A new trial carried out in Canada has found that fruit and vegetables, independent of calcium intake, was associated with higher bone mineral density in teenage boys.
It follows a study reported last year by researchers in Northern Ireland showing that 12-year-old girls with a high fruit consumption had significantly higher heel bone mineral density than moderate fruit consumers.
Bone mineral density during early adolescence is key to prevention of osteoporosis in later life. The brittle bone disease is now one of the biggest global health concerns according to the World Health Organisation, and is set to increase with ageing populations.
Yet many teenagers do not eat enough calcium nor do they consume the recommended five portions of fruit and vegetables each day.
Indeed the Canadian researchers, writing in the September issue of the American Journal of Clinical Nutrition (vol 82, no 3, 700-706) noted that less than 30 per cent of the 150 boys and girls they assessed were eating the recommended amount of fruit and vegetables.
But those boys who ate the most showed the greatest accumulation of mineral in their bones throughout childhood and adolescence, Dr Hassanali Vatanparast and colleagues found.
In contrast to the Northern Irish study, the data on girls did not support this effect. But the researchers said that girls tend to underreport their food intake and this might have affected the results.
It is not yet clear how fruit and vegetables help build bone mass, although the Northern Irish team suggests that "fruit's alkaline-forming properties mediate the body's acid-base balance".
Previous research, commissioned by the UK Food Standards Agency on more than 3,000 Scottish women, has also identified a possible link between eating fruit and vegetables and stronger hip bones in women before and around the time of menopause.
The Canadian data was gathered over a seven-year period from more than 150 boys and girls aged between eight and 20-years-old. Dietary intake was assessed by serial 24-hour recalls. Anthropometric measurements and physical activity were assessed every six months.
Total-body bone mineral content was assessed with dual-energy X-ray absorptiometry in autumn each year to measure bone mass.