Is there a connection between thyroid function and diet? Absolutely. While it’s well-known that iodine deficiency can lead to hypothyroidism, the thyroid requires more than just iodine to function properly. Not every type of hypothyroidism will benefit from iodine supplementation, so it's essential to understand the full picture.
Iodine Deficiency and Hypothyroidism
The thyroid gland produces two key hormones: thyroxine (T4) and triiodothyronine (T3). These hormones regulate our energy metabolism, influencing everything from body temperature to heart rate, weight, and bone metabolism. To produce T3 and T4, the thyroid needs iodine, a trace element that must be obtained through diet.
When the thyroid lacks iodine, it can’t produce enough hormones, potentially leading to hypothyroidism. The gland compensates by growing larger, resulting in a condition known as goitre. However, this condition is rare today. More common causes of hypothyroidism include inflammation, autoimmune diseases like Hashimoto’s, and hypothyroidism after thyroid surgery or radiation. If Hashimoto’s is the cause, iodine might worsen the symptoms, so getting the correct diagnosis is crucial.
In conventional medicine, hypothyroidism is typically treated with l-thyroxine, regardless of the underlying cause. However, if you wish to support your thyroid through diet in conjunction with medication, it’s important to have a thorough understanding of your condition.
Key Thyroid Tests
Standard blood tests for thyroid function usually measure thyroid-stimulating hormone (TSH) and free T4. If hypothyroidism is suspected, free T3 may also be checked. However, reverse T3 (rT3), which can inhibit thyroid function, is often overlooked. Measuring rT3 can provide additional insights if you’re still experiencing symptoms despite ‘normal’ thyroid levels.
Anti-thyroid antibodies, which indicate Hashimoto’s disease, are also rarely tested. Knowing whether you have Hashimoto’s is essential if you want to follow a thyroid-friendly diet.
Unfortunately, Hashimoto's is not curable, but symptoms can be managed through a low-sugar, potentially gluten-free diet, and intermittent fasting. The goal is to follow an anti-inflammatory diet that supports the immune system.
If you have Hashimoto's, testing for gluten intolerance is important, as it’s common among those with the condition. If you’re sensitive to gluten (1) or casein (2), your immune system may mistakenly attack your thyroid, worsening your symptoms. In this case, avoid gluten-containing grains and opt for gluten-free alternatives like buckwheat, quinoa, and amaranth.
Foods Your Thyroid Will Love
In addition to iodine, your thyroid needs selenium and zinc to produce and activate thyroid hormones. While zinc is generally abundant in food, selenium deficiency is more common due to depleted soil levels. Without selenium, T3 cannot be activated, and the trace element also has anti-inflammatory properties that benefit those with Hashimoto’s.
For optimal thyroid health, focus on a real food diet with minimal processing:
Protein: Include protein in every meal to stay fuller longer. Good sources are dairy (if tolerated), fish, meat, pulses, and mushrooms.
Vegetables: Pair with high-quality oils and low-sugar fruits like berries.
Fish: Sea fish like haddock and cod provide iodine and omega-3s. Seafood and seaweed are also rich in iodine.
Meat: Pork and offal are good sources of selenium.
Eggs: Provide protein, selenium, and iodine, especially in the yolk.
Gluten-Free Grains and Seeds: Opt for rice, buckwheat, quinoa, chia, and flaxseed.
Nuts: Brazil nuts are rich in selenium, and cashews provide iodine.
Omega-3 Fatty Acids: Found in fish and high-quality linseed or hemp oil, or consider algae oil supplements if you don’t eat fish.
Phytonutrients: From colourful vegetables and spices like dark cocoa, cinnamon, ginger, turmeric.
Probiotics and Prebiotics: Strengthen gut health with foods like sauerkraut, yoghurt, miso, and tempeh.
Foods to Avoid
Certain foods can negatively impact thyroid function:
Sugar and Refined Starches: These have a pro-inflammatory effect and should be avoided.
"Goitrogenic" Foods: These interfere with iodine metabolism and include uncooked cruciferous vegetables like broccoli, as well as soy foods (3) and millet (4). Cooking these foods or choosing fermented versions like sauerkraut and tempeh can reduce their goitrogenic effect.
What About Dairy?
Dairy products like milk, yoghurt, and cheese are good sources of selenium and iodine. However, dairy contains casein, a protein that can cause issues for some people. It’s worth getting tested for casein sensitivity, which is different from lactose intolerance. If casein affects your thyroid, eliminating dairy may improve your symptoms.
Strategies for a Healthy Weight
Maintaining a healthy weight can reduce inflammation and improve thyroid function, but hypothyroidism can make weight loss challenging. Intermittent fasting and a low-carbohydrate diet may help. Start with a 12-hour fasting window and gradually increase to 14-16 hours. Monitor your symptoms carefully, as fasting may not be suitable for everyone with thyroid issues.
If you’re interested in exploring dietary strategies to support your thyroid, I’m here to help. Don't hesitate to get in touch if you have any further questions!
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