Past a point, extra vitamin C has nowhere left to go
Plasma fills completely at 1000 mg a day and the white cells that fight infection at 100. Past a single 500 mg dose absorption falls off and the surplus leaves in urine.
What the study found
Vitamin C saturates blood at 1000 mg a day, immune cells at 100
There is a point past which extra vitamin C has nowhere to go. Plasma rises steeply to 100 milligrams a day and fills completely at 1000, while the white cells that fight infection are full at 100. Past a single 500 milligram dose, absorption falls off and the surplus leaves in urine.
The caveat · Seven volunteers on a near-zero diet
This curve was mapped in seven volunteers living in hospital on a near-zero vitamin C diet for four to six months, which buys precision at the cost of a very small and unusual sample. It describes concentrations in blood and cells, not illnesses avoided. The work is thirty years old.