Frozen vegetables. Buying fresh vegetables in season is an inexpensive way to get them, but frozen vegetables are a good option too, Begun says. They're picked at the peak of their flavor and aren't nutritionally inferior to fresh ones. The downside of fresh vegetables is they might be picked before their height of ripeness and often travel many miles to a grocery store, she says.
Peanut butter. This is another economic source of protein, rich in healthy fats, vitamins, minerals and antioxidants. Peanuts contain resveratrol, an antioxidant found in red wine, says Sharon Palmer, a Duarte, Calif.-based food and nutrition writer who covers plant-powered diets.
Protein bars. You may not want to make them the only part of your diet, but they obviously have protein in them and cost about $2 each. Andrew Ross and his wife, who live in Baltimore, eat a Quest protein bar from GNC every three hours from when the time they wake up until when they go to bed. They started this habit in April and he's lost 78 pounds so far.
They also eat Power Pak pudding once a day, which contains 30 grams of protein per can and less than 200 calories. The protein bars have 20 grams of protein and less than 200 calories. Ross estimates that they spend less than $400 per month on food and drinks, saving money by buying in bulk during sales.
The best answer to getting the most nutritional foods for your buck may be to simply buy fresh food that's in season and not to fall for the theory that fast food is cheaper than what you can purchase at the grocery store. "People don't think out of the box," Wasserman says. Fast food may be quicker than preparing a meal at home, but it won't beat buying fresh fruit and vegetables in taste or cost, she says.
Clarified on 01/16/2014: A previous version of this story mischaracterized fiber. It is a nutritional component.