What happens when you take collagen with vitamin C?
Collagen and vitamin C are biochemically inseparable. Collagen is the most abundant protein in the human body, forming the structural backbone of skin, tendons, ligaments, cartilage, and bone. But the body cannot make functional collagen without vitamin C. Two key enzymes — prolyl hydroxylase and lysyl hydroxylase — use vitamin C as an obligate cofactor to add hydroxyl groups to specific proline and lysine residues on the newly formed collagen chain. These hydroxylations are what allow the three collagen strands to twist into the famously strong triple helix and to crosslink with neighboring helices.
When you take hydrolyzed collagen peptides, you are feeding the body small fragments of the amino acid sequences (especially glycine, proline, and hydroxyproline) that fibroblasts and chondrocytes recognize and use to ramp up their own collagen production. Taking vitamin C at the same time ensures the hydroxylation step is not the rate-limiting bottleneck. The two together turn collagen synthesis into a smoothly running assembly line: peptides supply parts, vitamin C runs the riveting station.
Why is this important?
Vitamin C deficiency causes scurvy precisely because hydroxylation fails and the body cannot maintain its collagen matrix — gums bleed, wounds reopen, bones soften. Even at intakes far above the deficiency threshold, however, adding more vitamin C measurably increases collagen synthesis. A 2018 systematic review in the Journal of the International Society of Sports Nutrition reviewed studies in which subjects ate gelatin (a collagen source) plus vitamin C an hour before exercise — biomarkers of collagen synthesis (specifically the N-terminal propeptide of type I procollagen) rose significantly. In ex vivo engineered ligaments, collagen content and mechanical strength both increased.
For joints, the pair matters because the cartilage matrix is more than 50% collagen by dry weight. Anything that helps chondrocytes regenerate matrix has the potential to slow osteoarthritis progression. For skin, vitamin C also acts independently as an antioxidant, protecting collagen fibers from UV-induced damage and reducing the rate at which existing collagen breaks down.
Multiple randomized trials of collagen peptide products that include vitamin C have shown improvements in skin hydration, elasticity, and wrinkle depth, as well as reductions in joint pain in athletes and older adults. The vitamin C contribution may explain why studies that include it tend to report larger effect sizes than studies of pure collagen alone — though head-to-head data isolating the vitamin C contribution are limited.
What should you do?
For skin and general support, take 10 g of hydrolyzed collagen peptides per day with at least 50 mg of vitamin C. Most clinical trials use 2.5 to 10 g of collagen peptides per day; effects on skin elasticity and dermal density typically become measurable around the 8-week mark.
For tendons, ligaments, and athletic recovery, dose timing matters. The Baar lab at UC Davis showed that 15 g of gelatin or hydrolyzed collagen with 50 mg of vitamin C, taken 30-60 minutes before exercise, doubled circulating glycine and proline at the time of the workout and raised collagen synthesis markers afterward. The pre-exercise window appears to matter because blood flow to tendons is highest during loaded activity, delivering the amino acids and vitamin C exactly when synthesis is being stimulated.
Almost any form of vitamin C works — ascorbic acid, sodium ascorbate, or buffered C are all equally effective for this purpose. There is no need for expensive liposomal or time-released vitamin C unless you have GI sensitivity to plain ascorbic acid. Many collagen powders already include vitamin C in the blend, which is fine, but check the label — some include only token amounts (10-20 mg) that may not be enough.
Which specific products are affected?
Combination products that pair collagen peptides with vitamin C include Vital Proteins Collagen Peptides with vitamin C, Ancient Nutrition Multi Collagen Protein, Garden of Life Grass Fed Collagen Peptides, and Sports Research Collagen Peptides. Marine collagen products from brands like NeoCell and Doctor's Best similarly include vitamin C.
If your current collagen product does not include vitamin C, simply take a standalone vitamin C tablet (500 mg or even 250 mg) at the same time. The cost difference between a vitamin-C-fortified blend and a plain blend plus a separate vitamin C tablet is often substantial — buying them separately can be far cheaper.
For tendon and ligament protocols, gelatin powder is a cheap alternative to hydrolyzed collagen peptides. The amino acid profile is essentially identical, and gelatin's slower digestion means glycine and proline appear in the bloodstream at the same time the exercise is happening. Add vitamin C, stir into juice or coffee, and consume 30-60 minutes before training.
The bottom line
Vitamin C is a required cofactor for the enzymes that build functional collagen, so taking it alongside collagen peptides ensures the building blocks you swallow can actually be assembled into stable triple helices. Use 10 g of hydrolyzed collagen peptides with at least 50 mg of vitamin C daily for skin and joint support, and shift the dose to 30-60 minutes before exercise for tendon and ligament work. Expect skin effects after 8 weeks and joint effects to take longer.