This verse has been discussed in great depth by our scholars. We have hadiths that clarify what is meant by “food” in this verse. The hadith states it’s the grains (such wheat, barley, beans and so on). These are lawful for us. As for the meat, it must be slaughtered halal in order for us to eat it. Most scholars don’t accept Kosher meat as halal meat.
Now one may ask: if “food” in the verse means grains, not meat, then why did the Qur’an need to mention that? Isn’t obvious that we can eat grains from the People of the Book? The answer is: no it wasn’t obvious. Many Muslims thought they couldn’t do business with Christians/Jews and buy grains from them, or sell grains to them. The Qur’an clarified that it is permissible.