Medically reviewed by
Dr. Minako Abe, M.D., Board-certified emergency medicine physician researching the relationship between lifestyle and disease onset in relation to the immune system and cancer, Japan
Millions of people around the globe are affected by various thyroid disorders, and while genetics play a part, what you eat matters too. If you’ve been diagnosed with a thyroid disorder and are on (or considering switching to) a plant-based diet, you may have at some point wondered if this dietary choice can affect your thyroid and if there are specific foods you should avoid.
Addressing these concerns can actually be a little more complicated than expected. This is mainly because there are many different types of plant-based diets. Generally, vegetarians avoid meat, poultry, and fish, but may still consume dairy products (such as milk, cheese, and yogurt) and eggs. However, there are several variations of vegetarianism, such as lacto-vegetarian, ovo-vegetarian, lacto-ovo vegetarian, pescatarian, pollotarian, and flexitarian diets. Vegans, on the other hand, exclude all animal products from their diet, including meat, poultry, fish, dairy, eggs, and honey.
Both dietary lifestyles are usually adopted by people who are drawn to the range of health benefits these diets offer. Did you know that vegetarians and vegans tend to have lower cholesterol levels on average compared to meat-eaters? That’s a win for heart health, for sure! However, when it comes to the thyroid in particular, there are some unique considerations for those who follow a plant-based diet.
By answering the following questions, the rest of this article explores the link between plant-based diets and thyroid health, highlights some key nutrients vegans and vegetarians should consider, and offers tips for optimal thyroid function.
Can a plant-based diet affect my thyroid?
The short answer is yes, but it depends on the specifics of your diet and your actual nutritional needs. Now, here’s a more specific question you may have seen somewhere before: Do vegans and vegetarians have a higher risk of developing thyroid problems? Well, the answer to this isn’t so straightforward. By the end of this article, you will understand why.
Plant-based diets are by no means a “bad” thing. In fact, they have commonly been associated with effective weight management. This is mainly because they are usually lower in calories and fat. So, if you’re overweight due to your thyroid condition, a well-planned plant-based diet may be helpful in your weight management journey, alongside other lifestyle changes.
This raises the question of what a well-planned plant-based is. Simply put, it’s a plant-based diet that has been optimized to provide sufficient amounts of all the essential nutrients. This is very important because it addresses the main concern with plant-based diets within the context of thyroid health—potential nutrient deficiencies. Some essential nutrients for the thyroid, such as iodine, are not as abundant in plant food sources as they are in animal sources.
In the next section, we will look at how you can optimize your plant-based diet for your thyroid.
How can I support my thyroid with a plant-based diet?
Over the past couple of years, research studies on the link between vegan/vegetarian diets and thyroid function have presented some interesting results. While some studies suggest a possible protective effect of vegan diets against hypothyroidism, others also suggest a likely increased risk of iodine deficiency. Iodine deficiency is, however, a major cause of hypothyroidism.
One way to explain the seemingly contradictory or inconsistent findings is to acknowledge that the effect of a plant-based diet on thyroid function depends on several factors. In addition, some researchers have noted that goitrogenic compounds in some plant food sources may also be a cause for concern. The limitations of these studies must also be considered when analyzing and comparing their findings.
A study examining the dietary patterns of over 65,000 participants in North America in relation to the risk of hypothyroidism was published in 2011 in the Nutrients journal. The findings of this study showed that people who followed a vegan diet tended to have a slightly lower (but statistically insignificant) risk of developing hypothyroidism compared to those who ate meat. Interestingly, a lacto-ovo vegetarian diet (including dairy and eggs but no meat) showed a slight increase in hypothyroidism risk. As pointed out by the authors of the study, the reason for this result is unclear. It is nonetheless a surprising finding because if a lacto-ovo vegetarian diet can cause thyroid problems, wouldn’t vegans be at just as high a risk? Also, when you consider that lacto-ovo vegetarians are less likely to be iodine-deficient than vegans because dairy and eggs contain iodine, the findings of this study become even more interesting. It is, therefore, necessary to highlight some of the limitations of this study, such as relying on self-reported data and not measuring iodine intake directly.
Published in the same journal in 2023 is another study that investigated iodine intake in vegans compared to omnivores in Poland. The researchers found that vegans had lower iodine intake than omnivores (90% below recommended daily intake). This was mainly because plant-based alternatives often consumed by vegans lacked iodine fortification.
To address the valid concern of nutritional deficiencies associated with plant-based diets, here are some tips to plan a plant-based diet focusing on specific nutrients to support your thyroid health as a vegan or vegetarian:
- Iodine: Iodine is essential for thyroid hormone production. While some plant-based foods like seaweed contain iodine, it is generally less abundant in plant-based diets compared to animal-based diets including dairy and seafood. Iodized salt (in moderation for sodium intake) is a readily available source, and using it consistently is important for vegans. Vegetarians can include dairy products and eggs in their diet.
- Selenium: Selenium is another mineral involved in thyroid hormone metabolism. It’s essential for the conversion of T4 to the more active T3 hormone. Its deficiency has also been linked to autoimmune thyroid disease. The good news for vegans and vegetarians is that with just a few Brazil nuts a day, you can easily meet the recommended daily intake of selenium. But be careful not to eat too many Brazil nuts, as this can lead to a condition called selenosis. Other sources of selenium include sunflower seeds, whole-wheat bread, and tofu.
- Iron: Iron is a component of enzymes involved in thyroid hormone production. Iron deficiency has been reported to worsen hypothyroidism symptoms. While leafy greens are a good source of iron (specifically non-heme iron) in plant-based diets, the iron absorption by the body is lower compared to heme iron found in animal products. Including iron-fortified foods into your diet and pairing plant-based iron-rich foods with vitamin C-rich foods (like citrus fruits, bell peppers, and broccoli) can enhance iron absorption.
- Vitamin B12: Vitamin B12 is important for thyroid health and overall nerve and blood cell function. A deficiency of this vitamin can lead to fatigue, a common symptom of hypothyroidism. Vitamin B12 is only found naturally in animal products. For this reason, supplementing with B12 or consuming fortified foods (such as plant-based milk, breakfast cereals, and nutritional yeast) is recommended for individuals following plant-based diets.
- Zinc: Zinc also plays a role in thyroid hormone metabolism. According to a case study published in the International Journal of Trichology in 2013, zinc deficiency can contribute to the development of hypothyroidism. This case report discussed a patient (a 28-year-old woman) who experienced both hypothyroidism and zinc deficiency at the same time, resulting in significant hair loss throughout the scalp. Some plant sources of zinc include pumpkin seeds, cashews, chickpeas, and whole grains. However, zinc from these sources is generally less bioavailable (less readily absorbed by the body) compared to non-vegetarian diets. This is because plant sources of zinc typically contain a considerable amount of phytic acid, which hinders the bioavailability (absorption) of zinc. The good news is that some meal preparation methods such as cooking, fermentation, and soaking in water overnight can help reduce the levels of phytic acid before consumption.
It’s worth noting that while a well-planned vegan or vegetarian diet can provide all the necessary nutrients for thyroid health, it’s also important to make sure your diet is varied and balanced. Rather than having a monotonous diet, try including a wide range of fruits, vegetables, whole grains, legumes, nuts, and seeds to meet nutritional needs.
Aside from the essential nutrients, here are some additional considerations for optimizing your plant-based diet to your thyroid health:
- Consuming cruciferous and soy-based foods
If you have a hypoactive thyroid, chances are you’ve heard, at least once, that it’s best to avoid cruciferous vegetables and soy foods in order to protect your thyroid. This isn’t quite accurate. For most people with thyroid conditions, these foods are safe to eat, but with some important considerations.
Cruciferous vegetables like broccoli, kale, cabbage, and Brussels sprouts contain compounds called goitrogens, which can interfere with thyroid function (typically resulting in a goiter) when consumed in large quantities. However, this is usually only a concern for people with existing iodine deficiency. Cooking these vegetables, rather than consuming them raw, can deactivate goitrogens, reducing their potential impact on thyroid health.
Soy products contain compounds called isoflavones, which can be goitrogenic. In large amounts, they may interfere with thyroid hormone production and absorption. However, moderate consumption of soy foods is generally considered safe for your thyroid. You can also try fermented soy products like tempeh and miso because fermentation helps break down some of the goitrogenic compounds in soy.
- Consulting a healthcare professional
If you are on a vegan or vegetarian diet, you should consider consulting a healthcare professional, particularly a registered dietitian or nutritionist, to make sure that your nutritional needs are being met. They can perform tests to assess any nutritional deficiencies you may have.
Remember, effective communication with your endocrinologist or thyroidologist is also important. Don’t hesitate to make your concerns known to them. In addition to monitoring your thyroid function, they can also offer personalized guidance tailored to your specific health concerns.
Key takeaways
- Vegans and vegetarians can maintain healthy thyroid function with plant-based diets, but it’s important to be aware of the specific nutrients needed and make informed dietary choices.
- With some knowledge and dietary planning, you can ensure your plant-based lifestyle supports optimal thyroid function.
- Maintaining optimal thyroid health on a vegan or vegetarian diet requires attention to specific nutrients like iodine, selenium, iron, vitamin B12, and zinc.
- Consuming fortified plant-based foods can also be beneficial. Be sure to check the labels to ensure you’re getting a nutritional boost.
- Remember to consult with a healthcare professional or registered dietitian for personalized guidance based on your specific nutritional needs and health history.
