Thyroid-Modulating Activities of Olive and Its Polyphenols: A Systematic Review

Abstract

Olive oil, which is commonly used in the Mediterranean diet, is known for its health benefits related to the reduction of the risks of cancer, coronary heart disease, hypertension, and neurodegenerative disease. These unique properties are attributed to the phytochemicals with potent antioxidant activities in olive oil. Olive leaf also harbours similar bioactive compounds. Several studies have reported the effects of olive phenolics, olive oil, and leaf extract in the modulation of thyroid activities. A systematic review of the literature was conducted to identify relevant studies on the effects of olive derivatives on thyroid function. A comprehensive search was conducted in October 2020 using the PubMed, Scopus, and Web of Science databases. Cellular, animal, and human studies reporting the effects of olive derivatives, including olive phenolics, olive oil, and leaf extracts on thyroid function were considered. The literature search found 445 articles on this topic, but only nine articles were included based on the inclusion and exclusion criteria. All included articles were animal studies involving the administration of olive oil, olive leaf extract, or olive pomace residues orally. These olive derivatives were consistently demonstrated to have thyroid-stimulating activities in euthyroid or hypothyroid animals, but their mechanisms of action are unknown. Despite the positive results, validation of the beneficial health effects of olive derivatives in the human population is lacking. In conclusion, olive derivatives, especially olive oil and leaf extract, could stimulate thyroid function. Olive pomace residue is not suitable for pharmaceutical or health supplementation purposes. Therapeutic applications of olive oil and leaf extract, especially in individuals with hypothyroidism, require further validation through human studies.

Mediterranean Diet and Thyroid: An Interesting Alliance

“…A systematic review by Pang et al showed a thyroid-protective effect of EVOO in animal models. These mechanisms are unknown, but olive oil, olive leaf extract, and olive pomace residues seem to stimulate thyroid function in euthyroid and hypothyroid animals [ 53 ].…”

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

“…Many experimental studies have shown that olive derivatives, especially olive oil, have a stimulating effect on the thyroid gland (reviewed in [ 110 ]). The experimental studies were performed on various animal models: rats [ 111 , 112 , 113 , 114 ], chicken [ 115 , 116 ], lambs [ 117 ], goats [ 118 ] and calves [ 119 ].…”

“…The experimental studies were performed on various animal models: rats [ 111 , 112 , 113 , 114 ], chicken [ 115 , 116 ], lambs [ 117 ], goats [ 118 ] and calves [ 119 ]. The mechanism by which olive derivatives and olive oil affect the TSH and thyroid hormone levels is still unclear [ 110 ]. To our knowledge, only one study in humans has shown the effect of olive oil consumption on thyroid hormone levels [ 120 ].…”

Health benefits of olive oil and by-products and possible innovative applications for industrial processes

“…On the other hand, oxidative molecules can also control the functionality of the membrane transport system through oxidative-sensitive post-translational modifications [10]. Indeed, several transporters and channels can be subjected to S-glutathionylation, nitrosylation, or carbonylation that may alter protein stability, [11][12]. In euthyroid animals, administration of olive oil or OLE increased the active triiodothyronine (T3) and the inactive thyroxine (T4) and reduced the thyroid-stimulating hormone (TSH) [12][13][14].…”

“…Indeed, several transporters and channels can be subjected to S-glutathionylation, nitrosylation, or carbonylation that may alter protein stability, [11][12]. In euthyroid animals, administration of olive oil or OLE increased the active triiodothyronine (T3) and the inactive thyroxine (T4) and reduced the thyroid-stimulating hormone (TSH) [12][13][14]. Furthermore, oral administration of EVOO improves the TSH profile and the oxidative status of the thyroid gland in a rat model of hypothyroidism [15].…”