Rickets is a disease that happens in young children.  It happens in children who do not get enough vitamin D and calcium.  It causes larger spaces inside bones, and makes them dry, like sponges.  It can make the legs curve toward each other (so the knees touch) or away from each other.

Rickets in adults is called osteomalacia.

The word "rickets" comes from the Greek word rhakhis, which means "spine."

Cause 
People need both vitamin D and calcium to make their bones strong.

Vitamin D helps the bones absorb (take up) calcium.  Low vitamin D makes it hard to absorb calcium.

The human body makes vitamin D3 in the skin, from cholesterol.  Then the liver changes vitamin D3 into calcitriol, which sends calcium from the blood into the bones.  The bones need calcium to stay strong.  However, the skin will not make vitamin D3 unless enough ultraviolet light shines on it.  Sunlight contains ultraviolet light, so getting enough sun is one way of getting enough D3.

People need calcium for calcification. Calcification uses calcium to help make bones bigger and stronger.  Low calcium makes bones delicate and easier to break.

Prevention 
Rickets can be prevented if a person gets plenty of calcium and vitamin D.

The best way to do this is to get a lot of sunlight, and eat foods that have a lot of vitamin D and calcium in them.  However, people who cannot get enough vitamin D and calcium this way can take supplements (vitamin pills that have calcium and vitamin D in them).

Calcium

Foods that have a lot of calcium in them include:
 Milk and other dairy products like cheeses
 Some green vegetables, like broccoli, spinach, and kale
 Today, many products are "fortified" with vitamin D: the vitamin was added when the food was made.  These foods include some kinds of orange juice, breakfast cereals, breads, and even bottled water.  The food's label will say how much calcium it has in it.

Calcium is absorbed best by the bones when it is taken in amounts of 1000mg or less.  Because of this, doctors suggest eating smaller amounts of foods with calcium in them, at different times in the day, instead of all at once.

Vitamin D

There are three ways to get vitamin D: sunlight, foods, or supplements (vitamin pills that have vitamin D in them).  However, many people cannot get enough vitamin D just from their diet.

There are only a few foods that have a lot of vitamin D in them.  They include:
 "Fatty fish" that were caught in the wild, like mackerel, salmon, and tuna
 Cooked egg yolk
 Vitamin D is added to some foods, like some kinds of dairy products, cereals, and orange juices

Breast milk may not have enough vitamin D in it to prevent rickets.  Babies who are only breastfed, and not fed any other foods, may be given vitamin D drops to make sure they do not get rickets. However, this is not a significant risk if mothers and child have some exposure to sunlight. Children with dark skin are more likely to need additional vitamin D.

Risk factors
These things make a person more likely to get rickets:
They are between three and 36 months old.  Children this age are at the greatest risk for rickets because their bones are growing so quickly, and are supposed to get bigger and stronger during this time
 They were born prematurely (earlier than normal)
 They live in the Northern parts of the world, where there is less sunshine
They spend too little time outside

They always wear sunscreen when going out
 Even mild sunscreen decreases the amount of vitamin D the body makes by 95% (by stopping the body from taking in vitamin D from sunlight)
 However, people should still wear sunscreen when they might get sunburned
They do not eat enough food that has calcium or vitamin D in it, because of lactose intolerance or a strict vegan diet
They cannot make or use vitamin D because of a medical disorder, like coeliac disease, or because they take certain anti-seizure medications

Symptoms
Signs and symptoms of rickets include:
 Brittle (easily broken) bones or teeth
 Bleeding more than normal
 Stunted growth (not growing like a healthy child would)
 Sweating
 Weakness (feeling tired all the time)
 Body pain

Related pages
 Vitamin D
 Calcium

References

Diseases
Diseases and disorders of bones
Vitamin deficiencies