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Vitamins and supplements to support your immune system - Dr, Izzy Smith

Updated: Dec 16, 2020

Even without the world’s biggest pandemic in 100 years, coming into the winter months

means we should be thinking about health and what we can do to avoid pesky colds and

other winter viruses.

You may have wondered, why we get sick more frequently in winter? There are many theories

including spending more time indoors with closer proximity to other people (potential germ

factories) to the common cold virus “rhinovirus” living longer in cold damp conditions. Genes

that control our immune system and inflammation having seasonal variation likely also play a

role as could lower levels of vitamin D.

Should everyone take supplements? 

For the majority of people, supplements should be the cherry on top of other lifestyles

measures that are much more important to our health like getting enough sleep,

exercising, and having a varied colourful diet.

With the exception of vitamin D and people who live in cold climates or have darker

skin, most people don’t “need” to take supplements, however, there are some that

may benefit our health.

Walk into any pharmacy and you’ll see an array of vitamins, minerals and other supplements

marketed to help our immune system. A few actually have some pretty good evidence to

keep us well this winter, but many are definitely best left on the pharmacy shelf. Take a look

at our list of best to “definitely don’t bother”, and which foods are the best way to get these

vitamins and minerals without having to take a tablet.

Supplement/Vitamin #1: Zinc

If there’s one supplement that will likely help you keep winter snuffles away it’s Zinc.

Zinc is a mineral which our body needs in small amounts for many things including

immune health, reproductive health + more.

Zinc has been shown to directly inhibit replication of the common cold virus

“rhinovirus” and improve immune function. Unlike other supplements, Zinc has the potential to stop or prevent a cold rather than just decrease the severity of symptoms.

Zinc lozenges and syrups seem to be particularly effective but can have an

unpleasant taste and nasal sprays are generally not recommended as they can

permanently alter the sense of smell. Taking zinc continuously or just when you think

you’re getting a cold can both be beneficial.

Foods you can find it in: 

  • Tofu, shellfish, red meat, lentils, whole grains and mushrooms are great sources.

Who should/shouldn’t take these?

  • Zinc should generally be safe for everyone but nasal sprays have been shown to cause loss of smell and should be avoided.

Supplement/Vitamin #2: Vitamin D

Vitamin D is a fat-soluble vitamin that we primarily get from the sun acting on

cholesterol under our skin.

Vitamin D is important for calcium absorption and bone health and likely plays a role

in our immune system too. Some studies have shown that when people get lung

infections, those who have low vitamin D, generally get a more severe infection and

have poorer outcomes. Whether this is association vs causation is hard to tell, but

nonetheless, making sure our vitamin D levels remain normal though winter is

definitely a good idea.

Foods you can find it in: 

  • Mainly from the sun but animal products such as eggs, dairy, and fatty fish also contain small amounts of vitamin D and many plant-based milk varieties are fortified with vitamin D.

Who should/shouldn’t take these?

  • Essentially anyone in a cool climate should take vitamin D through winter and people with dark skin may need to take it all year round. People who can’t spend much time outside due to disability or frailty may also need vitamin D.

  • There are some conditions where vitamin D supplements may cause more harm than good such as sarcoidosis or hyperparathyroidism but these are very rare.

Supplement #3: Vitamin C

Vitamin C is an antioxidant that has many important roles in our body from collagen

production to immune health. Vitamin C supplements are often hailed as heroes for cold

prevention, but in reality, they are unlikely to do that much unless you’re deficient (scurvy),

which is almost unheard of in Australia.

Several studies have shown people who take vitamin C regularly (i.e. not just when you’re

sick) may shorten their symptoms of a cold by a half a day but unfortunately won’t prevent

you getting a cold in the first place. One group of people who did seem to get more benefit

from vitamin C and potentially decrease their chance of getting a cold were elite athletes

training in arctic type temperatures… Any cross-country skiers or bob-sledders reading this


Foods you can find it in: 

  • Citrus foods, almost all brightly coloured fruits and vegetables.

Who should/shouldn’t take these?

  • Vitamin C is safe for most people but taking more than 1000-2000mg a day can cause stomach upset or other gastrointestinal problems.

Supplement #4: Probiotics

Probiotics are living bacteria that are thought to be potentially beneficial for gut

health. Whether taking probiotics supplements actually change the bacteria in our

gut is still under debate but there is evidence that they may be beneficial to our

immune health. Studies have shown people who took probiotics regularly although

they weren’t less likely to get a cold, if they did, it was for a shorter duration of time

and their symptoms were less severe.

Foods you can find it in: 

  • Fermented foods such as yoghurt, kefir and sauerkraut.

Who should/shouldn’t take these?

  • Probiotics are generally safe for most people, however, people with impaired immune systems such as someone who’s had an organ transplant may not be able to take them. If you’re unsure if probiotics are right for you, your GP is the best person to speak to.

Supplement #5: Echinacea

Echinacea contains a phytochemical called alkylamide which is thought to stimulate

the immune system. However literally hundreds of studies on echinacea have

yielded disappointing results with no benefit compared to placebo for preventing

colds. One species (Echinacea purpura) may decrease the duration and severity of

colds but the evidence isn’t strong. In summary, echinacea is unlikely to help keep you

well this winter but if you are going to take some, make sure it’s the purported type.

Who should/shouldn’t take these?

  • Echinacea has been associated with liver failure and interfering with other medications. You should speak with a health professional before taking echinacea regularly

Supplement #6: Olive Leaf

Olive leaves contain several key polyphenols, such as oleoresin and oleuropein and have long

been used in Mediterranean traditional medicine.

There is potentially promising evidence for olive leaf extract and cardiovascular health and

even some cancers but the evidence for preventing coughs and colds isn’t strong. Some

research suggests taking it at the onset of an illness may decrease symptoms but it’s

unlikely to be your winter saviour. Olive leaf is safe for most people but can lower blood

pressure so should be taken under the guidance of a health professional, especially if you’re

on other medications for blood pressure.

Supplement #7: Garlic

Garlic contains allicin which has been found to exhibit antiviral and antibacterial activity.

There have literally been thousands of studies looking at the medicinal properties of garlic.

The results are mixed but some studies support that garlic supplements may prevent both

the chance of getting a cold and duration of symptoms.  

Who should/shouldn’t take these?

  • Garlic may upset people who cannot tolerate food maps, have allergies and vampires. For most other people it is generally safe and delicious.

Supplement #8: Multivitamins 

Multivitamins are a pinch of many different vitamins and minerals. If you’re deficient in

something it won’t be enough to replenish your levels and if you’re not deficient the doses

are too low to have a beneficial effect e.g. compared to taking a straight zinc supplement. 

There isn’t any evidence to suggest multi-vitamins will stop you getting sick this winter and

for most people just results in expensive wee! 


Of all these supplements listed, the evidence suggests zinc, vitamin D have the most

evidence for helping you stay well this winter. However with all this in mind, it’s important to

remember good sleep, regular exercise and a varied balanced diet will help your health so

much more than any supplement ever will. Getting a flu-shot, washing our hands and

minimising time in crowded areas are also superheroes when it comes to staying well as is

managing our stress levels and taking some breaks during those long winter months!

Author bio:

Dr Izzy Smith is a specialist medical doctor and practices in Sydney. She is passionate

about holistic medicine and looking after mental wellbeing to improve both physical and mental health. Izzy is also a distance runner and her number 1 tip for staying well this winter is to get more sleep!

She is a strong advocate for the physical and mental health benefits of exercise and is also the co-host of the mental health podcast Behind the Uniform Podcast and contributes to various health blogs, radio stations + more.

Instagram: @doctorizzyksmith