Vitamins · 4 min read ·

Vitamin C: more is not better

The body needs vitamin C to make collagen, and it is an important antioxidant. Fruit and vegetables usually give you enough — and large doses from tablets mostly leave in the urine.

C

In a nutshell

1What it does and how much you need

The body needs vitamin C to make collagen, carnitine and some hormones and nerve messengers, and it is also an antioxidant. A long-term deficiency leads to scurvy; but as little as 10 mg a day prevents it.1

EFSA recommendation 110 / 95 mg EFSA recommends 110 mg of vitamin C a day for men and 95 mg for women, 10 mg more in pregnancy and 60 mg more when breastfeeding. At an intake of about 100 mg a day, about 80% is absorbed.1
EFSA recommendation 50 µmol/L A blood level of 50 µmol/L means you have enough vitamin C. Above an intake of 100 mg a day the level rises only slowly, and the ceiling of about 70–80 µmol/L is kept only by long-term doses above 200 mg a day.1

2Where to find it

Data 184 mg A hundred grams of yellow pepper have 184 mg of vitamin C, red pepper 128 mg, kiwi 93 mg, raw broccoli 89 mg and strawberries 59 mg. In Europe, most vitamin C comes from fruit, vegetables, juices and potatoes.1,3

3Forms and absorption

Weak evidence — a small study 200 mg Seven volunteers spent 4–6 months in hospital on a diet almost free of vitamin C and were given various doses. A single 200 mg dose was absorbed completely; less was absorbed from doses of 500 mg and above, and the body excreted even that in the urine. White blood cells were saturated with vitamin C already at 100 mg a day.4
Moderate evidence — a review the same A review of studies: in all longer-term human studies, synthetic vitamin C (ascorbic acid) was absorbed just as well as vitamin C from fruit and vegetables.5
Weak evidence — a small study 4 g Liposomal vitamin C (wrapped in fatty droplets) raised blood levels more than the same 4 g dose in the ordinary form, but less than an intravenous dose. The study had 11 people and tested only one large single dose.6

In the EU, supplements may contain vitamin C as L-ascorbic acid, as sodium, calcium, potassium, magnesium or zinc ascorbate, and as ascorbyl palmitate.7

4Sport and kidney stones

Weak evidence — one study 11 weeks In a randomised study of 54 people, endurance trainees took 1,000 mg of vitamin C and 235 mg of vitamin E a day, or placebo, for 11 weeks. Maximal oxygen uptake and performance improved equally, but with the vitamins the muscles did not gain the markers of new mitochondria seen with placebo.8
Moderate evidence — large observational studies +43% In a follow-up of 40,536 men, those taking in 1,000 mg of vitamin C a day or more had a 43% higher risk of kidney stones than men with less than 90 mg. This was not seen in 156,735 women.9

EFSA has not set an upper level for vitamin C because there are not enough data.2 Whether vitamin C helps with colds is covered in the article Vitamins.

What to take from this

Sources

Written on , based on studies available at that date. Newer research may change the conclusions.

  1. EFSA NDA Panel (2013). Scientific Opinion on Dietary Reference Values for vitamin C. EFSA Journal 11:3418. doi.org/10.2903/j.efsa.2013.3418
  2. EFSA (2025). Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Nutrition (version 11). efsa.europa.eu
  3. USDA ARS (2018). FoodData Central — SR Legacy, vitamin C per 100 g: yellow bell pepper 183.5 mg (FDC 169383), red bell pepper 127.7 mg (FDC 170108), kiwi 92.7 mg (FDC 168153), broccoli, raw 89.2 mg (FDC 170379), strawberries 58.8 mg (FDC 167762). fdc.nal.usda.gov
  4. Levine M. et al. (1996). Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci USA 93:3704–3709. doi.org/10.1073/pnas.93.8.3704
  5. Carr A. C., Vissers M. C. (2013). Synthetic or food-derived vitamin C — are they equally bioavailable? Nutrients 5:4284–4304. doi.org/10.3390/nu5114284
  6. Davis J. L. et al. (2016). Liposomal-encapsulated ascorbic acid: influence on vitamin C bioavailability and capacity to protect against ischemia-reperfusion injury. Nutr Metab Insights 9:25–30. doi.org/10.4137/NMI.S39764
  7. Directive 2002/46/EC on food supplements, Annex II — forms of vitamins and minerals permitted in supplements (consolidated version 26 Nov 2025). eur-lex.europa.eu
  8. Paulsen G. et al. (2014). Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial. J Physiol 592:1887–1901. doi.org/10.1113/jphysiol.2013.267419
  9. Ferraro P. M. et al. (2016). Total, dietary, and supplemental vitamin C intake and risk of incident kidney stones. Am J Kidney Dis 67:400–407. doi.org/10.1053/j.ajkd.2015.09.005

This is general information and does not replace a doctor. Have kidney stones or kidney disease? Talk to a doctor about high doses of vitamin C.