It's caused by high uric acid levels. These are usually from proteins(meats), though some proteins are lower in purines(the cause of the elevated uric acid levels). Some veggies are thought to increase this(spinach asparagus), though their are conflicting ideas by researchers. Veggies though, if even a cause, would be far lower impact than meats.
Not sure if certain bugs would be a cause, would be a good study.