One you drop. One you take instead.
In three lines:
3. Taking mega vitamin C all year won't stop ordinary colds.
2. Starting a gram tablet after you already feel rough does almost nothing in the trials.
1. Start with food vitamin C. Keep a megadose only if you're in a short, extreme-stress window or you're testing a short course for yourself with eyes open.
OUT — the year-round “immune” gram
The Chemist Warehouse story is a 1,000 mg tablet every day because “I don't want to get sick.”
The Cochrane review (29 comparisons, 11,306 people) found that regular vitamin C at 200 mg/day or more did not cut cold risk in the general population. It shortened colds a little if you were already taking it regularly: about 8% in adults and 14% in children. That's a ten-day cold becoming roughly nine days. Taking vitamin C only after symptoms start didn't reliably shorten or soften the cold.
One real exception: five small trials of people under short extreme physical stress (marathon, ski, subarctic soldiers) found that regular vitamin C roughly halved cold risk. That's not your office winter.
If the job was “never get a cold,” park the year-round megadose. Food still matters. Smokers and people with low intake need a different conversation with a GP.
IN — food first. Megadose is optional and honest.
Adult food targets are about 75–90 mg/day (more if you smoke). An orange, capsicum, kiwi or portion of broccoli gets you there without a horse pill.
If you still want a pill for the modest duration effect, the trial territory is a modest daily dose in the 200–500 mg range, not a 2 g “immune blast.” The adult upper level from food plus pills is 2,000 mg/day; gut upset is the usual brake.
Don't promise prevention. Don't stack zinc lozenges from last year's letter without reading that issue again.
ASK (take this to the GP)
“I've been taking high-dose vitamin C every day for colds. Given Cochrane's general-population findings, is food-level vitamin C enough for me, or is there a reason I should keep a supplement, such as kidneys, medicines or diet?”
This swap is not for you if
You have a prescribed vitamin C regimen, malabsorption or a scurvy-risk diet. Keep following medical advice.
You're in a clinician-supervised high-dose protocol.
Extreme short-term physical stress is literally your job this month. The exception trials may apply; ask, don't guess.
Sources
Cochrane: Vitamin C for preventing and treating the common cold — cochrane.org
NIH Office of Dietary Supplements (NIH ODS), Immune Function (vitamin C / colds) — ods.od.nih.gov