4. Kiwis: Kiwis contain large amounts of water-soluble vitamin C, which is needed to produce collagen. This is a “connective” type of protein which helps to firm your skin. With aging, production of collagen decreases and the skin loses its elasticity. Kiwis are also full of vitamins C and E, which not only fight free radicals, but also help to repair and heal the skin. That’s why you can see many skin care products with kiwi extracts in them.