Thyroid Physiology
Thyroid disease affects 20 million Americans today (1). This disease is more common than diabetes or heart disease, but many are unaware of the diagnosis and thyroid functions in general. The thyroid gland is an organ in the neck responsible for releasing thyroid hormonestriiodothyronine (T3) and thyroxine (T4). These hormones play a role in metabolism and hormone regulation. Different functions consist of carb and lipid metabolism, temperature control, growth, development, and reproductive and nervous system processes (2,3). When any of these functions needs to be altered, the brain recognizes this and thyroid-stimulating hormone (TSH) production is increased or decreased from the brain to stimulate less or more production of thyroid hormones from the thyroid gland.
In conclusion, if TSH is high, it usually means T3 and T4 are low and hypothyroidism (underactive thyroid) is present. Symptoms of hypothyroidism include weight gain, fatigue, and depression. If TSH is low, then T3 and T4 are usually high which indicates hyperthyroidism (overactive thyroid). Symptoms of hyperthyroidism include weight loss, increased heart rate, and anxiety (4). These two conditions are the main types of thyroid disease and have their own specific nutritional recommendations.
Iodine’s Role
Nutrition comes in when we talk about how thyroid hormones are made. Iodine is responsible for serving as a structural component for T3 and T4 (5). One nutritional risk that affects the chances of developing thyroid disease involves this mineral. If you consume too much or too little iodine, the chances of thyroid disease go up. Each condition has their own treatment and nutrition tips. So, if you have hypothyroidism, should you supplement with iodine? And if you have hyperthyroidism, avoid iodine? Well, it’s not that simple. Iodine supplementation can be harmful, especially if deficiency isn’t present and intake is not monitored accurately. Supplementation can worsen hypothyroidism if your thyroid is damaged. It can also interact with medications and may not even be the cause of hypothyroidism (6). With hyperthyroidism, it is recommended to avoid very high iodine intake. A lower iodine diet may be recommended. For prevention and maintenance methods, following a healthy lifestyle is the best thing you can do(7).
Medication and Nutrient (calcium and iron) Interactions
When thyroid disease is present, medication and food interactions are prioritized as certain foods can drastically affect how well the medication is absorbed. With hypothyroidism or thyroid replacement drugs from hyperthyroidism treatment, calcium and iron impacts medication absorption. It is recommended to take thyroid medication on an empty stomach and avoid eating high calcium and iron foods at least 4 hours prior or post medication time (8). While avoiding iron and calcium close to medication time, they are still very essential for a healthy thyroid and overall body (9). Other hyperthyroidism medications can be taken with food.
Eating for the Thyroid
Dairy and raw goitrogenic foods should be avoided, and soy should be limited in your diet. Lastly, studies have shown that replacing grains with starchy vegetables helped improve thyroid function (7,10). Talk to your doctor about diet recommendations if diagnosed with thyroid disease. What works for some might not work for others, and it is important to make a plan that works with your condition, medications, and lifestyle.
