Foundational immune support: do vitamins and minerals make a difference?
So, in this section, there are probably no big surprises, although you may be surprised to find that zinc is the mineral with the highest evidence for supporting the immune system.
Zinc is critical for over 300 enzymes in the body, including those that help fight off pathogens. Research shows that taking zinc within 24 hours of a cold’s onset can shorten its duration by up to 33%.
Although zinc deficiency in the UK is thought to be around 10%, it is twice as common in Southern Asia and Sub-Saharan Africa. It was also hypothesised to be a significant reason for poorer outcomes in those populations during the pandemic.
While herbs and medicinal mushrooms can modulate the immune system, vitamins and minerals form the essential backbone of immune health. Deficiencies in these nutrients compromise normal immune function and, therefore, immune resilience, leaving the body more susceptible to infections and less able to recover swiftly. (1)
The four we have highlighted with the highest levels of evidence:
1. Zinc (dose 20-50mg)
Level of evidence: High. Multiple systematic reviews have consistently demonstrated the effectiveness of zinc in boosting the immune system.
Why We Chose It: Zinc is critical for immune cell development, particularly T-cells and B-cells, and is essential for adaptive immunity. It also has direct antiviral properties, impairing viral replication by interfering with specific proteins necessary for the virus to multiply.
During COVID, multiple studies showed the benefits and its immune-enhancing properties are well known.
Clinical Evidence: A 2011 study found that zinc lozenges could shorten the duration of colds by about 33%, particularly when taken early in the illness
Zinc deficiency is linked to a higher risk of infection, and mild deficiencies are common, particularly among older adults and those with chronic illness. (2)
2. Vitamin D3 (4,000 IU / 100mcg NRV 333%)
I have written on vitamin D in the past, including how to take vitamin D safely and the other things you should be taking alongside vitamin D.
So, it shouldn't be surprising that vitamin D is in here. Often dubbed the “sunshine vitamin,” Vitamin D is technically a prohormone that influences over 200 genes, many of which regulate immune function.
If there is one thing to take every day from September to April in the UK during winter, it's high-strength vitamin D (with K2).
Vitamin D is vital for respiratory health. It activates antimicrobial peptides in the lungs, which help prevent respiratory infections.
A large study showed that children with asthma supplemented with vitamin D during Winter reduced hospital admission by 50%. As a father of a son who had multiple hospital admissions when he was younger, to say I'm really disappointed that this is not more common knowledge is an understatement.
That study has now led to a large multi-centred trial called the DIVA study
Clinical Evidence: In a groundbreaking 2017 study published in the British Medical Journal, Vitamin D supplementation was shown to reduce the risk of respiratory infections significantly, particularly in people with low baseline levels. (4)
3. Vitamin C (1000mg minimum NRV 1250%)
Why We Chose It: Vitamin C is one of the most well-known immune-support nutrients, and for good reason. It boosts white blood cell production, especially neutrophils, the body's first infection responders. Additionally, Vitamin C acts as an antioxidant, protecting immune cells from oxidative damage caused by free radicals. This property is especially valuable during periods of immune activation, as cells are more vulnerable to damage.
It's odd that humans don't produce vitamin C in the liver like other mammals; a similar-sized mammal like a goat will make 3g per day and more when stressed or unwell. We need to get it from our diet.
Clinical Evidence: A 2013 meta-analysis highlighted Vitamin C’s potential to reduce both the duration and severity of colds, especially in physically stressed individuals like athletes
Vitamin C also plays a role in the skin’s defence system, enhancing barrier function and acting as a direct antimicrobial agent.When you are acutely unwell, taking an extra 1-3g is what you should be aiming for. This is one where dose is important.
4. Selenium (55mcg NRV 100%)
Why We Chose It: Selenium is a powerful antioxidant and immune-modulating nutrient that works at the cellular level to enhance immune function. It supports the production of glutathione peroxidase, an enzyme that protects cells from oxidative damage during an immune response. Selenium also strengthens the immune system's antiviral defences.
In a later blog, we discuss the importance of boosting the body's master antioxidant, glutathione. Although glutathione is expensive, it can be done just as effectively by taking NAC and boosting the GPX enzyme. Selenium deficiency is common in the developed world.
Clinical Evidence: Low.
Systematic reviews on selenium are mixed. On its own, it likely only gives limited benefits. However, there is much stronger evidence when used to boost glutathione along with NAC. It falls in to the nice to have rather than one of the essentials.
Research has linked selenium deficiency to an increased susceptibility to viral infections, such as influenza. Supplementation has been shown to restore immune function, making it essential for individuals with low selenium levels or those at risk of viral exposure. (1,3)
Summary
There are no big reveals here. Vitamin D, zinc and vitamin C are all essential for robust immune health. Vitamin D will help to prevent illness and vitamin C intake should be ramped up when you are unwell.
If you are prone to other respiratory illnesses or have kids who do, make sure to add in vitamin D during the Winter months.
Dr Geoff Mullan
Functional Medicine Doctor
References
- Crawford C, Brown LL, Costello RB, Deuster PA. Select Dietary Supplement Ingredients for Preserving and Protecting the Immune System in Healthy Individuals: A Systematic Review. Nutrients. 2022;14(21):4604. Published 2022 Nov 1. doi:10.3390/nu14214604
- Jafari A, Noormohammadi Z, Askari M, Daneshzad E. Zinc supplementation and immune factors in adults: a systematic review and meta-analysis of randomized clinical trials. Crit Rev Food Sci Nutr. 2022;62(11):3023-3041. doi:10.1080/10408398.2020.1862048
- Filippini T, Fairweather-Tait S, Vinceti M. Selenium and immune function: a systematic review and meta-analysis of experimental human studies. Am J Clin Nutr. 2023;117(1):93-110. doi:10.1016/j.ajcnut.2022.11.007
- Jensen ME, Mailhot G, Alos N, et al. Vitamin D intervention in preschoolers with viral-induced asthma (DIVA): a pilot randomised controlled trial.Trials. 2016;17(1):353. Published 2016 Jul 26. doi:10.1186/s13063-016-1483-1
