Winter Immunity (Part 1): The Importance of Vitamin D

Let’s start with a question.

In light of Covid-19 and general winter flu and ills, is there any way I can boost my immune system this winter?

Answer: This is the wrong question! You can no more ‘boost’ your immune system as you can grow taller or increase your foot size. Your immune system is part of you. It just is what it is.

The correct question is:

How can I make my immune system work better, especially more responsive to invaders and more efficient at dealing with them? The answer to this is, quite a lot.

Keeping healthy this winter

While Covid-19 has rightly dominated health news we also need to be aware that winter is coming and this increases our risk of general winter ills and flu. While there has been a lot of information about preventing the spread of Covid 19 there has been little said about improving the responses of your immune system.

Your immune system is like a full symphony orchestra. There are many parts and when it is operating properly is a powerful defence system against viruses, bacteria and other infections. It also is our main defence against cancer cells forming.

Rather than trying to explain how it all works I want here to identify practical things we can do to improve immune responses. In other words what we want is for the immune system components to operate as well as they can.

Like any type of cell or tissue your immune system needs the full complement of vitamins, minerals and antioxidants to operate properly. Of all the nutrients needed, the most important is Vitamin D. Scientists now know that immune cells have a high demand for vitamin D.

So much so that many immune cells including T and B lymphocytes actually produce their own active vitamin D (calcitriol) from circulating inactive vitamin D3 (cholecalciferol). While still more research is needed it appears that sufficient vitamin D can help these important disease and cancer fighting cells become more responsive.

How much Vitamin D do I need? The only real way to know your Vitamin D levels is through a blood test. You can go to your local blood testing service and pay for a self-referred Vitamin D test. This is about $40. The normal range is 50-150nom/l. This is a ridiculously wide range; I like to see people at always over 100nmol/l.

Knowing your vitamin D levels is very important for those with compromised immunity, those with autoimmune disease or those with, or have a higher risk of cancer. I include those with respiratory problems like asthma or sinus issues and those like eczema. All these issues have strong links to our immune system.

There is evidence on the role of Vitamin D to help prevent winter flu and associated respiratory problems.  Researcher Cynthia Arrow said:

The immune system defends the body from foreign, invading organisms, promoting protective immunity while maintaining tolerance to self. The implications of vitamin D deficiency on the immune system have become clearer in recent years and in the context of vitamin D deficiency, there appears to be an increased susceptibility to infection and a diathesis, in a genetically susceptible host to autoimmunity.” (Journal of Investigative medicine, 2012)

You can read the full article at:

Most people don’t really need to have their vitamin D levels tested. You just need to be supplementing (especially April-October) with an amount that will result in above normal levels.  At a minimum you should take on average 2000IU daily during this period. More is better. I personally target 5000IU daily. I get 1000IU in my daily 4 capsules of Cell-X and from about now till October I add another 4000IU daily. Alternatively your doctor can prescribe Vitamin D at 1.25mg (50,000IU) per dose. This is usually prescribed monthly which is fine for all but the winter months where I would still add another 1000-2000IU daily.

Note: Abundant Health has changed its manufacturing process and has been able to reduce the price of Vitamin D 1000IU (120 capsules) from $29.95 to $26.95 per bottle.

If you prefer personalised advice, or if you have questions, feel free to contact me by email or phone.

John Arts (B.Soc.Sci, Dip Tch, Adv.Dip.Nut.Med.) is a nutritional medicine practitioner and founder of Abundant Health. If you have questions or need help you can contact John 0800 423559.  You can email John at

Please note that the health advice given through this column is for general educational purposes only and is not intended to diagnose or treat any health problem. © John Arts 2020

Abundant Health Vitamin D3 capsules contain 1000IU per capsule. Unfortunately this is the maximum permitted under NZ health regulations.These come in very small capsules which are great for children and people who have difficulty with larger capsules. Vitamin D is essential for bone health, Immune system defences, cardiovascular and nerve health.

Extra vitamin D is important especially in the winter months to help maintain immunity and general health. Vitamin D supplementation is possibly the most important single health measure anyone can take.

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