Food is the primary source of nutrients necessary for proper development and functioning of the body. However, apart from components that positively impact our health, there are also anti-nutritive compounds present in food. These include oxalates, phytates, and goitrogens. They exhibit actions that limit and hinder the body’s use of nutrients supplied from the diet [1,2].
What are goitrogens?
Goitrogens, or thyrogenic compounds, are a group of anti-nutritive ingredients of both organic and inorganic origin whose action contributes to the disruption of iodine metabolism [1,2,4].
Where are goitrogens found?
Thyrogenic compounds are found in plant-based materials. Their highest quantities are present in cruciferous vegetables in the order Brassicales. These include, among others, broccoli, cauliflower, kale, Brussels sprouts, all kinds of cabbage, radish, turnip, and mustard [1,2].
Table 1. Goitrogen content in 100g of selected cruciferous vegetables [2]
Italian cabbage 18-31 mg Kale 3-25 mg Broccoli 10 mg Brussels Sprouts 10 mg Cauliflower 4-10 mg Yellow Turnip 9 mg Head Cabbage 3-6 mg Radish below 1 mg
Types
Primarily, the following are classified as naturally occurring goitrogens:
Thioglycosides (glucosinolates) are compounds with S-glycosidic bonds, characterized by the strongest thyrogenic action. They are found in all parts of cruciferous plants (e.g., cabbage, broccoli, cauliflower, kale, radish) and their products [1,2].
Cyanogenic glycosides are a group of toxic compounds found in cassava, lima beans, bamboo shoots, and the seeds of pitted fruits (pears, apples, almonds, apricots, peaches)—their thyrogenic action results from forming thiocyanate ions (SCN¯) during cyanide detoxification in the body. Linamarin is considered the most important representative of this group of glycosides [1,2].
Because polyphenols react with iodine, disrupting the synthesis of thyroxine, they are considered thyrogenic compounds. They are found in fruits, some vegetables (e.g., red cabbage), and peanuts (especially in the red-tinted hull) [1,2].
Hemagglutinins (lectins) are glycoproteins that show affinity for cell membranes, reducing the intestinal absorption of iodine. In addition, these compounds disrupt the resorption of thyroxine secreted with bile into the intestinal lumen. The primary sources of lectins include soy and beans [1,2].
Impact on the body
By reducing the iodine concentration in the body, goitrogens contribute to disrupting the management and metabolism of this micronutrient. Their adverse effect results from the ability to bind iodine, which prevents the correct incorporation of this element into thyroxine (T4) molecules and its later conversion into triiodothyronine (T3). A decreased level of T3 and T4 in the system directly contributes to an increase in the TSH level. Consequently, there is the development of hypothyroidism and an enlargement of its mass, resulting in the so-called goiter. However, it should be noted that the thyrogenic effect of goitrogens is stronger the smaller the iodine intake in the diet.
Who should limit consumption?
Due to the thyrogenic action of goitrogens, it is recommended that people suffering from hypothyroidism avoid foods that are a rich source of them. This does not mean excluding products such as cabbage, broccoli, cauliflower, or Brussels sprouts from the diet. However, it is crucial to remember moderate consumption of cruciferous vegetables and proper iodine intake. This way, the risk of adverse health consequences will be minimized.
Goitrogens in Hashimoto’s Disease
Hashimoto’s disease is a chronic lymphocytic thyroiditis. Due to the disturbances in hormone production occurring during its course, it can accompany or be a triggering factor for hypothyroidism.
As in the case of hypothyroidism, the most essential element of the dietary therapy for this disease is limiting the intake of goitrogens and balancing iodine metabolism. It should be noted that too high a level of this trace element in the bodies of individuals suffering from Hashimoto’s disease can contribute to worsening the gland’s inflammatory state.
How to Reduce the Content of Goitrogens in Food?
The primary source of thyrogenic substances is cruciferous vegetables. These include cabbage, Brussels sprouts, broccoli, and cauliflower. However, moderate consumption of the mentioned products by patients suffering from hypothyroidism is not entirely prohibited. This is possible thanks to the application of appropriate technological processing methods. These procedures mainly include soaking, freezing, boiling, and fermenting. However, the boiling process deserves special attention, as it reduces up to 30% in the content of goitrogens. This method must take place without a cover, enabling the evaporation of anti-nutritional substances and water vapor.
Conclusion
Goitrogens constitute a group of plant-derived anti-nutritional compounds. Their action disrupts the metabolism of iodine, contributing to the impairment of the thyroid’s secretory function. For this reason, it is recommended that individuals struggling with the hypofunction of this gland and Hashimoto’s disease limit the intake of products that are sources of them. It is worth noting that the thyrogenic action of goitrogens is stronger the lower the iodine intake is in the diet. Therefore, thanks to the proper fulfillment of the need for this trace element and the application of thermal processing, moderate consumption of cruciferous vegetables, among others, is possible.
Bibliography:
- Gawęcki, J. (2022). Żywienie człowieka. Podstawy nauki o żywieniu. (wyd. 3). Wydawnictwo Naukowe PWN. (Oryginał został opublikowany w 2010 r.)
- Orzeł D., Biernat J.(2012) Wybrane zagadnienia z toksykologii żywności. Wyd. UP
- Wiśniewska, B. M. (n.d.). Warzywa krzyżowe w niedoczynność tarczycy – czy powinniśmy się ich obawiać? Narodowe Centrum Edukacji Żywieniowej.
- Ratajczak, A.E., Moszak, M. i Grzymisławski M. (2017). Zalecenia żywieniowe w niedoczynności tarczycy i chorobie Hashimoto. Piel Zdr Publ, 7(4), 305–311
- Gawęcki, J., & Grzymisławski, M. (2022). Żywienie człowieka zdrowego i chorego (wyd. 2). Wydawnictwo Naukowe PWN.