Rich, chocolatey brownies may be delicious, but they definitely aren't very nutritious because they tend to be high in both fat and added sugars. You can make them a bit healthier by trading some or all of the butter for a more nutritious substitute. You won't lose the chocolate taste you crave and, depending on the substitute you choose, your treat may provide more nutrients than your original recipe.

Trading the butter in your brownie recipe for olive oil or other vegetable oils may not lower the fat or calories in your brownies, but they will greatly reduce the amount of saturated fat, replacing this harmful fat with more heart-healthy unsaturated fats. If you also replace the whole eggs in the recipe with egg whites, along with removing the butter, you'll remove all of the cholesterol in the brownies. If a recipe isn't already formulated to be low fat, you can often reduce the fat content by one-fourth when you switch from butter to oil, lowering the fat and calorie content a bit.

While you can't replace all of the butter in brownies with fruit purees, you can replace up to half. Good fruits to try include mashed banana, applesauce or pureed prunes or cherries. The brownies won't taste particularly fruity because the chocolate flavor overpowers the fruit flavor, especially if you choose one of the milder fruit purees such as applesauce. These purees keep your brownies nice and moist. If you have diabetes, the fruit puree will increase the carbohydrate content of the brownies. You may also need to remove the brownies from the oven sooner because these replacements can lower the cooking time by up to 25 percent.

Less traditional replacements for some of the butter in brownies include pureed vegetables, such as sweet potato or pumpkin. As with fruits, replacing more than half of the butter with these ingredients may make the end product suffer. However, using a vegetable puree will increase the fiber and nutrients in your brownies while lowering the fat and calories, making them a little bit less of a splurge.

A study published in the "Journal of the American Dietetic Association" in August 2005 found that you can replace up to half the fat in brownies calling for shortening with pureed cannellini beans without adversely affecting the taste or acceptability of the end product. Since butter is a solid fat like shortening, this replacement also works in brownie recipes calling for butter. You can also use other types of white beans or black beans, but the black beans may make a more noticeable change in the flavor of the brownies than the white beans, so you may want to replace less of the fat if you use these beans.