Stir together wheat bran and buttermilk and set aside. Preheat oven to 350°F (170°C). Line muffin pan with paper liners.

In a medium sized bowl, whisk together oil, egg, honey and vanilla. Add the bran-buttermilk mixture and stir to combine.

In a large bowl, stir together both flours, baking powder, baking soda and salt. Add the liquid mixture and stir together, just until there are no more flour clumps. Fold in raisins.

Spoon batter muffin wells. Bake muffins for about 18 minutes, until a toothpick comes out clean. Remove muffin pan to a wire rack and allow muffins to cool in pan for 10 minutes. Remove muffins from pan and cool completely on a wire rack. Tightly sealed at room temperature, muffins stay fresh for 2 days. They keep for one month in the freezer.