Vitamin C is one of the best-known essential micronutrients thanks to its role in promoting immune function in the body. But that’s not vitamin C is useful for: it’s also great for boosting muscle recovery and limiting soreness after tough training sessions, and is potentially useful for protecting cognitive function as you age.
Here’s what our research team uncovered about the wide-ranging benefits of vitamin C supplementation.
Vitamin C benefits
1. Our attraction to Vitamin C as a cure for the common cold started in the 1970s.
That’s when a man named Linus Pauling told the world to start taking heavy doses of Vitamin C. In his book How to Live Longer and Feel Better, he recommended megadoses (an actual scientific term) of the vitamin to ward off the common cold, among other things.
Why did the world listen to this man?
Because he was (and still is) considered one of the top scientific minds of all time (1). He pretty much single-handedly founded the fields of quantum chemistry AND molecular biology. He was awarded two different Nobel prizes, in two different categories (chemistry and peace).
The man was brilliant so the world listened when he told us to take way more Vitamin C than anyone thought was possible. So what if it brought on a “laxative” effect. Kidney stones? No sweat if it means no more colds. The word spread and soon Vitamin C and “cure for the common cold” were linked forever.
Even though Linus Pauling’s advice may not have produced results out the way he hoped, people still line up to buy Vitamin C to this day.
2. More scientific data has poured in since Pauling’s book came out
To try and help people sort out the facts, The U.S. National Library of Medicine has an official government statement on Vitamin C and colds: the research is “conflicting” (2).
This doesn’t seem very clear, and that’s because the efficacy of Vitamin C depends on who you are, where you live, and precisely what result you’re seeking when you take the supplement.
No studies have yet been able to establish a link between taking a Vitamin C supplement and preventing a cold.
3. Vitamin C may do something for colds, but not what you may think
Perhaps if you’re a long-distance runner living in Iceland, you will see a benefit from Vitamin C supplementation. The only shred of evidence supporting any positive effect of Vitamin C on the common cold was seen on people who were exerting themselves very heavily in winter environments. Details are as follows:
In 2007 a review study was conducted, and then updated in 2013 (3). What that means is researchers looked at all the controlled trials ever performed involving Vitamin C, dating way back to 1966.
That’s 40 years of Vitamin C research rolled into one totally succinct report.
The review study involved thirty trials comparisons and over 11,000 participants. It was found that taking Vitamin C supplements to prevent a cold was no more effective than taking the placebo.
In other words, mega-dosing yourself with C might not keep you from getting a cold.
But the part about the cold-weather endurance athletes holds true: the same review study found an 8% chance that the cold would end sooner if they took Vitamin C. They were skiers, marathon runners, and soldiers operating in sub-arctic environments.
Doctors speculate that the reason for the benefit is because these super athletic cold-weather types have a Vitamin C deficiency. By dosing themselves with C, they’re simply bringing their levels back up to normal.
So in no way should we deduce from that the need to mega-dose ourselves with Vitamin C in order to prevent, shorten, or treat the common cold.
4. Vitamin C may be outclassed by zinc for treating the common cold
Turns out we’ve been looking down the wrong supplement path the whole time. Researchers in the UK have revealed that Zinc, not Vitamin C, is the magic cold-fighter (4).
In another look-back study involving 67 different studies, remedies for the common cold, including Vitamin C supplements, were examined. There were no clear benefits to be found in any of the research for any of the traditional remedies except for zinc and washing your hands a lot.
Vitamin C side effects
It’s hard to take too much vitamin C. Vitamin C is a water-soluble supplement, which means that it is very hard to take too much. When your body gets excessive vitamin C, it can usually just excrete the extra vitamin C in your urine.
In fact, several clinical trials have used very high doses of vitamin C (10,000 mg of vitamin C per day) for up to three years without recording any significant adverse effects (5).
Very high doses of vitamin C can cause gastrointestinal problems, headaches, and insomnia. Still, according to the Mayo Clinic, too much vitamin C can cause mild to moderate diarrhea, nausea, cramping, headaches, and insomnia (6).
Most of these side effects are attributable to high concentrations of unabsorbed vitamin C pulling water into the digestive tract. These side effects are very unlikely to appear in anyone at doses of 2000 mg per day or less.
Vitamin C dosage
Most studies use 100 to 1000 mg of vitamin C. Vitamin C is typically studied in clinical trials at doses ranging from 100 to 1000 mg per day or more. On the other hand, the recommended minimum daily intake is only 90 mg for men and 75 mg for women (7).
Keep your vitamin C intake below 2000 mg per day. As noted above, the tolerable upper limit of vitamin C is 2000 mg per day for adults, which means that doses below this amount are well-tolerated and not expected to result in any side effects. As such, as long as you’re below this amount, the right dosage is going to depend on the explicit purpose of vitamin C supplementation that you are aiming at.
For athletic recovery, aim for 600-1000 mg. For example, if you are looking to prevent illness after a marathon, triathlon, or another long and difficult athletic event, 600 mg seems to be the right dosage.
Preventing muscle soreness may require much higher doses (1000 mg per day or more). On the other hand, lower doses have been studied for treating chronic inflammation among people with metabolic disease, and as little as 100 mg per day has been beneficial in observational research on reducing the risk of chronic diseases.
Vitamin C benefits FAQ
Q: How much vitamin C is too much?
A: In practice, it’s very hard to overload on vitamin C since it is a water soluble vitamin. The tolerable upper limit for vitamin C intake, established by the National Institute of Health’s Office of Dietary Supplements, suggests that up to 2000 mg of vitamin C per day is not likely to result in any adverse effects.
Clinical research has used doses beyond this level, up to 10,000 mg per day for up to three years, with no serious adverse effects, though at high doses it’s possible to get gastrointestinal issues merely from the volume of vitamin C dissolved in your stomach.
Keeping your supplemental vitamin C intake below 2000 mg per day is an easy way to make sure that none of these issues happen, while still getting any possible benefits from the supplement.
Q: What are the biggest benefits of vitamin C?
A: Vitamin C is a heavily studied vitamin, and the balance of the evidence suggests that, while vitamin C might not bring about the major changes in long-term health that many people hope for, it can be useful at several specific applications.
Its role in boosting your immune system seems to help prevent infections after tough athletic events like ultra marathons or triathlons, and some evidence suggests that it may help stave off cognitive decline.
Vitamin C is also very helpful if you are trying to boost your iron levels, because iron absorption is substantially enhanced in the presence of vitamin C. For these and other niche applications, vitamin C supplementation can make a lot of sense.
Q: What foods are highest in vitamin C?
A: Not surprisingly, the foods with the highest concentration of vitamin C per serving are pretty much all fruits and vegetables. Oranges, strawberries, kiwi fruit, bell peppers, broccoli, and Brussels sprouts are some of the foods that have the most vitamin C.
Each of these fruits and vegetables has at least 60% of your recommended daily intake of vitamin C per 100 grams of food, and bell peppers and kiwi fruit have over 100%.
These are some of the most efficient ways to get vitamin C in your diet from natural sources, though supplementation is also an option, especially if you are looking for high-dose vitamin C.
Related: Our best vitamin C picks
Vitamin C is best known for boosting your immune function, but might be more useful as a tool for muscle recovery after tough workouts and for protecting the brain as you get older.
Regardless, it’s one of the simplest and most powerful antioxidants out there, and is extremely safe from a side-effects perspective.