Thyroid Nutrition
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What does your thyroid do? In short, your thyroid’s main role is to control your metabolism.
I’ll get into more about thyroid hormones in a minute. But first, a quick orientation. This is the first in a series of posts where we dive into specific hormones and the connection with nutrition. Why am I doing this series? Because “hormones” is one of the latest buzz words in health on the internet. And, there’s both truth and manipulation intertwined in those messages. In this series I’m teasing out the scientific evidence so you can spot the manipulation. Let’s start with a definition of hormones. What are hormones? Hormones are chemicals that your body creates to send a signal from one part of the body, through your bloodstream, to another part of your body.
Now, let’s get into details about thyroid hormones.
Thyroid conditions are the most common hormonal problem that I see amongst clients. So, it seemed like a good place to start for this series.
What Are the Thyroid Hormones?
Specifically, your thyroid is a gland, located in your neck, that releases four hormones:
Triiodothyronine (T3): This is the active hormone that stimulates your metabolism.
Thyroxine (T4): This is a mostly inactive hormone. Think of it like the precursor to T3. It’s what gets converted to active T3.
Reverse Triiodothyronine (RT3): As the name suggests, this hormone reverses the effects of T3.
Calcitonin: Has a role in regulating the amount of calcium in your blood.
You may have heard of other thyroid hormones too. Especially if you’ve had bloodwork done to check your thyroid function, (what’s often called “checking your thyroid levels”). These hormones are created by other parts of your body (i.e., not in your thyroid itself) to control your thyroid’s functioning in a multi-step process. These hormones are:
Thyroid-Releasing Hormone (TRH): TRH is released by your hypothalamus to communicate to your pituitary gland.
Thyroid-Stimulating Hormone (TSH): Released by your pituitary gland when it’s stimulated by TRH. This hormone tells your thyroid to release T3 and T4 into your blood.
What Do Thyroid Hormones Do?
Something that you’ll notice as we cover each hormone in this series of blog posts, is that while each hormone has a primary role, they also have additional roles in your body. As we covered already, the primary role of your thyroid hormones is to control your metabolism. Their additional roles include playing a role in controlling your body temperature, digestion, heart rate, breathing, brain function, fertility, skin and bone.
Thyroid Problems
It’s because of thyroid hormones’ many roles that you can experience a number of symptoms if your thyroid isn’t working properly. Symptoms can include:
Weight gain or (unintended) weight loss
Problems with your heart rate (too fast or too slow)
Numbness, tingling, pain
Depression, anxiety
Problems in how food moves through your digestive system
Irregular menstrual periods and low fertility
You may have heard of the common thyroid problems:
Goiter: Enlarged thyroid gland.
Hyperthyroid: Overactive thyroid.
Hypothyroid. Underactive thyroid.
I’ll share a mental trick for remembering which is hyperthyroid and which is hypothyroid. When kids have too much energy, we call them “hyper” or “hyperactive”. Hence hyperthyroid is when your thyroid is too active/overactive. My trick for remembering hypothyroid is that hypothermia is being too cold, i.e., low temperature, so hypothyroid is low thyroid/underactive.
Hypothyroidism
People seek us out mostly for nutrition help for hypothyroid, so that’s what I’ll focus on regarding nutrition – nutrition to help keep your thyroid functioning so your metabolism doesn’t slow down.
Hypothyroidism can happen for a number of reasons. Women have higher rates of hypothyroidism and the rates of hypothyroidism increase with age. That’s why it’s fairly common amongst women in perimenopause and post-menopause. There is also some evidence that the hormone changes in the menopause transition (e.g., estrogen) and thyroid hormones interact. Hashimoto’s is an autoimmune condition that causes hypothyroidism. Hashimoto’s is a specific situation that requires a full blog post to itself. So here, I’m focussing on hypothyroid that isn’t Hashimoto’s. Hypothyroid can also be caused by surgery or radiation in the area including due to thyroid cancer.
Nutrition for Hypothyroid (Nutrition for Supporting Thyroid Function)
First, let’s start with what to eat to support your thyroid function. To fuel the fire of your metabolism. I’ll name some minerals here. While there isn’t sufficient scientific evidence to support you supplementing with any of these, I do recommend that you make food choices to ensure that you’re getting within the recommended range. If you want to supplement with any of these nutrients and you take thyroid medications, talk with your doctor or nurse practitioner before you start any supplements. Also, know that longer-term supplementation with some minerals can interfere with the absorption of other minerals (e.g., supplementing with zinc can decrease the absorption of copper). So, I recommend consulting with a dietitian before taking supplements. It’s also why we don’t give cross-the-board supplementation recommendations here. We work with individual clients to determine our supplementation recommendations for each individual.
Iodine: Iodine is widely found in vegetables and fruit, with a big caveat. It’s in vegetables and fruit only when the soil that they were grown in has sufficient iodine. Unfortunately, a lot of the soil in which our vegetables and fruit are grown is low in iodine. That’s why Canada and the US add iodine to salt. If you eat a lot of pre-packaged foods, such as canned soups and frozen meals, and eat out, then you’re likely getting enough iodine. Because prepackaged and restaurant foods are usually quite high in salt. And, the restaurants/ food companies most likely have used the less expensive, iodized salt. If you eat mostly food that you’ve cooked at home, and you use fancy salts like sea salt and Himalayan pink salt, you might be low in iodine. Please continue eating homemade meals. However, I recommend buying iodized salt. Seaweed is a good source of iodine. Some seafood, such as cod, and some dairy products, such as milk and yogurt also naturally contain iodine.
Iron: Iron deficiency interferes with thyroid function. If you are vegetarian or vegan, very physically active, have a digestive concern, or have heavy menstrual bleeding, I recommend having your iron levels tested (via blood test) yearly (or more frequently) as you’re at higher risk for iron deficiency. If you are feeling lethargic, have your iron tested. And, eat foods rich in iron. Here’s a list of iron-rich foods: Nutrients
Selenium: Brazil nuts are a selenium superstar. 6 nuts per week gives you more than 100% of the selenium recommended. In fact, they’re so high in selenium that you can overdo it. 6 nuts per day and you can be at overdose levels of selenium. So, I do recommend including Brazil nuts, but not too many. Stick with up to 6 nuts per week. Pacific oysters are also a good source of selenium.
Zinc: Zinc plays a role in activating T4. Oysters (both from the Atlantic and Pacific) are absolute rock stars for zinc. Other food that contribute zinc include liver, meat, poultry, crustaceans (e.g., crab, lobster), wheat germ, and pumpkin seeds.
Foods to Limit (Foods That Block Thyroid Function)
Soy: Scientific evidence is mixed regarding whether soy has a negative impact on thyroid function. A systematic review done a few years ago found that soy didn’t have an impact for most people. But soy did interfere with activating T4 amongst people with subclinical hypothyroidism. In other words, people who had low thyroid, but not so low that they were classified as officially being diagnosed with hypothyroidism. To err on the safe side, if you have hypothyroidism or if your thyroid is still within range, but you suspect that your thyroid is low, I recommend enjoying soy foods only occasionally.
Cruciferous vegetables, a.k.a. Brassicas: Veggies in this family include broccoli, cauliflower, kale, Brussels sprouts, cabbage, boy choy, gai lan, etc. Just like with soy foods, there isn’t enough scientific evidence to answer the question of whether or not these veggies lower thyroid function. Animal studies have shown that it is possible at very high consumption levels. Also, there have been case reports of individual people who consumed super high levels of these veggies and it caused a negative effect on their thyroid. But that doesn’t answer the question of whether eating normal levels of these, otherwise very healthy veggies, has a negative impact on your thyroid. The good news is that cooking these veggies stops the possible interaction with thyroid function. So, to err on the safe side, if you have hypothyroidism or you suspect that your thyroid function is low, I recommend enjoying these veggies cooked most often. It’s also another argument for my recommendation to eat a wide variety of veggies rather than getting fixated on one or two.
Get more scoop on metabolism here: How To Boost Your Metabolism Naturally
Photo by Tobias Rademacher on Unsplash
References
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Gietka-Czernel M. The thyroid gland in postmenopausal women: physiology and diseases. Prz Menopauzalny. 2017 Jun;16(2):33-37. doi: 10.5114/pm.2017.68588. Epub 2017 Jun 30. PMID: 28721126; PMCID: PMC5509968.
S Maria O’Kane and others, Micronutrients, iodine status and concentrations of thyroid hormones: a systematic review, Nutrition Reviews, Volume 76, Issue 6, June 2018, Pages 418–431, https://doi.org/10.1093/nutrit/nuy008
Otun, J., Sahebkar, A., Östlundh, L. et al. Systematic Review and Meta-analysis on the Effect of Soy on Thyroid Function. Sci Rep 9, 3964 (2019). https://doi.org/10.1038/s41598-019-40647-x
Winther, K.H., Rayman, M.P., Bonnema, S.J. et al. Selenium in thyroid disorders — essential knowledge for clinicians. Nat Rev Endocrinol 16, 165–176 (2020). https://doi.org/10.1038/s41574-019-0311-6
