferous vegetables, glucosinolates and S-methyl cysteine sulfoxide were studied. The study showed that these phytochemicals possess anticarcinogenic properties (a good thing), but show general inhibition of iodine uptake by the thyroid. (6)

(If you read Cruciferous Vegetables | A Superfoods Group article – coming soon – you learned that extracts do not work in the same way as whole foods and are not beneficial).

In 1996 Sartelet, Serghat and Lobstein used flavonoids extracted from fonio millet, a tiny variety of millet commonly eaten by inhabitants of semiarid regions, which showed antithyroid properties. Here were some of the problems with the study: 1) they used an extract; 2) the sample of the millet used in the study was collected in the middle of a severely iodine-depleted endemic, and 3) while this study was significant to the specific region where crop was collected, millet from there is not likely eaten anywhere else in the world. (8)

In 1997 Divi, Chang and Doerge extracted isoflavones from soybeans. They found that acidic methanolic extract of soybeans contains compounds that inhibit thyroid peroxidase (TPO) reactions essential to thyroid hormone synthesis. However, in the presence of iodine that action was inhibited. (7)

While not proving that soy is bad for consumption, these three made a very important discovery (yet again)—isolated parts of a healthy whole food, used in concentration, is not a good idea!

Soy protein isolate (SPI) is used in most infant soy formulas. SPI is a highly processed form of soybean, and it is likely to expose an infant’s digestive tract to unexpected proteins and protein components, which might increase risk of adverse reactions.

True Causes of Goiters

So far you have seen that the research on goitrogenic effects of foods is inconclusive at best, since many of the original studies which came up with the idea of “goitrogenic foods” were never replicated. You have also observed that the studies did not take into consideration other lifestyle and dietary factors.

Soy, which has been demonized for no reason, is actually found to be a great cancer preventing, iodine rich food. A review of 14 trials showed that

…collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function. (10)

You saw that whole foods were not used in studies, but rather concentrated extracts. You also learned that even if goitrogenic properties were a factor in foods, they can be simply deactivated by cooking or that their effect was nullified in the present of sufficient iodine intake; so you can still enjoy health properties of cruciferous vegetables, even if you cook/steam them.

You also learned that too much iodine can cause goiter problems, and induce hyperthyroidism or hypothyroidism. (4, 11, 12)

More recent studies suggest that chronic high iodine intake furthers classical thyroid autoimmunity (hypothyroidism and thyroiditis) and that iodine-induced hyperthyroidism may also have an autoimmune pathogenesis. (4)

It is safe to say that in the developed world iodine deficiency is not a problem. In the presence of a well-rounded plant food intake even iodine supplementation is not needed. Iodine can be found in plant foods in sufficient amounts to meet the recommended daily value of 150 micrograms of iodine each day; 220 micrograms for pregnant women, and 290 micrograms for breastfeeding mom.

Even if you were to select a diet with little variety, the likelihood of iodine deficiency is not likely to happen because even if we choose few foods, they would come from all over the country, and maybe even, the world. Even if our local soil was depleted of iodine, we can get it through foods from other regions.

Iodine Rich Foods

Just how easy is it to get enough iodine from whole foods, without supplementation or eating animal foods? Easier than you think!

Baked Potatoes (including skin) have 60 micrograms of iodine (40% DV).

Dried seaweed – a quarter-ounce serving contains 4,500 micrograms of iodine. That’s 3000% of the daily value. If you wanted to consume seaweed, you can add smaller portions over time in order to gain the health benefits.

Himalayan crystal salt—you know that we should ditch the table salt for many health reasons, so, switching to a mineral rich salt is a better option. Half a gram of Himalayan crystal salt provides 250 micrograms of iodine—over 150% of the amount the average body needs each day. 1/2 gram, 250 micrograms of iodine (167% DV).

Dried prunes—who would have thought that prunes are a good source of iodine? 5 prunes have 13 micrograms of iodine (9% DV).

Navy beans–1/2 cup has 32 micrograms of iodine (21% DV).

Bananas--1 medium banana has 3 micrograms of iodine (2% DV).

Strawberries—1 cup has 13 micrograms of iodine (9% DV).

Cranberries—4 ounces have 400 micrograms of iodine (267% DV).

Green Beans—1/2 cup, 3 micrograms of iodine (2% DV).

Other iodine rich foods

Any food grown near the sea is likely to contain iodine, but especially rich sources include:

  • artichokes
  • asparagus
  • carrots
  • blackstrap molasses
  • cabbage
  • coconut products
  • garlic
  • leafy greens
  • lima beans
  • mushrooms
  • onions
  • peas
  • pineapple
  • rhubarb
  • sesame seeds
  • soybeans
  • spinach
  • strawberries
  • Swiss chard
  • summer squash
  • tomatoes
  • turnip greens

These iodine rich foods have been analyzed based on micrograms per 100 grams of food:

  • Vegetables – 32 mcg
  • Strawberries 1 cup – 13 mcg
  • Fruits – 4 mcg

Dr. Elizabeth Pearce, an associate professor of medicine at Boston University, and her colleagues found that the average iodine level in a group of 63 vegans was lower than what’s recommended…however, their thyroid hormone levels were in the normal range. Now, while 63 people are hardly enough to constitute a great study, it is telling that their hormones were just fine! (13)


Cruciferous vegetables, soy, nuts and grains do not cause goiters. Iodine deficiency, excess iodine, mineral soil depletion, added synthetic minerals to water supply and soil, chemicals, medicines and other factors do.

If you want to optimize naturally occurring iodine, needed for thyroid health, try to eat organic when possible, drink good filtered water, avoid eating foods with bromine (buy organic whole grains and flour), avoid using plastic containers; eat organic; avoid junk foods and drinks and minimize exposure to chemicals and pollutants in your personal care products and environment.

Health can be this simple! And your food is that much more delicious for knowing the truth.

Share the Article and Your Thoughts

If you enjoyed this article, please share it with others. I also would love to hear what you think on this topic – leave a comment.


  1. http://www.ncbi.nlm.nih.gov/pubmed/2464986, Gaitan E
  2. Mudryi IV. Effects of the mineral composition of drinking water on the population´s health (review). (In Russian.) Gig Sanit 1999; 1: 15-18. (more on this topic)
  3. http://tpx.sagepub.com/content/18/2/239.short
  4. http://www.ncbi.nlm.nih.gov/pubmed/20172475 Bürgi H, International Council for the Control of Iodine Deficiency Disorders (ICCIDD), CH-4500 Solothurn, Switzerland.
  5. F.W. Clements M.D, Insitute of Child Health, University of Sydney Australia, Naturally Occurring Goitrogens, 1959.
  6. http://www.ncbi.nlm.nih.gov/pubmed/7797181 Stoewsand GS. Bioactive organosulfur phytochemicals in Brassica oleracea vegetables—a review. Food Chem Toxicol 1995;33:537–43 [review]
  7. http://www.ncbi.nlm.nih.gov/pubmed/9464451 Divi RL, Chang HC, Doerge DR. Anti-thyroid isoflavones from soybean: isolation, characterization and mechanisms of action. Biochem Pharmacol 1997;54:1087–96.
  8. http://www.ncbi.nlm.nih.gov/pubmed/8724380 Sartelet H, Serghat S, Lobstein A, et al. Flavonoids extracted from fonio millet (Digitaria exilis) reveal potent antithyroid properties.
  9. http://www.ncbi.nlm.nih.gov/pubmed/16571087 Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature
  10. http://www.ncbi.nlm.nih.gov/pubmed/16571087 Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature
  11. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1977387/, L. A. Akslen, S. Nilssen, and G. Kvåle, Br J Cancer. 1992 May; 65(5): 772–774.
  12. DHHS/ATSDR; Toxicological Profile for Iodine p. 63 (2004)] **PEER REVIEWED** http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+7553-56-2
  13. http://www.americanvoiceinstitute.org/PHHealth201203.htm


Holistic Master Health & Life Coach

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