According to the article by Denis Chabrol “We are eating ourselves to death with the imported foods we eat.”
If every country takes a similar approach, what will be the likely outcome for the global food market? Related thoughts are presented in this 2013 post on "National Food Safety Programs and Initiatives"
No country is completely self-sufficient. Even for wealthy countries, food import restrictions are bound to limit available varieties of food.
In some instances, food import restrictions could potentially cost lives. Take, for instance, this June, 2016 Food and Agriculture Organization of the United Nations report about food insecurity in Yemen. One of the reported causes of food insecurity is food import restrictions. War may have a big part to play in this instance but varied are the situations that necessitate global food trade and/or exchange.