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Vitamin D: Do you really need supplements?

Updated: Jun 3, 2020

Of all the common vitamins, it is perhaps vitamins C and D that get the most attention.

There have been recent reports speculating on what role, if any, vitamin D may play in reducing the severity of COVID-19 infection.

These observational studies have looked at outcomes and suggest that vitamin D has an effect on the immune response to infection.

These are observations and unfortunately cannot be relied upon as an actual cause and effect relationship between vitamin D supplements and outcomes from COVID-19 infection. More studies are needed.

Let’s review and discuss the claims about vitamin D and its ability to prevent or improve a wide range of conditions.

Vitamin D has been touted to benefit everything from autoimmunity and bone mineral disease to several cancers, diabetes, cardiovascular disease, and multiple sclerosis.

First, let's start with what vitamin D does in the body.

Vitamin D is a fat soluble vitamin, this means once it is absorbed in the diet the body stores it in the fatty tissues. Other fat soluble vitamins include vitamins A, E and K.

Vitamin D is synthesized when our skin is exposed to sunlight, and it is also present in some foods.

The most important role of vitamin D in the body is the regulation of calcium levels. This aids in strengthening bone and preventing osteoporosis, a condition where bones become weak.

What else does vitamin D do?

There are many claims about what vitamin D may or may not do.

Several recent studies have suggested that vitamin D may benefit heart failure, diabetes, some cancers, certain infections, autoimmune disease and even hair loss.

Below we will look at what recent studies have found about the actual benefits of vitamin D.

What does vitamin D deficiency cause?

Many adults in the United States have low levels of vitamin D when blood levels are tested. Some studies suggest that more than 40 percent of adults in the United States are vitamin D deficient.

Typical symptoms of vitamin D deficiency may include joint, muscle or bone pain. Other symptoms may include fatigue, breathing problems, and low mood or what is commonly referred to as seasonal affective disorder.

So do you really need vitamin D supplements?

Here we look at some of the more recent data to answer this question.

Chronic Pain

Some have theorized that low levels of vitamin D might cause or worsen chronic pain.

A recent review of the current literature on this topic was conducted and the conclusion was there is some, but no definitive evidence that vitamin D deficiency may contribute to chronic pain.

However, to date the evidence does not support a connection between vitamin D deficiency and chronic pain.

Autism Spectrum Disorder (ASD)

In a study looking at the effects of vitamin D alone, and in combination with omega 3 fatty acids researchers found significant improvements in social awareness and greater improvements when these supplements were taken together in social skills in children 3 to 8 years of age with ASD.

Respiratory (Lung) Infections

Researchers have found that vitamin D supplementation significantly reduced the risk of acute respiratory infections. This has been misinterpreted as vitamin D can replace the flu vaccine. This is incorrect and part of a malicious mis-information campaign to mislead the public. The flu vaccine is the best way to prevent the flu.

Vitamin D does have effects on the immune system, and may optimize the way our lungs respond to viral and bacterial infection. So there is clearly a potential benefit in COVID-19 infections.

Having said that, Vitamin D does have effects on the immune system, and may optimize the way our lungs respond to viral and bacterial infection. So there is clearly a potential benefit in COVID-19 infections.


Low levels of serum vitamin D (less than 30ng/ml) is associated with higher blood sugar levels.

Heart Failure

Several studies have suggested that vitamin D could offer protective benefits against heart disease.

However, the mechanism is poorly understood and no definitive benefit has been proven. More research is needed in the area to answer this question.

Alzheimer’s Disease

To date no study has concluded that there is an association with vitamin D deficiency and the risk of Alzheimer’s disease.


We have seen observational links between obesity and lower levels of vitamin D.

However, there is no definitive proof that vitamin D deficiency causes excess fat to be stored around the abdomen.


Higher levels of vitamin D may be associated with lower risk of breast cancer.

Some studies have tried to establish a link between vitamin D deficiency and colorectal cancer. Unfortunately these results have not been replicated in other follow up studies.

Take away points:

Vitamin D is a hot topic right now. It is important to note that sunlight is the best source of vitamin D. However, depending on geography and the season, this may not be feasible.

The National Institutes of Health (NIH) recommends increasing vitamin D levels by eating vitamin D containing foods daily. These include oily fish, fortified milk, beef liver, egg yolks, mushrooms, and fortified breakfast cereals.

We looked at several studies about vitamin D and really need to stress the need for further investigation and clinical trials to validate these results, especially regarding the claims about COVID-19 infection.

Our general take is that if taken in appropriate doses, vitamin D is generally considered safe.

Please remember that medical information provided by us must be considered an educational service only. This blog should not be relied upon as medical advice and does not replace your physician’s independent judgement. Please seek the advice of your physician regarding any issues related to your health.


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