Intake of > 2 g of vitamin C a day may cause nausea and diarrhea, interfere with the healthy antioxidant–pro-oxidant balance in the body, and, in patients with thalassemia or hemochromatosis, promote iron overload.
Vitamin C plays a role in collagen, carnitine, hormone, and amino acid formation. It is essential for bone and blood vessel health and wound healing and facilitates recovery from burns. Vitamin C is also an antioxidant, supports immune function, and may facilitate the absorption of iron (see table ).
Dietary sources of vitamin C include citrus fruits, tomatoes, potatoes, broccoli, strawberries, and sweet peppers.
The upper limit for vitamin C intake is 2000 mg (2 g)/day.
Up to 10 g/day of vitamin C is sometimes taken for unproven health benefits, such as slowing or reversing the progression of cancer or atherosclerosis or preventing or shortening the duration of viral infections such as the common cold (1). Such doses may acidify the urine, cause nausea and diarrhea, interfere with the healthy antioxidant–pro-oxidant balance in the body, and, in patients with thalassemia or hemochromatosis, promote iron overload. High doses of vitamin C may also cause hyperoxaluria, which may contribute to the formation of calcium oxalate renal stones.
Intake of vitamin C below the upper limit does not have toxic effects in healthy adults.
Reference
1. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;2013(1):CD000980. Published 2013 Jan 31. doi:10.1002/14651858.CD000980.pub
