To understand where the uric acid comes from, let's start with purines, which, together with pyrimidines, are nature's most common nitrogen-containing heterocycles.
These crystals can form as a result of increased consumption of purines, like from consuming purine-rich foods like shellfish, anchovies, red meat or organ meat.
Also, though, they can result from increased production of purines, for example high-fructose corn syrup containing beverages could contribute to the formation of uric acid by increasing purine synthesis.