The Vitamin C Problem No One Talks About. Vitamin C is one of the most widely used supplements in the world — and yet, most people are still underdosing, over-acidifying, and barely absorbing it. The reason? Not all vitamin C is created equal. Most products on the market use a cheap, synthetic form of ascorbic acid. It’s highly acidic (with a pH around 2), often causes stomach upset in higher doses, and requires your body to do all the work of buffering and absorbing it. Even worse — its bioavailability can be shockingly low. Studies show that beyond a certain threshold (usually ~200mg), oral ascorbic acid absorption sharply decreases due to limited active transport mechanisms in the gut.