5. Baking soda
The jack-of-all-trades of kitchen ingredients: baking soda. This all-purpose wonder can whiten your teeth as well. Mix a few teaspoons of baking soda with some water or lemon juice to make a paste, apply it to your teeth, leave it for a minute and rinse it off. Or you can make the homemade toothpaste found on the previous page, which also uses it as an ingredient.