Also called MMPs, a group of 23 different enzymes that cause substances in the body to break down. Of the 23 types, MMP-1, also known as collagenase, is responsible for the destruction of collagen. Generated primarily by unprotected sun exposure and the aging process, it is also present in sebum (which may be a cause of acne) (Sources: Journal of Investigative Dermatology, October 2005, pages 673–684; Photochemistry and Photobiology, October 2003, pages 355–360; and Photodermatology, Photoimmunology, and Photomedicine, April 2001, pages 178–183).

One of the primary ways to decrease MMPs in skin, particularly MMP-1 is smart sun behavior and use of well-formulated sunscreens. There is also research showing that epigallocatechin-3-gallate (a derivative of green tea), retinoic acid (RA), eicosapentaenoic acid (an omega-3 fatty acid), beta-carotene, DHEA (though this is controversial), polysaccharides, vitamin E, and vitamin C, and flavonoids, to name a few, can inhibit MMPs and increase TIMPs (tissue inhibitors of metalloproteinases; when TIMPs increase in skin, MMPs decrease).