London: Popeye`s yen for a can of spinach before bulging his biceps has a genuine scientific basis, as researchers have found that the green leafy vegetable really boosts the muscle power.
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.
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.
The researchers then gave a small dose of nitrate,
equivalent to that found in a plate of spinach, to exercising volunteers and found it reduced their need for oxygen.
Their improved muscle performance was due to increased efficiency of the mitochondria that power cells. They suggest their finding could offer one explanation for the health benefit of eating fruit and vegetables, the mechanism of which still remains unclear.
"Well, it is if you eat spinach. For people who don`t eat their vegetables it will be more tricky," Hernandez added.
While no effect could be seen in the so-called slow-twitch muscles used for moderate exercise and endurance, the scientists observed a clear change in the fast-twitch muscles used for strength and more high-intensity exercises, Hernandez said.
The tricky question, Hernandez said, was determining why this happened: The protein increase in turn led to higher quantities of calcium released in the muscles, pointing out that "if you have more calcium released, you have a stronger contraction."
Nitrate could also increase endurance, Hernandez said, pointing out that when stronger, the fast-twitch muscles, which fatigue faster than other muscles, do not need to contract as frequently.
This is not only good news for exercise buffs looking to improve their performance but also for those who are involved in several muscle ailments.
"The really exciting part is to go ahead and look at people with muscle weakness, with muscle diseases, and even ageing, and see if this can actually improve their muscle function," Hernandez said.
He said the research team aimed to conduct a few more studies on mice but hoped to also carry the studies on humans soon.