Once upon a time everyone ate locally. Every family had a garden and they only bought the food that they couldn’t supply themselves. Then the farmers of the world discovered economies of scale. They realized that by specializing in one crop or another that they could grow more of it for less money and they could make a profit on it.
Today our agriculture is almost entirely specialized and most Americans’ food travels more than fifteen hundred miles to get to them. One would think that this travel time would make food more expensive, but it actually makes it cheaper. Every crop has different needs to survive and it can be hard for small local farms to manage the differing conditions needed for different plants. This results in those small farms having a higher cost for each item produced. The big single crop farms may rely on chemicals, but every plant on their land has the exact same needs as the plant before it. This means they can buy their needed items in bulk and at a cheaper cost.
Cheap crops, like grains, can be grown just about anywhere in the United States and aren’t likely to become a part of a locally grown diet. If people were to make the switch to mostly locally grown produce then the price of that healthy produce would go up because those smaller farms are paying more for inputs. Unfortunately, the prices of low costs grain products such as corn syrup would stay the same. In fact, they might even get cheaper! As farmers would stop growing other produce because they would have nowhere to sell it they would likely start growing grains. That would increase the amount of grains in the market and make them cheaper.
The poor already have a higher rate of obesity, so demanding that locally grown foods be all that are available in the super-market would only drive the poor to more grain based foods. Those foods would still be relatively cheap. The question then becomes this: are the poor better off eating chemically treated fresh fruits and vegetables or are they better off on a pure grain diet?
That is a hard question to answer. Is it unfair that wealthier people can afford healthier food? Yes, but you have to think about the poor around the world. In nations like Africa the poor are literally starving to death; in the United States the poor are eating themselves into an early death. This is happening because cheaper foods actually tend to have more calories than their more expensive counterparts.
Unfortunately, it is a simple question of economic circumstance. If you have the money then it’s probably healthier to eat locally, but if you are poor then you are better off with processed foods from the super-market because it’s all you can afford and it’s better than nothing at all. This dynamic is not likely to change anytime soon because the world’s population continues to grow while the available farm land does not. The efficiency of single-crop farms will make them the only way to grow enough food for more people on the same number of fields.