I know a lot of you have questions about thyroid and diet.
What is the thyroid gland?
The thyroid is a 1/2-3/4 oz, butterfly-shaped gland that’s located on the front of your neck. It’s an endocrine gland, which means that it secretes hormones directly into the blood (versus via a duct, if you want to get specific). Other endocrine glands include (but aren’t limited to) the pancreas, ovaries, and pituitary gland.
Women usually have larger thyroid glands than men, and the thyroid increases in size during pregnancy. Pregnancy can really throw your thyroid out of whack, but more on that later.
The thyroid is nothing without the hormones that it produces. Let’s talk about those.
What are thyroid hormones?
The thyroid makes T3, otherwise known as Triiodothyronine (no, I can’t pronounce it either), and T4, otherwise known as Thyroxine.
It also produces calcitonin, which is a peptide hormone that regulates calcium and phosphate in the blood. We’re going to leave that one alone for today.
Your thyroid produces a lot more T4 than T3 – 80-90% versus 10-20%. That’s because most of your T4 gets converted into T3, which is the active form of hormone, in the blood. T3 and T4 are carried around by blood proteins, and are released from those proteins as the body needs more of the hormones.
Just as an FYI, T3 is called that because it contains 3 iodine atoms. T4 has four. So, T3 and T4 are made with iodine, which is found only in food (your body can’t make it). If you don’t consume enough iodine, the result is that you can’t make enough thyroid hormone. You can then develop chronic hypothyroidism resulting in a goiter, or a condition called cretinism.
Iodine deficiency is more common in underdeveloped countries where seafood is rare (seafood being a good source of iodine) and the salt isn’t fortified with iodine like it is here in North America (by law, to prevent iodine deficiency).
When you get routine thyroid bloodwork at the doctor’s office, they usually measure your TSH, which stands for Thyroid Stimulating Hormone. TSH isn’t produced in the thyroid; it’s made in the pituitary gland, which is located in your brain and controlled by the hypothalamus.
TSH’s job is to regulate your thyroid hormones by telling the thyroid how much T3 and T4 to secrete. When T4 levels in your blood dip, the pituitary gland secretes more TSH to balance things out. If T4 levels in your blood are high, TSH gets reeled in. It’s what we call a feedback loop.
The thyroid gland might be small, but it’s mighty. Thyroid hormones influence almost every bodily function and tissue, including and not limited to:
Cholesterol production and disposal
Carbohydrate and fat metabolism
Growth and maturation of the body
Thought processes and concentration
As you can see, the thyroid is pretty damn important!
So what happens when yours is out of whack? I’ll bet some of you have this problem, so let’s dive into it.
What can affect thyroid function?
Speaking as someone whose thyroid went ballistic after I had my second kid, I can tell you that having a messed up thyroid is not fun. I knew something was wrong when I lost a ton of weight, and my heart rate was 200 BPM AT REST. After I ate anything, or when I picked Isabel up, I’d get really hot and my heart would start pounding. I felt really weird and super exhausted. I finally went to an endocrinologist who told me that my T3 and T4 were positively off the charts. As in, the highest she had ever seen. Whoa. I had hyperthyroidism from my pregnancy, no doubt.
The doctor put me on medication to slow my heart rate (and told me not to work out or I could basically have a heart attack and die), and soon enough my thyroid bounced back…the other way. After ping-ponging around, everything settled down and went back to normal. Whew. I still need to get my thyroid hormones checked every single year because of all that craziness.
Not everyone is so lucky to have such a quick resolution to their thyroid issues. Pregnancy is only one thing that can throw your thyroid off; some other causes are:
Autoimmune diseases such as Hashimoto’s Thyroiditis
Too little or too much iodine
Pituitary gland malfunction
Viral infections causing an inflammation of the thyroid gland
It’s easy to measure thyroid function with a simple blood test.
Hyperthyroidism vs hypothyroidism
Hyperthyroidism means that your thyroid gland is producing too much thyroid hormone.
It’s typically diagnosed if someone has low TSH and high T3 and T4 levels in their blood. Somehow, even though the pituitary gland is shutting off the TSH to stop your thyroid from producing T3 and T4, an overactive thyroid just doesn’t hear it. It keeps on producing hormones.
The symptoms of hyperthyroidism are:
- fatigue or muscle weakness
- hand tremors
- mood swings
- nervousness or anxiety
- rapid heartbeat
- heart palpitations or irregular heartbeat
- skin dryness
- trouble sleeping
- weight loss
- increased frequency of bowel movements
- light periods or skipping periods
Hypothyroidism means that your thyroid gland is producing too little thyroid hormone.
It’s typically diagnosed if someone has high TSH and low T3 and T4 levels in their blood. The TSH is high because the body detects the absence of T4 and therefore secretes more TSH to tell the thyroid gland to make T4. But because the thyroid gland isn’t working properly at that point, the T4 levels remain low.
The symptoms of hypothyroidism are:
- Weight gain or increased difficulty losing weight
- Coarse, dry hair
- Dry, rough pale skin
- Hair loss
- Cold intolerance (you can’t tolerate cold temperatures like those around you)
- Muscle cramps and frequent muscle aches
- Memory loss
- Abnormal menstrual cycles
- Decreased libido
Hashimoto’s Thyroiditis, otherwise known as chronic lymphocytic thyroiditis, is the most common cause of hypothyroid in the United States (and probably Canada, I’m guessing). Hashimoto’s occurs when the thyroid gland is attacked by the body’s own immune system, causing it to make too little thyroid hormone.
The immune system is supposed to protect our body, but sometimes it malfunctions and its cells attack our own tissues instead. This is called having an autoimmune disorder.
The symptoms of Hashimoto’s are the same as the ones for hypothyroid, as hypothyroid is the result of having this disease.
Graves’ Disease, otherwise known as toxic diffuse goiter or Basedow’s disease, is also an autoimmune disease, and is the most common cause of hyperthyroidism. In Graves’ disease, the body produces antibodies that cause the thyroid gland to enlarge and produce too much thyroid hormone. One of the common hallmarks of Graves’ disease are bulging eyes and eye issues, stemming from inflammation of the muscles surrounding the eyes. Another sign of Graves’ is thickening of the skin on the shin area of the leg.
Both of these diseases are thought to be hereditary in some cases, and they affect far more women than men. Because of this, there are suggestions that both diseases have something to do with the female sex hormones. No one really knows.
Diet and thyroid function.
If you have a thyroid issue, the first thing you’ll want to do is get rid of the symptoms. Trust me, I feel you.
A lot of people want to know if diet really affects thyroid disease, and certainly you don’t have to look very far to find a ton of ‘diet for thyroid’ BS online. Sorry to be so upfront about it, but stay with me here.
A study published in August 2021 actually found that eating a diet high in high glycemic foods is associated with decreased TSH levels and increased T3/T4. Weirdly enough, it also found an link between diets high in saturated fats and protein, and higher TSH levels.
But despite all the wonderful claims and promises found online about thyroid diets, there’s little to no good evidence that eating any specific food will improve your thyroid condition, unless you’re deficient in certain things. Iodine is one of them.
So, the one solid recommendation for everyone is to ensure that you’re getting enough iodine. That doesn’t mean supplements – those can have their own side effects, such as exacerbating Hashimoto’s. Don’t go there without the advice of a physician who knows your hormone levels.
Get your iodine from foods – good sources are iodized salt, and also fish, grains, eggs, and beans. Iodine deficiency in developed countries is rare, though – and if you eat a wide variety of foods, you’re probably getting enough.
You may have heard that seaweed is a good source of iodine. It is, and in some cases, maybe even too good. Some seaweeds like kombu and wakame have far too much iodine to be consumed regularly. If you’re like me and can eat a ton of those roasted seaweed snacks, you’ll want to watch that, even though nori (which is what most of them are made of) is fairly low in iodine.
Vitamin D and Selenium
Being deficient in either of these can possibly exacerbate symptoms of thyroid disease. I do not recommend selenium supplements because those can have side effects. Get selenium from food (one single Brazil nut a day works).
Some other diet considerations are:
I’ve had quite a few clients who have thyroid issues, and they’ve read on the internet that they need to avoid kale and broccoli. This is because those foods are ‘goitrogenic’.
Goitrogenic foods like cruciferous vegetables, kale, and soy release a compound called ‘goitrin’ when they’re broken down, and goitrin can interfere with the synthesis of thyroid hormones and aggravate hypothyroidism. So can someone with hypothyroidism still eat these foods? The answer is yes…if you’re not deficient in iodine, and if you don’t eat a truckload of them, you should be fine. It’s also better to cook these foods – that denatures most of their goitrin.
Hypothyroidism caused by goitrogenic foods is only a risk if a person is iodine deficient.
The rest of you probably will not get hypothyroidism from eating too much broccoli.
So yes, you still do need to eat your vegetables.
Celiac disease is autoimmune, just like Hashimoto’s or Graves’ disease. Research has actually connected celiac and thyroid disease, so if you have one of these, you most definitely should be tested for the other. Celiac and Hashimoto’s share some common symptoms – fatigue, bloating/weight gain – so it may be hard to detect what symptom is due to which disease.
Hypothyroid can cause weight gain and difficulty losing weight, so it’s not shocking that some people may want to try a low carb or ketogenic diet to remedy that situation. Research suggests (this is a study done on children, FYI) that ketogenic diets may actually cause hypothyroid. This may happen because: the hypothalamus, which is a part of the brain, uses glucose for energy.
When the brain is deprived of glucose, it believes that it’s starving, so the hypothalamus is affected. The hypothalamus is what tells the pituitary gland to produce TSH, which in turn tells the thyroid to produce T3 and T4. So it’s a chain reaction that may ultimately affect your hypothyroidism. See? Sometimes a diet isn’t just a diet.
The study above is the only recent one measuring the effects of ketogenic diets on thyroid health. All other studies were mostly very small and very old: We’re talking 1970s and 80s here.
If you’re looking to lose weight, my recommendation would be to not go as low carb as a ketogenic diet. Low carb – around 150g per day – maybe, but not virtually carb-free, just to ensure that your thyroid doesn’t suffer any effects. As always, ask your doctor before starting any diets or new plans.
The best way to manage hypothyroidism is to take thyroid hormones. Levothyroxine is the one that’s most frequently prescribed, and it’s manufactured to act really like your own thyroid hormone would. When dosage is optimized, you should not have any symptoms of hypothyroidism at all.
Hyperthyroidism is managed much the same, but with different medications called antithyroid drugs. In some cases, other treatments may be necessary.
Lastly, check your neck.
Checking your neck can help detect any lumps or enlargement of your thyroid.