How much vitamin C you actually need per day

What people ask us next.

Q01

How much vitamin C do I need per day?

The RDA is 90 mg a day for adult men and 75 mg for women, rising to 85 mg in pregnancy and 120 mg while breastfeeding, with an extra 35 mg for smokers (NIH ODS). These are small amounts easily met by food: a single orange, kiwi, or half a red bell pepper covers a full day. Most people do not need a supplement, because any diet with some fruit and vegetables reaches the target comfortably.

Q02

Is it safe to take 1,000 mg of vitamin C a day?

It is below the 2,000 mg upper limit, so it is generally safe for healthy people, but it is also largely unnecessary. The body's tissues saturate around 200 to 400 mg a day, so most of a 1,000 mg dose is simply excreted (NIH ODS). At doses approaching or above 1,000 mg, some people experience diarrhea and stomach upset, and very high intakes can raise urinary oxalate and kidney stone risk in susceptible people. For most, there is no benefit over meeting the RDA from food.

Q03

Does vitamin C prevent colds?

Not for most people. Large reviews find that regular vitamin C supplementation does not prevent colds in the general population and shortens them only marginally, by less than a day on average (NIH ODS; Cochrane). There may be a small benefit for people under extreme physical stress, such as marathon runners. The popular belief in megadose vitamin C for colds dates back decades but has not been borne out by trials, partly because the body cannot use much beyond its saturation point.

Q04

Can you take too much vitamin C?

Yes, from supplements. The tolerable upper intake level is 2,000 mg a day, above which unabsorbed vitamin C commonly causes diarrhea, nausea, and abdominal cramps by drawing water into the gut (NIH ODS). Very high doses also increase urinary oxalate, which can raise kidney stone risk in susceptible people, and people with iron-overload conditions like hemochromatosis should be cautious because vitamin C increases iron absorption. You cannot overdose from food, only from high-dose supplements.

Q05

Should I take a vitamin C supplement?

For most people, no. The RDA of 75 to 90 mg is easily met by a normal diet, since a single serving of many fruits and vegetables covers a full day, and the body cannot store or use much beyond its saturation point around 200 to 400 mg (NIH ODS). Supplements make sense mainly for people with very restricted diets, certain medical conditions, or documented deficiency. For everyone else, food is the better source and provides fiber and other nutrients alongside the vitamin C.