"The present results demonstrate that orange and grapefruit juice positively affect serum antioxidant capacity and bone strength and delay the femoral fracture rate," wrote lead author Farzad Deyhim from Texas A&M University.
Osteoporosis is estimated to affect about 75m people in Europe, the USA and Japan. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is € 31.7bn in Europe, and $17.5bn in the US (2002 figure). The total annual cost of osteoporosis in the UK alone is over £1.7bn (€ 2.5bn), equivalent to £5m (€ 7.3m) every day.
The new study, published in the May issue of the journal Nutrition (Vol. 22, pp. 559-563), looked at the effects of orange and grapefruit juice on 36 male Sprague-Dawley rats who had their testes removed (orchidectomised).
As men reach the age of 40 and beyond, the level of testosterone is said to decrease by about one per cent per year, leading to weaker muscles and thinner bones. The researchers castrated the rats to model low testosterone levels on bone strength and the subsequent effects of citrus fruit juices.
The mice were divided into four equal groups. The first group were not castrated and acted as the control. The three other groups were castrated, with one group's AIN-93M diet supplemented with freshly squeezed orange juice, and another group supplemented with grapefruit juice for 60 days.
At the end of the study the researchers found that the femoral (hip bone) strength of the orange juice group increased by 6.3 per cent compared to the castrated, unsupplemented group, and had a 9.5 per cent reduction in femoral fracture rate.
Supplementation with grapefruit juice increased femoral strength by 3.7 per cent and reduced the fracture rate by 6.8 per cent, compared to the castrated, unsupplemented group.
However, compared to the control (uncastrated) group had an eight per cent stronger hip bone than the castrated, unsupplemented group, and an reduced fracture rate of 10.2 per cent.
The serum antioxidant capacity of the citrus fruit group also increased compared to the castrated, unsupplemented group.
"Such effects could be associated with bioactive flavonoids in citrus juice that possess antioxidant properties that protect tissue against oxidative injury," said Deyhim.
This conclusion agrees with another recent study by the same researchers (Journal of Agricultural and Food Chemistry, Vol. 53, pp. 2009-2014), which reported that flavonoids and limonoids could potentially improve bone health.
"The fact that citrus juices affect bone quality support exploration of citrus juice as a natural food source that potentially benefits skeletal health," concluded Deyhim.
The researchers called for further studies to identify the active compounds, the precise mechanism of action, and to verify if such benefits are applicable to humans.
North America is by far the biggest global market for juice and nectars, according to industry analysts Canadean, accounting for over 35 percent of sales. Canada's consumption has risen by more than 45 per cent since 1997, giving Canadians the highest per capita consumption in the world.
While the US is the biggest single market in pure volume terms, it is Canada and Germany, which lead the pack when it comes to per capita consumption. Orange is particularly popular there, with a share some 18 percentage points higher then the global average.