Thyroid Diet: What's the Facts?
Very often I receive questions from patients about dietary interventions through which to treat or reverse their thyroid disease. What supplements can they take, what toxins can they avoid to reduce the symptoms of thyroid disease beyond standard medical treatment, how can they reduce the titer of anti-thyroid antibodies and how much of certain foods or supplements should they consume.
Truth be told the information circulating on the internet is fascinating. From a purely scientific point of view, however, these data are of low quality to be included in clinical guidelines. Let's examine the most popular thyroid-related nutritional topics one by one.
In order for the body to produce thyroid hormones it must have sufficient iodine either through food or supplements. Inadequate intake leads to a risk of developing or worsening pre-existing hypothyroidism. The recommendations of international organizations refer to 150 μg/day for adults, 220 μg/day for pregnant women and 290 μg/day for lactating women. The sources from which we take in iodine are iodized salt, seafood (fish, seaweed) and some types of bread and seeds. It should be noted here that sea salt, despite its name, does not contain iodine. It is difficult to calculate the daily amounts of iodine that someone takes in through food as it is not written on food labels and measuring it in blood or urine is not a simple process. Dietary supplements advertised as iodine for thyroid health usually contain vast amounts above the recommended daily dose in a single tablet. Other products containing spirulina or kelp also contain large amounts. By taking these huge amounts we can drive the thyroid to either "shut down" and cause hypothyroidism or cause hyperthyroidism. There is evidence that chronic exposure to increased amounts of iodine induces the development of autoimmune thyroiditis
The term refers to substances whose consumption leads to the creation of a goiter, i.e. an increase in the volume of the thyroid gland. The most common examples are cruciferous or cruciferous vegetables and soy products.
They include broccoli, cauliflower, Brussels sprouts, cabbage, radishes. Consumption of the above in large quantities per year can cause hypothyroidism. But how much is considered too much? Unfortunately, there is insufficient data, but a recent study of euthyroid subjects who received daily broccoli juice for 12 weeks showed no changes in thyroid parameters. As a recommendation to patients referring to these specific foods, I would say that the latest clinical studies confirm that there is no reason to stop eating cruciferous vegetables. Of course, the logic of the measure always applies, although we do not have sufficient data as to what the measure is.
Products containing soy are rich in isoflavones which belong to the class of phytoestrogens. These substances can increase the risk of developing hypothyroidism. It has also been observed that hypothyroid patients who consume increased amounts of soy products require an increase in the dose of thyroxine they receive. In clinical practice, studies have shown that the consumption of even large amounts of soy led to small increases in thyroid-stimulating hormone without affecting peripheral thyroid hormones. In general we recommend to patients that a reasonable daily use of sogis products is safe and there is no reason to avoid it. Caution only in infants with neonatal hypothyroidism fed soy-based foods. The dose of thyroxine administered should be increased
Selenium is considered important in thyroid function. The recommended daily dose of selenium is 55μg. Sources of dietary intake are seafood, meat, poultry, eggs, bread and seeds. Maximum tolerated doses are up to 400 μg/day and exceeding them can rarely lead to toxicity. Selenium is not recommended except for mild ophthalmopathy due to Graves' disease. Taking 200 μg/day for 6 months improves quality of life and has a favorable effect on the progression of thyroid eye disease. Zinc, copper and magnesium Based on the clinical data we have, it is not recommended to take these specific trace elements for the purpose of improving thyroid function
Fluoride is found naturally in the environment or in the water with which it is enriched as well as in dental products. Studies have shown an increase in the value of thyroid-stimulating hormone in adults who lived in areas with iodine deficiency, and in their urine increased amounts of fluoride were found. With the available data we cannot conclude to what degree fluoride exposure affects thyroid function.
OTHER DIETARY INTERVENTIONS
Gluten-free diet. There are currently no data for such a recommendation in non-celiac patients for the health of patients with or without established thyroid disease. Avoiding sugar also has no documented benefit. Finally coffee, tea and alcohol have not been associated with an increased incidence of thyroid cancer. The role of vitamin D administration also remains unclear.
As endocrinologists we must explain to our patients that the relationships between thyroid disease, diet and supplements are complex. Further investigations are needed. With today's data, the only safe recommendation is daily intake of iodine supplements of 150 μg/day in people who are on a diet, in pregnant, lactating or women who are thinking about pregnancy. Avoiding cruciferous vegetables or soy in adults is not recommended when their consumption is reasonable. Specialist advice on taking selenium in Graves' eye disease is also recommended. Other dietary interventions marketed on the internet for thyroid health are not supported by secure data.