Vitamin C 500 mg
It does not prevent colds. It shortens them slightly — and that is about it.
The short version
What it does During periods of intense physical load — training block, competition, cold — it halves the risk of catching a cold.
What it does not do Outside that specific case, it does not prevent colds. That is the Cochrane review’s main finding, and it is negative.
What the studies say
Hemilä and Chalker’s Cochrane review is one of the most complete in the field. Its main result is negative: taking vitamin C as prevention does NOT make you catch fewer colds. But it contains one subgroup where the effect is clear: in people under intense, brief physical stress — marathon runners, skiers, soldiers exercising in subarctic conditions — they catch half as many colds.
Outside that subgroup, the benefit is limited to a very modest reduction in duration. That is why we rate it as limited evidence despite a high-quality source: the source is solid, it is the result that is thin.
One defensible use case: periods of extreme physical load. For everyone else, food is amply sufficient.
How to take it
Relevant in intensive preparation, in competition, or during periods of physical load and cold. Also relevant alongside iron, for absorption. Pointless as ordinary cold prevention.
500 mg a day during the loading period. With iron: in the same dose. Split it if you go above 500 mg, as absorption saturates.
If you take it for immunity outside a period of heavy load, you can stop: the data does not support that use.
What is inside
Ascorbic acid, identical to the molecule in fruit. “Liposomal” or “buffered” forms cost more with no demonstrated clinical benefit.
Plain ascorbic acid is enough. A 500 mg tablet costs a few cents; patented forms sell for ten times more for the same clinical result.
Megadoses of 2 g and above: digestive upset, and an increased risk of oxalate kidney stones in predisposed people.
Cautions
- History of oxalate kidney stones
- High doses: digestive upset
The three options
Analysed ascorbic acid
Quali®-C label, a single ingredient
“100 % vitamin C powder (L-ascorbic acid)”, an identifiable European raw material, where anonymous vitamin C almost always comes from elsewhere. In powder: you dose what you want.
For whom — Use during a period of intense load.
1,000 mg, two ingredients
1,000 mg, two ingredients
L-ascorbic acid and microcrystalline cellulose, 200 tablets, 375 reviews. Above 500 mg per dose, absorption plateaus: cut the tablet in half if you want to spread it.
For whom — Use during a load period, or alongside iron.
Buffered vitamin C, 365 capsules
Buffered: no stomach burning
Calcium ascorbate rather than ascorbic acid. It is the one case where buffering is an advantage: the neutral pH avoids the burning of high doses. 365 capsules, from maize fermentation, tested in Germany.
For whom — Tight budget — no need to pay for a liposomal form, the data does not support it.
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