The World Health Organization recommends a daily calcium intake of 500 mg. This is because of the high protein consumption in the United States. Excess protein consumption can cause calcium to be lost from the skeleton. The United States and other countries with high consumption of dairy products have much higher rates of osteoporosis than countries where dairy consumption is much lower. Calcium deficiency due to insufficient dietary intake is virtually unknown.
Calcium deficiency is caused by loss of the mineral from the skeleton.
Strength-building exercise is as important as diet in maintaining bone density. Vegans looking for calcium-rich foods have plenty to choose from , including dark green leafy vegetables, nuts, and seeds. Elsewhere I've written more about calcium needs and America's obsession with dairy products . Most humans in modern society cannot obtain sufficient B12 from plants alone because the microorganisms are destroyed in the farming and cleaning processes. Although B12 stores in the intestines can last for years, all vegans should take a reliable source of B12 daily, as deficiency can cause irreversible nerve damage.