Foods with high protein, saturated fatty acids linked to better thyroid function
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Eating more foods that are high in protein and saturated fatty acids is associated with better thyroid function, according to findings from a cross-sectional study published in Nutrition.
“This is the first study to analyze the influence of a comprehensive set of dietary factors on plasma free triiodothyronine, free thyroxine and thyroid-stimulating hormone levels,” Dubravka Brdar, MD, a specialist in the department of nuclear medicine at University Hospital Split in Croatia, and colleagues wrote. “The study showed a negative effect of frequent consumption of foods with a high glycemic index on thyroid function. At the same time, ‘healthy foods’ with high protein concentration and foods rich in saturated fatty acids that are not limited in consumption nowadays showed positive effects on thyroid function.”
Researchers recruited 4,585 adults from three regions of Croatia to participate in the study (60.1% women; mean age, 53.5 years). All participants had blood samples taken to measure plasma free T3, free T4 and TSH levels. A food frequency questionnaire was administered at recruitment to evaluate consumption of 58 different foods and beverages. The list of food items was broken down into 18 dietary groups. Researchers analyzed associations between each dietary group and free T3, free T4 and TSH levels.
Researchers found women had higher TSH levels and lower free T3 and free T4 levels compared with men. Participants who smoked had lower TSH levels than nonsmokers and former smokers.
Of the study cohort, 4,217 participants had free T3 levels within the normal range. Adults who ate higher amounts of bacon and sausages had higher free T3 levels (beta = 0.02; P = .044), whereas eating high amounts of mushrooms and pickled vegetables was negatively associated with free T3 (beta = –0.03; P = .023).
Of the study cohort, 4,124 participants had free T4 levels in the normal range. Eating a high amount of pork, beef and eggs (beta = –1.22; P = .004), mushrooms and canned or pickled vegetables (beta = –0.15; P = .001) or butter and animal fat (beta = –0.091; P = .027) was associated with lower free T4. Eating high amounts of fish (beta = 0.162; P < .0001), white bread instead of whole grain bread (beta = 0.191; P < .0001), fruit juices, Cedevita vitamin drinks and nonalcoholic drinks (beta = 0.14; P = .001), bacon and sausages (beta = 0.137; P = .001) and powdered soups and vegetable juice (beta = 0.115; P = .006) was positively associated with free T4.
“Frequent consumption of white fish, blue fish, seafood, squid, octopus and dried fish, foods with a low glycemic index, showed an association with high levels of free T3 and free T4,” the researchers wrote. “This can be explained by the high levels of iodine in seafood, the main dietary source of iodine.”
The study cohort had 3,866 participants with normal TSH levels. Consuming high amounts of fruit juices, Cedevita vitamin drinks and nonalcoholic drinks was negatively associated with plasma TSH levels (beta = –0.021; P = .043), whereas consuming a high amount of venison or fish was negatively associated with plasma TSH (beta = –0.03; P = .006).
“The strengths of our study are the large sample size and the fact that the participants originate from an iodine-sufficient area,” the researchers wrote. “The limitation of this study is its cross-sectional design, meaning only associations could be inferred. Furthermore, all variables in the food frequency questionnaire were self-reported. Qualitative assessment of food intake has limitations; however, it still provides relevant dietary information.”
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