In 30 seconds
- EFSA sets a reference intake of 110 mg a day for men and 95 mg for women. Exercise does not change that official figure.
- A medium orange provides about 70 mg and half a cup of raw red pepper about 95 mg: with fruit and vegetables every day, you get there easily.
- In a meta-analysis of 18 trials, 400-3,000 mg of vitamin C before exercise reduced markers of oxidative stress over the following 2 hours.
- Megadoses do not improve performance: with 1,000 mg a day for 11 weeks, VO2max improved just as much as with placebo.
If you exercise, you need the same vitamin C as other adults: 110 mg a day if you are a man and 95 mg if you are a woman, according to EFSA. Fruit and vegetables cover it easily, and studies find no performance advantage in megadoses.
What vitamin C does
It is a vitamin that dissolves in water and that your body stores in small amounts: between about 300 mg and 2 g in total 2. That is why it is a good idea to get it every day.
European legislation recognises these functions, among others 7:
- Vitamin C contributes to the normal function of the immune system.
- Riboflavin (vitamin B2), vitamins B6, B12 and C, niacin, pantothenic acid and folate contribute to the reduction of tiredness and fatigue.
A varied and balanced diet and a healthy lifestyle are important.
It is also an antioxidant, which accounts for much of the interest it attracts in sport.
How much you need
The European Food Safety Authority calculated how much is needed to maintain good stores in the body 1:
| Reference intake | |
|---|---|
| Men | 110 mg |
| Women | 95 mg |
| Pregnancy | 105 mg |
| Breastfeeding | 155 mg |
Source: EFSA, 2013. Population reference intake for adults.
If you smoke, you need more: the US reference adds 35 mg a day for smokers 2.
Where to find it
In fruit and vegetables, especially raw ones 2:
| Food and portion | Vitamin C |
|---|---|
| Raw red pepper, half a cup | 95 mg |
| Orange juice, a small glass (about 180 ml) | 93 mg |
| Medium orange | 70 mg |
| Medium kiwi | 64 mg |
| Cooked broccoli, half a cup | 51 mg |
| Sliced strawberries, half a cup | 49 mg |
Source: Office of Dietary Supplements (NIH). Cooking and storing food for a long time reduces its vitamin C.
An example of an ordinary day: an orange, a kiwi and a salad with red pepper add up to more than 200 mg. Bear in mind that cooking and storing food for a long time reduces its vitamin C 2.
How much you use
Above a certain amount, it barely adds anything
Do you need more if you exercise?
The official reference is the same. What does change is that, if you do a lot of exercise, research has looked at whether extra vitamin C changes anything in your immune defences or your recovery.
A useful fact before going on: with about 100 mg a day your cells are already practically saturated, and above 200 mg the level in your blood barely rises 2. With moderate amounts, from 30 to 180 mg, you absorb 70-90%; above 1 g, less than half 2.
Vitamin C and immune defences: what the studies say
Vitamin C contributes to the normal function of the immune system 7. Beyond that function, the Cochrane review brought together the placebo-controlled trials that used at least 200 mg a day, many of them with people under extreme physical loads, such as marathon runners, skiers and soldiers on subarctic exercises 3.
We cover it in detail in vitamin C and exercise: what the studies say.
Vitamin C and recovery
A meta-analysis of 18 trials with 313 people tested doses of 400 to 3,000 mg before an exercise session 5. Vitamin C reduced markers of oxidative stress in the following 2 hours and the rise in a signal of inflammation, IL-6.
What did not change: muscle soreness, markers of muscle damage or loss of strength 5.
Vitamin C a day
What you need, compared with a megadose
You do not need megadoses
More is not better. In one trial, 54 men and women trained for 11 weeks, mainly by running. Half of them took 1,000 mg of vitamin C and 235 mg of vitamin E a day 4.
VO2max and running performance improved just as much as with placebo. But markers of new mitochondria formation, the muscle's “power stations”, only rose in the group without supplements 4.
According to the summary by the US National Institutes of Health, the free radicals produced by exercise also seem to act as a signal for muscle to adapt, and high doses of antioxidants may dampen that signal 6. The vitamin C you need is your daily reference amount, not megadoses.
How to cover it without thinking
- Fruit every day: an orange or a kiwi already gives you 64-70 mg 2.
- Raw vegetables: peppers, in a salad or as crudités, are among the richest sources 2.
- At breakfast: a small glass of orange juice adds more than 90 mg 2.
- If you eat little fruit and veg: start by adding one piece a day; it is the simplest way to raise your vitamin C.
Can you take too much?
Any excess is passed out in urine. In very high doses it can cause diarrhoea, nausea or stomach discomfort, and the US reference sets the maximum for adults at 2,000 mg a day 2. If you have had kidney stones, check with your doctor before taking supplements.
The vitamin C in Nitrus
Each serving of Nitrus Isotonic provides 80 mg of vitamin C, 100% of the NRV, together with the other 12 vitamins, five electrolytes, BCAAs and taurine.
Vitamin C contributes to the normal function of the immune system. Riboflavin (vitamin B2), vitamins B6, B12 and C, niacin, pantothenic acid and folate contribute to the reduction of tiredness and fatigue. If you want to know more about the B vitamins, you will find it in B vitamins, energy and tiredness.
Frequently asked questions
How much vitamin C do I need a day if I exercise?
EFSA's reference is 110 mg a day for men and 95 mg for women, and it does not change with exercise. You can cover it with a couple of pieces of fruit and some vegetables a day.
Which foods have the most vitamin C?
Above all, raw fruit and vegetables: half a cup of raw red pepper provides about 95 mg, a medium orange about 70 mg and a kiwi about 64 mg.
Is it bad to take a lot of vitamin C?
Any excess is passed out in urine, but very high doses can cause digestive discomfort. The US reference sets the maximum at 2,000 mg a day. If you have had kidney stones, check with your doctor.
Does vitamin C help you recover after training?
In 18 trials it reduced markers of oxidative stress and inflammation in the hours after exercise, but it did not change muscle soreness, muscle damage or loss of strength.
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific opinion on dietary reference values for vitamin C. EFSA Journal. 2013;11(11):3418. View publication
- Office of Dietary Supplements, National Institutes of Health. Vitamin C: fact sheet for health professionals. Updated 31 July 2025. View publication
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1):CD000980. View publication
- Paulsen G, Cumming KT, Holden G, et al. Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial. J Physiol. 2014;592(8):1887-1901. View publication
- Righi NC, Schuch FB, De Nardi AT, et al. Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials. Eur J Nutr. 2020;59(7):2827-2839. View publication
- Office of Dietary Supplements, National Institutes of Health. Dietary supplements for exercise and athletic performance: fact sheet for health professionals. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
