Vitamin D And The Immune System – What You Need To Know

Martin Caparrotta
By Martin Caparrotta
Updated on July 22, 2020

Vitamin D plays a number of key roles in the body, including supporting the immune system.

Most people know Vitamin D as the ‘sunshine’ vitamin, because our bodies make it naturally when our skin is exposed to direct sunlight containing UVB rays.

Vitamin D is also found in some foods such as oily fish and eggs, and it’s a common ingredient in vitamin supplements, too.

You probably already know that Vitamin D plays a number of important roles in the body, and so it’s important to make sure that you have sufficient levels.

But what are the key things we should all know about Vitamin D and what specific functions does it support in the body?

In this article, we’re going to take a detailed and specific look at the role of Vitamin D in the body and how it can help when it comes to supporting your general health.

We’re going to specifically focus on the role Vitamin D plays in helping to support a strong and healthy immune system, as well as a number of other things including bone health and more.

We’re also going to examine the best ways to ensure that you maintain healthy levels of Vitamin D throughout the year to support your health.

So, with the introductions out of the way, let’s start taking a closer look at Vitamin D and why it plays such a crucial role in maintaining good health.

Vitamin D – What You Need To Know

Vitamin D plays a number of important roles in the body for supporting overall health.

Among them is its role in helping to regulate the amount of calcium and phosphate in the body, which are important nutrients for a variety of reasons.

But what about its other functions in the body? Let’s take a closer look at what Vitamin D is needed for in the body, and why it’s important to make sure that you have sufficient levels.

Vitamin D

(Photo: Adobe Stock)

In the European Union, there are a limited number of health claims that food and supplement manufacturers can make when it comes to the ingredients in their product.

Only claims that are deemed to be proven, safe and responsible are authorised for use with products by the European Food Safety Authority (EFSA).

This is also the case when it comes to the Vitamin D that is available as a food supplement.

At the time of writing, the following health claims about Vitamin D have been authorised on the EU Register. Let’s take a closer look at them all.

• Vitamin D contributes to normal absorption / utilisation of calcium and phosphorus – As we mentioned above, Vitamin D plays an important role in regulating use of both calcium and phosphorus in the body. These are both important nutrients.

• Vitamin D contributes to normal blood calcium levels – Again, this claim is related to Vitamin D’s role in regulating the levels of calcium in your blood. Calcium is an important mineral that is required for a number of bodily functions.

• Vitamin D contributes to the maintenance of normal bones and normal teeth – Vitamin D helps to support both normal bone and tooth health. This one is pretty self-explanatory.

• Vitamin D contributes to the maintenance of normal muscle function – This claim confirms that Vitamin D helps to support the function of the muscles in the body, which is clearly very important for overall good health.

• Vitamin D contributes to the normal function of the immune system – This claim should come as no surprise, as it’s what this article is focused on. There is lots of evidence that Vitamin D plays a very important role in supporting a healthy immune system.

• Vitamin D has a role in the process of cell division – Another pretty self-explanatory one. Vitamin D plays a role in helping to support the normal process of cell division in the body.

• Vitamin D is needed for normal growth and development of bone in children – Vitamin D is also important for children, especially when it comes to bone development in early years.

• Vitamin D contributes to the normal function of the immune system in children – Again, Vitamin D plays an important role in helping to support a healthy and strong immune system in children.

As you can no doubt see for yourself, Vitamin D is needed for a wide range of bodily processes, so it should be no surprise that keeping your levels up is important to overall health.

Vitamin D And The Immune System

As we have touched upon above, Vitamin D plays a role in helping to support a healthy and strong immune system.

The human immune system involves a complex network of cells, tissues and organs that protect the body against pathogens by recognising and destroying substances that contain antigens.

An antigen is any foreign substance that triggers an immune response. Antigens carry marker molecules (usually proteins) that identify them as foreign.

There is lots of evidence that suggests that Vitamin D plays a key part in keeping your immune system healthy, so that your body is better able to fight off infections.

When people think of vitamins for immunity, Vitamin C usually springs to mind. Vitamin C is important in its own right, partly because it too supports a healthy immune system.

However, it’s also worth bearing in mind that Vitamin D is also key when it comes to immune system health.

How Much Vitamin D Do I Need?

Your body makes Vitamin D naturally when your skin is exposed to direct sunlight containing UVB radiation.

However, whether your body will be able to make enough Vitamin D this way depends on a large number of factors, including the time of year, the time of day, latitude, cloud cover, and your skin colour. We will be focusing more on Vitamin D and sunlight below.

It’s important to make sure that you are getting enough Vitamin D all year round, even in the winter months.

In the United Kingdom, Public Health England recommends the following when it comes to Vitamin D intake (from all sources):

• Babies up to the age of one year need 8.5 to 10 micrograms of vitamin D a day.

• Children from the age of one year and adults need 10 micrograms of vitamin D a day. This includes pregnant and breastfeeding women, and people at risk of vitamin D deficiency.

Based on the numbers above, Public Health England recommends that adults and children over the age of one year should consider taking a daily supplement containing 10 micrograms of Vitamin D, particularly during autumn and winter.

Important: The figures above are in micrograms. The word microgram is sometimes written with the Greek symbol μ followed by the letter g (μg).

Vitamin D supplements also sometimes state their ingredients in International Units (IU). One IU is equal to 0.025 micrograms, so 1000 IU is the same as 25 micrograms of Vitamin D.

It is also worth bearing in mind that the recommendations above are specific to England in the United Kingdom. That means that they have been made with regards to the strength of the sun throughout the year in the UK. You should check your own country’s guidance related to Vitamin D if you do not live in the UK.

Getting Vitamin D From Sunlight

Vitamin D is made naturally by your body when the skin is exposed to sunlight containing UVB radiation.

This process converts 7-dehydrocholesterol (7-DHC) in the epidermis (the outer part of your skin) to previtamin D, which is followed by a process called thermal isomerisation to make Vitamin D.

Unfortunately, however, it is not simply a case of ‘getting in the sun’ to maintain healthy Vitamin D levels.

Vitamin D Supplement

There Are Many Vitamin D Supplements Available (Photo: Adobe Stock)

Exposure of the skin to UVB radiation from the sun is influenced by many factors. These include the time of day, season, latitude, altitude, cloud cover, air pollution, clothing and sunscreen use.

You also need to consider how long you are in the sun for and how much of your skin is exposed to the UVB rays.

One of the most important factors to consider when it comes to Vitamin D production from sunlight is the latitude of your location.

UVB radiation is only present in sunlight when the sun reaches a high enough angle in the sky.

It is also worth nothing that UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce Vitamin D.

Generally speaking, if you live at a latitude below 37°, there will be enough UVB radiation in sunlight for your body to maintain healthy Vitamin D levels throughout the year.

However, this is clearly not the case in a country like the United Kingdom, where the lowest latitude is 49° and the highest latitude is 60°.

In the UK, there is not enough UVB radiation present in sunlight from around October to March to trigger Vitamin D synthesis, and it’s for this reason that the UK government recommends dietary sources during the winter months (and perhaps all year round for some people).

The UK government recommends that most people can make enough Vitamin D from being out in the sun daily for short periods with their forearms, hands or lower legs uncovered and without sunscreen from late March or early April to the end of September, especially from 11am to 3pm.

The UK public authorities, however, stop short of saying exactly how much time you should be spending in the sun to make adequate levels of Vitamin D.

This is because it’s actually not known exactly how much time is needed in the sun to make enough Vitamin D to meet each person’s requirements.

As mentioned above, this is because there are a large number of factors that can affect how Vitamin D is made by the body, such as your skin colour and how much skin you have exposed.

Indeed, people with dark skin will need to spend longer in the sun to produce the same amount of Vitamin D as someone with light skin.

Quite clearly, UVB exposure through sunlight is crucial for maintaining healthy Vitamin D levels. However, you should be careful not to burn in the sun and so it’s important to cover up before your skin turns red or burns.

Getting Vitamin D From Food

Vitamin D is found in a small number of foods, including oily fish. This includes fish such as salmon, sardines, herring and mackerel.

It is also found in red meat, liver, egg yolks and some fortified foods (foods which have Vitamin D added to them).

Vitamin D

Vitamin D

Getting Vitamin D From Supplements

Another good source of Vitamin D is from food supplements.

There are many different Vitamin D supplements on the market. They are inexpensive, and you’ll be able to find one with the correct dose to ensure that you’re able to keep your Vitamin D levels topped up throughout the year.

For example, if you’re an adult living in the UK and are looking for a daily supplement of Vitamin D, then one which contains 10 micrograms (or 400 IU), would ensure that you are meeting the recommendations from the public authorities.

Anything Else To Consider?

Clearly, Vitamin D plays an important role in supporting good health. But sticking to a healthy balanced diet and exercising regularly are both also incredibly important for your health, as well as making sure that you are getting enough quality sleep.

As always, you should speak to your doctor if you have any medical concerns.

The information featured in this article is intended for informational purposes only and is not medical advice – and it is not intended to treat, diagnose or cure any disease.

Wrapping Things Up – Our Final Thoughts

That brings us to the end of our in-depth look at Vitamin D and the immune system.

We’ve walked you through the basic things you need to know about Vitamin D, the roles it plays in the body, and how to ensure that you have enough to support good health.