Vitamin A vs Vitamin C: Key Differences

Quick answer

Vitamin A is fat-soluble and stored mostly in the liver; vitamin C is water-soluble and mostly passed in urine. Adults need 700 to 900 mcg RAE of vitamin A and 75 to 90 mg of vitamin C a day. Upper limits: 3,000 mcg a day of preformed vitamin A, 2,000 mg of vitamin C.^1,2

Key facts

Vitamin A is counted in mcg RAE: 1 mcg RAE equals 1 mcg of retinol or 2 mcg of beta-carotene from supplements. Vitamin C is counted in plain mg.^1,2
The body stores the excess of vitamin A, mostly in the liver, where it can build up. It holds only about 300 mg to 2 g of vitamin C.^1,2
The body absorbs 70% to 90% of the preformed vitamin A in supplements. For vitamin C the share is similar at 30 to 180 mg a day but falls below half above 1 g a day.^1,2
Only the preformed share of vitamin A counts toward its upper limit, and beta-carotene has none. Vitamin C has a single limit of 2,000 mg a day from food and supplements combined.^1,3
Both have EU-permitted statements for normal immune function. Vitamin A's covers normal skin and mucous membranes, and vitamin C's covers collagen formation for the normal function of skin.^4,5

Two different ways the body handles a vitamin

The most useful difference is solubility. Vitamin A dissolves in fat and is kept mainly in the liver. Vitamin C dissolves in water, and what the body cannot use leaves in urine. That single fact explains why their upper limits, and the problems that come with taking too much, look so different.^1,2

Because vitamin A is fat soluble, the body stores the excess, mostly in the liver, and the amount stored can build up.¹

The body holds about 300 mg to 2 g of vitamin C. White blood cells, the eyes, the adrenal and pituitary glands and the brain hold the highest concentrations.²

About 70% to 90% of vitamin C is absorbed at intakes of 30 to 180 mg a day. Above 1 g a day, less than half is absorbed, and the absorbed excess is passed in urine.²

What each one does

The two vitamins meet in a few places, notably immune function and skin, but they arrive by different routes. The statements below are quoted with their grades, and the skin entries are the ones to read most closely.

Contributes to the maintenance of normal skin and mucous membranes*^1,4

Moderate evidence

Both are on the EU list of permitted nutrient-function statements for vitamin A, after EFSA review, and NIH describes vitamin A's role in normal cell growth and specialization. They are about getting enough. They are not evidence that extra vitamin A from supplements changes how skin looks, and regular high intakes of preformed vitamin A can dry the skin. Retinoid creams and prescription retinoids are different products and are not covered by these statements.

Amount studied: The recommended intake: 900 mcg RAE a day for men and 700 mcg RAE for women, from food and supplements together

Contributes to normal collagen formation for the normal function of skin, gums, teeth, bones, cartilage and blood vessels*^2,5,6

Moderate evidence

A well-established nutrient function. NIH states that vitamin C is required to make collagen, an essential part of connective tissue, and EU regulators permit this wording, as six separate statements, for foods that are at least a source of vitamin C. Normal skin holds high levels of vitamin C. The claim describes what the body needs vitamin C for. It does not show that extra vitamin C changes how skin looks in someone who already gets enough, and how creams and serums compare with getting enough in the diet is poorly understood.

Amount studied: Recommended intake: 75 mg a day for women and 90 mg for men, from food and supplements

May raise the antioxidant activity measured in skin*⁷

Early evidence

One small placebo-controlled trial. Thirty-three volunteers took vitamin C or a placebo for four weeks, and the skin's ability to neutralize free radicals was measured with a magnetic resonance method. It rose 22% with 100 mg a day and 37% with 180 mg a day, and did not change with placebo. In the people also measured at two weeks, the rise had already reached its peak. It is one study of a laboratory measure, not of how skin looks or ages.

Amount studied: 100 or 180 mg a day for four weeks

Contributes to the normal function of the immune system*^1,4

Moderate evidence

NIH describes vitamin A as involved in immune function, and the EU permits this wording, after EFSA review, for foods that are at least a source of vitamin A. The illness research NIH summarizes was done in young children in low-income countries who were short of vitamin A, so it does not show that extra vitamin A helps well-fed adults. The statement is about getting enough.

Amount studied: The recommended intake: 900 mcg RAE a day for men and 700 mcg RAE for women, from food and supplements together

Contributes to the normal function of the immune system*^2,5,8,9

Moderate evidence

A well-established nutrient function. NIH describes roles for vitamin C in both the first-line and the learned parts of the immune system: it helps keep barrier tissues intact and helps white blood cells multiply and do their work, and these cells hold far more vitamin C than blood does. EU regulators permit this wording for foods that are at least a source of vitamin C. It is about getting enough. NIH notes that when people are not short of a nutrient, routine supplements probably add little, and most people in the United States get enough vitamin C from food.

Amount studied: Recommended intake: 75 mg a day for women and 90 mg for men, from food and supplements

Contributes to the maintenance of normal vision*^1,4,10

Moderate evidence

A long-established role of the vitamin. NIH describes vitamin A as an essential part of rhodopsin, the light-sensitive protein in the retina, and as needed for the normal working of the cornea and the membranes that cover the eye. The EU list of permitted nutrient-function statements, based on reviews by the European Food Safety Authority (EFSA), includes this wording for foods that are at least a source of vitamin A. It describes what getting enough does; it is not a finding that extra vitamin A changes eyesight in people who already get enough.

Amount studied: The recommended intake: 900 mcg RAE a day for men and 700 mcg RAE for women, from food and supplements together

Increases iron absorption*^2,5,11,12

Moderate evidence

A well-established nutrient function, permitted in this wording by EU regulators for foods that are at least a source of vitamin C. NIH says vitamin C raises absorption of nonheme iron, the form in plant foods and fortified foods, and that mixed diets with meat, seafood and vitamin C let the body absorb about 14% to 18% of their iron, against 5% to 12% for vegetarian diets. In a typical Western diet these effects make little difference to most people's iron status.

Amount studied: Vitamin C eaten in the same meal as plant sources of iron

None of these statements says that extra helps someone who already gets enough. On skin in particular, vitamin A's entry is about maintaining normal skin and mucous membranes, vitamin C's is about collagen, and the one skin trial of vitamin C measured a laboratory marker rather than how skin looks. A 2017 review found it poorly understood how creams compare with getting enough in the diet.^1,6,7

Vitamin A and vitamin C side by side

Vitamin A and vitamin C compared for adults^1,2,3
Question	Vitamin A	Vitamin C
Dissolves in	Fat	Water
Forms to know	Preformed (retinol, retinyl acetate or palmitate) and provitamin A (beta-carotene)	Ascorbic acid, and mineral ascorbates
Unit on labels	mcg RAE; older labels use IU	mg
Recommended a day, men	900 mcg RAE	90 mg
Recommended a day, women	700 mcg RAE	75 mg
Upper limit, adults 19 and over	3,000 mcg a day of preformed vitamin A	2,000 mg a day
Where the body keeps it	Mostly the liver, and the store can build up	Small stores, highest in white blood cells; the excess leaves in urine
Absorbed from supplements	70% to 90% of preformed vitamin A; 8.7% to 65% of beta-carotene	70% to 90% at 30 to 180 mg a day; under half above 1 g a day
Best-known food sources	Beef liver and other organ meats, fish, eggs, dairy, orange vegetables	Citrus fruit, peppers, kiwifruit, broccoli, strawberries

Units and labels

Vitamin A is the harder one to read. Its label unit has changed, and what counts toward the upper limit depends on the source. Vitamin C has no such wrinkles: the number on the label is the number of mg.^1,2

Vitamin A is measured in mcg of retinol activity equivalents (RAE). One mcg RAE equals 1 mcg of retinol, 2 mcg of beta-carotene from supplements, 12 mcg of beta-carotene from food, or 24 mcg of alpha-carotene or beta-cryptoxanthin from food.¹

Labels used to give vitamin A in IU. One IU of retinol or of supplemental beta-carotene equals 0.3 mcg RAE, so 900 mcg RAE is 3,000 IU from those sources; one IU of beta-carotene from food equals only 0.05 mcg RAE.¹

Many multivitamins combine preformed vitamin A and beta-carotene. Only the preformed share counts toward the upper limit: NIH's example is a 3,000 mcg RAE product with 60% from beta-carotene, which supplies 1,200 mcg RAE of preformed vitamin A.¹

Foods that carry one or both

Cantaloupe and tomato products appear on the food lists of both vitamins, so a mixed plate can supply both. Cooking pulls the two in opposite directions, though.^1,2

From food, the body may absorb 75% to 100% of retinol but usually only 10% to 30% of beta-carotene. Cooking and heating can make the beta-carotene in vegetables easier to absorb.¹

Long storage and cooking reduce the vitamin C in food, because it dissolves in water and is destroyed by heat. Steaming or microwaving may lessen the losses, and many of the best sources are eaten raw.^2,3

What’s in ours

Men's Multi: Vitamin A, 600 mcg RAE per serving, from the label

What’s in ours

Men's Multi: Vitamin C, 150 mg per serving, from the label
Immune Support: Vitamin C, 180 mg per serving, from the label

Men's Multi lists both vitamins on its label. Our immune formula lists vitamin C and no vitamin A.

Where too much looks different

Because the body stores vitamin A, a high intake does not clear in a day, and the harms are the more serious of the two. Vitamin C leaves in urine once the body has what it needs, and its best-known high-dose effect is an upset stomach, though kidney stones and iron overload are flagged for some people.^1,2

The upper limit for preformed vitamin A is 3,000 mcg a day for adults 19 and older, including in pregnancy and while breastfeeding, and 2,800 mcg for teens 14 to 18. It counts food, drinks and supplements, and it is lower for children: 600 mcg up to age 3, 900 mcg at 4 to 8 and 1,700 mcg at 9 to 13. The limits do not apply to people taking vitamin A under a doctor's care. No upper limit is set for beta-carotene, but the Food and Nutrition Board advises against beta-carotene supplements for the general population except as a source of vitamin A.^1,10

Too much preformed vitamin A in pregnancy can cause birth defects, including malformations of the eye, skull, lungs and heart.^1,10

The upper limit for adults is 2,000 mg a day from food and supplements combined, including during pregnancy and breastfeeding. It is 1,800 mg for teens aged 14 to 18 and lower for children. It does not apply to people given vitamin C as medical treatment by a doctor.^2,3

High doses can cause diarrhea, nausea, stomach cramps and other gut upset, because vitamin C that is not absorbed draws water into the gut.^2,3

Avoid the combination unless your doctor advises it

The isotretinoin label says to avoid using it with supplements that contain vitamin A, because isotretinoin is closely related to vitamin A and the combination may lead to isotretinoin's adverse reactions. NIH says retinoid medicines taken with vitamin A supplements can raise the risk of vitamin A toxicity, and MedlinePlus lists vitamin A supplements among the products that may interact with isotretinoin.^1,13,14

On the medicine's label

Do not take a supplement with preformed vitamin A if you take isotretinoin, and ask first if you take orlistat, acitretin, bexarotene or another retinoid.¹
Ask first if you are pregnant, could become pregnant or are breastfeeding, before any vitamin A beyond a prenatal vitamin.¹
Ask first if you smoke, used to smoke or have worked with asbestos, before a supplement with beta-carotene or vitamin A.¹
Ask first if you have a liver condition or one that affects fat absorption, such as Crohn's disease or cystic fibrosis, before vitamin A.¹
Ask first about vitamin C if you have hemochromatosis or another cause of iron overload, have had kidney stones, or take levothyroxine, a statin or an amphetamine medicine.^2,3

Choosing between them

There is no ranking to give, because the two do not compete for the same job. If your question is skin, each vitamin has a statement about normal skin function, and each describes what getting enough does. If your question is how careful to be, vitamin A calls for more attention to amounts, since the body stores it and its upper limit counts food, drinks and supplements together. Smoking pulls the two in opposite directions: people who smoke need 35 mg more vitamin C a day, while NIH advises smokers to avoid large amounts of beta-carotene or vitamin A.^1,3,4,5

Questions people ask

Is vitamin A or vitamin C better for skin?

Neither is better; the EU lists them for different things. Vitamin A contributes to the maintenance of normal skin and mucous membranes, and vitamin C contributes to collagen formation for the normal function of skin. Both statements are about getting enough, and neither shows that extra from a supplement changes how skin looks.^4,5

Can you take vitamin A and vitamin C together?

Both are in many multivitamins. The two NIH fact sheets do not describe one changing how the other is absorbed, and we found no study of the pair on its own. The number to keep in view is the 3,000 mcg a day upper limit for preformed vitamin A.^1,2

Which of the two does the body store?

Vitamin A. The body keeps the excess, mostly in the liver, and the amount stored can build up. Vitamin C is held in small amounts, mainly in white blood cells and a few organs, and what it cannot use leaves in urine.^1,2

Which is easier to take too much of?

Vitamin A. Regular high intakes of preformed vitamin A can dry the skin and cause muscle and joint aches, and too much in pregnancy can cause birth defects. Vitamin C's upper limit is 2,000 mg a day, and the usual effect of going past it is an upset stomach.^1,2

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.