How Vitamin D Benefits & Boosts Your Immune System

Did you know having good vitamin D levels may help fight disease, regulate mood, improve depression, and even support weight loss? A simple place to start today is being intentional about your vitamin D intake.

8 min read


How Vitamin D Benefits & Boosts Your Immune System

The global coronavirus pandemic took the world by storm, thankfully what is left in its wake is not all negative. Work flexibility, more family time, and an easier pace of life were just a few of the reported positive outcomes of COVID-19 (1).

An aftereffect I've noticed reverberating throughout the fitness, health, and wellness industry is an uptick in both awareness and intentionality toward living a healthier lifestyle. Taking better care of your physical and mental health is trending.

The question remains, how can you take better care of yourself? Well, one simple way to boost your mental, physical, and even immune health is to meet your recommended daily intake of vitamin D.

That's right, studies show that vitamin D can help boost your immune system, your body's key defense in protecting you from a variety of viruses and diseases (2). Below, I'll explain what vitamin D is, how it can benefit you, and how to get enough of it.


What is Vitamin D?

Vitamin D is an essential fat-soluble vitamin your body needs. The key functions of vitamin D are assisting in immune system function, as well as the body's absorption of healthy calcium and phosphorus levels which are crucial for building and maintaining strong bones.

Vitamin D acts slightly differently than other vitamins in that it's one of only two vitamins your body can produce on its own (also vitamin K), and you can also get it from other sources like food or supplements.

You've likely heard the old joke as someone walks out the door and remarks that they're 'off to get their vitamin D for the day'; and, if it's a sunny day, they're not wrong.

The most natural way to obtain vitamin D is to expose your skin to sunshine. Vitamin D is produced in your body when ultraviolet light from the sun hits your skin, triggering vitamin D synthesis.

While you may think it'd be easy to get your daily needs of a vitamin you can absorb just by stepping out your door, as of 2014, experts predicted nearly 1 billion people worldwide have low levels or deficiency of vitamin D, making it one of the most common vitamin deficiencies in the world (2).


What Are Benefits of Vitamin D?

@sunnyhealthfitness Make sure to get plenty of sun so you can have enough vitamin D 🌞 #sun #vitamind #beachlife #beachside #fitness #health ♬ original sound - SunnyHealthFitness

Once thought of as the vitamin for strong bones (2), vitamin D does a lot more for your body. According to research vitamin D may help fight disease, regulate mood, improve depression, and even support weight loss. The latest research is packed below.


Vitamin D Fights Disease

There is a load of evidence suggesting the role of vitamin D in supporting immune health, reducing the risk of Multiple Sclerosis, Heart Disease, and other severe illnesses.


Reduces Risk of Multiple Sclerosis

A 2018 review of population-based studies revealed that low levels of vitamin D are linked with an increased risk of Multiple Sclerosis (3).


Reduces Risk of Heart Disease

A 2019 review suggests that low levels of vitamin D may be linked to an increased risk of heart disease, heart failure, and stroke. However, they did conclude more research needs to be done to determine if the link is direct, or if the results are simply related to overall poor health (4).


Plays a Strong Supporting Role in Immune Health

One of the main functions of vitamin D is to help activate T cells, which are cells in your body that detect and destroy pathogens like viruses.

A 2020 review revealed that low vitamin D levels can contribute to acute respiratory distress syndrome. Which, where the immune system is concerned, makes a case for keeping vitamin D levels in check (5, 6).

Although, research supporting the role of vitamin D in decreasing the severity of flu and COVID-19 infections is mixed (7, 8). It appears more research is in order before concluding vitamin D's overall role in helping to fight viruses and infections.


Reduces Likelihood of Severe Illness

Studies have even revealed that people who do not have adequate vitamin D levels might be at increased risk of infections and autoimmune diseases such as rheumatoid arthritis, type 1 diabetes, and inflammatory bowel disease (9).


Vitamin D Regulates Mood & Reduce Depression

Interested in improving your mood? A 2020 meta-analysis found that those who were experiencing negative emotions experienced improved symptoms after taking vitamin D (10), meaning vitamin D could help you naturally boost your mood.

Another 2020 study even revealed low vitamin D levels as a risk factor for more severe fibromyalgia symptoms, anxiety, and depression (11).

So if you, like many, have experienced the ups and downs of anxiety and depression in the passing months, vitamin D may help to pick you back up.


Vitamin D May Support Weight Loss

If weight loss was one of your 2022 New Year resolutions, ensuring your vitamin D levels are optimal may help your efforts. A 2018 trial disclosed those who followed a weight loss diet plan and took vitamin D lost more weight and fat mass than the control group who followed the same weight loss diet plan and took a placebo (12).

The research also supports that people with higher body weights have a higher risk of low or deficient vitamin D levels (12), so if you consider yourself in that category, it's only more evidence for keeping on top of your vitamin D intake.


Are You at Risk of Vitamin D Deficiency?

While we've already covered the amazing reasons why vitamin D is important for you, I also touched on vitamin D being one of the most common deficiencies. Below are some factors that may affect your ability to get adequate vitamin D from sunlight alone.

You may be less likely to absorb enough vitamin D from the sun if you (2):

  • Live in an area with high pollution
  • Use sunscreen
  • Spend most of your time indoors
  • Live in a big city where can buildings block sunlight
  • Have darker skin (the higher levels of melanin, the less vitamin D your skin can absorb)

These factors can increase your risk of vitamin D deficiency. That's why it's important to get some of your vitamin D from non-sunlight sources.


    How Much Vitamin D Should You Take?

    While amounts of vitamin D may differ depending on how much sun you can get, the time of year, and other factors (see above), the recommended daily intake (RDI) for different populations are as follows (2):

    • Infants (0-12 months): 10 mcg (400 IU)
    • Children and teens: 25 mcg (600 IU)
    • Adults (18-70 years): 15 mcg (600 IU)
    • Adults (70+ years): 20 mcg (800 IU)
    • Pregnant or breastfeeding women: 15 mcg (600 IU)

    Keep in mind, you may need to adjust your levels depending on your diet and sun exposure, so be sure to talk to your doctor.


    What Are the Best Sources of Vitamin D?

    So how can you increase your vitamin D intake if you're running low? There are three key sources of vitamin D:

    • Exposure to Sunlight
    • Food Sources
    • Vitamin D Supplements

    While sunlight is a great source of vitamin D, in some cases, it may not be enough which is where increasing intake through food sources and supplements can come into play. Below I've listed some of the common food sources you can incorporate into your diet to increase your natural vitamin D levels.

    Vitamin D Food Sources

    Naturally Occurring Food Sources:

    • Salmon
    • Sardines
    • Herring
    • Canned Tuna
    • Cod Liver Oil
    • Beef Liver
    • Egg Yolk
    • Shrimp
    • Mushrooms

    Fortified Food Sources:

    • Milk
    • Cereal & Oatmeal
    • Yogurt
    • Orange Juice


    In Closing

    Vitamin D is an incredible vitamin that plays a powerful role in boosting your immune system and keeping your bones strong. Recent research has shown it may even aid in weight loss and reduce your risk of disease.

    So, I ask you to revisit the question that started it all: how can you take better care of yourself? A simple place to start today is being intentional about your vitamin D intake. The benefits speak for themselves.


    (1) “Positive outcomes associated with the COVID-19 pandemic in Australia” National Library of Medicine, 2021. Accessed 17 March, 2022
    (2) “Vitamin D” National Institutes of Health, 2021.  Accessed 17 March, 2022
    (3) “Vitamin D and Multiple Sclerosis: A Comprehensive Review” National Library of Medicine, 2021. Accessed 17 March, 2022.
    (4) “Vitamin D status and cardiovascular outcome” National Library of Medicine, 2019. Accessed 17 March, 2022.
    (5) “Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data” BMJ, 2017. Accessed 17 March, 2022.
    (6) “Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis” Health Technology Assessment, 2019. Accessed 17 March, 2022.
    (7) “Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths” National Library of Medicine, 2020.”338/ Accessed 17 March, 2022.
    (8) “Low vitamin D levels do not aggravate COVID-19 risk or death, and vitamin D supplementation does not improve outcomes in hospitalized patients with COVID-19: a meta-analysis and GRADE assessment of cohort studies and RCTs” BMC, 2021. Accessed 17 March, 2022.
    (9) “Vitamin D’s Effect on Immune Function” National Library of Medicine, 2020. Accessed 17 March, 2022.
    (10) “The effect of vitamin D supplement on negative emotions: A systematic review and meta-analysis” National Library of Medicine, 2020. Accessed 17 March, 2022.
    (11) “Fibromyalgia Symptom Severity and Psychosocial Outcomes in Fibromyalgia Patients with Hypovitaminosis D: A Prospective Questionnaire Study” National Library of Medicine, 2020 Accessed 17 March, 2022.
    (12) “Effect of vitamin D supplementation along with weight loss diet on meta-inflammation and fat mass in obese subjects with vitamin D deficiency: A double-blind placebo-controlled randomized clinical trial” National Library of Medicine, 2019.  Accessed 17 March, 2022.


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