DND supports a study that will test the validity of the excessive calcium hypothesis, regarding osteoporosis. This animal experiment will evaluate the life-term effects of high versus low calcium intakes on eventual bone strength in old age.
Osteoporosis is a prevalent disease characterised by brittle bones that readily break. Current osteoporosis prevention and treatment is based on the idea that high calcium intakes are beneficial, as they increase bone mineral density and strength, and thus decrease fracture risk. Osteoporosis however, is a disease that comes with age. Therefore we don't just need to know the short-term effects, but we also need to know what the lifetime effects are of a high calcium diet on eventual bone health.
About 60 very young female Sprague-Dawley rats will be divided in 3 groups of 20 rats each. The rats will be given a standard diet, only adjusted for calcium, magnesium and phosphorus. Group A will receive a moderately low-calcium diet, group B a moderately high-calcium diet and group C a very high-calcium diet. After about 10 months bone mineral density of all rats will be measured, using DEXA scan. Eventually, after natural death, each rat will be tested on bone strength, using 3-points bending tests.
We particularly need to know the long-term effects of high calcium intakes because the following facts give us food for thought:
- Osteoporosis-related bone fracture incidence in the elderly (adjusted for age) is highest in countries where calcium intakes are highest (eg Scandinavia, Switzerland, The Netherlands, USA, UK).
- In the countries mentioned above, average bone mineral density in young adults is greatest.
- Humans infants need the most calcium per kg bodyweight, as their yet flexible bones need hardening. Nevertheless mother's milk contains 4 times less calcium than cow's milk. In percentages this equals the level of calcium in oranges and other low-calcium foods. Adults only need to maintain the level of calcium in their bones, and therefore relatively need less calcium.
- Calcium levels in mother's milk of various mammals vary per species and correlate with how fast the young mammal needs to grow, and reversely correlate with how long its bones need to last (lifespan). Calcium levels in mother's milk of humans, elephants and (long-living species of) whales are lower than those of donkeys, goats and cows, subsequently.
- The specific bone cells (osteoblasts) that need to create new bone die at a faster rate when more calcium is absorbed, and are the cells that are underrepresented in brittle bones.
For more specific information, and scientific references, please check out the hypothesis published in a scientific journal.