How Vitamin D Boosts Your Immune System

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Please note, I'm not a doctor, and this isn't medical advice. This is just a summary of everything I've read and researched. Consult your doctor or naturopath for advice on anything you read here. 
There is also (at the time of this writing) no cure for Coronavirus disease (COVID-19). Remember that social-distancing, washing your hands and just being smart will help you fight this virus.

Vitamin D is essential to our immune system by helping keep it balanced, as well as acting as an anti-inflammatory.

Basically, it helps moderate how our immune system works. Too much stimulation and you could be susceptible to autoimmune diseases. Too little, and you may be prone to infections.

While lots of people get a significant amount of Vitamin D from the Sun (moderate outdoor time with no sunblock), much of the world lives in climates that are too cold to expose skin to the sun most of the year, or have lifestyles that don’t promote much outdoor time in the sun.

Research has shown that a “[d]eficiency in vitamin D is associated with increased autoimmunity as well as an increased susceptibility to infection.”(source)

Low levels of Vitamin D have also been associated with an increased risk of respiratory diseases such as asthma, chronic obstructive pulmonary disease, and tuberculosis. While research is still being done on these topics, the trend of low levels of Vitamin D are very apparent. (source)

While low levels of Vitamin D has been associated with worsening conditions of autoimmune diseases, it should be noted that the underlying cause of the autoimmune disease is not a lack of Vitamin D.

What we can take from this is that to maintain a healthy immune system, we need to ensure that our levels of Vitamin D are sufficient.

This is especially important in anyone with underlying issues when dealing with potential viral infections, like Covid-19.

While there is no definitive proof of Vitamin D’s role in helping your body fight Covid-19, we can start to assume that a stronger immune system is better than a weak one. This means that anything you can do to help your immune system against viral diseases, flues or common colds isn’t a bad idea.

How Much Vitamin D Do I Need?

There have been numerous studies on how much Vitamin D you need to maintain a healthy immune system, and how often to take it.

Much depends on your lifestyle, as well as location. People that get regular sun throughout the year normally have a good amount of Vitamin D in their systems. Since a lot of people don’t get enough sun exposure year-long, a supplement is needed.

A 2011 study showed that large doses taken monthly had no effect on upper respiratory issues in a test group of 5100 adults – 74.1% in the vitamin D group still reported an infection versus 73.7% in the placebo group over a 1.6 year period. (source)

So monthly large-dose shots are out.

Another well referenced study in 2016 showed that daily or weekly doses of a Vitamin D supplement did reduce the risk of an acute respiratory tract infection, and found that the supplements are safe to take regularly. (source)

So how much should you take?

For a normal adult who has a low initial levels of Vitamin D, the suggested daily supplement is from 400–4000 IU/day, which is a huge range. The average suggestion goes around 1000-1400 IU/day – which is a normal single dose for many supplement providers.

You can find Vitamin D supplements in various forms, but normally in pills and in liquid drops. My preference is the drops – partly because it absorbs faster, partly because I already have enough supplements in pill form to take and change is good. They flavor it to tastes like mint (like this one from SBR Nutrition) or orange – not sure why as its just a couple drops, but it means you do have variety.

Vitamin D Supplements for Kids

Our kids are not immune to viruses, and like adults can benefit from a healthy lifestyle and added supplements. According to studies, kids from birth to 18 require a 400IU Vitamin D supplement each day. (source)

You can assume you get 200IU from food and sun, but a supplement is required to maintain the levels needed for proper health.

There are a number of supplements styles for kids – from chewables to easily absorbed drops. Drops are great to easily add into milk bottles or other foods if they’re not into chewing tablets yet. Make sure to check how many drops you need to reach the 400UI – many are just one drop, but some require 4 drops so they deplete your container faster.


Vitamin D can help stabilize and help your immune system to function as good as it can. There is research that shows a healthy level of Vitamin D can decrease your chances of getting a respiratory disease. While Vitamin D is available in foods and from the sun, a supplement is necessary in most cases.

Have you experienced a positive (or negative) health change from taking Vitamin D supplements? Let me know in the comments below!

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