What's Really Causing Your Skin to Age? (Part 1 - Skin Age)

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• Matrix metalloproteinases are the mechanism most people have never heard of, and they are not inherently harmful. MMPs exist to remodel and repair tissue after injury — the problem is overactivation by UV exposure, pollution, oxidative stress and inflammation. MMP-1, MMP-2 and MMP-9 are particularly implicated in breaking down collagen and elastin. Dr. Lin's image is a construction crew given more energy than work, which starts demolishing the building to stay busy.
• Advanced glycation end products stiffen the fibres directly. When sugar binds to proteins and lipids, the resulting products make elastic fibres brittle and less elastic — she compares it to a soft springy sponge that gets coated in syrup and hardens. The elastic fibres themselves also degenerate structurally with age, becoming thicker, more curved and fragmented so they no longer fit together well enough to snap back.
• Collagen supplements do not work the way the marketing implies, and the actual mechanism is more interesting. Eaten collagen is digested like any protein — it does not travel intact to your skin. What happens is that it breaks into bioactive dipeptides, principally prolyl-hydroxyproline and hydroxyprolyl-glycine, which are absorbed into the bloodstream, reach the dermis and stimulate fibroblasts to produce more collagen and elastin. Studies show increased expression of collagen type I and elastin genes in human dermal fibroblasts treated with collagen peptides, and the peptides additionally inhibit MMPs.
• The dose and duration matter more than the brand: 2.5 to 10 g of hydrolysed collagen peptides daily for at least three months is what the studies use, with improvements in hydration, elasticity, appearance and wrinkles. On whether collagen beats ordinary protein, Dr. Lin's honest answer is that general protein is excellent for overall health, and collagen's advantage is containing specific bioactive peptides aimed at skin — plus being pre-broken-down and therefore easier to digest for people who struggle with large protein loads.
• The strongest sun protection evidence is a randomised controlled trial that ran four and a half years, in which daily broad-spectrum sunscreen users showed 24% less skin aging than those applying it less regularly. The spectrum matters: UVB causes sunburn and superficial DNA damage driving skin cancer risk, while UVA penetrates deeper and directly breaks down collagen and elastin, making it the major contributor to premature aging and wrinkles. Visible light and short infrared also contribute oxidative stress, which is what broad spectrum is for.
• Dr. Lin prefers mineral over chemical sunblock, and her reasoning is about uncertainty rather than proven harm. Mineral formulations sit on top of the skin rather than being absorbed, which sidesteps the unresolved questions about chemical filters entirely. She also discloses a personal reason — chemical sunscreens caused her eye sensitivity problems — and notes the better mineral formulations now avoid the white cast, with tinted versions offering slight colour correction. Her bigger point is that clothing, shade and avoiding peak hours between roughly 10am and 4pm remain more effective than any product.
• Resistance training improves skin measurably, which is not how most people think about lifting. Studies show it increases circulation delivering oxygen and nutrients to skin, boosts dermal thickness, stimulates collagen and elastin production, and reduces inflammation. Aerobic work contributes through circulation and reduced oxidative stress. Dr. Lin's framing is that skin responds to controlled challenge the same way muscle and brain do.
• Topical hydration works through humectants that pull water in rather than seal it. Glycerol draws water from the environment or from deeper skin layers, and hyaluronic acid — naturally present in the body — can hold up to a thousand times its weight in water, which is what keeps skin plump and firm. A 12-week study of 120 mg of oral hyaluronic acid also showed significant improvements in elasticity, hydration and wrinkles, and injections improve skin quality without adding much volume, lasting up to a year.
• Vitamin A is the most established topical intervention and the one requiring the most care. Retinoids drive cell turnover and boost collagen production, with prescription tretinoin more potent than over-the-counter forms — and a pea-sized amount covers the entire face, since overuse causes retinoid burn and the delicate skin around the eyes should be avoided. The oral versions carry real risk: isotretinoin requires blood monitoring and strict pregnancy precautions because it is teratogenic, and can cause liver inflammation and disordered triglycerides. Retinoids also increase UV sensitivity, so skipping sunscreen while using them can produce worse outcomes than not using them at all.
• Her vitamin C caveat is about chemistry rather than efficacy. She describes having been dismissive of vitamin C serums before concluding they do penetrate deeply enough to act as an antioxidant and support collagen synthesis. But vitamin C degrades almost immediately on air exposure — so a large tub of vitamin C moisturiser has likely lost its active ingredient long before you finish it. She prefers single-use vials, while acknowledging the expense and waste.
• Her general position is food over pills, with specific reasons. Fat-soluble vitamins are the ones you can overdo — vitamin E in larger capsule doses raises bleeding risk, niacinamide can cause flushing and stomach upset, and high-dose beta-carotene has been associated with increased lung cancer risk in smokers, with excess producing harmless but visible orange-yellow carotenemia. Her actual recommendations are collagen peptides or whole protein, omega-3s, probiotics, and topical hyaluronic acid, with vitamin D as the supplement she does endorse — alongside a cautionary case of a patient who reached the cardiac ICU with heart block from over-supplementation.

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