How much vitamin C do you need per day?

The RDA for vitamin C is 90 mg a day for adult men and 75 mg for adult women.

These are the reference amounts used on US food labels and in dietary guidance, not personal targets. What you need shifts with age, pregnancy, medication and health conditions. The % Daily Value shown on every food page here is calculated against the FDA Daily Value for vitamin C, which is 90 mg a day.

What this means for you

Ninety milligrams a day sounds like a target you have to work at. For most people it is not. One cup of orange sections gets you there on its own. Half a red pepper does it. Even a cup of raw broccoli, which nobody thinks of as a vitamin C food, carries 69 mg.

So the honest question is not how to get more. It is whether you are one of the few people who might be short.

Two groups usually are. If you smoke, or live with someone who does, your body burns through vitamin C faster than other people's. And if your diet has very little variety, the same few cooked dishes week after week with no fruit and nothing raw, you can drift low without noticing. That happens to people more often than you would think. During a hard month, after a move, in hospital, in a pregnancy where nothing appeals.

One change that works

Add one raw thing a day, somewhere it will actually get eaten. A clementine in your bag, pepper strips next to lunch, fruit on top of yogurt. Raw matters more here than for most nutrients, because vitamin C dissolves in water and breaks down in heat. In broccoli, every domestic cooking method tested except steaming caused significant losses, and boiling was the worst of them. If you boil, keep the water for the soup or the sauce. Steaming and roasting hold on to more. Even so, five varied servings a day can supply more than 200 mg, which is twice what the label asks for.

Myth. Vitamin C does not stop you catching colds. This has been tested many times in ordinary people and the effect is not there. Taken every day it does shorten a cold a little, by around 8 per cent in adults and 14 per cent in children, which for a week-long cold means roughly half a day.

Not for everyone. High doses are not harmless. Above about two grams a day the reliable results are diarrhoea, nausea and cramps, and in people who already form kidney stones, a higher chance of another one. If you take a supplement, a small one with food does everything a large one does.

What ninety milligrams does to a blood level

The figure on the label is 90 milligrams a day for adult men and 75 for women. What an intake of that size does to the vitamin C in your blood has been modelled, and the spread around the average is the part worth having.

Sixty milligrams a day puts the middle of a group of adults at 42 micromoles per litre. Reaching 50, the level European bodies settled on, takes about 100 milligrams a day. The interesting part of that modelling is how far people spread around it. At the same 60 milligrams, younger adults sat at 44 micromoles, older people at 31 and smokers at 34. One number on a label cannot cover that.

There is a second reason the floor and the target are different things. Plasma between 11 and 28 micromoles per litre is enough to keep scurvy away. In a survey of 8,210 Americans, people sitting in exactly that range had about half again as much bleeding from the gums and bleeding in the retina as people above it. Survey data shows association rather than cause. Still, not having scurvy and having enough turn out to be two different questions.

Unsettled. Does more than the recommendation buy anything? One small study raised the dose every two weeks and watched markers of oxidation in the blood. They kept falling up to 500 and 1,000 milligrams a day and then stopped, with 2,000 adding nothing that 1,000 had not already done. Ten people, eight of them on vitamin C, everyone escalating in the same order, and the thing measured was a laboratory marker rather than an illness. That is a reason for somebody to run the study properly. It is no reason to buy the big tablets.

What the food studies show, and how soft they are

Across 69 long-term studies, each extra 100 milligrams of vitamin C a day from food went with about 11 per cent fewer deaths from any cause, and similar drops in heart disease and stroke. The researchers who pooled that read it as an argument for fruit and vegetables. Vitamin C marks the kind of diet someone eats more than it acts on its own inside it.

Unsettled. Every one of those numbers carries the same weak link. When what people say they eat is checked against the vitamin C actually in their blood, the two agree only moderately, around 0.35 to 0.46. A correlation that size means the questionnaire accounts for under a fifth of the difference between one person and the next. The association is real. The precision is not what the decimal places suggest.

One last thing about running out, because it is often described in a way that frightens people for no reason. Scurvy is real, and it appears within about a month of eating almost no vitamin C at all, below roughly 10 mg a day. That is a diet with no fruit and no vegetables in any form. If you eat produce at all, this is not your problem.

Two more numbers from the Cochrane review itself. Taken every day, vitamin C shortened colds by 8 per cent in adults and 14 per cent in children, and a separate meta-analysis found severity fell by 15 per cent, with the effect landing on severe symptoms rather than mild ones. Started after the symptoms begin, it did nothing consistent in seven comparisons. So the daily habit buys a few hours. The panic dose on day one does not. And the review of both is here.

What survives the pan gets in perfectly well

Heat takes a share of the vitamin C in a vegetable. What is left behind reaches your blood as well as anything else does, and those are two separate questions. Sixty-eight men on a controlled diet were topped back up with vitamin C from a tablet, from an orange, from orange juice or from cooked broccoli. Every one of those raised their blood level by the same amount. Raw broccoli was the odd result at about a fifth lower, and the researchers who found it say that gap is unlikely to matter in a mixed diet.

Juice is the one to watch, because it changes in the fridge. Orange juice made up from frozen concentrate carried 117 mg per 8 fl oz on the day it was opened and 89 mg a week later. Ready chilled juice went from 69 to 64, which is no real change at all. The number printed on a carton belongs to the day it was filled.

The expensive form

Liposomal vitamin C means vitamin C wrapped in fat so that more of it gets past the gut. It costs several times what plain ascorbic acid costs, and the first part of the sales pitch is true. In 27 adults who took both, a single 500 mg liposomal dose put 27 per cent more vitamin C into plasma than the same dose of the plain kind, and 20 per cent more into white blood cells.

Then the number starts shrinking. Pooling ten studies of the same question, nine found liposomal higher, by anything from 1.2 to 5.4 times at the peak. In the studies where people already had normal vitamin C to start with, around 50 micromoles per litre, the gap came down to about 1.3 to 1.4 times. Most people reading this are in that second group.

Unsettled. Nobody has checked where the extra goes. Across all ten studies not one measured how much vitamin C left in the urine, only two looked at uptake into cells, and only two measured any biological effect at all. In the two that did, one found both forms gave comparable protection against lipid oxidation, and in the other about 50 per cent more in the plasma bought a small rise in antioxidant potential at two hours and no better protection of cells. The reviewers say plainly that the clinical significance of those differences is uncertain and likely to be minimal. Higher in the blood for a few hours has been shown. Better for you has not.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Foods highest in vitamin C on this site

• Guavas, common, raw — 376.7 mg per 1 cup (419% DV)
• Guava sauce, cooked — 348.4 mg per 1 cup (387% DV)
• Grapefruit juice, white, frozen concentrate, unsweetened — 248 mg per 1 can (6 fl oz) (276% DV)
• Apple juice, grape and pear blend, and calcium — 126.8 mg per 8 fl oz (141% DV)
• Lemons, raw, without peel — 112.4 mg per 1 cup, sections (125% DV)

All vitamin C sources ranked →

Full guide: Vitamin C: what it does, how much you need, and what it will not do