Mistake #7: You're simmering away vitamins and minerals
Boiling may seem like a simple, no-fuss way to prepare vegetables without adding oil, but this cooking method can cause up to 90 percent of a food's nutrients to leak out. Minerals like potassium and water soluble vitamins like B and C end up getting tossed out with the water.

Solution: To keep these essentials from draining away during the cooking process, try steaming (use a minimal amount of water with a steamer basket), microwaving, or stir-frying. A study from the University of Essex in England showed that when certain vegetables were prepared using these techniques, most of the nutrients they contained were spared. And stir-frying scores even more points when you're cooking dark green or orange vegetables. These are rich in beta-carotene, and the oil you use in stir-frying them can increase the amount of the antioxidant you absorb by up to 63 percent, according to a study published in the journal Molecular Nutrition & Food Research. You don't need to use a lot of oil; even just a tablespoon will do.

Mistake #8: You don't wash all your produce before eating it
Most of us remember to rinse plums and berries before noshing on them, but when was the last time you doused a banana, orange, cantaloupe, or mango with water? It may seem strange to wash peel-and-eat produce, but harmful bacteria lingering on the surface could be transferred to your hands or even to the inside of the fruit when you cut into it.

Solution: To clean produce, simply run each piece under the tap and gently scrub. Using your hands to rub fruits like oranges, bananas, and peaches under water is sufficient. When you're done, dry the items with a clean cloth or paper towel. It's important to wash your hands with soap and warm water for at least 20 seconds before and after you handle the items to further reduce the spread of bacteria. Throw away the outer leaves of greens like cabbage and lettuce before washing, as they've been handled the most and can have the highest levels of bacterial contamination.

Mistake #9: You're not pairing foods properly
Many of us think about getting enough iron only when we feel lethargic or fatigued. But we should pay attention to our iron intake every day, before symptoms occur. Our bodies absorb about 15 to 35 percent of heme iron (found in meats and seafood), but just 2 to 20 percent of non-heme iron (from beans, whole-grain cereal, tofu, and dark, leafy greens).

Solution: Maximize how much iron you take in by pairing non-heme iron with vitamin C–rich foods and beverages, such as citrus fruits and juices, tomatoes, hot and sweet peppers, strawberries, and melons. Avoid drinking tea or coffee at meals as this can inhibit iron absorption by up to 60 percent; these beverages contain compounds called polyphenols that bind to the iron. Wait until you've completely finished your meal before putting the kettle on to boil.