Diosgenin, the plant steroid in Smilax and Yam

Twenty or thirty years ago, thousands of bodybuilders took extracts from plants such as Smilax officinalis [sarsaparilla] and Dioscorea esculenta [wild yam]. These contained the steroid-like diosgenin [structural formula shown here]. And lo: a Japanese animal study published recently in the Journal of Steroid Biochemistry and Molecular Biology suggests that diosgenin does indeed have an anabolic effect.


Supplements containing Smilax would boost your testosterone levels, announced supplement manufacturers thirty years ago. Unlikely, as anyone with a bit of biochemistry knew.


Nevertheless, recent, reliable studies suggest that diosgenin does indeed initiate anabolic processes in cells. And, according to the animal study that researchers at Ritsumeikan University in Japan are about to publish in the Journal of Steroid Biochemistry and Molecular Biology, diosgenin might be interesting for athletes who want to build muscle mass.



The Japanese wondered whether diosgenin, which resembles DHEA, boosts muscle cells’ glucose uptake as DHEA does. They injected 10 mg diosgenin into the small intestine of diabetic rats. The human equivalent of this dose is about 400 mg. [DIO]

The diosgenin caused the rats’ glucose level to go down. This did not happen in the animals that had been given no active ingredients [CON], nor did it happen in the animals that were given diosgenin together with an inhibitor of the enzyme 5-alpha-reductase [DIO-In]. 5-Alpha-reductase converts DHEA and testosterone into DHT. This conversion is crucial for the anti-diabetic effect of DHEA, and apparently also for that of diosgenin.



Diosgenin boosted the concentration of DHEA and DHT in the muscles, and also in the animals’ blood. This increase in concentration of DHT in the muscles didn’t happen in the rats that were also given the 5-alpha-reductase inhibitor.

Diosgenin activated the anabolic switches Akt and protein kinase C in the muscles, thus boosting the manufacture of the glucose transporter GLUT4 in the muscles. Diosgenin also stimulated GLUT4 to make its way to the muscle cells’ membrane and from there to absorb glucose from the bloodstream.



The Japanese also did the same experiments but using yam powder. They gave the rats 1 g powder and the results were almost identical.

The researchers don’t know how diosgenin boosts the concentrations of DHEA and DHT. Is it that diosgenin then converts into DHEA? Or does diosgenin do something to the enzymes that are involved in the steroid production?

The study was financed by the Japanese government.

Acute administration of diosgenin or dioscorea improves hyperglycemia with increases muscular steroidogenesis in STZ-induced type 1 diabetic rats.


Acute dehydroepiandrosterone (DHEA) administration improves hyperglycemia in rats with streptozotocin (STZ)-induced type 1 diabetes mellitus. Diosgenin, a steroid structurally similar to DHEA (dehydroepiandrosterone), is contained highly levels in dioscorea; however, it is still unclear whether this natural product improves hyperglycemia in the type 1 diabetes model rats through an increase muscular GLUT4 signaling. After 1 week of STZ injection, fasting glucose level was measured in blood taken from the tail vein every 30min for 150min after injection of diosgenin or dioscorea (3mg/kg). On another day, muscle was resected 150min after diosgenin or dioscorea injections. Serum DHEA level increased significantly 120min after diosgenin or dioscorea injections; concomitantly, blood glucose level decreased significantly. Moreover, GLUT4 translocation, as well as phosphorylation of Akt and PKC ?/?, increased significantly by diosgenin or dioscorea administration. However, these effects of diosgenin and dioscorea were blocked by a 5?-reductase inhibitor that inhibits synthesizing dehydrotestosterone (DHT) from testosterone. Additionally, significant correlations were observed between blood glucose level, GLUT4 translocation level, and muscular sex steroid hormone level 150min after the administrations. These results suggest that the diosgenin-induced increase in the DHEA level may contribute to the improvement of hyperglycemia by activating the muscular GLUT4 signaling pathway in type 1 diabetes model rats.

PMID: 24607838 [PubMed – as supplied by publisher]

Source: http://www.ncbi.nlm.nih.gov/pubmed/24607838