Vegetarians and vegans should aim to consume 50 percent more zinc than their meat-eating counterparts each day.
One of the problems with the Recommended Dietary Allowances (RDAs) is that they make a few assumptions (for example, that everyone eats meat).
In all fairness, they kind of have to since these figures are meant as average daily intakes sufficient for 97% of the population.
The issue with vegetable sources of zinc, as with iron, is their low bioavailability.
Therefore, if you are over the age of 18 and do not eat meat (by "meat" I mean beef, poultry, pork, and seafood), your requirement increases from 8 milligrams a day to approximately 12 or 13.