Google has extended ‘category filtering beta’ to ads in AdSense for feeds. To set up, from Ad Review Center, make sure you select a Client-ID that starts with ca-feed-pub. Note that this allows you to select different categories for your feed than for your site, but also means you’ll need to select filters for both your feed and your site in order for filters to be applied to both these content types. To see whether category filtering has been enabled for your location, sign in and visit the Ad Review Center, located under the 'AdSense Setup' tab.