Anyone Can Spend Less for Food
I can say without fear of contradiction that you're spending more than necessary for your food. That's a good thing — eating well is one of the great pleasures of life, and you can almost certainly afford to eat a more interesting and varied diet than the cheapest possible. But it's worth taking a minute to look at just how cheaply you could eat, if you had to.
If you want to check that a particular diet provides adequate nutrition, there are any number of nutrition calculators on line. I've previously linked to the USDA's Food and Nutrition Information Center. Their calculator seemed to have some problems today, so I ended up using a similar one at fitday.com.
You can drive yourself crazy trying to produce an optimal diet from scratch. It simplifies things a lot to start by drawing on some traditional diet. For example, the traditional diet of the Scots used to be oats and kale, so I've cranked up an example based on that.
According to fitday, 5 cups raw kale, 5 cups raw oats, and 3 cups of 1% milk comes in at just over 2000 calories. It provides 100 grams of protein, which is ample, and tops 100% of the US RDA for nearly every nutrient. (It's a little short of niacin and B12, which the Scots probably got from barley, fish, and small amounts of meat from the goats and sheep that they raised for milk and wool.)
There are as many alternatives as there are traditional peoples who have lived on the earth. I did much the same calculation for corn, beans and squash (Native Americans), rice and lentils (South Asians) and potatoes and dairy (Ireland). You have to throw in some vegetables — one carrot and one turnip, for example — but it's easy to make a balanced diet.
Any particular diet may be unsuitable for some people — people with celiac, for example, shouldn't eat a diet that's mostly oats, and people with irritable bowel syndrome might find a diet high in beans or lentils unsatisfactory — but there's an endless list of possible diets, and some of them are really, really cheap.
My point is not that you ought to eating mostly oats and kale (or rice and beans). My point is that an extreme frugal option like this ought to be out at the far end of your array of choices. By all means, spend more than this if you can afford to. A varied diet is not just a pleasure; it also provides protection against the possibility (the certainty, really) that we don't know everything about nutrition, and against the possibility that your nutritional needs are different in some way from those of an average person. Just understand that, if you're paying more than what a diet like this would cost, you're paying for wants rather than needs. Paying for wants is a good thing — it's what makes life worth living. But you ought to be thoughtful in your choices; part of being thoughtful is to include these extreme frugal choices in your thinking.
Of course, I'm not the first person to think about this. For example, Xin just reviewed a book by a couple of people who wrote about trying to eat for just $1 a day.
Start by figuring out what you really need and allocating enough resources to cover what that costs. Then take what's left over and cover some of your wants. But if you don't even consider really, really frugal eating as an option, you might be paying for food that doesn't provide as much satisfaction as something else you could have chosen instead.