Protein Sources. Men require 55 grams of protein a day, and women must have at least 45 grams. Protein sources for non-vegetarians include meat and seafood. Beef, pork and chicken are the most readily available. Game meats such as venison, elk and even goose and pheasant are good sources of gas-free protein. Worldwide, a number of other creatures from ostriches to goats provide meat protein.