But we obviously know you can be diligent and still develop yellowing. Yellowing and stains happen for two reasons, as we learned here from holistic dentist Mark Burhenne, DDS: The first is intrinsic, which happens with age. The second is the one you have a more active part in: extrinsic, which happens on the enamel. This happens when we consume things like coffee, tea, wine, blueberries, and grapefruit. (These are some of the big culprits; consider swishing your mouth with water after you consume these as it helps keep stains from setting, Burhenne tells us.) Aotto Teeth Whitening Activated Coconut Charcoal Powder ($9); amazon.com White Birch Activated White Charcoal Teeth Whitening Toothpaste, ($13); amazon.com Mr. Brite Mint Natural Whitening Mouthwash ($9); amazon.com GuruNandaOil Pulling Oil ($15); amazon.com Tom’s of Maine Botanically Bright ($8); iherb.com Hello Naturally Whitening Toothpaste ($20 for four); amazon.com Lumineux Oral Essentials Medically Developed Whitening Strips ($50); amazon.com Dr. Ginger’s Coconut Oil Whitening Pen ($20); amazon.com