Gout - Causes of gout

Gout is caused by a build-up of uric acid in the blood. Uric acid is a waste product that forms when the body breaks down chemicals in the cells known as purines.

Most uric acid is removed from the body through the kidneys. A small amount is removed through the digestive system.

Sodium urate crystals

Uric acid usually remains dissolved in your blood and passes through your kidneys into your urine so it can be passed out of your body.

If you produce too much uric acid or excrete too little when you urinate, the uric acid will build up and may cause microscopic crystals of sodium urate to form, usually in joints or surrounding tissue.

The crystals may spill over from the joint cartilage into the joint space, where they trigger a reaction from the soft lining (synovium), which produces the intense pain and inflammation associated with a gout attack.

Gout attacks occur most frequently in the joints of the feet and hands, possibly because the temperature in these joints is often lower than the rest of the body, which increases the likelihood of crystals forming. The knees and elbows are the next most commonly affected. Joints close to the body, such as shoulders, hips, the neck or back are very rarely affected.

Risk factors

Some things can increase the amount of uric acid in your blood, making you more likely to develop gout. These risk factors fall into one of three categories:

medical conditions known to increase levels of uric acid
lifestyle factors – such as diet or certain types of medication
genetics – certain genes you inherit from your parents may make you more likely to develop gout

These risk factors are discussed in more detail below.

Medical conditions

Medical conditions that can increase your risk of developing gout include:

high blood pressure (hypertension)
diabetes – both type 1 diabetes and type 2 diabetes
kidney disease
having high levels of fat and cholesterol levels in your blood
having osteoarthritis in your feet, knees or hands

Medication

Certain types of medication can increase your uric acid levels and your risk of developing gout. These include:

diuretics (water tablets), which are used to treat high blood pressure or an abnormal build-up of fluid in your body
other drugs used to treat high blood pressure, such as beta-blockers, ACE inhibitors and calcium channel blockers
low-dose aspirin
niacin, which is used to treat high cholesterol

Gender

Men are more likely to develop gout than women because their uric acid levels rise during puberty and remain higher than women through adulthood.

During the menopause, women experience a similar, albeit smaller, rise in their uric acid levels. This explains why symptoms usually start later in women than in men.

Diet

Foods naturally high in purines include:

red meat – such as beef, lamb and pork
seafood – especially shellfish and oily fish
offal – such as liver, kidneys and heart

Alcohol

Alcoholic drinks raise the level of uric acid in the blood by increasing its production in the liver and reducing how much is passed out in urine.

Beer and spirits do this more than wine, and beer also contains significant quantities of purines. Moderate consumption of wine – one or two glasses a day – should not significantly increase your risk of gout.

Sugary drinks

Research has shown a possible link between gout and certain sugary drinks.

Specifically, a study found that men who regularly drank sugar-sweetened soft drinks and drinks with high levels of fructose (a naturally occurring sugar found in many fruits) had an increased risk of gout.

Diet soft drinks were not found to increase the risk of gout.

Family history

Studies have shown that gout often runs in families. Around one in five people with gout have a close family member who also has the condition.

Susceptibility

It is still uncertain why some people are more susceptible to crystal formation and gout than others with equally high blood levels of uric acid. Many people with a high level of uric acid in their blood and tissues never develop gout.