I guess he's saying that for food to be this cheap seen with our eyes, there needs to be a substantial oversupply. And since there are physical limitations to how much food we are able to actually eat, if there's an oversupply a bunch of it will be thrown away, whether by farmers, distributors or consumers:
Either they fail to sell the food, or the low prices gets consumers to buy more than they need.
Either they fail to sell the food, or the low prices gets consumers to buy more than they need.