What’s the best diet for hypothyroidism?

As a dietitian, I get a lot of questions about the best diet for hypothyroidism because it’s such a common diagnosis these days. So let’s talk! This post will cover important nutrients to consider along with my thoughts on the best foods for hypothyroidism and foods to avoid (including the research on gluten and soy). There is SO much misinformation out there so it’s time to set the record straight.

What is hypothyroidism?

Do you have hypothyroidism? If you do, you’re not alone: subclinical hypothyroidism is estimated to occur in between 3-15% of the population and is more common in women, those who are older or those with low iodine status. A major cause of hypothyroidism is Hashimoto’s, or autoimmune, hypothyroidism.

Hypothyroidism occurs when your thyroid gland doesn’t produce enough thyroid hormone. It can be overt, where T4 hormone is low, or what is called ‘subclinical’ meaning that T4 is within the normal range but thyrotropin, or TSH, is low. If you want to learn more about hypothyroidism, this is a great overview.

Signs of hypothyroidism

It’s important to be mindful of how you’re feeling and pay attention to what your body is telling you. If you are experiencing any of these chronic signs + symptoms of hypothyroidism, you should talk to your doctor: 

• Cold intolerance
• Fatigue
• Cognitive + mood changes (forgetfulness, depression and irritability)
• Hair loss
• Low libido
• Unexplained weight gain
• Constipation

Best diet for hypothyroidism

Despite what the internet will tell you, there is zero scientific literature studying any one dietary pattern for hypothyroidism. Yep, that’s right, ZERO. Meaning everything you’re reading about going keto, or vegan, or gluten free is someone’s opinion. 

Of course, just because the evidence hasn’t given us the ‘perfect’ diet for hypothyroidism doesn’t mean that you shouldn’t try to nourish yourself. We do have a bit of insight into specific nutrients and foods that might be an issue for someone with low thyroid function. 

What’s more, hypothyroidism can increase your risk for cardiovascular disease and may increase constipation so we definitely want to address this with the food choices we make. My advice? Eat more plants, of course! My take on an anti-inflammatory diet is a nutrient-dense healthy dietary pattern filled with whole plant foods and based on one of the best-researched dietary patterns in existence: the Mediterranean diet.

Eating more high fibre plant foods such as whole grains, fruits, vegetables will support healthy movement of the gut, helping you to minimize constipation. These same plants flood your body with vitamins, minerals and anti-inflammatory phytochemicals to help support overall health and healing. Eating more plants will also help decrease your intake of saturated fats that can increase cholesterol levels while providing heart-healthy monounsaturated fats from avocados, extra virgin olive oil and nuts and seeds.

Now that the boring (yet EFFECTIVE), ‘let’s just be healthy!’ advice is out of the way, let’s look at what the research has to say on specific nutrients. 

And whew, let’s just say that if you are on a vegan or plant-based diet, it’s time to take note: most of the nutrients of concern with regards to thyroid health are also nutrients to watch when going vegan.

Specific nutrients to watch when you have hypothyroidism

Iodine

Iodine is critical for the production of thyroid hormone. Iodine is typically found in seafood, sea vegetables as well as dairy. Iodine content of plant foods is generally low to nonexistent and at the mercy of soil iodine levels which of course will diminish when the soil is further from the sea. Iodine deficiency is a leading cause of thyroid issues which is why in 1949 Canada created a public health mandate to iodize salt. Let’s say that again: far from being a health hazard like the wellness conspiracy crowd tries to sell you, iodized salt was created as a food-first strategy to protect our thyroid.

We need 150mcg of iodine a day and if you have anything going on with your thyroid, it is NOT recommended that you take a supplement because excess iodine is harmful too. The iodine content of seaweed can vary widely (from low to extremely high!) so is also not considered a suitable option. Instead, eat fewer hyper-processed foods, which tend to be filled with too much salt, and then enjoy healthy homecooked meals seasoned with iodized salt to get what you need. If you prefer sea salt, you can actually get iodized versions of sea salt too – which is what I use.

Selenium

Selenium is an important trace mineral that helps to fight oxidative damage in the body as part of the antioxidant enzyme superoxide dismutase (SOD). For this reason, it is thought that selenium may help protect the thyroid from further autoimmune damage but clinical trials have had mixed results. For this reason – and the fact that excess selenium is dangerous – supplementation isn’t recommended. But getting enough selenium from food definitely is! For those of us on a plant-based diet, I’ll keep it simple: eat a Brazil nut a day. Really, that’s all you need! There aren’t a lot of plant foods rich in selenium so lucky for us, Brazil nuts have a ton.

Vitamin D

While we typically think of it as a bone-health vitamin, vitamin D has both anti-inflammatory and immune-modulating functions. Lower levels of vitamin D are commonly associated with autoimmunity, but evidence has been less clear in hypothyroidism. In one community-based trial, achieving sufficient vitamin D status was associated with a 30% decreased risk of hypothyroid. And in another 2015 meta-analysis, those with autoimmune hypothyroid had lower vitamin D status than those without. Because of the importance of vitamin D to overall health, and how common insufficiency is, I highly recommend getting your vitamin D levels tested if you are able so your doctor can recommend the right dose to bring your levels up. If not, I recommend 1000IU of vitamin D3 in the brightest 6 months of the year and 2000IU of vitamin D3 as a safe and conservative dose for the long term.

Vitamin B12

Decreased B12 status has been associated with increased hypothyroid disease in clinical trials. Those on a highly plant-based or vegan diet, as well as those over the age of 50, need to know that a daily B12 supplement is critical for maintaining stores of this nutrient vital for metabolism. This may also be important if you have celiac disease or inflammatory bowel disease, which may impair your absorption of the nutrient. We need 2.4mcg a day but most supplements offer more than that. If you can find a 50mcg or 500mcg supplement, excellent – but most common is 1000mcg and it isn’t harmful.

Foods for hypothyroidism

Hemp Hearts

Hemp contains omega 3 fatty acids to help fight inflammation as well as ample amounts of zinc, which is important not only for thyroid metabolism but also minimizing inflammation and supporting appropriate immune response.

Brazil Nuts 

1-2 Brazil nuts a day will give you all the selenium you need. No supplement necessary! It’s worth noting that Brazil nuts are so high in selenium that you don’t want to overdo it. Stick to your 1-2 serving.

Berries

Berries are incredibly nutrient-dense, in particular fibre to support healthy digestion as well as anti-inflammatory phytochemicals that help squelch oxidative damage. Oxidative stress is thought to increase inflammation that makes cellular damage in the thyroid worse. One older study suggests that hypothyroidism may be associated with higher levels of oxidative stress.

Steel cut or thick old-fashioned oats

Oats contain soluble fibre that helps to bind cholesterol and remove it from the body, helping to lower blood cholesterol levels. A cup of cooked oats has about 5 grams of total fibre, as well as 1.5-ish milligrams of zinc for the immune system. Metabolism and digestion can slow in hypothyroid, making slow-burn, high fibre carbs super important to keep your blood sugar rise and energy levels stable.

Lentils

Lentils contain hefty amounts of protein, fibre and iron – which is critical for the production of thyroid hormones. Hashimoto’s and anemia are common co-occurrences and it’s important to ensure proper iron status.

Vegetables

Yes, all vegetables (more on that in the ‘avoid’ section). To take care of your heart, your gut and fight inflammation, you want all the nutrient density you can get. Try making half your plate vegetables at almost every meal.

Foods to avoid for hypothyroidism

Stuff to vilify ‘avoid’ is where the internet excels. Honestly, most of this avoid section is mythbusting and medication management. So let’s dive into the myths here.

Should you avoid gluten?

As a blanket recommendation, this is 99.9% without evidence. It stems from the fact that as an auto-immune condition, Hashimoto’s can overlap with celiac disease and the potential for immune cross-reactivity between gluten and thyroid tissues. If you think that gluten is making things worse (think: gut issues, joint pain, hard to manage thyroid levels) ask your doc to screen you for celiac disease. For the rest of us? The evidence simply doesn’t justify ditching gluten for your thyroid. I could only find 1 pilot trial of 34 women that suggests some benefit. And I managed to find another study that saw a higher incidence of Hashimoto’s in a group with non-celiac wheat sensitivity but again, this can’t really be applied to the general public. I will definitely challenge the notion that gluten is bad for the thyroid, but also acknowledge that everybody is different. If for you personally, not eating gluten makes you feel good, that’s fine as long as you have support to ensure you’re getting the fibre and minerals you so desperately need which can be low when gluten free. 

Should you avoid soy?

This one has a bit more theoretical science behind it…but yes, you can still enjoy soy foods like soy milk, tempeh and tofu if you’re low thyroid. Soy contains phytochemical compounds that can interfere with the uptake of iodine by the thyroid when eaten in large amounts – but this is mostly an issue if you are LOW in iodine. See how vegans need to pay attention here? If you don’t use iodized salt and eat 3 servings of soy a day, it might shift things! But the main issue is that soy can interfere with how thyroid meds work. So take your meds, and wait AT LEAST 2 hours before enjoying soy. Also, soy will NOT cause hypothyroidism unless you are also iodine deficient.

Should you avoid cruciferous vegetables like kale?

Oh heck no! Like soy, the story here is of dose and…you guessed it…how’s your iodine intake? Thiocyanates in cruciferous veggies like bok choy, kale and Brussels sprouts can interfere with thyroid hormone production if consumed in large amounts (one case study found an elder wrecked her thyroid by eating 2-3 pounds of bok choy A DAY) or if you’re iodine is low. So I probably wouldn’t juice a whole bunch of kale everyday on top of eating broccoli and Brussels sprouts. But I would absolutely advocate for eating a normal size serving of crucifers because those thiocyanates are also dang good for you and an important part of a healthy, plant-based diet. Also, cooking may help lessen the impact of these compounds on your thyroid.

Alcohol

It appears that occasional moderate drinking does not harm the thyroid but there isn’t a large degree of new research examining this relationship. In one 2013 review, it was suggested that alcohol is directly harmful to thyroid cells as well as the regulation of thyroid function yet also suggested a small protective effect against both autoimmune thyroid disease as well as thyroid cancer with moderate drinking. There is more data on how chronic heavy drinking negatively affects regulation of the thyroid gland as well as decreases thyroid hormone levels. Sage advice? If you don’t drink, don’t start…but try and keep it to 1-2 drinks at a sitting on no more than 1-3 days a week.

Other things that mess with your thyroid meds

Avoid taking iron, calcium supplements with your meds. And save your coffee and tea for later too. Plus, biotin can interfere with the measurement of thyroid hormone so avoid supplements for a week before getting your labs done.

The bottom line on diet and hypothyroidism

There are a LOT of opinions on the internet – including from health professionals – about the best diet for hypothyroidism but most of it has little or no basis in actual scientific evidence. This article is so long we didn’t even get a chance to talk supplements or the emerging role of the microbiome in thyroid disease! So be wary of the ‘strong and wrong’ approach and instead listen to your body. What foods help you feel your best? Not sure? Start by experimenting with the (transformative) basics: 

• eat as many whole plant foods as possible
• drink lots of water
• get enough sleep
• move your body daily, if even for 15 minutes
• Oh, and use iodized salt!