Vitamin C
Vitamin C (ascorbic acid) is the vitamin the body needs to make collagen and to absorb iron from plants. Adults need 75 to 90 mg a day, a single orange gives about that, and a red bell pepper about twice as much.
75-90 mga day for adults, US RDA
80 mg on EU food labels (NRV), the figure behind label percentages
Upper limit · 2,000 mg a day (US); EFSA set none
- Most per 100 g 228mg Guava
- Most per portion 169mg 1 medium bell pepper
- Main sources Peppers, citrus and berries then broccoli, cabbage and potatoes
- Absorbed 70 - 90% at usual intakes; under 50% above 1 g
Daily amount: the US RDA for adults aged 19 and over (NIH). Smokers need 35 mg more. Food figures per 100 g from USDA FoodData Central.
Foods High in Vitamin C
Ranked per 100 g, with what a usual portion gives, limited to 3 foods per category. Foods with a Caltide calorie page link to it.
G
Guava
126 mg in 1 fruit
228mg / 100 g
R
Red currants
203 mg in 1 cup
181mg / 100 g
A
Ataulfo mango
168mg / 100 g
O
Orange bell pepper
158mg / 100 g
B
Brussels sprouts
143mg / 100 g
B
Bell pepper
169 mg in 1 medium
Nutrition facts
142mg / 100 g
S
Sweetbreads
74 mg in 1 pair
39.1mg / 100 g
O
Orange juice
38 mg in 1 fun size box
Nutrition facts
30.1mg / 100 g
C
Chestnuts
26mg / 100 g
C
Chicken liver
20 mg in 4 oz
17.9mg / 100 g
A
Agave syrup
3.4 mg in 1 tablespoon
17mg / 100 g
A
Arugula
15mg / 100 g
Per 100 g vs. a Usual Portion
Why the food that ranks first per 100 g can give less in a real serving.
| Food | Usual portion | Per 100 g | Per portion |
|---|---|---|---|
| Bell pepper | 1 medium (119 g) | 142mg | 169mg |
| Orange | 1 fruit (154 g) | 56.2mg | 87mg |
| Kiwi | 1 medium (69 g) | 58.8mg | 41mg |
| Strawberries | 1 cup (152 g) | 59.6mg | 91mg |
| Broccoli | 1 cup (76 g) | 91.3mg | 69mg |
| Potato | 1 medium (200 g) | 12.7mg | 25mg |
Citrus has the reputation, but one red bell pepper gives 169 mg against 87 mg in an orange. Even a boiled potato, rarely thought of as a vitamin C food, adds a useful amount because people eat a lot of it.
What Is Vitamin C?
Most animals make their own vitamin C from glucose. Humans cannot, because the gene for the last enzyme in that pathway stopped working in human ancestors. So every milligram has to come from food or supplements, and the body keeps only a modest reserve.
What Vitamin C Does
Its best-known job is building collagen, the protein that holds together skin, gums, blood vessels, tendons and bone. Two enzymes that finish collagen fibers need vitamin C to work, so without it new collagen is weak. This is why scurvy brings bleeding gums and wounds that will not heal.
Vitamin C is also needed to make carnitine, which carries fat into cells to be burned, and some brain signaling chemicals. It is a water-soluble antioxidant, and it helps restore vitamin E after vitamin E has neutralized a free radical.
The effect people can use most directly is on iron. Vitamin C in the same meal turns the iron in beans, grains and greens into a form the gut absorbs more easily. Heme iron from meat and fish is absorbed well without it.
Vitamin C in a Day of Food Without Citrus
One ordinary day built only from foods in the Caltide food library, in usual portions, with no orange, juice or supplement. Vegetables at dinner carry it.
| Meal | Food | Amount | Vitamin C |
|---|---|---|---|
| Breakfast | Oats | 40g | 0mg |
| Breakfast | Banana | 120g | 14mg |
| Lunch | Tomatoes | 123g | 20mg |
| Lunch | Rice | 160g | 0mg |
| Snack | Apple | 165g | 7.6mg |
| Dinner | Chicken breast | 135g | 0mg |
| Dinner | Potato | 200g | 25mg |
| Dinner | Broccoli | 76g | 69mg |
| Total | 136mg |
How Cooking and Storage Reduce Vitamin C
Vitamin C is one of the most fragile vitamins in food. It dissolves in cooking water and breaks down with heat, air and time in storage. Steaming and microwaving keep more of it than boiling, and the water from boiled vegetables carries away part of what was there. Library figures for raw foods are the upper end of what reaches the plate.
Common Vitamin C Mistakes
Taking more to absorb more. The gut absorbs 70 to 90% of vitamin C at intakes of 30 to 180 mg a day. Above 1 g, it takes up less than half, and the kidneys pass the excess into urine. Large doses mostly raise what leaves the body.
Starting it when a cold begins. In reviews of trials, taking vitamin C only after symptoms started did not reliably shorten colds. The small benefit seen came from taking it every day beforehand.
Forgetting that smoking raises the need. Smoking uses up vitamin C faster, so the US adds 35 mg a day for smokers. People exposed to secondhand smoke also tend to have lower levels.
Vitamin C Supplements and Who Should Be Careful
Supplements are also a source of vitamin C, in multivitamins and on their own, often at many times the daily amount.
Vitamin C Forms on Supplement Labels
Ascorbic acid is the standard form and the same molecule as in fruit. Sodium ascorbate and calcium ascorbate are buffered forms, less acidic in the stomach, and add a little sodium or calcium. None of them has been shown to be absorbed better than plain ascorbic acid.
When to Ask a Doctor About Vitamin C Supplements
- You have hemochromatosisextra vitamin C raises iron absorption, which can worsen iron overload
- You are having cancer treatmentit is unclear whether antioxidant supplements interfere with chemotherapy or radiation
- You have had kidney stoneshigh doses may raise oxalate in urine
Sources: NIH Office of Dietary Supplements, EFSA. Not medical advice.
Vitamin C in Caltide
- Logged automaticallyCaltide adds up the vitamin C in every food you log from the food library and shows it against the amount for your age and sex in the Nutrition tab.
- Supplements count tooAdd your tablet once with its milligrams of vitamin C as an ingredient. Each day you tick it off, it counts toward your total.
Vitamin C Sources and References
The figures and claims on this page are checked against these sources. Food amounts come from USDA FoodData Central.
Questions About Vitamin C
The US sets 90 mg a day for men and 75 mg for women, plus 35 mg for smokers. EFSA sets 110 mg for men and 95 mg for women, and the EU label reference is 80 mg.
In the Caltide food library, guava: 228 mg per 100 g, then Red currants (181 mg) and Ataulfo mango (168 mg). An orange has 56.2 mg per 100 g, well behind a red bell pepper.
Not for most people. Taking at least 200 mg a day did not lower how often people caught colds in reviews of trials, but shortened colds a little, by about 8% in adults. In people under heavy physical stress, such as marathon runners, it halved the risk of a cold.
Yes, the iron in plant foods. Eaten in the same meal, vitamin C turns plant (non-heme) iron into a form the gut absorbs more easily, so peppers with beans or orange with fortified cereal help.
The US upper limit is 2,000 mg a day for adults. Above it, vitamin C can cause diarrhea, nausea and stomach cramps, because the gut absorbs less and the rest draws water into the bowel. EFSA set no upper limit.
Partly. Vitamin C dissolves in water and breaks down with heat and long storage, so steaming or microwaving vegetables keeps more of it than boiling. Raw fruit and vegetables keep the most.
The disease of severe vitamin C deficiency. It can begin after about a month of less than 10 mg a day, with tiredness, swollen and bleeding gums, small red spots on the skin, joint pain and wounds that heal slowly.
No. The ascorbic acid in food and in supplements is the same molecule, and the body absorbs both about equally. Buffered forms such as sodium or calcium ascorbate add a mineral but have not been shown to work better.
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