Is fresh really best? Not necessarily, says a recent study which found that canned foods can offer as many nutrients as fresh produce, but more cheaply and conveniently. In fact, when you factor in the cost, waste and preparation time, canned foods can be one of the most affordable sources of nutrients, explain the researchers from Ketchum Global Health and Wellness.

The key is to pick the healthier options such as these:

Stock up on these nutritious canned foods

Pinto beans

Canned pinto beans are a rich source of protein and fiber, and cost $1 less than dried beans when you take the cost of preparation time into consideration -- it takes only six minutes to prepare a can of pinto beans, and almost 2.5 hours for dried beans to be meal-ready.

Tomatoes

They're rich in dietary fiber, vitamin C, and an antioxidant compound called lycopene which may cut cancer risk. It is 60 percent more expensive to obtain dietary fiber from fresh tomatoes than from a can, and they also take longer to prepare.

Corn

Corns are high in fiber, vitamin C and magnesium. Fresh corn may be less expensive than canned or frozen at purchase price, but when the cost of waste (i.e. the cob) is factored in, as well as time to prepare, you'll have 25 percent savings by buying canned corn for the same amount of dietary fiber.

Tuna

Tuna is an excellent source of healthy, lean protein. Compared to fresh tuna, canned is convenient and cheaper. For lower sodium options, look for tuna packed in water instead of brine.

Spinach

These leafy greens are high in vitamin C, folate, fiber, and carotenoids. Canned spinach has a lower per-serving cost than fresh or frozen, offering vitamin C at an 85 percent savings.