The secret to this inexpensive home whitening method is malic acid, which acts as an astringent to remove surface discoloration. Combined with baking soda, strawberries become a natural tooth-cleanser, buffing away stains from wine, coffee, and dark sodas. While its no replacement for a bleaching treatment at your dentists office, “this is a fast, cheap way to brighten your smile,” says Adina Carrel, DMD, a dentist in private practice at Manhattan Dental Arts in New York. “Be careful not to use this too often, though, as the acid could damage the enamel on your teeth.”