Osteomalacia: how do 'soft' bones come about?

My mother has been diagnosed with osteo-malacia - her bones are too "soft". What is the difference between brittle and soft bones?

Dr Fred Kavalier answers your health question:

Osteomalacia is the adult equivalent of rickets. It usually affects the frail elderly, and in the UK it is often diagnosed in people of South Asian origin. Normal bone development depends on plenty of calcium, phosphorus and vitamin D. If any of these are in short supply, the bones become soft; in osteoporosis, the bones become thin and brittle. Osteomalacia causes bone and muscle pain, usually in the legs and back. A lack of vitamin D is the most common cause. Humans get some vitamin D from diet, but most of it is made in the skin in response to sunlight exposure. Dark-skinned people make less vitamin D than fair-skinned. Dietary sources of vitamin D include margarine, eggs and fish such as herrings, mackerel, sardines and kippers. The Arthritis Research Campaign has a booklet on osteomalacia (08708 505 000; www.arc.org.uk).

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.