The Not-So-Great 8: Foods to Avoid for Thyroid Health

By: Adrienne Klein, CTNC

Average Read Time: 6 minutes

Despite what conventional media will tell you, we are not walking, talking mathematical equations of calories in vs. calories out. Our bodies are delicate ecosystems that thrive based on our own individual biology. What works for some, doesn’t work for all. However, we also know that there are certain foods that help or harm the thyroid and its ability to function optimally. We’ve already discussed eight foods that are great for thyroid health; now, let’s talk about those that may harm the thyroid.

1. Gluten


Gluten is a family of proteins found in grains like wheat, barley, andrye. The two main proteins are glutenin and gliadin. Gliadin is responsible for most of the negative effects associated with gluten consumption.

Gluten can cause intestinal permeability, otherwise known as leaky gut, which leads to a whole list of issues, including inflammation. Leaky gut can impair your body’s ability to absorb thyroid medication, as well as micronutrients vital to thyroid health. It is also associated with the development of autoimmune diseases like Hashimoto’s, Graves’, Lupus, and Multiple Sclerosis. Many thyroid patients benefit from eliminating gluten from their diet, and experience a decrease in inflammation and improved intestinal health.

2. Soy

This legume, once revered for its supposed health benefits, has become a cautionary food choice due to its high estrogenic and goitrogenic effects on the body. It has also become one of the top food allergens, especially in children.

Goitrogenic vegetables such as broccoli, cabbage, brussels sprouts, and bok choy lose (or greatly reduce) their goitrogenic effects when cooked. That is not the case for soy.

Soy is also an estrogenic food, which means that soy and soy isoflavone mimic estrogen in the body. Too much estrogen in the body can lead to estrogen dominance, ovarian and breast cancer, autoimmune issues, and hypothyroidism.

up next: The Great 8: Foods for Optimal Thyroid Health

3. Dairy

With its high inflammatory properties, all forms of dairy decrease the effectiveness of thyroid medication, and contribute to a leaky gut.

People who are dairy sensitive and have Hashimoto’s will have a reduction in thyroid symptoms and antibodies going dairy free.

-Dr. Izabella Wentz, Pharm D

Unfortunately, substituting cow’s milk for goat or sheep’s milk won’t solve the problem, because both goat and sheep’s milk proteins are so similar to cow’s milk proteins that they cause a 60-75% cross reaction. This means that about 60-75% of people sensitive to cow’s milk will also react to goat/sheep’s milk.

It’s also important to check with your pharmacist and doctor about your thyroid medication. Many commonly prescribed thyroid medications contain lactose, the main sugar component of milk. However, there are a variety of medications available that are lactose-free.

4. Sugar

Of all the foods to eliminate, sugar tends to be the hardest because it is present in so many foods and drinks. Sugar activates powerful reward systems in the brain, making it very difficult to resist, and even potentially addicting. But is it really that bad for you? You bet.

The following are just a few of the effects sugar has on the body:

Sugar is found in soda, candy, pastries, honey, maple syrup, agave nectar, and many more. It can also be hidden in places you wouldn’t expect, e.g. in ketchup, yogurt, salad dressing, BBQ sauce and frozen meals. This is one reason why it’s important to always read labels.

While natural sugars derived from things like coconut or maple sap may be preferable to refined white sugar, they still have negative effects on the body and should be seldom consumed. There are a few safe sugar alternatives, like Stevia and Monk fruit. Stevia is derived from a plant, has zero calories and is not made with harmful chemicals like other sugar substitutes. Monk fruit is also natural and calorie free. It has been used as a sweetener for centuries in Asia and has recently become available worldwide.  

5. Grains

Many years ago, grains changed the way we lived. Where we were once hunters and gatherers following our food, the agriculture of grains meant we were no longer nomads, and could therefore pursue the advancements agriculture allowed us. However, the grains we consume today have a high inflammatory response in the human body.

Grains include wheat, rye, spelt, semolina, rice, oats, corn and more. The problem with grains are the lectins, phytates and phytic acid that they contain. Lectins promote inflammation, which can lead to leaky gut. Phytates and phytic acid inhibit the absorption of vitamins and minerals that are so vital to thyroid health. Removal of grains, even for just 30 days, can sometimes provide thyroid patients with relief from their symptoms.

up next: 10 Simple Ways to Improve Your Gut Health

6. Industrial Seed Oils

Industrial seed oils include:

These highly processed oils, once marketed as healthy, are actually quite damaging. They are very high in Omega-6 fatty acids, which can lead to inflammation and potential heart disease. These oils are also easily damaged through oxidation, which can occur at temperatures as low as room temperature.

So, what oils can we use? Olive oil is a great choice for cold preparations like salad dressings and homemade mayonnaise. You can also choose saturated fats, especially for cooking, as they are the most stable in high heat.

Saturated fats include:

Check out our handy cooking fats and oils infographic by clicking here.

7. Caffeine

With so many of us dependent on multiple cups of coffee (or caffeinated drinks) to get through the day, it’s a wonder we get any sleep at night. Although caffeine is so widely consumed, we still don’t know all of its long-term effects. We do know, however, that caffeine has been shown to activate the HPA axis.

HPA AXIS = Hypothalamo-Pituitary-Adrenocortical Axis

The HPA axis is a linked system of the hypothalamus, pituitary gland and the adrenal glands. It controls and regulates body temperature, digestion, the immune system, mood, and the body’s reaction to trauma and stress.

When the body experiences perceived or actual stress, the adrenal glands secrete two hormones: epinephrine (also called adrenaline) and cortisol. Adrenaline increases your respiratory rate, heart rate and blood pressure. Cortisol releases stored glucose, which is needed during times of stress.

Caffeine consumption increases adrenaline and cortisol, even at rest. Caffeine makes the body think it’s in a constant state of stress, and can therefore overwork the adrenals. When the adrenals are fatigued, thyroid health declines.

Negative Effects of Caffeine on the Thyroid:

Caffeine plays a large role in how well your thyroid functions. You can support your adrenals by removing caffeine, eating a whole foods diet, getting quality sleep, and including restorative movement like yoga or walking.

8. Alcohol

Alcohol is particularly harmful for those with thyroid conditions because it affects the liver. The liver is responsible for much of the conversion of the inactive T4 hormone into the active T3 hormone. When alcohol reaches the liver, it produces an enzyme called acetaldehyde. Acetaldehyde is a poisonous enzyme that can damage liver cells and cause permanent scarring. When the liver isn’t in tiptop shape, thyroid hormone conversions go down and thyroid health deteriorates.

Gut health is another reason alcohol is lousy for thyroid patients. Alcohol is one of the most destructive toxins for gut flora. Alcohol exposure can stimulate growth of Gram negative bacteria, which can lead to a buildup of endotoxin. These endotoxins permeate the gut lining and trigger inflammation.

Need another reason to reconsider your nightly nip? All alcohol is estrogenic. That includes beer, wine and all liquor. Estrogenic activity can cause adverse health effects in mammals: early puberty in females, altered functions of reproductive organs, obesity, altered sex-specific behaviors, and increased rates of some cancers. It also makes it more difficult to lose weight – a major frustration for many with thyroid issues. Show your liver and your thyroid some love by reducing or eliminating your alcohol intake.


About the Author

Adrienne Klein, CTNC is a Billy Joel fan and a Certified Transformational Nutrition Coach. In that order. As an Autoimmune Hypothyroid patient of 20 years herself, she’s been through the blood, sweat and tears that is an autoimmune disease. After graduating from the Institute of Transformational Nutrition as a CTNC and certified in Digestive Health, Weight Loss and Autoimmune Disease, she now works with thyroid patients to eliminate or decrease symptoms that persist even with medication. Click here to visit The Thyroid Whisperer.