Abstract
: BackgroundMuch research suggests that Mediterranean eating habits and lifestyle contribute to counteract the risk of chronic diseases while promoting longevity, but little information is available on the effects of the Mediterranean diet (Med-Diet) on thyroid function, particularly among overweight/obese subjects. Nevertheless, consistent data reported a slight increase in serum levels of the thyroid-stimulating hormone (TSH) and a higher rate of conversion of thyroxine (T4) to triiodothyronine (T3) in obesity. This cross-sectional study was aimed at investigating the relationship between adherence to the Med-Diet and circulating thyroid hormones in a cohort of overweight/obese subjects from Apulia (Southern Italy). Methods: We studied 324 consecutive outpatient subjects (228 women and 96 men, age range 14–72 years) taking no drug therapy and showing normal levels of thyroid hormones, but complicated by overweight and obesity (body mass index (BMI) ≥ 25 Kg/m2). The PREDIMED (PREvención con DIeta MEDiterránea) questionnaire was cross-sectionally administered to assess the adherence to the Med-Diet, and hormonal, metabolic, and routine laboratory parameters were collected. Results: Higher adherence to Med-Diet was found to be inversely related to free T3 (p < 0.01) and T4 (p < 0.01) serum levels. Considering each item in the PREDIMED questionnaire, people consuming at least four spoonfuls of extra-virgin olive oil (EVOO) per day, as well as those consuming at least two servings of vegetables per day, had lower free T3 levels (p 0.033 and p 0.021, respectively). Furthermore, consuming at least four spoonfuls of EVOO per day was found to be associated to lower free T4 serum concentrations (p 0.011). Multinomial logistic regression models, performed on tertiles of thyroid hormones to further investigate the relationship with Med-Diet, corroborated the significance only for free T4. Conclusion: Increased adherence to the Med-Diet was independently associated to a slightly reduced thyroid function, but still within the reference range for free T3 and T4 serum levels. This first finding in this field opens up a research line on any underlying biological interplay.
Highlights
The traditional Mediterranean diet (Med-Diet) is the heritage of millennia of cultures, food patterns, and customs of the inhabitants of the entire Mediterranean basin, characterized by the main consumption of typical agricultural foods produced by local, small and medium-sized rural enterprises
A Spearman’s correlation matrix between the PREDIMED score and all continuous biochemical and anthropometric variables showed that a higher adherence to Med-Diet was significantly related to lower circulating FT3 (p 0.019), FT4 (p 0.001), and uric acid (p 0.047) serum levels
After analyzing the relationship between free thyroid hormones (FT3 and FT4) and each of the PREDIMED items using the Wilcoxon sum rank test, we found that the use of at least four tablespoonfuls of extra-virgin olive oil (EVOO) per day and the consumption of a serving of vegetables at least twice a day were the only features of the Med-Diet that showed a significant negative correlation with FT3 (p 0.033 and p 0.021, respectively); the consumption of a serving of vegetables at least twice a day was the only Med-Diet feature showing a significant inverse association with FT4 serum levels (p 0.011)
Summary
The traditional Mediterranean diet (Med-Diet) is the heritage of millennia of cultures, food patterns, and customs of the inhabitants of the entire Mediterranean basin, characterized by the main consumption of typical agricultural foods (i.e., olive oil, fruits, vegetables, and cereals) produced by local, small and medium-sized rural enterprises. A moderate consumption of alcohol (primarily red wine) during meals [2,3,4,5] On this basis, the Med-Diet has been referred to as a high-fat diet (approximately 40% of total energy intake), given the wide consumption of EVOO as major cooking fat in place of animal sources (i.e., butter), that is high in complex carbohydrates and fibers, mostly derived from vegetables and fruits. The Med-Diet has been referred to as a high-fat diet (approximately 40% of total energy intake), given the wide consumption of EVOO as major cooking fat in place of animal sources (i.e., butter), that is high in complex carbohydrates and fibers, mostly derived from vegetables and fruits This dietary pattern provides a low quantity of saturated fatty acids and a high amount of antioxidants and fibers, as well as a considerable intake of monounsaturated fatty acids and n-3 PUFAs (Polyunsaturated Fatty Acids), mainly derived from
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