While moderate amounts of calcium (around 700 mg a day) are vital for maintaining healthy bones, there is no need to start increasing calcium intake in order to reduce the risk of fractures or osteoporosis in later life, finds a paper published on the British Medical Journal website.
As people age, their bones lose calcium and they are more at risk of fractures and osteoporosis -- this is especially the case for women. As well as causing individual suffering, fractures are a huge drain on health services.
With aging populations, this burden will increase in the coming years and therefore preventing them is a major public health issue, say the authors, led by Dr Eva Warensjö from Uppsala University in Sweden.
The importance of increasing calcium intake to compensate for the loss of calcium has been debated for a long time and there is still no clear advice. This is reflected by the wide range of daily calcium recommendations for the over fifties -- in the UK it is currently 700 mg; it is 800 mg in Scandinavia and 1,200 mg in the US.
In order to investigate the links between long-term dietary calcium intake and the risk of fractures, the authors reviewed data from a large population study of Swedish women carried out in 1987.
Over 61,433 women (born between 1914 and 1948) took part in the Swedish Mammography Study and of these 5,022 participated in a smaller sub-research group. All participants were followed up for 19 years.
During the follow-up, 14,738 (24%) women had a first fracture and, of these, 3,871 (6%) had a first hip fracture. Twenty percent of the sub-group had osteoporosis.
The researchers used a series of questionnaires to gain in-depth knowledge of the participants' changing diet and in particular their calcium intake and use of supplements and multivitamins.
The women also provided information about their menopausal status, whether or not they used post-menopausal oestrogen therapy, their weight, height, smoking habits, how much physical activity they did and their educational attainment.
The results show that women had the lowest risk of having a fracture when they consumed around 750 mg a day of calcium. However, the fracture risk in women who started to increase their calcium intake over time did not decrease.
There is some evidence that high intake of calcium may actually increase the rate of hip fractures, though the authors stress that this result needs to be interpreted with caution.
The authors conclude that while low levels of calcium intake (less than 700 mg per day) increase the risk of fractures and osteoporosis, there is no need to start increasing calcium intake above the amount. Increases did not further reduce the fracture and osteoporosis risk.
Simple steps in youth and middle age can bring big payoffs in bone strength.
"It's very important to know that our skeletons are sort of like a big house for the body -- and we really do need to maintain it," said Gail Frank, a professor of nutrition at California State University, and a spokeswoman for the American Dietetic Association.
According to Frank, the human body tends to build bone until age 30. "No one wants to think that at 30 they're 'mid-life,' but that's the way it is for bone," she said.
"Bone needs what I like to call a 'matrix of nutrients,' " Frank explained. Besides calcium, she listed phosphorous, magnesium, zinc -- "what I call a 'bone soup,' a kind of matrix that supports bone, allows for the creation of enzymes and different proteins needed to keep that bone healthy."