Here’s a giant list of studies about natural, dietary MMP inhibitors (MMPs – matrix metalloproteinases – are enzymes expressed following UV exposure that break down skin collagen. Preventing over-expression of these will preserve your skin collagen and allow you to enjoy more sunshine.)
Orally Administered Green Tea Polyphenols Prevent Ultraviolet Radiation-Induced Skin Cancer in Mice Through Activation of Cytotoxic T Cells and Inhibition of Angiogenesis in Tumors (2005)
Conclusion: Two groups of hairless mice were UVB-irradiated daily for 10 days and then 3x per week for six months to intentionally initiate and promote skin cancer. One group was given plain water to drink during this time, the other group was given water infused with green tea polyphenols. The green tea group suffered 35% fewer tumors, 63% less tumor multiplicity, and 55% less tumor growth compared to the plain water group. They also experienced reduced expression of matrix metalloproteinases (MMPs), the enzymes that break down skin collagen. “Green tea polyphenols have potential for development as a complementary and alternative medicine to prevent UV-induced nonmelanoma and melanoma skin cancers.”
Green Tea Polyphenols Prevent Ultraviolet Light-Induced Oxidative Damage and Matrix Metalloproteinases Expression in Mouse Skin (2004)
Conclusion: This experiment testing the capability of orally-consumed green tea polyphenols to prevent UV-induced photodamage in mice found that green tea provides a photoprotective effect by inhibiting oxidative damage to skin from sun exposure and also reducing the expression of UV-induced matrix metalloproteinases (MMPs), which cause the breakdown of skin collagen.
Coffea Arabica Extract and its Constituents Prevent Photoaging by Suppressing MMPs Expression and MAP Kinase Pathway (2011)
Conclusion: Coffee leaf extract stimulates collagen expression and inhibits UV-induced expression of matrix metalloproteinases (MMPs), the enzymes responsible for breaking down collagen and elastin in skin.
Photoprotection of UV-Irradiated Human Skin: An Antioxidative Combination of Vitamins E and C, Carotenoids, Selenium and Proanthocyanidins (2002)
Conclusion: Randomized control trial of young women tested out an antioxidant supplement containing carotenoids, vitamin E, vitamin C, selenium, and proanthocyanidin plant polyphenols for it’s effectiveness at reducing post-UV exposure erythema (sunburn) and matrix metalloproteinases expression (enzyme responsible for skin collagen breakdown). The treatment group demonstrated slower and less-severe sunburn development compared to the placebo group and reduced expression of matrix metalloproteinases.
Molecular Evidence That Oral Supplementation with Lycopene or Lutein Protects Human Skin Against Ultraviolet Radiation: Results from a Double‐Blinded, Placebo‐Controlled, Crossover Study (2016)
Conclusion: Randomized control trial found that lycopene supplementation can completely suppress post-UV exposure expression of matrix metalloproteinases, the enzymes responsible for skin collagen breakdown.
Note: Comprehensive article explaining the mechanisms through which fish-source omega-3 and omega-6 fatty acids support skin repair and photoprotection by increasing ceramide production (the glue that holds your skin cells together), inhibiting expression of matrix metalloproteinases (UV-stimulated enzymes the break down skin collagen), reducing inflammation, increasing people’s minum erythemal dose (sunburning threshold), improving skin hydration, improving skin wound healing, and deterring skin cancer development.
Dietary Aloe Vera
Conclusion: Hairless mice were given an oral aloe vera supplement and exposed to UVB irradiation for 7 weeks to evaluate the ability of dietary aloe vera to protect against photoaging. Researchers found that the aloe vera supplement was effective for improving post-UVB exposure skin dryness and wrinkle formation and reduced post-UVB skin collagen degeneration by reducing expression of matrix metalloproteinases, the enzymes responsible for skin collagen breakdown.
Oral Administration of Aloe Vera Gel Powder Prevents UVB-Induced Decrease in Skin Elasticity via Suppression of Overexpression of MMPs in Hairless Mice (2016)
Conclusion: Hairless mice were given an oral aloe vera supplement for 8 weeks and subjected to UVB irradiation for 6 of those weeks to test the photoprotective effects of dietary aloe vera. Researchers found that the aloe vera supplement was significantly effective for reducing post-UVB exposure reduction in skin elasticity and that this is because the supplement effectively reduced expression of matrix metalloproteinases, the enzymes responsible for skin collagen breakdown. These effects were not observed in a control group that received UVB irradiation, but no aloe vera supplement.
Dietary Aloe Vera Supplementation Improves Facial Wrinkles and Elasticity and It Increases the Type I Procollagen Gene Expression in Human Skin in vivo (2009)
Conclusion: 30 older women were given either a low dose or high dose of an oral aloe vera gel supplement for 90 days. The results were that facial wrinkles improved significantly, facial skin elasticity improved, collagen levels increased, and MMP levels decreased. “In this study, we found that aloe vera gel supplementation clinically improved facial wrinkles and elasticity, while it increased type I procollagen and it decreased the MMP-1 gene expressions in the photoprotected skin.”
Effects of Collagen Tripeptide Supplement on Photoaging and Epidermal Skin Barrier in UVB-exposed Hairless Mice (2012)
Conclusion: To test the ability of oral fish collagen supplements to heal photodamage, scientists induced UVB photodamage in groups of hairless mice for 14 weeks. Two groups received the collagen supplements during this time and the other groups did not. The collagen groups enjoyed fewer wrinkles, better skin hydration, less sunburn, increased skin elasticity, and reduced expression of matrix metalloproteinases (MMPs), the enzymes responsible for skin collagen breakdown.
Conclusion: Technical article explaining how astaxanthin protects against photodamage by reducing expression of matrix metalloproteinases, the enzymes responsible for post-UV exposure skin collagen breakdown.
Conclusion: Randomized control trial tested the effectiveness of oral astaxanthin for skin photoprotection. 65 women were split into three groups where they were given either a placebo, 6mg astaxanthin supplement (low dose), or 12mg astaxanthin supplement (high dose) daily for 4 months. Skin samples were taken from the participants and studied in vitro for changes in UV-response. The skin sample observations found that astaxanthin was effective for reducing expression of matrix-metalloproteinases (MMPs, the enzymes responsible for skin collagen breakdown).
Enriched Astaxanthin Extract from Haematococcus pluvialis Augments Growth Factor Secretions to Increase Cell Proliferation and Induces MMP1 Degradation to Enhance Collagen Production in Human Dermal Fibroblasts (2016)
Conclusion: In vitro study found that application of astaxanthin to human skin samples reduces expression of matrix metalloproteinases, the enzymes responsible for post-UV exposure skin collagen breakdown.
Also see studies on
Dietary Sunburn Prevention
Dietary Skin Cancer Prevention