Eating healthier food can add almost 10 percent to the average American’s food bill — and that is just to boost a single nutrient like potassium. Researchers from the University of Washington looked at the economic impact of following new U.S. dietary guidelines, which recommend eating more potassium, dietary fiber, vitamin D and calcium, and avoiding saturated fat and added sugar… In an article in Health Affairs published on Thursday, the researchers reported that eating more potassium, the most expensive of the four nutrients, can add $380 to the average person’s yearly food costs.