Does vitamin C actually prevent colds?

Short answer: no. Not for most people, not at any sensible dose, and not for as long as anyone has bothered to measure.

Here is what the trials actually measured, and the one group where the answer flips.

What did the Cochrane review actually find?

The best summary of this question is a Cochrane review, which is the sort of thing that gathers decades of placebo-controlled trials and pools them rather than cherry-picking the flattering ones. It covered 29 comparisons and more than 11,000 people.

Two findings came out of it, and they point in different directions:

• Taking vitamin C regularly did not change how often people got sick. The number of colds in the vitamin C groups looked like the number in the placebo groups.
• Taking it regularly did reliably shorten colds, once people had them. Modestly. Not dramatically. But consistently enough to survive being pooled across thirty years of trials.

So the fair framing is not "vitamin C stops colds". It is closer to "vitamin C very slightly shortens the ones you were going to get anyway".

What was measured	What the review found
Number of colds caught (most people)	No difference from placebo
Length and severity of colds already caught	Modestly, reliably shorter
Number of colds caught (marathon runners, soldiers, skiers)	Lower with regular vitamin C
Trials pooled	29 comparisons, 11,000+ people
Amount in Moat	180 mg per two-capsule serving

What is the exception worth knowing?

There is one group where the prevention finding does change: people under heavy, sustained physical stress. Marathon runners, soldiers on exercises, skiers. In those trials the incidence did drop.

That exception gets quoted constantly by people selling vitamin C to office workers. If you are not currently running an ultramarathon, it is probably not about you.

Then why is it in the bottle?

Because "it does not prevent colds" is not the same as "it does nothing". Vitamin C is an essential nutrient. Your body cannot make it, it has a real job in collagen production and antioxidant defence, and a genuine deficiency is a genuine problem.

We put 180 mg in a two-capsule serving. That is a nutritional amount, meant to keep you topped up, and it sits alongside the rest of the formula rather than pretending to be a cure on its own.

Unless you are training like that most weeks, the everyday finding is the one that applies to you.

So what is vitamin C good for?

Vitamin C is a genuinely useful everyday nutrient with a clear Daily Value, and the review found it takes a little of the edge off a cold once you have one. That is a pleasant, ordinary thing for a vitamin to do, and it is why there are 180 mg of it in Moat.

If you want to get comfortable reading these numbers yourself, we wrote a ninety second guide to supplement labels.

The vitamin C figure in Moat, and why it sits at the everyday nutritional amount rather than a megadose, is on the vitamin C ingredient page.

FAQ

Does vitamin C prevent colds? No, not for most people. A Cochrane review of 29 comparisons and over 11,000 people found regular vitamin C did not lower how often people caught colds.

Does vitamin C shorten a cold once you have one? Yes, modestly. The same review found regular intake reliably, if slightly, shortened colds already underway.

Who does prevention actually work for? People under heavy, sustained physical stress, such as marathon runners, soldiers on exercises and skiers, in whom the trials did show fewer colds.

Why is there vitamin C in Moat if it does not prevent colds? Because it is a genuinely essential nutrient your body cannot make on its own, with a real job in collagen production and antioxidant defence. The 180 mg is a nutritional amount, not a cure.

Sources

• Hemilä and Chalker, Vitamin C for preventing and treating the common cold, Cochrane Database of Systematic Reviews
• NIH Office of Dietary Supplements, Vitamin C fact sheet

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.