There’s something empowering about hitting the supermarket to shop for your week’s meals. Rather than putting yourself at the mercy of the local Chinese take-out restaurant or succumbing to the lure of the drive-through, you’re taking dinner—and your waistline—into your own hands. “Eating out less and cooking more may be one of the most effective things you can do to keep fat and calories in check,” says Cheryl Forberg, R.D., author of Stop the Clock! Cooking. “Plus, building your diet around produce, whole grains, beans, and lean protein practically guarantees you’ll reach your recommended targets for most vitamins and minerals.” But while we may be tossing the freshest, most wholesome foods into our carts, many of us are storing and preparing them in ways that rob them (and our bodies) of the very nutrients we’re seeking. Nutritionists and food-safety experts point to nine typical kitchen blunders that negatively impact the quality of our diets. Fortunately, you can sidestep all of them easily. Follow this advice to make your next meal healthier.

MISTAKE #1

You’re overloading on produce
Sure, making one big grocery run at the start of the week seems like a no-fail way to get your five a day. After all, if those carrots, greens, apples, and berries are around, you’ll eat more of them and therefore get more nutrients, right? Wrong. “The vitamins and minerals in fruits and vegetables begin to diminish the moment they’re harvested,” says Geri Brewster, R.D., a wellness consultant at Northern Westchester Hospital in Mt. Kisco, New York. That means the longer you store produce, the fewer nutrients it will contain. After about a week in the fridge, for example, spinach retains just half of its folate and around 60 percent of its lutein (an antioxidant associated with healthy eyes), concludes a study in the Journal of Food Science. Broccoli loses about 62 percent of its flavonoids (antioxidant compounds that help ward off cancer and heart disease) within 10 days, according to a study in the Journal of Agricultural and Food Chemistry. “You’re better off buying smaller batches at least twice a week,” says Brewster. If you can’t shop every few days, pick up frozen produce. These fruits and veggies are harvested at their peak and are flash-frozen immediately. Because the produce isn’t exposed to oxygen, the nutrients stay stable for a year, according to researchers at the University of California, Davis. Just be sure to avoid frozen products packed in sauces or syrups. These additions can mean extra calories from fat or sugar, and sometimes they’re high in sodium as well.

MISTAKE #2

You’re stashing foods in see-through containers
If you’re still buying your milk in clear plastic jugs, consider switching to cardboard cartons. Milk is rich in the B vitamin riboflavin; when exposed to light, a chemical reaction is kicked off that reduces the vitamin’s potency, according to researchers from Ghent University in Belgium. Other nutrients, such as amino acids (the building blocks of protein) and vitamins A, C, D, and E, are also affected. And because lowfat and nonfat milk varieties are thinner than whole milk, light can penetrate them more easily. “This process, known as photo-oxidation, can change the flavor of the milk and create disease-causing free radicals,” says Susan Duncan, Ph.D., a food scientist at Virginia Tech. Since grain products (especially whole grains) are also high in riboflavin, they too are susceptible to this breakdown of nutrients and production of free radicals. Duncan recommends avoiding the practice of storing dry goods like pasta, rice, and cereals in clear containers on your countertop. Instead, keep them in their original boxes or in opaque containers and stash them in your kitchen cabinets, where they’ll be shielded from light.

MISTAKE #3

You’re too quick to cook your garlic
Legend has it that these pungent little bulbs can ward off vampires, but science shows that if you cook them correctly, they may have the power to fight off an even more frightening villain: cancer. “Chop, slice, or crush your cloves, then set them aside for at least 10 minutes before sautéing,” says John Milner, Ph.D., chief of the nutritional science research group at the National Cancer Institute in Rockville, Maryland. “Breaking up garlic triggers an enzymatic reaction that releases a healthy compound called allyl sulfur; waiting to cook garlic allows enough time for the full amount of the compound to form.”

MISTAKE #4

The only time you eat avocados is in guacamole
Adding this green fruit to salads and sandwiches is an easy way to raise your nutritional bar. Avocados are exceptionally rich in folate, potassium, vitamin E, and fiber. It’s true that they’re also high in fat, but it’s the heart-healthy monounsaturated kind. And half an avocado has just 153 calories. One novel way to work them into your diet is to use them as a fat substitute in baking. Many of us have been using applesauce or puréed prunes in place of butter and oil in brownie and cookie recipes for years. Researchers at Hunter College in New York City wanted to see if avocado could work in the same way without affecting the taste. They replaced half of the butter in an oatmeal cookie recipe with puréed avocado. Not only did this swap cut the total fat count by 35 percent (avocados have fewer fat grams per tablespoon than butter or oil), it also made the resulting treats softer, chewier, and less likely to crumble than cookies made according to the original recipe. If you’re still wary of using such a nontraditional ingredient in sweets, try adding it to savory baked items, such as quick breads and muffins.

MISTAKE #5

You skimp on seasonings
Herbs and spices not only enhance the flavor of your cooking without adding fat or sodium, many of these fragrant ingredients also protect you from food poisoning. After testing 20 common seasonings against five strains of bacteria (including E. coli, staphylococcus, and salmonella), researchers at the University of Hong Kong found that the higher the antioxidant value of the spice, the greater its ability to inhibit bacterial activity. Cloves, cinnamon sticks, and oregano were the most effective at fighting off these food-borne pathogens. A separate study published in the Journal of Agricultural and Food Chemistry shows that rosemary, thyme, nutmeg, and bay leaves are also antioxidant-rich. Of course, you can’t ignore standard food safety practices, but adding half a teaspoon of herbs or spices to salads, vegetables, and meats can give you extra peace of mind and boost your intake of disease-fighting antioxidants.

MISTAKE #6

You’re a serial peeler
Most of the antioxidants and polyphenols in produce are located very close to the surface of the skin or in the skin itself. A study published in the journal Nutrition Research found that most fruit peels exhibited two to 27 times more antioxidant activity than the pulp of the fruit. “Many of us remove the skins from eggplant, bell peppers, peaches, apples, and nectarines while preparing recipes, but we’re really just tossing away nutrients and fiber,” says nutritionist Forberg. She recommends gently scrubbing potatoes and carrots rather than removing their skin, and using a vegetable peeler or sharp knife to pare away as thin a layer as possible from fruits and veggies that must be peeled.

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 leech out, says Karen Collins, R.D., a nutrition advisor to the American Institute for Cancer Research in Washington, D.C.

“Minerals like potassium and water-soluble vitamins like B and C end up getting tossed out with the water,” she says. 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 anti-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. 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,” says Ruth Frechman, R.D., a dietitian in Burbank, California, and a spokeswoman for the American Dietetic Association. 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. Frechman also suggests throwing out 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). We can maximize how much iron we take in by pairing the latter group with vitamin C–rich foods and beverages, such as citrus fruits and juices, tomatoes, hot and sweet peppers, strawberries, and melons. On the other hand, drinking tea or coffee at meals can inhibit how much iron we absorb by up to 60 percent, says Marla Reicks, R.D., a professor of nutrition at the University of Minnesota in St. Paul. That’s because 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.

Amanda Pressner