Cysteine sulfoxides in onions increase testosterone levels
In recent years we have written more than once about the curious ability of onions to increase testosterone levels. Japanese researchers at the research department of Nisshin Pharma have discovered which substances in onions cause this hormonal effect: sulfoxides of the amino acid cysteine [structural formula above].
The researchers exposed testes cells in test tubes to increasing concentrations of onion extract, and saw that this increased the concentration of progesterone in the cells. Progesterone is a precursor to testosterone.
The extract, a Nisshin Pharma product, consisted of 6 percent cysteine sulfoxides. The three main ones were isoalliin [PCSO] (accounting for 2.4 percent of the extract, methyiin [MCSO] (0.8 percent) and cycloalliin [CA] (4.1 percent). Structural formulas are shown below.
The researchers then exposed the testes cells to the three components in the extract individually. Isoallin [PCSO] and methylin [MCSO] were found to be the active substances in the extract. You can see that above.
The researchers were also able to find out how isoallin and methyiin increase the hormonal production by the testes. The sulfoxides stimulate the enzyme protein kinase A [PKA].
The article on which we base this post appeared in Molecules in 2020. However, the authors knew years earlier that isoallin and methyiin were testosterone enhancers. We found a Japanese patent from Nisshin Pharma from 2016 describing testosterone-enhanced supplements or functional foods, with zinc and isoalliin as active ingredients. [JP2016150911A]
In 2017, the same authors published a human study in Japanese Pharmacology and Therapeutics, in which men aged 50-79 were given 30 milligrams of cysteine sulfoxides from onions every day for a month. [Jpn Pharmacol Ther. 2017;45(4)595-608.] After two weeks of supplementation, the men felt better because of the supplement and had significantly more testosterone in their saliva.
Another two weeks later, however, no more ...
We will continue to follow this line of research. We will report any new developments.
Molecules. 2020 Oct 14;25(20):4694.
Onion extract boosts testosterone level too 29.03.2014
Onion juice: helps boost rats' testosterone, has pro-sexual effect 28.03.2014
Onion juice triples testosterone levels 25.02.2010
Onions have androgenic effect, says 1967 animal study 14.12.2008