Rickets usually occurs because of a lack of vitamin D or calcium, although it can also be caused by a genetic defect or another health condition.

The most common cause of rickets is a lack of vitamin D or calcium in a child's diet. Both are essential for children to develop strong and healthy bones.

Sources of vitamin D are:

• sunlight – your skin produces vitamin D when it's exposed to the sun, and we get most of our vitamin D this way
• food – vitamin D is also found in some foods, such as oily fish, eggs and fortified breakfast cereals
• dietary supplements

Calcium is commonly found in dairy products, such as milk, cheese and yoghurt, and green vegetables, such as broccoli and cabbage.

Over time, a vitamin D or calcium deficiency will cause rickets in children and soft bones (osteomalacia) in adults.

See preventing rickets for more information and advice about ensuring your child gets enough vitamin D and calcium.

Who's at risk?

Any child who doesn't get enough vitamin D or calcium can develop rickets, but there are certain groups of children who are more at risk.

For example, rickets is more common in children of Asian, African-Caribbean and Middle Eastern origin because their skin is darker and needs more sunlight to get enough vitamin D.

Babies born prematurely are also at risk of developing rickets because they build up stores of vitamin D while they're in the womb. Babies who are exclusively breastfed, especially for longer than 6 months, may also be at risk of vitamin D deficiency.

It is recommended that:

• adults, including pregnant and breastfeeding women, and children over 4 years old should consider taking a daily supplement containing 10 micrograms (mcg) of vitamin D from at least October to March
• babies from birth to 1 year of age, whether exclusively or partially breastfed, should be given a daily supplement containing 8.5 to 10mcg of vitamin D, to make sure they get enough
• babies fed infant formula do not need a vitamin D supplement until they are receiving less than 500ml (about a pint) of infant formula a day, because infant formula is fortified with vitamin D
• children aged 1 to 4 years old should be given a daily supplement containing 10mcg of vitamin D

For more information, read should I take a vitamin D supplement?

Rare forms of rickets can also occur in some inherited (genetic) disorders. For example, hypophosphatemic rickets is a genetic disorder where the kidneys and bones deal abnormally with phosphate.

Phosphate binds to calcium and is what makes bones and teeth hard. This leaves too little phosphate in the blood and bones, leading to weak and soft bones.

Other types of genetic rickets affect certain proteins in the body that are used by vitamin D.

Occasionally, rickets develops in children with rare forms of kidney, liver and intestinal conditions. These can affect the absorption of vitamins and minerals.