The thyroid gland — located in the front of your neck — is responsible for releasing thyroid hormone, which regulates your body’s metabolism (how it uses or stores energy). There are two main forms of thyroid hormone: triiodothyronine (T3) and thyroxine (T4). When your levels of these hormones are too low, the pituitary gland — located at the base of your brain — produces thyroid-stimulating hormone (TSH), which signals to your thyroid gland that it should produce more thyroid hormone. If your thyroid gland can’t produce enough thyroid hormone for some reason — such as Hashimoto’s disease, in which your immune system attacks your thyroid gland — then levels of TSH are likely to be high as your pituitary gland tries to raise your thyroid hormone levels, while levels of T3 and T4 are likely to be low.
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The new study is the first major effort to look at how a wide range of dietary factors affect thyroid hormone levels. Researchers looked at thyroid hormone levels in 4,585 healthy adults living in the Dalmatian region of Croatia, and compared these measurements with their responses in a food frequency questionnaire that covered 58 food items. The researchers then calculated the estimated intake of different dietary components based on these responses — carbohydrate, protein, fat, and more.
Overall, the researchers observed lower levels of thyroid hormone (T3 and T4) and higher levels of TSH in women compared with men, suggesting that women are more likely to have reduced thyroid function. People with higher fasting glucose levels tended to have higher blood levels of T4, while smokers tended to have lower levels of TSH compared with nonsmokers.
Dietary factors linked to thyroid function
When it came to diet, several different factors were linked to levels of T3, T4, and TSH, as described in a Healio article. There were 4,217 participants with T3 levels in the normal range. Higher levels of T3 were seen in people who ate greater amounts of bacon and sausage, while lower levels of T3 were seen in those who ate greater amounts of mushrooms and pickled vegetables.
There were 4,124 participants with T4 levels in the normal range. Those with higher levels of T4 were more likely to eat fish, white bread rather than whole-grain bread, fruit juices, and bacon and sausage. Those with lower levels of T4 were more likely to eat pork, beef, eggs, mushrooms, pickled vegetables, and butter and animal fat.
Overall, the researchers found that foods with a higher glycemic index — those that raise blood glucose levels the most — had a negative effect on thyroid function, while foods high in protein or saturated fat had a positive effect on thyroid function. This findings suggest that when it comes to your metabolic health, it’s best to avoid carbohydrate-heavy foods that spike glucose levels the most, while eating more protein and animal fat may actually help your thyroid gland function at its best.
Want to learn more about keeping your thyroid healthy? Read “Diabetes and Thyroid Conditions.”