A Pharmacist’s Guide to Supporting Your Immunity – Vitamin C, Vitamin D, Zinc and more, explained!

Does vitamin C prevent colds? 

The age-old question! Vitamin C is probably one of the first supplements people think of when they feel a cold coming on. 

Research indicates that taking vitamin C regularly does not significantly reduce the likelihood of catching a cold in the general population. However, regular supplementation has been associated with a modest reduction in the duration of colds. Starting high-dose vitamin C only after symptoms appear has not consistently been shown to shorten a cold. 

So, is vitamin C worth taking every day? It can be useful if your diet does not provide enough, but most people can meet their requirements through food. 

Did you know?  

Your body also needs vitamin C to make collagen, the protein that helps keep your skin and blood vessels healthy and supports wound healing. While the HSE recommends 40 mg of vitamin C daily for adults aged 19–64, about half the amount in a medium orange, this recommendation is designed to prevent conditions like scurvy, rather than optimising for potential health benefits. 

Vitamin C supplements at Millie’s 

If you are considering a supplement, the best choice is one that suits your needs, budget and preferences. 

Vitamin C is also available in foods, including peppers, strawberries, kiwis, oranges and broccoli. For most people, regularly eating a variety of these foods is a sensible foundation. 

Let’s talk about Zinc 

Zinc is an essential mineral involved in many processes throughout the body, including normal immune function, wound healing and cell division. 

You can usually obtain enough zinc through your diet. Meat, shellfish, dairy products, wholegrains and nuts are useful sources. 

If you are considering zinc, check how much you are already getting from multivitamins or other supplements. Taking too much zinc over time can interfere with copper absorption, potentially contributing to anaemia and other problems. In Ireland, HSE guidance advises not taking more than 25 mg of zinc from supplements per day unless your GP advises otherwise. 

My advice is not to add a separate zinc supplement automatically, particularly if you already take a multivitamin or an all-in-one nutritional product. 

Vitamin D: particularly important during the Irish winter 

Vitamin D deserves particular attention in Ireland because sunlight is not strong enough for our skin to produce sufficient vitamin D from around October to early March. 

Vitamin D contributes to the normal function of the immune system, as well as normal bones and muscles. Some studies have also linked low vitamin D levels with a greater likelihood of mood-related disorders, although it is not yet clear whether low vitamin D directly causes these symptoms. Maintaining adequate vitamin D levels is important for overall health, particularly during the Irish winter. 

For adults looking for a straightforward option, AYA Vitamin D 1000IU or Solgar Vitamin D3 1,000 IU are convenient daily options. The right dose depends on your needs, so if you have been prescribed a higher dose or lower dose, make sure you follow this medical advice.  

Avoid taking multiple vitamin D products together without checking the total dose. For example, Vitamin D is in many multivitamin products. We should never assume that vitamins or supplements are harmless, and if you have a medical condition, are taking any medication, or are pregnant or breastfeeding, you should always check with your Pharmacist or GP before taking a supplement. 

Vitamin C, vitamin D and Zinc – do they go together? 

These nutrients can be found together in combination supplements, and there is no general rule that they must be taken separately. The important consideration is the total amount of each nutrient you are getting. 

For example, Revive Active contains vitamin C, vitamin D and zinc alongside other nutrients. It may appeal to people who prefer an all-in-one supplement rather than several separate products. Personally, I love taking Revive Active Zest, as I get my daily dose of immune-supportive ingredients like Vitamin C, D and Zinc, along with amino acids, beta glucans, and other vitamins and minerals, like selenium, copper and choline. 

‘Immune-Boosting’, Debunked. 

The phrase “immune boosting” is widely used in supplement marketing, but it can be misleading. 

The immune system needs to respond appropriately to threats while also regulating itself. Simply trying to increase immune activity is not a sensible health goal, and an “immune-boosting” label does not prove that a product prevents infections or helps you recover faster. What we really want to do is support our immune system. 

Be cautious if ever you see a product that promises outright to stop you getting sick, guarantees rapid recovery or suggests that a long list of ingredients will dramatically strengthen your immune defences. Look for clear ingredient quantities, sensible dosing guidance and claims that are supported by appropriate evidence. 

How to support your immune system this winter 

Supplements are only one small part of the picture. These everyday habits are important to incorporate into your day-to-day life, first and foremost: 

If you frequently feel unwell, have persistent symptoms or are concerned that you may have a nutritional deficiency, speak to your GP rather than relying on supplements alone. They can assess whether further investigation or treatment is needed. 

My pharmacist’s takeaway 

There is no single supplement that guarantees a healthy, bug-free winter, unfortunately. Vitamin C, vitamin D and zinc all have important roles in normal immune function, but the benefits of supplementation depend on your diet, nutritional status and individual circumstances.