Broccoli sprout beverage is safe for thyroid hormonal and autoimmune status: Results of a 12-week randomized trial

Abstract

Sulforaphane is a redox-active natural product present in cruciferous vegetables like broccoli. Broccoli sprout-derived products are promising agents for the prevention of oxidative stressrelated diseases, but some have long been suspected of thyroidal toxicity. Recent findings also raise the possibility that long-term exposure to sulforaphane, or to other natural substances or drugs that modulate the activity of the transcription factor Nrf2 (NFE2-related factor 2) may lead to thyroid dysfunction or thyroid autoimmune disease, questioning the safety of trials with sulforaphane-containing products. Previous studies addressing possible effects of sulforaphanerelated compounds from natural product extracts on the thyroid were quite short and/or inconsistent. To investigate whether long-term exposure to a beverage enriched with sulforaphane and its precursor glucoraphanin may affect thyroid function, we analyzed biochemical measures of thyroid function and thyroid autoimmunity in 45 female participants in a randomized clinical trial at baseline and after 84 days of beverage administration. Serum levels of thyroid-stimulating hormone, free thyroxine and thyroglobulin were not affected by the treatment, and neither was the thyroid autoimmunity status of participants. These results provide evidence in favor of the safety of chemoprevention strategies that target the activation of Nrf2 to protect against environmental exposures and other oxidative stress-related pathologies.

Impact of Antioxidant Natural Compounds on the Thyroid Gland and Implication of the Keap1/Nrf2 Signaling Pathway

“…While the health benefits associated with natural compounds found in plants in low amounts are generally well accepted, attention should be drawn to potential toxicities arising from the use of concentrated extracts that may contain excess amounts of phytochemicals. For instance, a daily dose of 600 µmol glucoraphanin and 40 µmol sulforaphane in the form of broccoli sprout extracts over 12 weeks has been shown to be effective against the detoxification of airborne pollutants [234], and this dosing scheme was proven to be safe for the thyroid [187]. Table 4.…”

“…bination, as found in cabbage, can lead to increased thyroid size [186]. Of note, in a recent randomized clinical trial, we showed that daily administration of a sulforaphane-rich broccoli sprout extract to healthy volunteers did not have any detrimental effect on thyroid function or the thyroid autoimmunity status [187]. The most abundant sulfur-containing compound from garlic, Sallylcysteine (SAC), has a potential beneficial effect in diabetes.…”

Keap1/Nrf2 Signaling: A New Player in Thyroid Pathophysiology and Thyroid Cancer

“…It therefore appears prudent to monitor both thyroid function and thyroid volume (at least by palpation) in patients treated with Nrf2-activating compounds on a therapeutic or experimental basis. In that sense, consumption of a broccoli sprout beverage (yielding pharmacologically active amounts of the Nrf2-activating compound sulforaphane) has been recently shown to be safe for thyroid hormonal, and autoimmune status during a 12-week randomized trial (28). Other Nrf2-activating regimens should also be tested on an individual basis, to ensure their safety for the thyroid gland.…”

Interaction of Genetic Variations inNFE2L2andSELENOSModulates the Risk of Hashimoto's Thyroiditis

“…Selenium supplementation is recommended for the treatment of orbitopathy associated with autoimmune hyperthyroidism (Graves' disease) (61), and it is also currently being tested in a randomized controlled clinical trial as a therapeutic measure for chronic autoimmune thyroiditis (HT) (62). In view of the present findings, it might be interesting to test combinations of selenium with Nrf2 activating compounds, such as SLF-containing natural extracts, whose safety for the thyroid has actually been shown in a recent clinical trial (63).…”