Researchers from Edith Cowan University tracked the diets of 1420 West Australian women aged over 70 and found that those who ate more nitrate-rich vegetables like spinach, rocket and lettuce had significantly better muscle strength and physical function.
Muscle strength was assessed by measuring each participant’s grip strength. Physical function was quantified using the timed-up-and-go (TUG) test, which measures how long it takes to rise from a chair, walk three metres then return to the chair to sit down.
Lead researcher Dr Marc Sim from ECU’s School of Medical and Health Sciences said a decline in muscle strength and physical function are associated with greater risk of disability and even premature death.
He says previous research in older populations has shown that a 1kg decline over 12 months in grip strength is associated with a 33% increased mortality risk. Every one second slower TUG time increases mortality risk by 8% over three years.
“Poor strength and function are also associated with other adverse outcomes such as falls and fractures, which substantially compromise an individual’s independence,” he said.
“In our study we found that eating one cup of spinach, rocket or lettuce a day may increase grip strength by up to 2kg and improve TUG time by up to 1.6 seconds.”
Nitrate and blood flow
Dr Sim said while it was unclear exactly how nitrate positively influences muscle function, one possible mechanism could be improved vascular function and blood flow.
“We know from previous research that nitric oxide is a vasodilator, which means that it widens your blood vessels, potentially allowing greater blood flow to your muscles. In fact, nitrate supplements are used by athletes to improve endurance and performance.
“It could be that higher daily nitrate intake consistently increases muscle blood flow, thereby facilitating musculoskeletal health,” he said.
The study follows on from previous ECU research that found a link between eating nitrate-rich vegetables and a lower risk of death from stroke and heart disease.
The next step in the research is an intervention study to test precisely how nitrate-rich vegetable consumption influences muscle function.