The European food safety authority (EFSA) was unable to derive a safe maximum daily intake due to a lack of data with very high doses of vitamin C.
| In addition to conventional dietary intake, EFSA considers a daily amount of 1,000 mg of vitamin C in the form of supplements to be safe. The amount of 1,000 mg of vitamin C considered safe is 12.5 times the EU recommended daily intake (Nutrient Reference Value, NRV). |
Data from the NVS II (National Nutrition Survey II, 2008) on the daily intake of vitamin C from all sources (conventional diet and dietary supplements) suggest that an unintentional excess of 1,000 mg of vitamin C per day in the German population is unlikely.
Vitamin C is a water-soluble vitamin and excess amounts are usually excreted through the kidneys and intestines.
The so-called LOAEL (Lowest Observed Adverse Effect Level) – the lowest dose of a substance at which adverse effects were just observed – is 3,000 mg vitamin C. Based on the LOAEL of vitamin C, the NOAEL (No Observed Adverse Effect Level) was derived: 2,000 mg of vitamin C is the highest dose that has no detectable and measurable adverse effects even with continued intake.
Accordingly, the RDA for vitamin C is 25 times lower than the highest dose at which no adverse effects were observed.
Adverse effects of excessive vitamin C intake include diarrhea (diarrhea) and increased risk of nephrolithiasis (kidney stone disease) in susceptible individuals (with hyperoxaluria/increased oxalic acid excretion with urine, extensive bowel resection, chronic bowel disease).
Diarrhea occasionally occurred after single doses greater than 3,000 mg in some studies. Only after doses of 10,000 mg (equivalent to 125 times NRV) did osmotically induced diarrhea almost always occur.
In susceptible individuals (with hyperoxaluria, extensive bowel resection, chronic bowel disease), there could be an increased risk of nephrolithiasis with high doses of vitamin C. This is due to an increase in oxalic acid. The reason is increased oxalic acid excretion in the urine. Increased oxalic acid excretion has been found in susceptible individuals at levels of 500 mg vitamin C and above. In contrast, in the healthy population, an increased risk for nephrolithiasis is not expected at high vitamin C intakes (1,500 mg and above).