Butter or Margarine? Experts Reveal What's in Their Grocery Cart

As supermarkets offer more choices, a simple trip to the grocery store can be an agonizing outing.

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Legend has it that grocery shopping used to be a one-hour gig. Now it's full of nutrition decisions: skim or whole? Fresh or frozen? Good fat, bad fat? U.S. News asked two nutrition experts to tell us what they put in their carts and why:

Olive or canola oil? While canola has been touted in recent years as superior to olive oil, both have high proportions of polyunsaturated and monosaturated fatty acids (good fats) and are heart healthy when consumed in moderation. "Although both are relatively low in saturated (bad) fat, the debate arose when olive oil was found to contain a slightly higher amount," says Karen Congro, a registered dietician and director of the Wellness for Life Program at Brooklyn Hospital Center. While Congro prefers olive oil for everyday use because of its higher level of monounsaturates, it does have a distinctive flavor and is significantly more expensive than canola.

Butter or margarine? For those who believe butter is healthier because it's "natural," Congro has bad news. "It's made from animal fat, [so it] contains cholesterol and very high levels of saturated fat," she says. Margarine is made from vegetable oils, and plant products contain no cholesterol. It's also higher in "good" fats than butter. But some kinds of margarine may be even worse than butter because of their content of trans fats, a particular heart risk. In general, the more solid the margarine, the higher the proportion of trans fat. Steer clear of stick margarine, advises Congro: "Go for the tubs of heart-healthy margarine made with omega-3 oil," such as Promise or Smart Balance.

[Read: Greek Yogurt Vs. Regular Yogurt: Which Is More Healthful?]

Low-fat or skim milk? Let's face it—the higher the fat content, the better the taste, but skim and 1 percent are clearly better nutritional choices, says Dawn Jackson Blatner, a dietitian and spokesperson for the American Dietetic Association. How much better, though? "The higher you climb in percentage of milk fat, the bigger the bite you're taking out of your daily recommended value of saturated fat," says Blatner. According to the U.S. Department of Agriculture, the maximum recommended daily intake of saturated fat for the average active adult is 20 grams. One serving of skim milk can have no more than .4 of a gram of saturated fat, with 1 percent weighing in at 1.5 grams and 2 percent at 3 grams. "If you have two glasses of 2 percent milk, you've already consumed almost a third of your daily saturated fat," says Blatner. "Stick to skim and 1 percent." Or go for the 2 percent but keep the saturated fat content in mind.

Fresh or frozen veggies? "Fresh sounds better," says Lona Sandon, a nutritionist at the University of Texas Southwestern Medical Center and a spokesperson for the American Dietetic Association, "and if you picked them out of your garden or at a farmer's market that sells locally grown produce, you can be assured they haven't lost nutrients in transit." But keep in mind that "if." Research at Pennsylvania State University found that a bag of spinach stored at slightly below 40 degrees Fahrenheit for eight days lost half its folate, which prevents birth defects, and carotenoids, compounds that fight heart disease. Higher temperatures accelerated the breakdown. At 50 degrees, half of the compounds were gone after six days. It took just four days at 68 degrees to drop by half. On an 80- or 90-degree day at an outdoor farm stand, the process clicks up several notches. "Frozen fruits and vegetables are processed at their peak ripeness, a time when—as a general rule—they are most nutrient-packed," says Sandon. "When you buy frozen, you know exactly what you're getting."

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