Preheat oven to 350°F (175°C).

Prepare a 12-muffin tin with liners or grease it well.

In a large bowl, combine wheat bran, oat bran, whole wheat flour, baking soda, salt, cinnamon, nutmeg, and ginger.

In a separate bowl, whisk together low-fat buttermilk, egg, vanilla, and oil.

Add the mashed banana and honey to the wet ingredients and mix well.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in shredded coconut and dried currants (if using).

Pour batter into prepared muffin tin, filling each cup about 2/3 full.

Bake for 24 minutes, or until a toothpick inserted into the center comes out clean.

Let cool in the muffin tin for a few minutes before transferring to a wire rack to cool completely.