Food – Thyroid Interactions

I have a family member who had thyroid cancer and, as a result, had to have her thyroid removed. She is now on lifelong medication to regulate her body, the primary function of the thyroid. This has me interested in certain questions: Can food effect the “thyroid replacement” meds she is on? Is there food that can help people with hypothyroidism?

Currently, there’s no such thing as a hypothyroidism diet. But there are claims about such diets all over the internet, and among alternative medicine advocates. Again, at this point, I could find no evidence that eating or avoiding certain foods improves thyroid function in people experiencing hypo- or hyperthyroidism. What we do know, however, is that adequate dietary-iodine is essential for normal thyroid function and that can be affected by diet.

Remember: I am not a doctor, nutritionist, nor dietition. I am just a cook and am looking into these issues as a cook who wants to feed her family and friends healthy, biologically supportive food.

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The Thyroid Story

The thyroid is a 2” long endocrine gland in our neck that uses dietary-iodine to produce two hormones (thyroxine and triiodothyronine) into our body, so our cells function normally (1). Our thyroid regulates our metabolism and affects various bodily functions, such as: how fast our heart beats, how deep we breathe, our temperature, cholesterol levels, weight, and even our menstrual cycles (2). This post looks into food that may, or may not, be helpful in ongoing management of thyroid functions.

Thyroid Issues

Growing Goiters

Growing up in Germany, many decades ago now, I saw elderly people, mainly women, with goiters. A goiter is an abnormal enlargement of the thyroid gland, and produced big lumps on their necks (3), that many tried to hide behind scarfs. Even back then, I knew it was most likely from a lack of iodine in their diet. These days regular table salt has iodine added to it and, over time, this condition is rarely seen in Europe or North America. Likewise iodized salt has been put into instant noodle packages and is used throughout parts of Africa and Asia that use Millet as their base grain. So, goiters are still around, where iodine is hard to naturally come by (4).

But goiters can also happen due to injury, genetics, Hashimotos Thyroiditis, or when someone has Graves’ disease.

Hypo or Hyper Thyroidism

For a healthy body, we must have a thyroid that produces just enough hormones for what our body needs, but the reality is much can go wrong, including producing too much, too little, or none of the hormones.

• Hypothyroidism (underactive thyroid) – the most common ailment, is when not enough thyroxine is produced. Slows metabolism and heart rate, leads to goiters, memory problems, dry skin, feeling cold, weight gain, hair loss, constipation, sluggishness, and depression (5).
• Hyperthyroidism (overactive thyroid) – too much thyroxine is produced, leading to irritability, weight loss, speeding heart rate, and feeling weak.

But I never gave food a thought as important to these conditions.

That is, until I experienced a family member having issues with their thyroid medication and periodic metabolism changes; the ups and downs of the last year has made me more aware than ever of the role food may be playing. Even so, it never crossed my mind to look into what she may be eating until I ran across a TV show, House, that had a scene where the doctor indicated that bok choy had lots of glucocilonates which can block necessary iodine absorption (6).

That caused one of those ah-ha moments, for I knew she had been eating a fair amount of bok choy, and other foods containing glucocilonates. In fact, much of these foods are part of her everyday diet.

Pro and Con of Glucocilonate Foods

Benefits

In general, glucocilonates are those foods with a spicy or bitter taste and pungent aromas, although not always. When eating cruciferous vegetables, their glucosinolates are broken down into metabolites compounds. These compounds affect the pace of metabolism, trigger enzymatic reactions to protect cells from damage, and thus may prevent the type of damage that lead to cancers.

Some studies suggest cruciferous veggies may have protective benefits for cardiovascular diseases (heart attack and stroke), and cancers of the lung and alimentary systems (7). Other studies (8) found that cruciferous vegetables have an almost antibiotic-like effect to help prevent bacterial, viral, and fungal intestinal infections. 

Benefits may be lessoned if these foods are cooked at high temps. Many (9) write that it is best to not boil or microwave cruciferous vegetables. So consider eating them raw or lightly steamed to maximize their sulforaphane content.

Problems

But my question today is what is too much? Studies have shown that normal intake of these veggies, by people with normal thyroids and no iodine deficiency does not cause problems. But high intakes of cruciferous vegetables, have been found to cause hypothyroidism in animals (10), can this happen with people too?

People who have hypothyriodism (11), as part of treatment, may be advised to limit or remove cruciferous vegetables from their diet. The reason is that in certain situations, these veggies may interfere with how the thyroid gland uses or absorbs iodine.

One site quotes Luis O. Rustveld, PhD, RD, a dietitian and assistant professor at the Baylor College of Medicine in Houston: If you have an underactive thyroid or iodine deficiency, you should avoid juicing cruciferous vegetables,” he adds, since juicing makes it easy to ingest large quantities of produce.

There is yet no study I found to address if these foods interfere or impact thyroid medication for those people who no longer have the gland.

Science is Mixed

For many people, the brassicaceae family of plants contain components thought to fight off cancer.

• ScienceDirect writes: Glucosinolates and other biologically active compounds are found in the Brassicaceae family of plants, which includes broccoli, cabbage, cauliflower, rapeseed, mustard, and horseradish. Recent studies show the beneficial effects of glucosinolates, including regulatory functions in inflammation, stress response, phase I metabolism, and antioxidant activities, as well as direct antimicrobial properties.
• However, livestock fed rations high in glucosinolates exhibit adverse effects. Another study on this site explains: In humans, higher levels of GSL breakdown products may be associated with reduced iodine uptake by the thyroid gland (Fenwick, Heaney, & Mullin, 1983).
• The issue is that the breakdown of glucosinolates critically affect nutritional status of animals, hormone metabolism, N-nitroso compound development, and indole transformation reactions (Tiedink et al., 1991; Tripathi and Mishra, 2007).

There is not enough study of the dietary effects on people to decide if reducing or increasing dietary intake of glucosinolate-rich food helps or hinders health.

There is no evidence that cruciferous vegetables slow down our thyroid or damage it.

Food with Glucocilonate

Food List

An OregonState site writes that Cruciferous or Brassica vegetables are so named because they come from plants in the family known to botanists and biologists as Cruciferae or alternately, Brassicaceae. The Brassicaceae family, which includes the model plant Arabidopsis thaliana, comprises approximately 375 genera and over 3,000 species.

Table 21.1. from the book Functional Foods, Aging and Degenerative Diseases lists the commonly consumed foods containing glucosinolates and their sources.

Other foods containing glucosinolates include:

• Arugula
• Kale
• Bok choy
• Chinese cabbage
• Capers
• Rutabaga
• Collard greens
• Radishes
• Rapeseed
• Swiss Chard
• Mustard greens and seeds
• Wasabi

Glucosinolate Content

I looked to see how much each veggie contained, but it was hard to find. Here is one table that was posted on the web, adapted from McNaughton SA, Marks GC. Development of a food composition database for the estimation of dietary intakes of glucosinolates, the biologically active constituents of cruciferous vegetables. Br J Nutr. 2003;90(3):687-697. 

What to Do?

Eat glucosinolate foods in moderation (12). Like I always suggest, moderation and variation will do our bodies good. Drinking glasses of juiced kale everyday, or only eating broccoli as your veggie all the time, are not a healthy diet.

Try not to totally avoid glucosinolate foods, as they contain lots of good nutrients that help our bodies work and stay healthy.

When on a diet that lists specifically what ingredients to eat, make sure you mix it up a bit and not eat just one veggie type all the time. Get a good mix of nutrients to serve all aspects of your body, by mixing up your veggies.

If you have iodine-deficiency hypothyroidism limit glucosinolate foods, after speaking with your medical advisor. There is nothing I have found that indicates the elimination of these foods as a cure, but everyone seems to urge caution with their consumption if you have certain medical conditions.

If you suspect a thyroid issue, be aware that you may still be making some of your own thyroid hormones (albeit in low amounts) and goitrogenic foods could play a part in further depletion. Before doing anything, please speak with your medical professional to find out what is happening and what to do.

If eating glucosinolate veggies are a concern, consider adding seaweed to your diet to up the natural iodine back into your diet to help counter the iodine depleting foods. Or add organic yoghurt, eggs, fish, shellfish, prunes, and salt that is rich in iodine and minerals. A nutritionist or dietician can help plan out your diet.

Be careful on juicing which can intensify the properties of the veggies you are consuming. I am not supportive of juicing, for it removes all the fiber, which is a very important component of food that our modern diets do not have enough of. Perhaps consider adding a daily Brazil nut (not more than 1) to increase selenium, which supports a healthy thyroid.

Cooking these veggies have been found to reduce the amount of glucosinolate in the veggie. The rawer the food, the more it has.

Some bloggers tell stories of newly converted vegans and vegetarians who developed thyroid symptoms after replacing meat with lots of soy and goitrogenic foods. In general, my suggestions is that when you are converting your diet to eliminate all of one thing, please discuss the change with your doctor, nutritionist, or dietitian. It is very easy to accidentally remove a necessary nutrient and cause harm to your body.

— Patty

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