Preheat the oven to 425 degrees Fahrenheit (218 degrees Celsius). Lightly spray or line one muffin tin, and set aside.
In a small glass measuring cup or bowl, whisk together the buttermilk, yogurt, egg, oil, brown sugar, and vanilla.
In a separate mixing bowl, whisk together the bran, flour, baking powder, baking soda, salt, and cinnamon. Gradually pour the wet ingredients into the bowl of dry ingredients, mixing just until combined.
Gently fold in the berries, dried fruit, or nuts into the bran mixture.
Scoop the batter into the prepared pan, dividing it evenly between the wells. Place in the oven and bake for 14-16 minutes or until the tops are golden brown and spring back when touched.
Remove from the oven and allow to cool in the pans for 5 minutes before transferring to a wire rack to cool completely.
Notes
*I opted to make my own "low-fat buttermilk" by adding 1 tbsp. of lemon juice to 1 c. of 1% milk and allow it to sit for 5 minutes before using.**If you prefer your muffins on the sweeter side, add an additional 1 tbsp. of brown sugar.***You can use only whole-wheat flour, only all-purpose flour, or 1/2 c. whole-wheat flour + 1/2 c. all-purpose flour. They taste great no matter what you use!STORE these bran muffins in an airtight container at room temperature for 3-4 days. To FREEZE, place them in a zip-lock bag and store them in your freezer for up to 3 months.To REHEAT, thaw if frozen, then warm in the microwave for 20-30 seconds or in a preheated oven at 350 degrees Fahrenheit (175 degrees Celsius) for about 5 minutes until everything has warmed through.