Tips to get enough vitamin C

Vitamin C is essential for our body to work properly, but unlike some other nutrients, the body cannot make it on its own. It is involved in a wide range of important biological processes. Which foods have vitamin C and in what amounts? What is the recommended daily intake, when is it worth supplementing vitamin C and can you overdose on it? We answer these questions in this article.

What will you learn in this article?

1. What foods are rich in vitamin C?
2. Absorption and bioavailability
3. Do I get enough vitamin C from food?
4. Recommended daily intake of vitamin C
5. Maximum dose of vitamin C: can you overdose?
6. What do vitamin C and stress have in common?
7. Tips for getting enough vitamin C and minimizing nutrient losses
8. Key takeaways

Unlike some animals, the human body cannot make vitamin C, as we lost this ability during evolution. It is also water-soluble, so the body excretes any excess in urine. Since we cannot store it either, we need a regular daily supply from food. The recommended daily intake varies by age and sex, from 20 mg for infants to 110 mg a day for adult men ^[1]. However, the real need is very individual and depends on many factors.

What foods are rich in vitamin C?

Great sources of vitamin C include blackcurrants, rose hips, sea buckthorn, gooseberries, red and green peppers, kiwi, broccoli, sorrel, Brussels sprouts, parsley, strawberries, fennel, of course citrus fruits and also tropical acerola, one of the richest natural sources of vitamin C. Just a handful of parsley (about 25 g) can cover roughly 40% of the nutrient reference value (80 mg). That makes it a perfect addition to a morning vegetable juice or a lunchtime basil and parsley pesto.

Vitamin C foods list (raw, per 100 g) ^[2]

The actual content varies with variety, ripeness and storage.

Try to eat as many different types and colours of fruit and vegetables as you can. All fruits and vegetables contain vitamins, minerals and other nutrients that work together and support your health.

Absorption and bioavailability

How well vitamin C is absorbed depends on how much of it we take in. Smaller amounts are absorbed very well, while absorption decreases with larger doses: a single dose of 200 mg is absorbed almost completely, while from 500 mg upwards absorption drops and the body excretes the excess in urine ^[3]. It is therefore best to spread your intake throughout the day.

Vitamin C is very important, but it is also one of the most sensitive nutrients. It is easily degraded by air, light and heat. That is why it is better to cut fruit and vegetables just before eating them. Short cooking at high temperatures is better than long cooking, and it is better to keep the skin on when possible. High temperatures and long cooking times cause particularly severe losses of vitamin C (they can exceed 50%), with boiling in water causing the biggest losses and microwaving the smallest ^[4]. On the other hand, acidity or freezing can help preserve vitamin C in food. Frozen vegetables and fruit should not be thawed before cooking.

Do I get enough vitamin C from food?

If our diet is rich in fruit and vegetables, we can usually cover our daily needs from normal food. But what counts as enough? The World Health Organization (WHO) recommends eating at least 400 g of fruit and vegetables a day ^[5]. The more types and colours you combine on your plate, the better, because the colour of a fruit or vegetable can tell us a lot about the substances it contains. If we want to eat nutrient-rich fruit and vegetables, it is worth choosing quality sources, following the seasons and preferring local food. Fresh papaya, guava and citrus fruits are great sources of vitamin C, but we often do not know how long and in what conditions they travelled to us.

Recommended daily intake of vitamin C

The European Food Safety Authority (EFSA) has set the recommended daily intake of vitamin C at 110 mg for adult men and 95 mg for adult women. During pregnancy, the need increases by 10 mg a day and during breastfeeding by 60 mg a day. Infants aged 7–11 months and children aged 1–3 years need 20 mg a day, and teenagers aged 15–17 years need 90–100 mg ^[1]. The nutrient reference value (NRV) you see on supplement labels is 80 mg.

Vitamin C when you are ill: vitamin C contributes to the normal function of the immune system. A Cochrane review found that regularly taking at least 200 mg of vitamin C a day did not reduce the number of colds in the general population, but it shortened their duration by 8% in adults and 14% in children. In people under heavy physical stress (such as marathon runners), the number of colds was roughly halved. Taking higher doses only after symptoms started had no consistent effect ^[6].

Organic Acerola

Maximum dose of vitamin C: can you overdose?

Vitamin C is water-soluble and the body excretes any excess in urine, so overdosing from food is practically impossible. EFSA has not set an upper intake level for vitamin C because there is not enough data. According to EFSA, however, a supplemental intake of 1,000 mg a day on top of a normal diet is not associated with adverse effects on digestion. Higher doses, in the range of several grams a day, can cause diarrhoea or other digestive problems ^[7]. High single doses are also absorbed less well ^[3].

Caution is advised for people prone to kidney stones: in a Swedish study, men who regularly took high-dose vitamin C supplements (usually 1,000 mg) had about twice the risk of developing kidney stones. This finding does not apply to vitamin C from food ^[8].

What do vitamin C and stress have in common?

Are you exposed to long-term stress or heavy physical activity? Then it is all the more important to protect your cells from negative effects of oxidation and to think more about your intake. Vitamin C contributes to the protection of cells from oxidative stress and to maintaining the normal function of the immune system during and after intense physical exercise. In a study in which healthy adults took 3,000 mg of vitamin C a day for 14 days, participants had a smaller rise in blood pressure during a stress test, felt less stressed, and their levels of the stress hormone cortisol returned to normal faster ^[9]. Higher vitamin C needs apply to smokers (35 mg a day more) ^[10], pregnant and breastfeeding women ^[1], and people with infectious or chronic diseases or malabsorption. Our adrenal glands respond to stress by releasing corticoids such as corticosterone and cortisol. These and other hormones trigger the "fight or flight" response that prepares us for action when we are in danger. They also suppress the immune system, the body's first line of defence against disease. Vitamin C contributes to the normal function of the immune system and to normal psychological function.

Alcohol, caffeine, some medications and heavy metals are other factors that deplete our body's vitamin C levels. If, for any reason, we cannot cover our daily intake of this nutrient from food, a quality dietary supplement is a perfect option, for example natural vitamin C from Organic Acerola.

Tips for getting enough vitamin C and minimizing nutrient losses

• Freshness first: Choose fresh produce from quality, local sources.

• Eat seasonally: Follow the rhythm of nature. It is not only cheaper and more environmentally friendly, but produce harvested when ripe also contains the most nutrients.

• Store properly: Wash fruit and vegetables just before preparing them, not before putting them in the fridge (excess moisture speeds up decay).

• Peel and cut just before use: Do not leave food soaking in water, especially once it is cut (vitamin C is water-soluble).

• Gentle cooking methods: Choose methods without direct contact with water (quick stir-frying, steaming, or at least cooking with the skin on).

Key takeaways

Sources:

[1] EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for vitamin C. EFSA Journal, 2013; 11(11): 3418. https://www.efsa.europa.eu/en/efsajournal/pub/3418

[2] U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. https://fdc.nal.usda.gov/

[3] Levine M, Conry-Cantilena C, Wang Y, Welch RW, Washko PW, Dhariwal KR, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proceedings of the National Academy of Sciences of the USA, 1996; 93(8): 3704–3709. https://doi.org/10.1073/pnas.93.8.3704

[4] Lee S, Choi Y, Jeong HS, Lee J, Sung J. Effect of different cooking methods on the content of vitamins and true retention in selected vegetables. Food Science and Biotechnology, 2018; 27(2): 333–342. https://doi.org/10.1007/s10068-017-0281-1

[5] European Commission, Health Promotion and Disease Prevention Knowledge Gateway. Dietary recommendations for fruit and vegetable intake (WHO recommendation), 2021. https://knowledge4policy.ec.europa.eu/health-promotion-knowledge-gateway/fruit-vegetables-4_en

[6] Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, 2013; Issue 1: CD000980. https://www.cochrane.org/CD000980/ARI_vitamin-c-for-preventing-and-treating-the-common-cold

[7] EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Opinion related to the Tolerable Upper Intake Level of Vitamin C (L-ascorbic acid, its calcium, potassium and sodium salts and L-ascorbyl-6-palmitate). EFSA Journal, 2004; 59: 1–21. https://www.efsa.europa.eu/en/efsajournal/pub/59

[8] Thomas LDK, Elinder CG, Tiselius HG, Wolk A, Åkesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Internal Medicine, 2013; 173(5): 386–388. https://doi.org/10.1001/jamainternmed.2013.2296

[9] Brody S, Preut R, Schommer K, Schürmeyer TH. A randomized controlled trial of high dose ascorbic acid for reduction of blood pressure, cortisol, and subjective responses to psychological stress. Psychopharmacology, 2002; 159(3): 319–324. https://pubmed.ncbi.nlm.nih.gov/11862365/

[10] National Institutes of Health, Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals, 2021. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/