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Triiodothyronine, or T3, is a hormone that affects many organs and tissues throughout the body, playing a key role in metabolism and protein synthesis. Free T3 is a measure of the portion of the hormone that is not bound to protein in the blood. (source)
Low free T3 levels can stem from physiological factors affecting the thyroid gland, which produces T3, a hormone that is crucial for metabolism regulation. Nutritionally, inadequate intake of essential nutrients like iodine, which is necessary for thyroid hormone synthesis, can contribute to lower T3 levels. (source, source)
Prioritize selenium-rich foods: Consumption of selenium has been shown to increase free T3 levels. (source) Selenium is vital for the proper functioning of enzymes that convert T4 into its active form, T3. (source) This mineral is an essential component of selenoproteins, compounds that facilitate hormone conversion, leading to increases in free T3 concentrations. (source, source) Recommendation: Eat at least one serving of selenium-rich foods three times per week.
One serving examples: Brazilian Nuts (1 oz), Yellowfin Tuna (3 oz), Sardines (3 oz), Beef (3 oz), Chicken (3 oz)
Avoid cold exposure: Cold exposure is associated with reduced free T3. (source) When chronically exposed to extreme cold, the body undergoes non-shivering thermogenesis to produce heat. This heat is produced, in part, by an increased use of T3, which decreases circulating free T3 levels. (source, source) Avoiding chronic exposure to cold temperatures increases free T3. Recommendation: Limit exposure to cold temperatures.
Food journal: Individuals in a caloric deficit were shown to have lower free T3. (source) Under-eating can cause the metabolism to slow down to conserve energy, which reduces the conversion of T4 to T3, thus decreasing serum T3 levels. Ensuring adequate caloric intake regulates free T3 concentrations. (source) Recommendation: Ensure adequate caloric intake.
Supplement with selenium: Supplementation with selenium has been shown to increase free T3 levels. (source) Selenium is vital for the proper functioning of enzymes that convert T4 into its active form, T3. (source) This mineral is an essential component of selenoproteins, compounds that facilitate hormone conversion, leading to increases in free T3 concentrations. (source, source) Recommendation: Supplement with at least 50 mcg of selenium.
Elevated free T3 levels can often stem from physiological factors affecting thyroid function and metabolism. From a nutritional perspective, an excess of certain nutrients like iodine and zinc can support thyroid hormone production and conversion, potentially leading to higher T3 levels. (source, source, source)
Limit selenium-rich foods: Consumption of selenium has been shown to increase free T3 levels. (source) Selenium is an essential component of compounds that convert T4 to T3. Limiting the intake of selenium regulates free T3 levels. (source, source) Recommendation: Monitor and limit excess consumption of selenium-rich foods, like organ meats, seafood, and Brazil nuts.
Eat slowly: Eating slowly has been shown to increase satiety and reduce calorie intake. (source, source) Individuals in a caloric deficit have been shown to have lower free T3 levels. (source) Under-eating can cause the metabolism to slow down to conserve energy, which reduces the conversion of T4 to T3, thus decreasing serum T3 levels. (source) Recommendation: Make each meal last at least 20 minutes when consumed.
Avoid selenium: Supplementation with selenium has been shown to increase free T3 levels. (source) Selenium is an essential component of compounds that convert T4 to T3. Limiting the intake of selenium regulates free T3 levels. (source, source) Recommendation: Monitor intake and supplement concentrations of selenium.
