Q. How can some brands of peanut butter claim “zero trans fats,” but still list hydrogenated oil in the ingredients list?

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A. With the new trans-fat nutrition-labeling rules, products labeled “0 trans fats” can still contain up to half a gram of trans fat per serving. You can assume that “trans-free” peanut butter still contains a small amount of trans fat if partially hydrogenated oil is listed as an ingredient.

Trans fats help make peanut butter shelf-stable, smooth and creamy. But now that trans fats’ heart-damaging effects are widely known, many peanut butter manufacturers are replacing them with palm oil. While palm oil is trans-fat-free, about half of its fat is saturated, adding about 1.5 grams sat fat to each 2-tablespoon serving.

Have we traded one “bad fat” for another? Could be. While you may have heard that palm oil has less of a cholesterol-raising effect than other tropical oils, the research isn’t conclusive. Your best bet is to choose natural peanut butters that contain neither added palm oil nor trans fats.

See the winners of our Natural Peanut Butter Taste Test.