A bunch of studies from 2012 "confirms the ability of copper peptides to improve aging skin conditions, which make them indispensable in anti-aging and protective cosmetic products." Several research theories suggest that "bioactive peptides hold great potential for cancer therapy and diagnostics." Thereby indicating that peptides are safe for topical use
The concept draws from hormesis, a biological phenomenon where low-dose exposure to a substance produces beneficial effects while higher doses might produce neutral or even counterproductive outcomes
Rinkevich, Y., Lindau, P., Ueno, H., Longaker, M
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The most common fermented foods that naturally contain probiotics, or have probiotics added to them, include yogurt, kefir, kombucha, sauerkraut, pickles, miso, tempeh, kimchi, sourdough bread, and some cheeses