Sugars contribute moisture and tenderness to baked goods. Flour or starch components serves as a protein and gives the dessert structure. Fats contribute moisture and can enable the development of flaky layers in pastries and pie crusts. The dairy products in baked goods keep the desserts moist. Many desserts also contain eggs, in order to form custard or to aid in the rising and thickening of a cake-like substance. Egg yolks specifically contribute to the richness of desserts. Egg whites can act as a leavening agent or provide structure. Further innovation in the healthy eating movement has led to more information being available about vegan and gluten-free substitutes for the standard ingredients, as well as replacements for refined sugar.