Purines are chemicals found naturally in some foods. When you digest purines, your body produces a waste product called uric acid. Some people experience a build-up of uric acid that causes their joints to swell and become tender, leading to chronic pain. This condition is a type of arthritis known as gout. Watching your diet will help relieve symptoms and should be part of your gout treatment. Here’s how to choose low-purine foods so that gout symptoms will be less likely.