FAQ · Collagen
Why is vitamin C taken alongside collagen?
Vitamin C is the essential cofactor for the enzymes that convert ingested collagen and amino acids into structural collagen in your body. Without adequate vitamin C, the hydroxylation steps that stabilise the collagen triple helix do not proceed efficiently. The strongest collagen RCT for tendon outcomes (Shaw 2017) used 15 g hydrolysed collagen plus 50 mg vitamin C taken 60 minutes pre-exercise. Most quality collagen products either include vitamin C or note it as a recommended pairing.
The biochemistry
Collagen synthesis requires proline and lysine to be hydroxylated (an oxygen-adding chemistry step) to form hydroxyproline and hydroxylysine. The enzymes responsible (prolyl hydroxylase and lysyl hydroxylase) use vitamin C (ascorbate) as a redox cofactor. Without adequate vitamin C the hydroxylation is incomplete, the triple helix is unstable, and collagen synthesis fails. This is why scurvy (vitamin C deficiency) causes connective tissue breakdown.
The Shaw 2017 protocol
The strongest RCT on collagen for tendon and connective tissue outcomes (Shaw, Lee-Barthel, Ross, et al. 2017, Am J Clin Nutr): 15 grams of hydrolysed gelatin (effectively the same molecule as hydrolysed collagen) plus 50 mg vitamin C, taken 60 minutes before exercise. The pre-exercise timing matters because exercise-induced blood flow to connective tissue is when the amino acids are most rapidly incorporated.
How much vitamin C
50 to 100 mg per dose is sufficient. The UK RNI (Reference Nutrient Intake) for vitamin C is 40 mg/day; cofactor function for collagen synthesis is well-saturated above 100 mg. There is no benefit to mega-doses (2,000+ mg) for collagen specifically; vitamin C plasma saturation plateaus and excess is excreted.
Products that bundle the two
Several UK collagen brands include vitamin C in the formulation: Gold Collagen Forte, Revive Collagen, Boots Marine Collagen with Vitamin C. Otherwise, a separate vitamin C supplement or vitamin-C-rich food (citrus, kiwi, peppers) at the same time as the collagen is sufficient.
Related: When to take collagen · Best UK marine collagen.