The point of converting a portion of your wealth to gold or other precious metals before SHTF is not so you have something to buy food with during the chaos, its so that you can carry a chunk of your wealth from the current system to whatever replaces it after the chaos subsides.

Eventually the chaos will subside and when it does you don't want to have spent your entire life's savings on basic survival and then have to start from scratch when the world gets back to normal (or establishes a "new normal") especially since after a major SHTE/EOTWAWKI the dollar will likely not exist.