Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly grease with nonstick spray.

In a large bowl, whisk together all-purpose flour, whole wheat flour (if using), baking powder, baking soda, cinnamon, nutmeg (if using), and salt.

In a separate bowl, whisk eggs with brown sugar and granulated sugar until smooth. Whisk in the oil, 1–2 tablespoons reserved pineapple juice, and vanilla.

Fold the grated carrots and well-drained crushed pineapple into the wet mixture. If using coconut or nuts, stir them in now.

Pour the wet ingredients into the dry ingredients and gently fold with a spatula just until no streaks of flour remain. Do not overmix. Fold in raisins if using.

Divide the batter evenly among the muffin cups, filling each about 3/4 full.

Bake 18–22 minutes, rotating the pan once, until the tops spring back and a toothpick inserted into the center comes out clean or with a few moist crumbs.

Cool in the pan for 5 minutes, then transfer muffins to a wire rack to cool completely.

Optional glaze: Whisk powdered sugar with enough reserved pineapple juice to make a drizzle. Spoon over cooled muffins.

Storage: Keep in an airtight container at room temperature up to 3 days or refrigerate up to 1 week. Freeze up to 3 months; thaw at room temperature and warm 10–15 seconds in the microwave if desired.