Their two-year long study is likely to prove influential among doctors around the world. Many researchers are investigating how to maximize the accumulation of bone mass during childhood in order to protect bones into later years, a growing need as people age and incidence of osteoporosis rises.
But although some trials have shown that taking calcium supplements during childhood can improve bone mineral density, none of these took into account the different speeds at which children grow, says Dr Sulin Cheng from the University of Jyväskylä.
Growth makes higher demands on calcium, but people tend to end up with the same bone mass.
Writing in this month's issue of the American Journal of Clinical Nutrition (vol 82, no 5, pp 1115-1126), Dr Cheng's team report on their double-blind, four-arm trial involving 195 girls aged between 10 and 12.
The girls had a calcium intake below the National Nutrition Council recommended levels (less than 900 mg a day.)
They were randomly assigned to receive either 1000 mg of calcium in pills, 1000 mg calcium and 200 IU vitamin in pills, low-fat cheese offering 1000 mg of calcium or a placebo.
The researchers measured the effects of calcium supplementation on bone mass and body composition, and also used a new model that takes into account the rate of body growth.
Girls in the cheese group had a greater change in the cortical thickness of the tibia than any other group, initially suggesting that the dietary calcium was more effective than supplements.
But when the researchers accounted for each individual's growth speed, they found no beneficial effect from any of the interventions.
"It might be that the growth is masking the benefits, or it might be that there are no benefits," Dr Cheng told NutraIngredients.com.
She noted that only 1 per cent of the study subjects had calcium levels of less than the recommended lower limit of 400mg per day, and by the end, all had an intake of around 900mg per day.
"If you have a clear dietary intake that exceeds recommended levels, you won't get any benefit," Dr Cheng suggests.
The findings are similar to another trial that only assessed the impact of calcium supplements. It found that the supplements have no effect on the bone mineral density in young women after a certain threshold level of intake has been achieved.
Dr Cheng added that more studies are needed to investigate the calcium levels required by children, warning that some may be taking too much.
"This overloads the kidneys," she said.