• Dr. Shantai Watson

Vitamin D and your Immune System

With the recent news, we are all looking for ways to protect ourselves and boost our immune system. One very under-rated vitamin for immune support is Vitamin D.

Ever wonder why colds and flus seem to hit us harder during the winter months? A study showed that subjects are more likely to shed a virus they are exposed to in December (40%) rather than September (16%). Several theories have been proposed to explain this phenomenon:

1. People congregate indoors during the winter.

However people also congregate indoors during the summer months. For the majority of the population, the majority of our waking hours are spent at work, where we are in the same close quarters and dealing with the same number of people in the winter and summer. So this can’t be the exclusive factor.

2. Colder weather.

Remember grandma telling you to bundle up or else you’ll get sick? Well, please listen to your grandma and put on your gosh darn coat... but it hasn’t proven to be true that you will get sick if you don’t. You will BE cold, but that does not necessarily mean you are going to GET a cold. There is no evidence that being cold suppresses your immune system.

3. Less sun exposure meaning less Vitamin D production.

Vitamin D is produced with direct exposure to UVB rays - 10-15 minutes of exposure per day is recommended, and optimally at noon when the sun is highest in the sky. These rays cannot penetrate well through windows. So, it’s safe to say that a large portion of the population is not getting this daily exposure to the sun during the cold winter months. So why would Vitamin D affect your likelihood of getting sick? Come along and let’s explore Vitamin D and it’s relationship to your immune system!

What is Vitamin D?

Did you know that Vitamin D is actually a hormone? It can be obtained through our diet or can be produced by our own bodies when UVB light hits our skin. Once light hits our skin, a precursor is made and shuttled to the liver. It then goes to the kidney where the active form of Vitamin D is produced.

What does Vitamin D do?

We have known for a long time that Vitamin D is necessary for Calcium and Phosphorous absorption which is essential to build strong bones.

More recently however, scientists have found Vitamin D receptors on more tissues than we had ever expected. This includes the intestines, pancreas, prostate and cells of the immune system. It turns out that these Vitamin D receptors regulate the expression of more than 900 genes. Along with calcium and phosphorous regulation, Vitamin D also plays an essential role in cellular proliferation and differentiation, and the immune response.

Vitamin D stimulates the expression of potent anti-microbial peptides, which exist in our immune cells, and play a major role in protecting the lungs from infection.

What happens when you are deficient?

Chronic extreme Vitamin D deficiency leads to a disease called Rickets. Rickets causes stunted growth and short stature, teeth and skeletal deformities such as bowed legs or an oddly shaped skull.

Chronic moderate Vitamin D deficiency can lead to thin, brittle and misshapen bones, and may contribute to Osteopenia or Osteoporosis.

It is becoming increasingly clear that microbes slow down immune reactivity by dysregulating Vitamin D receptors with the goal of increasing their chance of survival.

Basically, this means that if we are deficient in Vitamin D (causing down-regulation of Vitamin D receptors), microbes have more leverage to mess with our immune systems. This may explain why low Vitamin D levels have been associated with upper respiratory tract infections, including influenza. This also helps to explain the long-standing association of Rickets with pulmonary infections.

Furthermore, there has been published research demonstrating an association between Vitamin D deficiency and several chronic diseases, along with a higher risk of cancer, heart disease, MS and type 1 diabetes. Insufficient Vitamin D levels are also associated with a doubled likelihood that a woman will experience more prolonged menstrual cycles (and who wants that!), and is also associated with some forms of sleep apnea.

How much Vitamin D do I need?

According to the Vitamin D Council, a serum level of 50 ng/ml is recommended to be maintained at all times. If you test your Vitamin D levels, and they are anything lower than 40 ng/ml, you are considered deficient. It is estimated that 41.6% of the population is deficient in this important vitamin on any given day. That means this prevalence rate could be even higher during the winter months.

So where do I get Vitamin D?

Ideally getting your daily dose of Vitamin D can be accomplished through 10-15 minutes of direct exposure to sunlight without sunscreen. Noon is the ideal time. However, if you live in a city with a latitude of 52 degrees North (the latitude of London, UK), or more Northern, NO Vitamin D can be made from the skin between October to March!! For reference: Edmonton, AB (my home town in Canada!) Has a latitude of 53.5 degrees North, while Denver, CO has a latitude of 39.7 degrees N. This inability to produce Vitamin D is because atmospheric Ozone filters out the UVB radiation unless the sun is high enough in the sky.

Vitamin D may be obtained from fatty fish, like tuna, mackerel, and salmon. It can also be obtained from foods fortified with vitamin D, like some dairy products, orange juice, soy milk, and cereals, beef liver, cheese and egg yolks. However, it is very difficult to obtain enough Vitamin D from diet alone, if you are not exposed to the sun.

How do I know if I am Vitamin D deficient?

The best way to know your Vitamin D status is through a lab test. However if you live in a Northern latitude and can not possibly get enough sun exposure during the winter months, or on days where you do not sunbathe, the Vitamin D Council recommends the following maintenance doses:

Children: 1000 IU per 25 pounds of body weight, up to 125 pounds.

Adults: 5000 IU

Pregnant & Breastfeeding: 5000 IU daily

Vitamin D toxicity is very rare. There is no evidence that Vitamin D toxicity can occur from prolonged sun exposure. Most cases of Vitamin D intoxication have been attributed to taking more than 40,000 IU per day for a prolonged amount of time. Toxicity may cause kidney stones or calcification of the heart and kidneys. For this reason, the European Food and Drug Administration currently recommends to stay below 4000 IU per day, with the tolerable upper limit being 10,000 IU.

Since this tolerable upper limit of Vitamin D is high, the benefit of supplementing Vitamin D on days you do not sunbathe far outweighs the risk.

What do I look for in a Vitamin D supplement?

Vitamin D3 (Cholecalciferol) is the natural form of vitamin D that your body makes from sunlight, and it is therefore the most recommended form of Vitamin D to supplement. Recent research has demonstrated a synergistic relationship between Vitamin D and Vitamin K (K2 in particular). I therefore recommend looking for a Vitamin D supplement that also contains Vitamin K. Take vitamin D with food or your Omega 3 capsules!

Here is a link to the Vitamin D supplement that I trust and recommend to my patients. This can be purchased on my Fullscript account for cheaper than Amazon. It is safe for babies and children in smaller doses (recommended dose found above).


With all the news lately, it’s not uncommon to become a bit of a “hermit”. However, I hope this blog inspires you to step out and get in the sun for 15 minutes. Or, at least, to take your Vitamin D while you’re all cooped up. Your body and your immune system in particular will thank you for it!

Take care!

Dr. Shantai Watson, BSc, DC

Elite Chiropractic & Wellness

Call 720 509 9379 or email

To book your appointment.


Located at Elite Chiropractic and Wellness.
5002B E Hampden Ave, Denver, CO, 80222


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