Immune support supplements like vitamin C, zinc and quercetin can help you cover your nutrient basics, but the research says they will not stop you catching a cold or the flu. In Australia, the best-supported steps for cold and flu season are the yearly flu vaccine, enough sleep, a varied diet and washing your hands, with supplements as a small extra on top.
Here is what the evidence actually shows for each one, how much is sensible, and which products at Supps247 are worth a look.
Vitamin C, zinc and quercetin at a glance
| Vitamin C | Zinc | Quercetin | |
|---|---|---|---|
| Daily target in Australia | 45 mg (adults) | 14 mg (men), 8 mg (women) | None set |
| Upper limit | healthdirect advises no more than 1,000 mg a day from supplements | 40 mg a day from all sources | None set |
| Main research on colds | No fewer colds in the general population, colds about 8% shorter in adults | Little or no effect on catching colds, may shorten them (low certainty) | One large trial found no overall effect |
| Good food sources | Capsicum, kiwi fruit, strawberries, oranges, broccoli | Red meat, seafood, wholegrains, legumes | Onions, apples, berries |
| Example at Supps247 | NOW Vitamin C-1000 (100 tablets), $29.95 | Swanson Zinc Picolinate 22 mg (60 caps), $24.95 | Nutricost Quercetin 1,000 mg (120 caps), $59.95 |
Prices are at the time of writing. The targets come from the NHMRC Nutrient Reference Values and healthdirect.
Start with the basics, including the flu vaccine
No supplement comes close to the flu vaccine. The Australian Immunisation Handbook recommends a flu vaccine every year for everyone aged 6 months and over, because the circulating strains change each season. Your GP or local pharmacist can give it, and it is free for some groups under the National Immunisation Program.
After that, the everyday habits matter most: regular sleep, enough protein and plenty of fruit and vegetables, washing your hands, and staying home from the gym when you are unwell so you do not pass it on. Supplements make the most sense when your diet is patchy, not as a replacement for any of the above.
Vitamin C: a small effect on how long colds last
The best summary of the research is a Cochrane review by Hemilä and Chalker (2013). Across 29 trial comparisons with more than 11,000 people, taking vitamin C every day did not reduce how often people in the general population caught a cold. It did make colds a little shorter, by about 8% in adults. Starting vitamin C only once symptoms began showed no consistent benefit.
There was one interesting exception. In five small trials of people under heavy physical stress, such as marathon runners, skiers and soldiers in subarctic conditions, regular vitamin C was linked to about half as many colds. That is a small set of studies in extreme conditions, so it does not mean the same result for a normal week of gym training.
Most people can reach the 45 mg target from food. A kiwi fruit or half a red capsicum gets you there. If you still want a supplement, NOW Vitamin C-1000 gives 1,000 mg of vitamin C per tablet, and the 100 tablet bottle is $29.95, or about $0.30 a day. healthdirect advises no more than 1,000 mg a day from supplements, as high doses can cause stomach cramps and diarrhoea, so one tablet is the ceiling, not the starting point for more.
Zinc: get enough, but do not overdo it
Zinc is needed for normal immune function, and the NHMRC sets the daily target at 14 mg for men and 8 mg for women, with an upper limit of 40 mg a day from all sources. A 2024 Cochrane review of 34 studies with about 8,500 people found zinc had little or no effect on the chance of catching a cold. It may shorten a cold by around two days, but the authors rated that evidence as low certainty, and the trials used very different doses and forms, including lozenges and nasal sprays. Zinc also caused more minor side effects, such as nausea and a bad taste.
If your diet is low in red meat, seafood or wholegrains, a moderate dose can help you reach the target. Swanson Zinc Picolinate 22 mg is one capsule a day with food, at $24.95 for 60 capsules. Before adding it, add up the zinc in everything else you take. Multivitamins, ZMA-style night formulas and some test-support products all contain zinc, and it is easy to go past 40 mg without noticing. Read more in our zinc supplements guide.
Quercetin: interesting, but early days
Quercetin is a plant compound found in onions, apples and berries. The largest trial we found, Heinz and colleagues (2010), gave 1,002 adults 500 mg or 1,000 mg of quercetin a day for 12 weeks. Overall, there was no difference in upper respiratory illness compared with placebo. In a subgroup of fitter adults aged 40 and over, the 1,000 mg dose was linked to milder symptoms and fewer sick days, but subgroup results like this need confirming in new trials.
If you still want to try it, Nutricost Quercetin 1,000 mg gives 1,000 mg per two capsule serve, with 60 serves for $59.95, about $1.00 a day. If you take prescription medicines, check with your pharmacist first.
A note on combination products: Life Extension Vitamin C with Bio-Quercetin Phytosome ($39.95) has 1,000 mg of vitamin C per tablet, but its 15 mg Bio-Quercetin blend provides only about 5 mg of quercetin, according to the US label. That is far below the trial doses, so think of it as a vitamin C tablet, and do not take it with another 1,000 mg vitamin C product.
What about a multivitamin?
If your diet is up and down, a multivitamin is often a better fit than single nutrients because it covers several gaps at modest doses. CNDMND Multi by Condemned Labz gives 90 mg of vitamin C, 11 mg of zinc and 20 mcg of vitamin D3 per two tablet serve, with 30 serves for $59.95. If you take it, you probably do not need extra zinc on top. Compare more options in our best multivitamin guide.
Which immune support supplement should you choose?
- Diet already good: you likely do not need any of these. Get the flu vaccine and focus on sleep.
- Diet patchy: a multivitamin such as CNDMND Multi covers vitamin C and zinc at sensible doses.
- Training hard through winter: a daily vitamin C tablet is cheap and has the most research behind it, though the effect is small.
- Low zinc intake: Swanson Zinc Picolinate 22 mg, as long as your total stays under 40 mg a day.
- Curious about quercetin: try it, but know the evidence is limited and mixed.
Our pick for most people is the flu vaccine plus a good diet, with NOW Vitamin C-1000 as the low-cost extra if you want one. Browse our quercetin range. Online orders ship Australia-wide with free shipping on orders of $99.99 or more, and click and collect and Afterpay are available. If you are often unwell, or a cold lasts longer than usual, see your GP.
Shop the products in this guide
NOW Vitamin C-1000 100 tablets$29.95
Swanson Zinc Picolinate 22 mg$24.95
CNDMND Multi 30 serves$59.95
Nutricost Quercetin 1,000 mg$59.95
Browse all quercetin supplements.
FAQs
Does vitamin C stop you from getting a cold?
Not for most people. A Cochrane review of 29 trial comparisons found daily vitamin C did not reduce how often people in the general population caught a cold, though colds were about 8% shorter in adults. Taking it only after symptoms start showed no consistent benefit. The one exception was people under heavy physical stress, such as marathon runners, where colds were roughly halved in a small number of trials.
How much zinc is safe to take a day?
The NHMRC daily target is 14 mg for men and 8 mg for women, and the upper limit for adults is 40 mg a day from all sources, including food, multivitamins and other products. Long-term high intakes can upset your stomach and reduce copper absorption. A 22 mg supplement plus a normal diet is usually fine, but add up the zinc in everything you take before adding more.
Can I take vitamin C and zinc together?
Yes. Vitamin C and zinc are often taken together and there is no known problem combining them at normal doses. Many multivitamins already contain both. Just keep supplemental vitamin C to 1,000 mg a day or less, as healthdirect advises, and keep your total zinc under 40 mg a day. If you take prescription medicines or have a health condition, check with your pharmacist or GP first.
Is quercetin worth taking for immune support?
The evidence is limited. In the largest trial, 1,002 adults took 500 mg or 1,000 mg of quercetin a day for 12 weeks, and there was no overall difference in upper respiratory illness compared with placebo. A subgroup of fitter adults over 40 did better on 1,000 mg, but that needs confirming. Quercetin is optional, and onions, apples and berries are good food sources.
Can supplements replace the flu vaccine?
No. The Australian Immunisation Handbook recommends a flu vaccine every year for everyone aged 6 months and over, because the circulating strains change each season. No vitamin, mineral or herbal supplement has been shown to do the same job. You can get vaccinated at your GP or most pharmacies, and it is free for some groups. Supplements are, at most, a small extra alongside it.
Sources: Australian Immunisation Handbook: influenza; healthdirect: vitamin C; NHMRC Nutrient Reference Values: zinc; Hemila and Chalker, Cochrane review: vitamin C for the common cold (2013); Cochrane review: zinc for the common cold (2024); Heinz et al. Quercetin supplementation and upper respiratory tract infection (2010); product labels and brand nutrition panels, checked October 2026.
Order online with Australia-wide delivery, free on orders of $99.99 or more, with Afterpay available at checkout. You can also use click and collect at a store that offers it, or visit a Supps247 store in Melbourne, regional Victoria or Brisbane to compare products in person. Members can use our member price match on full-priced items.
Prices and stock were checked on 29 October 2026 and can change at any time. Always read the label and follow the directions for use. If you have a medical condition, are pregnant or take regular medication, check with your doctor first.
