Calcium is arguably the most important mineral in our body. In addition to it’s bone health functions, calcium has functions that go against blood clotting. It also acts as a messenger for muscle contraction and as the transmitter of nerve impulses. Furthermore, calcium activates certain enzymes in our metabolism and has other functions in our body (see health claims below). The European RDA (recommended dietary allowance) for calcium is 800 mg daily.
Low bone density is known as osteoporosis (bone atrophy). It increases the risk of bone fracture, which can become life threatening in old age. For strong and healthy bones, calcium is very important, but the rate of calcium absorption decreases with age. This is how diseases such as osteoporosis can occur. However, other factors besides enough supply of calcium also have an impact on our bones. These include a supply of vitamin D and other nutrients such as vitamin K. Vitamin D is closely related to calcium metabolism because it provides adequate absorption of calcium through the intestinal mucosa and encourages excretion through the kidney as needed. The vitamin also acts on bone metabolism by maintaining the continuous process of tissue building and degradation at a healthy level. Along with vitamin D, vitamin K is also essential for bone health.
In terms of calcium intake, vegans are (with an average of 550-600 mg daily) well below the intake of vegetarians and omnivores (slightly less than 1000 mg/day on average). Those with a very low calcium intake of less than 500 mg/day have a lower bone density, while vegans with a calcium intake of more than 500 mg daily are in comparable range to vegetarians and omnivores in terms of bone density. It is totally possible to meet daily calcium requirements through a fully plant-based diet, as calcium is present in many plants. But for people with an inadequate diet or the elderly, it may be useful to supplement it.