Spinach has long been associated with strength, but why the leafy vegetable makes us stronger has remained unknown until now.

Researchers at the Karolinska Institute say that nitrate, found naturally in spinach and several other vegetables, significantly increases muscle strength.

In the study, the team placed nitrate directly into the drinking water of a group of mice for seven days and then compared their muscle strength to a control group. According to the researchers, the amount of nitrate given to the mice was roughly the equivalent to that which a human would obtain by consuming 200 to 300 grams of fresh spinach or 2 to 3 beetroots a day.

Spinach and beetroot are two of the main sources of nitrate, but it is also found in several other vegetables, such as chard and lettuce.

After 7 days, the researchers examined different muscles on the mice’s legs and feet. They discovered that those given nitrate had significantly stronger muscles than mice in the control group. According to the researchers the greatest effect were observed in the extensor digitorum longus muscle, which extends down the tibia, and the flexor digitorum brevis muscle of the foot.

Furthermore, the team found that the nitrate mice had higher concentrations of two different proteins, CASQ1 and DHPR, found naturally in the muscles. These proteins, which is assumed to explain the greater muscle strength, are used for storing and releasing calcium, which is essential for making muscles contract.

The researchers now want to conduct further studies in order to determine how their findings can be applied to individuals with muscle weakness.

Dr Andrés Hernández, researcher at the Department of Physiology and Pharmacology, explained:

“From a nutritional perspective our study is interesting because the amount of nitrate that affected muscle strength in mice was relatively low. 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.”

The research was funded by the Swedish Research Council, the Swedish National Centre for Research in Sports, Association française contre les myopathies, AFM (French Association against Myopathies) and the National Institute for Arthritis and Musculoskeletal and Skin Diseases (NIAMS).

Written By Grace Rattue