It isn't all that difficult to eat a healthy diet on a budget, but the biggest question here is not so much about the budget as what constitutes optimum nutrition. What's considered healthy changes all the time. First eggs were evil, now they aren't; same with fat (as long as it's unsaturated); and it is a fairly sure bet that carbs, once sainted, now tainted, will go the same way.
Author Michael Pollan breaks it down into three simple phrases: Eat food. Not too much. Mostly plants. By food, he means real food that your great-grandmother would recognize as food. In other words, food that is a plant or comes from plants, rather than food that is made in a plant. Unfortunately, manufactured food is cheap. Eating nutritious foods may take a bit more time and effort than stuff that comes in a box, but it's better for you and also budget-friendly. Each of these 26 healthy foods and meals will cost about $1 per serving or less.