As against the earlier notion that the iron content of spinach accounted for its status as a superfood, researchers at the Karolinska Institute in Sweden have found that it is the inorganic nitrate in the vegetable which is the secret behind its strength-giving property.
The study found mice supplied with nitrate in their drinking water developed significantly stronger muscles by stimulating two key proteins, the Daily Mail reported.
The quantity of nitrate that the mice received was roughly equivalent to that which a person would obtain by eating 200 to 300 grams of fresh spinach or two to three beetroots a day.
The research team divided the mice into two groups, one which was given nitrate in their drinking water for seven days.
A week into the experiment the team examined different muscles on the mice's legs and feet.
They found that the mice that had been on consistent nitrate had much stronger muscles, the greatest effect being observed in the extensor digitorum longus muscle, which extends down the tibia, and the flexor digitorum brevis muscle of the foot.
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The researchers then discovered that the nitrate mice had a higher concentration of two different proteins in their muscles, which is assumed to explain the greater muscle strength.
The teams now want to take their discoveries further and study how they can be applied to people with muscle weakness.
"From a nutritional perspective our study is interesting because the amount of nitrate that affected muscle strength in mice was relatively low," Dr Andres Hernandez, researcher at the Department of Physiology and Pharmacology said.
"Translated to humans it means that we can obtain the equivalent volume by eating more of a vegetarian diet, as nitrate is found naturally in several leafy vegetables, especially in beetroot juice, for example. There are currently no dietary supplements containing nitrate," Hernandez said. (MORE)