Jodie Flaws, professor in comparative biosciences from the University of Illinois and one of the lead authors on the study, argued that although the study did not demonstrate these effects in humans, it is likely that they could have serious implications for fertility.
The study, published in Reproductive Toxicology, was the first to study the effects of a liquorice compound, isoliquiritigenin, on the ovary. Professor Flaws' team exposed mouse ovarian follicles to isoliquiritigenin in vitro, and found that it led to reduced expression of genes involved in sex hormone production. For example, production of aromatase, an enzyme which converts testosterone to oestrogen, was reduced by 50 percent.
Professor Flaws said: 'In general, when you start to have lower hormone levels, you could start to have problems with reproduction. And because oestrogen is also important for healthy brains, healthy bones, a healthy cardiovascular system, if the levels are depleted for too long, you could have problems with those systems.' However, she emphasised that these effects had not been shown in the study, and were just possibilities.
Apart from being used as an ingredient in a wide range of foods, liquorice root and isoliquiritigenin are also used in herbal medicines, such as to relieve menopausal symptoms. Studies indicate liquorice also has anti-cancer properties, and aromatase inhibitors are used in cancer treatment to reduce tumour growth. These inhibitors may have adverse effects on fertility, so the researchers stress the potentially complicated effects of isoliquiritigenin.
'[This] could lead to a good outcome in certain tissues, depending on dose and timing of exposure. On the ovary though, if you reduce aromatase, you're also reducing oestrogen, so you could be interfering with fertility,' Professor Flaws said.
She added that further research in live animals and humans is needed before anything can be concluded about the potential effects of isoliquiritigenin on fertility.