Busting Immune Boosting Myths

By Student Dietitian, Grace Ingram

dietitian drinking smoothieWhat does it mean to “boost” your immune system?

The immune system is the body’s defence force. A healthy immune system can prevent you from getting sick, by helping to fight off some of the “bad guys”, such as viruses and bacteria.

However, if the soldiers in your immune system misfire, they are also capable of attacking the good guys, including your own cells! (1). Allergies and autoimmune diseases, including coeliac disease, rheumatoid arthritis, and Type 1 Diabetes, are products of an overactive immune system. Therefore, instead of “boosting” your immune system, we like to think about how we can optimize the immune system to best perform its desired function – keeping you healthy and free and sickness!

Many claims exist around certain nutrients and foods and their power to “boost” your immune system. So, should you really be chomping down on raw garlic, or religiously taking vitamin C tablets to avoid the common cold and flu?

Let’s take a look at five nutrients and foods that have had their moment in the immune-boosting spotlight.


Vitamin C

If you haven’t been told to take vitamin C to prevent colds and the flu, you’ve been living under a rock. Although it is one of the oldest tricks in the book, it actually does have some merit!

White blood cells are one of the star soldiers in your immune system defence force. They contain a huge amount of vitamin C compared to other blood cells. Research shows that white blood cells need vitamin C to mature and work at their best (2). Think of vitamin C like an upgrade for these fighters, giving them better pathogen destroying abilities.


In practice, vitamin C doesn’t prevent you from getting a cold, however, research shows that it can reduce the severity and duration of cold and flu symptoms (3). The supercharged white blood cell soldiers can’t stop the virus from getting in, however, they are better fighters once a threat is present.


Vitamin DVitamin D

In terms of vitamin D, the best thing you can do for your immune system is avoid deficiency. Vitamin D deficiency is associated with increased incidence of respiratory infections. Furthermore, while there is some evidence to suggest supplementation supports the immune system, this is only effective in people who are deficient (3). If you haven’t been diagnosed with a vitamin D deficiency, you can supply your immune system soldiers with enough vitamin D by eating a healthy, balanced diet and getting some sun exposure each day.



Zinc is another important nutrient for the immune system and is often included in immunity supplements. Though it won’t prevent you from getting sick in the first place, research has shown zinc to be effective in reducing the duration of the common cold by enhancing the immune system through several pathways (3).


But don’t go too crazy on the zinc supplements just yet! The upper limit for zinc intake in Australia is 40mg/day for adults (4). While it is difficult to exceed this amount through diet, the average zinc tablet contains 25mg (sometimes more!), so consume with care. Too much zinc can suppress the immune system (3), making you feel unwell for longer and more susceptible to illness. Before reaching for a supplement, try adding in some more zinc-rich foods like shellfish, meat, and legumes into your daily diet.



Have you ever thrown cloves of raw garlic into a smoothie when you’re sick in a desperate attempt to feel a little better? If you have, you might actually have been doing your immune system a favour! Numerous forms of garlic have shown promising results in immune support research.


One study demonstrated that consuming aged garlic extract reduced the occurrence and severity of cold and flu symptoms. This is thought to be thanks to an amino acid called S1PC, which is present in trace amounts in raw garlic, but increases when garlic is aged (5).


Raw garlic has also had some wins. A clinical trial had unwell participants consume raw garlic daily and observed antimicrobial effects. Benefits were only observed with participants consuming 4 cloves of raw garlic/day (6), which is a fair amount if you’re not a die-hard garlic fan and may have some serious bad breath side effects!


Echinacea is a common staple in “immune boosting” supplements. Some studies show promising effects for this pretty pink flower helping the immune system; however, some show no effect at all (8). Generally, echinacea’s immune-supporting powers work in a petri dish but haven’t been shown to provide the same benefit in the body just yet (3). When an effect is observed, research suggests that you need to be taking it well before you get sick, where it may have a small protective effect from catching a cold in the first place (9). While it won’t harm you, echinacea should not be your holy grail of immunity.


While the above foods and nutrients may have a small beneficial effect on your immune system, general healthy habits are the benchmark for keeping your immune army functioning well. A healthy, balanced diet of all five food groups is likely to cover all the nutrients your immune system needs. On top of this, regular exercise, quality sleep, and stress management also support your sickness-fighting soldiers, to ensure the whole immune system can function at the top of its game (9).












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