Can Supplements Support Your Immune System?

As winter bugs start circulating, it’s tempting to reach for supplements that promise to “boost” your immune system. But do these products actually work, or are they just an expensive habit that doesn’t live up to the hype?

The nutrients your immune system really needs

Your immune system relies on many different nutrients to function properly: Vitamins A, D, E, and C, along with minerals such as zinc, iron, and selenium, all play an essential role in supporting immune cell development, signalling, and providing antioxidant protection. When levels of these nutrients are low, immune function can be impaired, which is one reason why deficiencies can make you more susceptible to illness.

You don’t want to “boost” your immune system

It might sound counterintuitive, but you don’t actually want an overactive immune system. Immune “boosting” is often used as a marketing phrase, but an overstimulated immune response is what underpins autoimmune conditions, where the body mistakenly attacks its own healthy cells.

Something else that is important to be aware of is that some nutrients, including fat-soluble vitamins (A, D, E, and K) and certain minerals, are stored in the body. Taking large doses when you're not deficient isn't always harmless, and may actually cause harm. Excessive intake of these nutrients can lead to negative health effects and, in some cases, toxicity. More is not better, and supplementing “just because” isn’t a wise strategy.

Vitamin C and colds: what does the research say?

Vitamin C is commonly associated with preventing colds, and it does play a key role in immune health. It supports collagen productio, which helps maintain the integrity of your skin and mucous membranes (your body’s first line of defence), and it functions as an antioxidant, protecting immune cells from damage. However, despite its popularity, there’s no solid evidence that high-dose vitamin C prevents colds or the flu. Research findings are mixed: some studies suggest it may slightly reduce the duration or severity of symptoms, while others find no benefit—or even that placebo groups fare better.

Zinc is another nutrient that is often promoted for immune support, and here, the evidence is a bit more encouraging. Some research indicates that zinc lozenges, taken at the onset of symptoms, may shorten the duration of a cold by around two days. The effect depends on the form and dose however, and results aren’t consistent across all studies. As with vitamin C, correcting a deficiency makes a difference, but taking unnecessary high doses doesn’t necessarily add any benefit.

So what can help support your immune system?

Megadoses of supplements aren’t likely to stop you catching winter bugs, unless you’re actually deficient in a particular nutrient. Instead of relying on high-dose pills or powders, focus on the everyday habits that help support your immune system:

• A varied, whole-food diet: A diverse diet rich in plants provides the vitamins, minerals, antioxidants, and phytonutrients your immune system relies on. It also helps ensure you meet your nutrient needs without risking excess.

  
  

• Supporting your gut health: Around 70% of your immune system is housed in the gut, and your gut microbes play a central role in immune regulation. A thriving microbiome supports proper immune signalling, helps maintain the gut barrier, and influences inflammation throughout the body. You can support your gut by eating a wide variety of plant foods, especially foods high in prebiotic fibre (for example onions, garlic, leeks, asparagus, oats, and legumes), and include some fermented foods in your diet (yoghurt, kefir, sauerkraut, kimchi and more!).