Vitamin C has mainly three effects on the body. It up-regulates different collagen genes, it’s an antioxidant, and it competes with glucose at the glut-4 receptor. However, vitamin D3, vitamin A (animal: retinol), and vitamin K2 (animal: MK4) also up-regulates these collagen genes and many more, rendering vitamin C unnecessary for collagen production (skin, hair, nails, joints, etc.).
So, you can only get scurvy if you lack these fat-soluble vitamins. If you get these vitamins, and you get none, or very little vitamin C, you will still be fine. The body is not stupid, there are several methylation pathways.
While vitamin C may activate production of collagen, so does vitamin A (retinol) – and retinol will activate other needed enzymes and methylation pathways, which vitamin C cannot do. So, taking a lot of vitamin C will do nothing for proper collagen synthesis if you’re deficient in the animal derived fat-soluble vitamins. And that is why we see rapid aging and deterioration of the skin in vegans after only a year or two. They run out of stored nutrients which their starvation diet cannot supply, and they start to break down.
A high intake of vitamin C while lacking fat-soluble vitamins will lead to skin spots, skin tags, cysts, bumps, and so on; which is simply uncontrolled skin growth and matrix metallopeptidases (MMPs) due to lack of fat-soluble vitamins. These skin conditions are very common in vegans.
Finally, since vitamin C competes with glucose at the glut-4 receptor, and since glucose metabolism release a lot of free radicals; the more carbohydrates you consume, the more vitamin C and other antioxidants you’ll need.
However, if you consume our natural diet, which is based on animal foods, your vitamin C requirement will be negligible and consuming only a few slices of meat will give you more vitamin C than you’ll need.
So, if you have any kind of skin condition – and/or if you actually care about your health, well-being and longevity – make sure to get some liver a couple of times a week, and preferably a lot of muscle meat, some egg yolks, and the occasional aged cheese or raw diary, and you’ll be fine.