London - A nutrient found in steak and ice cream could give pensioners an energy boost.
Mince, milk and cheese are also rich sources of carnitine, which improves stamina.
Animals given carnitine supplements were able to run 30 percent further than normal - and it is hoped that people will also benefit.
It is thought the nutrient may be particularly helpful for the old and frail, for whom simple tasks like vacuuming and climbing stairs can be exhausting.
Making exercise easier would not only improve their health but also help them maintain their independence, researchers said.
In experiments on mice, the US scientists showed carnitine helped muscles work more efficiently. As a result, the animals had more stamina.
Researcher Deborah Muoio, of Duke University in North Carolina, said: “Although our body makes carnitine, the amount produced declines with age and in certain disease states, implying that supplements might be beneficial in some cases.”
The experiments were carried out on young, healthy mice and it is not known whether the nutrient would have the same effect on people. However, more research is being done. Dr Muoio said: “Exercise intolerance becomes a problem when reduced strength and stamina prevent normal, routine activities such as mowing the lawn or climbing stairs, or when physical activity causes extreme discomfort.
“So, finding ways to optimise exercise could have a tremendous impact on overall health.”
Named after carnus, which is Latin for flesh, carnitine plays a crucial role in energy production. Animal protein, including meat, fish and dairy products are the best sources - with red meat being particularly high in the nutrient. Carnitine supplements are already taken by some athletes trying to improve their performance.
However, at high doses it can cause side-effects, from nausea and vomiting to a fishy body odour.
Writing in the journal Cell Metabolism, the scientists said further research could lead to people being prescribed carnitine - although they added that the supplements would not be suitable for everyone. They said: “We need to move beyond the ‘one size fits all’ approach to optimal nutrition and instead work towards more personalised prescriptions that consider underlying genetics.”
Daily Mail