High salt diet reduces bone density in girls
calcium differently, say researchers, claiming this may explain why
races have different rates of high blood pressure and osteoporosis.
Based on a small study, scientists at the Purdue University in the US suggest Caucasian girls lose more calcium in their urine than African-American girls.
But both races lose calcium at an accelerated rate when they consume a high-salt diet.
"Salt is processed differently in the races, but too much salt in the diet reduces bone density in both races," say the researchers.
Osteoporosis is second only to cardiovascular disease in terms of global healthcare burden, according to the World Health Organisation, and currently affects some 200 million people. The number of sufferers is however set to increase steadily with growing numbers of elderly living longer, and obesity adding extra strain on bones.
According to the Purdue researchers, one out of four Caucasians will be diagnosed with osteoporosis, a bone-loss disease that costs Americans $14 billion (€10 billion) a year in health care.
The disease strikes one out of 10 African-Americans, but studies show they are more susceptible to hypertension, says Connie Weaver, head of Purdue's department of foods and nutrition.
"Sodium causes water retention, which leads to high blood pressure, and that could be related to the high prevalence of hypertension in adult blacks," adds Weaver.
High blood pressure is a contributing factor in the rising incidence of heart disease, the world's number one killer.
Propelled by these health implications, consumer and healthcare groups in Europe are cracking down on salt consumption, including pushing food manufacturers pushing them to slash salt in food recipes.
And recent figures from the UK's food agency claim that every day at least 26 million people eat more than the recommended daily limit of 6g of salt. Men are eating the most with a daily average of 11.0g of salt while women consume an average of 8.1g a day.
The research results were based on figures from Purdue's 'Camp Calcium' - a camp, funded by the US National Institutes of Health since 1990, designed to investigate various aspects of calcium metabolism in adolescent girls and boys.
Thirty-five participants - 22 African-American girls and 13 Caucasian girls between the ages of 10 and 15 - were involved in two, 20-day summer camps separated by two weeks.
While on campus, the girls ate a controlled diet that provided "certain amounts of calcium and other nutrients", say the researchers, under 24-hour supervision.
"Salt intake affects how the body uses calcium at a critical time of bone development in young girls, but in whites more than in blacks," concludes Weaver from the findings.
The researchers suggest adolescent girls need to consumer the equivalent of four cups of milk a day to maximise the time when their bodies can develop peak bone mass. Adolescent girls keep 25 per cent of the net calcium they consume, but by the time they are young women, it drops to 5 per cent.
Full findings are published in the April edition of the American Journal of Clinical Nutrition .