Gout is a chronic form of arthritis caused by too much uric acid in the body. This excess uric acid can settle in tissues, particularly the joints. From time to time, the uric acid can form needle-shaped crystals in the joint space. The body reacts to these crystals by launching an attack that causes inflammation, redness, and pain. This is a gout attack.
While high uric acid is necessary to cause gout, it is not sufficient on its own to cause gout. In fact, not everyone with high uric acid levels develops gout. The reasons for this are not well understood.
There are three main causes of high levels of uric acid that can lead to gout:
- A diet high in foods that contain high levels of chemicals called purines can increase the risk of developing gout, but they don't cause the disease on their own. Purines are a group of chemicals present in all body tissues and in many foods. Our bodies are continually processing purines, breaking them down and recycling or removing the byproducts. (It's important to note that most people who have a high-purine diet don't get gout. A person with normal uric acid levels could eat enough high-purine foods to cause gout. It's more likely that overdoing certain foods or alcohol might cause problems for someone whose body already doesn't get rid of enough uric acid or makes too much.)
- A high production of uric acid by the body. This can happen for unknown reasons, or as a result of inherited genetic metabolic disorders or leukemia, or during chemotherapy for cancer.
- The kidneys are not excreting enough uric acid. This can be caused by kidney disease, starvation, excessive alcohol use, or medications called diuretics.
Uric acid is a chemical that is naturally produced by the body as it breaks down purines. The body excretes uric acid out of the body with urine. For most people, uric acid is made and excreted without any problems. But for some people the kidneys don't get rid of enough uric acid. This can lead to a buildup of uric acid in the bloodstream, a condition called hyperuricemia, which can lead to gout.
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Certain factors can raise your risk of gout and increase your chances of gout attacks. While these factors can make gout more likely (largely because they lead to higher uric acid levels), they don't cause gout.
Some of the factors that increase your chances of gout include:
- Diet. Eating lots of high-purine foods increases your chances of gout. The same goes for drinking excessive amounts of alcohol, which reduces the amount of uric acid removed by the kidneys. Beer can be particularly aggravating because it contains a lot of purines. Research has found that consuming food and drinks sweetened with high-fructose corn syrup has been linked to gout.
- Excess weight. People who are overweight or obese tend to make more uric acid than people who are not. Overweight is defined as a body mass index (BMI) of 25 to 29.9, and obesity is a BMI of 30 or greater. (BMI is an estimate of body fat based on a person's height and weight.) Studies have found that the heavier people are, the greater their risk of gout — a tenfold or more risk for the heaviest people.
- Family history. We know that certain genes increase the risk of gout and that people with family members who have gout are more likely to get it.
- Certain health conditions, including diabetes, obesity, and heart or kidney disease. People with kidney disease are at risk because the kidneys are key players in getting rid of uric acid. Impaired kidney function can lead to high uric acid levels. And research has shown a link between diabetes and gout.
- High blood pressure. People with high blood pressure are up to twice as likely to have gout as those with normal blood pressure. It gets complicated, though, because the medications (called diuretics) taken to lower high blood pressure increase uric acid levels.
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About 90% of people with gout are men older than 40. In general, gout strikes men three times as often as women.
Gout becomes more common with age. Women rarely have gout before menopause, perhaps because estrogen helps to keep uric acid levels low. After menopause, the risk of gout increases for women. Men of any age can have gout, but it tends to be more common after middle age.
While diet may aggravate the condition, it does not cause gout. As mentioned above, foods that are high in purines tend to form more uric acid when they break down. These foods may trigger a gout attack in someone whose body already has levels of uric acid that are too high due to an underlying condition.
Foods that increase the risk of a gout attack include:
- high-purine foods such as red meat and some kinds of fish, especially scallops, sardines, and tuna
- alcohol, especially beer
- beverages sweetened with sugar or fructose (including high-fructose corn syrup).
Can gout be prevented?
Lifestyle changes such as losing weight, limiting alcohol, and eating fewer purine-rich foods may help prevent future attacks.
Following a healthy diet, drinking plenty of fluids, and trying to lose weight if you're overweight or obese can lower uric acid levels. Some research suggests that vitamin C, as well as low-fat dairy products, may help lower uric acid levels.
A study published in JAMA Network Open found that more than three-quarters of gout cases affecting men might be completely avoided with the following four factors:
- normal body mass index (BMI)
- no alcohol consumption
- no use of a diuretic medication (commonly used to treat high blood pressure and other conditions)
- following a DASH-style diet, a heart-healthy diet originally developed to counter high blood pressure.
If you have frequent gout attacks, your doctor will also discuss with you whether you should start taking a drug that will lower uric acid levels. In most cases, medications that lower uric acid are highly effective at preventing attacks of gout. Note that going on and off a uric acid–lowering medication can provoke gout attacks.