Olive oil may help to strengthen the bones, a study has shown.
Evidence of the effect emerged from a study of men consuming an olive oil-rich Mediterranean diet.
Their blood was found to contain boosted levels of osteocalcin, a marker of healthy bone formation.
Previous laboratory studies have suggested that olive oil may protect against the brittle bone disease osteoporosis
Incidence of osteoporosis is also known to be lower in Mediterranean countries than in the rest of Europe.
"This is the first randomised study which demonstrates that olive oil preserves bone, at least as inferred by circulating bone markers, in humans," said study leader Dr Jose Manuel Fernandez-Real, from the Dr Josep Trueta Hospital in Girona, Spain.
The study participants were 127 men aged 55 to 80, all of whom had at least three known heart disease risk factors or a diagnosis of type 2 diabetes.
They were put on one of three diets for two years: a Mediterranean diet with mixed nuts, a Mediterranean diet with virgin olive oil, and a regular low-fat diet.
Measurements were taken of osteocalcin, blood glucose and cholesterol.
Only consumption of the Mediterranean diet with olive oil was associated with a significant increase in levels of osteocalcin and other bone formation markers, the scientists found.
The results are due to appear in the Endocrine Society's Journal of Clinical Endocrinology and Metabolism.
Osteocalcin was associated with preserved insulin secretion in men consuming olive oil, which may help guard against diabetes.
"Osteocalcin has also been described to increase insulin secretion in experimental models," said Dr Fernandez-Real.