Endocrinological aspects of dietary habits

Dietary habits reflect both the recent economic possibilities and the cultural history of individual human populations. They may influence endocrine systems and thus affect the health of the respective populations in several manners: (1) People consuming exclusively local products may lack certain micronutrients. This is important especially in areas with low levels of iodine and/or selenium in the environment. Thyroid gland insufficiency resulting from the iodine deficiency was widespread in many areas of Central Europe until the introduction of iodine supplementation in the second half of 20<sup>^th </sup>century. Iodine deficiency is still a serious problem in many areas of Africa and Asia. (2) Numerous cultural plants contain compounds able to influence important metabolic pathways. Iodine deficiency is usually worsened by thyroidal peroxidase inhibitors, so-called goitrogens. Phenolic and terpenoid compounds may interfere in the metabolism of steroid hormones. Glycyrrhetinic acid from licorice is a potent inhibitor of 11-beta-hydroxysteroid dehydrogenase. Isoflavonoids from legumes (e.g. genistein and daidzein) and their metabolites (e.g. equol) were found to inhibit the following enzymes: aromatase, 5alfa-reductase, 7alfa-hydroxylase, 3beta-hydroxysteroid and 17beta-hydroxysteroid dehydrogenases, etc. Isoflavonoid sulphates influence local availability of steroids by inhibiting sterol sulphatases. (3) Plant-derived compounds are able to interact with nuclear receptors and act either as hormone agonists or as antagonists. Recently, the attention has been paid namely to the phenolic substances interacting with oestrogen receptors so-called phyto-oestrogens.