Popeye may have been right - eating lots of spinach really can give you muscles.

Researchers have discovered a steroid chemical in leafy greens which ramps up the manufacture of muscle protein.

US scientists at Rutgers University in New Jersey extracted the compounds, known as phytoecdysteroids, from spinach. "When they placed the liquid extract on samples of cultured human muscle, it sped up growth by 20%," New Scientist magazine reported.