Although brown sugar will change the color of your finished cookie, both white and brown sugar have the same function in cookie dough, and you can use them interchangeably. The nutritional differences between brown and white sugar are minimal; both will increase your added sugar intake.
How Each Is Produced
Both white and brown sugar are commonly made from sugar cane syrup that has been processed and refined. While white sugar is processed until all molasses is removed from the granules, brown sugar contains some molasses, which is either left in during the refinement process or added back in afterward to color and change the texture and taste. Brown sugar can be light or dark, depending on the amount of molasses in it.
A 1-teaspoon serving of brown sugar has 11 calories, which increases to 17 calories if you pack the sugar, as many recipes require. A teaspoon of granulated white sugar has 16 calories. Neither contains any protein, fat or fiber. Brown sugar also has a slightly higher amount of essential minerals -- calcium, potassium, iron and sodium -- while white sugar doesn't have any. However, the difference is so slight that it makes little nutritional difference.
Added Sugar in Your Diet
A diet high in added sugars increases your risk of weight gain and obesity. The American Heart Association recommends you limit the amount of added sugar you eat to no more than 6 to 9 teaspoons per day. The calories from sugar are considered "empty" because they contain no essential nutrients.
To make your cookies healthier, you can use a no-calorie natural sweetener, such as stevia, in place of the sugar. Because stevia contains no calories, unlike other natural sweeteners such as agave, it won't unnecessarily increase your calorie consumption. Stevia is between 100 and 300 times sweeter than sugar, and you can use it as a substitute in baked goods. In general, you can substitute 1 cup of sugar with 1 teaspoon of powdered stevia, or use a single pinch of stevia for 1 teaspoon of sugar.