Vitamin D: Here's What You Need to Know (Updated 2020)

In recent weeks and months, several publications and studies have suggested that maintaining adequate levels of vitamin D would seem potentially beneficial in fighting the COVID-19 infection. This article explains what you need to know about vitamin D.

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin, meaning that it dissolves in fats and oils and can be stored in your body for a long time.

Two main dietary forms exist (Trusted Source):
  • Vitamin D3 (cholecalciferol). Found in some animal foods, like fatty fish and egg yolks.
  • Vitamin D2 (ergocalciferol). Found in some plants, mushrooms, and yeasts.
Of the two, D3 (cholecalciferol) seems to be almost twice as effective at increasing blood levels of vitamin D as D2 (ergocalciferol) (Trusted SourceTrusted Source).

Symptoms of vitamin D Deficiency

Vitamin D deficiency is one of the most common nutrient deficiencies.

Some people are at a greater risk than others. In the United States, 41.6% of the total population is deficient, although minorities fare worse — 82.1% and 69.2% of blacks and Hispanics are deficient, respectively (Trusted Source).

Additionally, older adults are at a much greater risk of being deficient (Trusted Source). Those who have certain diseases are also very likely to be deficient. One study showed that 96% of people who had experienced heart attacks were low in vitamin D (Trusted Source).

Overall, vitamin D deficiency is a silent epidemic. The symptoms are usually subtle and may take years or decades to surface.

The most well-known symptom of vitamin D deficiency is rickets, a bone disease common in children in developing countries. Rickets has been mostly eliminated from Western countries because of the fortification of some foods with vitamin D (Trusted Source).

Deficiency is also linked to osteoporosis, reduced mineral density, and increased risk of falls and fractures in older adults (Source).

What’s more, studies indicate that people with low vitamin D levels have a much greater risk of heart disease, diabetes (types 1 and 2), cancer, dementia, and autoimmune diseases like multiple sclerosis (Trusted Source).

Finally, vitamin D deficiency is linked to a reduced life expectancy (Trusted SourceTrusted SourceTrusted Source).

That said, it’s unclear whether deficiency contributes to these diseases or whether people with low levels are just more likely to get them.

Vitamin D Deficiency Increases Your Risk for COVID-19

study at the University of Chicago of over 4,000 patients found that untreated vitamin D deficiency was associated with an increased risk for COVID-19 infection. Another observational study involving 212 patients in Southeast Asia found that of those with a critical or severe case of COVID-19, only 4% had normal levels, while 96% of those with a mild case of COVID-19 had normal vitamin D levels.

Mark Alipio with GrassrootsHealth conducted a retrospective multicenter study involving 212 patients in Southeast Asia who had COVID-19. He too found a strong correlation between vitamin D levels and disease severity. Those with the mildest disease had the highest vitamin D levels, and vice versa.

Another study, published in the Irish Medical Journal (May 2020) showed that the calculated COVID-19 mortality rate from 12 European countries shows a significant (P = .046) inverse correlation with the mean 25(OH)D plasma concentration.

Vitamin D and COVID-19: The Evidence

recent publication (Aug 2020) from the International Journal of Infectious Diseases, highlighted that the majority of the Western population is deficient in Vitamin D. According to the author:

 Vitamin D3 supplementation also requires additional vitamin K2 intake.
• The immunoregulating function of vitamin D is promising and might decrease the global epidemic mortality.

A preprinted study published in June 2020 from Singapore (CW Tan, MedRxiv 2020), among 43 patients age 50 or older who were hospitalised with COVID-19, found that those who were started on a daily oral dose of vitamin D3 (1,000 IU), magnesium (150 mg) and vitamin B12 (500 mcg) within the first day of hospitalisation and continued up to 14 days were significantly less likely to require oxygen therapy and further intensive care.

According to an editorial review (Aliment Pharmacol Ther. 2020) published in June 2020 by Irish researchers, people with vitamin D deficiency appear to be far more prone to severe COVID-19 infections.

The epidemiology of COVID-19 provides evidence that vitamin D might be helpful in reducing risk associated with COVID-19 deaths. A May 6, 2020, report published in Aging Clinical and Experimental Research (its prepublication featured in the Daily Mail) found that countries with lower vitamin D levels also have higher mortality rates from COVID-19.

Another May 6, 2020 report (Nutrients. 2020) in the journal Nutrients pointed out that vitamin D concentrations are lower in patients with positive PCR (polymerase chain reaction) tests for SARS-CoV-2. As noted in this report, which retrospectively investigated the vitamin D levels obtained from a cohort of patients in Switzerland.

The Irish Longitudinal Study on Ageing (TILDA) published in April 2020, suggested that vitamin D deficiency could have serious implications for COVID-19. Results from the Irish Longitudinal Study on Ageing (TILDA), showed that vitamin D plays a critical role in preventing respiratory infections, reducing antibiotic use, and boosting the immune system response to infections.

Another study, published in the journal Nutrients (April 2, 2020), carries the telling title, "Evidence That Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Death."

A preprinted study published in May 2020, looked at Vitamin D levels and inflammatory markers in hospitalized COVID-19 patients in Germany, South Korea (S. Korea), China (Hubei), Switzerland, Iran, UK, US, France, Spain, Italy (Daneshkhah, MedRxiv 2020). Patients with the lowest Vitamin D levels were about 15% more likely to get severe COVID-19 and cytokine storm. Vitamin D3 plays a role in inhibiting the cytokine storm that causes viral infections to become lethal.

In a May 18, 2020, letter to the Federal Chancellor of Germany, Angela Merkel; Bernd Glauner and Lorenz Borsche highlight these and other studies and ask whether a nationwide supply of vitamin D has been considered in Germany.

Although there are currently no large randomised controlled studies demonstrating vitamin D’s effectiveness in COVID-19, there are many such studies underway. As of September 2020 there were over 25 studies in progress on the use of vitamin D in COVID-19. By the end of 2020 we should have some of the results of these trials.

How Much Should You Take?

The only way to know if you are deficient — and thus need to supplement — is by having your blood levels measured.

Your healthcare provider will measure the storage form of vitamin D, which is known as calcifediol. Anything under 12 ng/ml is considered deficient, and anything above 20 ng/ml is considered adequate.

If you think this is too troublesome, you could opt to optimise your diet with foods that are rich in vitamin D and to take a vitamin D supplement that provides a dosage that is within the RDI (Reference Daily Intake).

The RDI for vitamin D is as follows (
  • 400 IU (10 mcg): infants, 0–12 months
  • 600 IU (15 mcg): children and adults, 1–70 years old
  • 800 IU (20 mcg): older adults and pregnant or breastfeeding women
Although adequacy is measured at 20 ng/ml, many health experts believe that people should aim for blood levels higher than 30 ng/ml for optimal health and disease prevention (Trusted Source).

Additionally, many believe that the recommended intake is far too low and that people need much more to reach optimal blood levels (Trusted Source).

According to the U.S. National Academy of Medicine, the safe upper limit is 4,000 IU (100 mcg) per day (

A 3-year study published in the Aug. 27, 2019 issue of JAMA found that, compared with people who took moderate amounts of vitamin D (400 IU), adults who took large amounts daily (4,000 IU) not only didn't see additional gains in bone density, but in some cases ended up worse off.

Optimize Your Other Nutrients

It's important to keep in mind that nutrients usually don't work in isolation. Many of them depend on one another, and increased intake of one nutrient may increase your need for another.

Some researchers claim that fat-soluble vitamins work together and that it’s crucial to optimize your vitamin A and K intake while supplementing with vitamin D3 (Trusted SourceTrusted Source).

This is especially important for vitamin K2, another fat-soluble vitamin that most people don't get enough of ( One can also take 150 to 200 mcg of vitamin K2 per day, as it works synergistically with vitamin D. The only concern is that if you are on Coumadin (anticoagulant), you have to discuss vitamin K2 with your doctor as it will interfere with Coumadin.

Magnesium — another important mineral often lacking in the modern diet — may also be important for vitamin D function (Trusted Source). This is because magnesium helps to activate vitamin D, as the enzymes that metabolize vitamin D in the liver and kidneys require magnesium. In fact, about  half of those taking vitamin D supplements are unable to normalize their vitamin D levels until they take magnesium (BMC Med. 2013).

What Happens if You Take Too Much?

Vitamin D toxicity is extremely rare, but does occur with extreme doses. It is almost impossible to get too much vitamin D from sunlight or food.

Vitamin D toxicity usually develops over time, since extra vitamin D can build up in the body.

Nearly all vitamin D overdoses result from taking high amounts of vitamin D supplements.

The main symptoms of toxicity include confusion, lack of concentration, drowsiness, depression, vomiting, abdominal pain, constipation, and high blood pressure (Trusted Source).

A recent case report (BMC Geriatrics. 2020): a Brazilian retired 64-year-old female, presented to the emergency service with vomiting, abdominal pain, frontal headache, fatigue, weight loss of 18  kg, severe itchiness, musculoskeletal pain in the limbs and high blood pressure. Due to the rarity of vitamin D toxicity, the definitive diagnosis was prolonged. The diagnosis was confirmed with a Vitamin D blood test. Lab results also showed high level of blood calcium (hypercalcemia) and acute kidney injury.

Vitamin D and Omega 3

Harvard Medical School professor Dr. JoAnn E. Manson is the principal investigator of the ongoing Vitamin D and Omega-3 Trial (VITAL), a large study (more than 25,000 participants nationwide) investigating whether vitamin D and omega-3 supplements can lower risks for cancer, cardiovascular disease, and other conditions. She says while there is strong support for vitamin D's role in bone health and growing evidence that it may reduce cancer-related deaths, the evidence that it prevents conditions unrelated to bone health is not yet conclusive. "Research on vitamin D supplementation has been mixed, and especially when it comes to randomized clinical trials, it has not shown clear benefits," she says. Longer-term follow-up of VITAL and results from other ongoing trials may provide additional information about any links between vitamin D and disease prevention.

So far, Dr. Manson and her team have published two meta-analyses (which combine data from multiple studies) of randomized trials of vitamin D. One, published in Annals of Oncology in February, found that vitamin D does appear to help reduce the risk of death from cancer, but doesn't seem to prevent cancer itself. This might mean vitamin D could make tumors less aggressive, less invasive, or less likely to metastasize, she says. The benefits emerged after people had been in the trial for at least one year.

However, when it came to heart disease, vitamin D supplementation seems to fall short. A meta-analysis that Dr. Manson and her team published in June in JAMA Cardiology showed no benefit from vitamin D supplements in preventing heart attack or stroke.

In the coming months, more results from VITAL are expected to show whether vitamin D plays a role in protecting cognitive function; warding off such conditions as depression, heart failure, and diabetes; and reducing frequency of infections.


When it comes to vitamin D there are some simple strategies you should follow to protect your bones.

Stick to moderate amounts. It's reasonable to take a small or moderate amount of vitamin D, such as 1,000 IU a day, if you're concerned about whether you're getting enough .Supplements are best for people who tend to have little vitamin D in their diet.

Good food sources include fatty fish, such as salmon, tuna, and sardines, fortified dairy products, including milk, cheese, and yogurt, and cereals.

People who spend very little time outdoors in the sun may also want to take a supplement. Vitamin D is nicknamed "the sunshine vitamin" because your body produces it after sun exposure. Your skin is less able to produce vitamin D as you age. People over age 65, generate only one-fourth as much vitamin D as they did in their 20s.

Address unique risks with your doctor. Large doses of vitamin D (such as more than 4,000 IU a day) should be taken only under the advice of your health care provider.

Taking too much supplemental vitamin D can be toxic in rare cases. It can lead to hypercalcemia, a condition in which too much calcium builds up in the blood. This could cause deposits to form in the arteries or soft tissues. It may also predispose you to painful kidney stones, which are small, pebble-like masses, formed when high levels of minerals in your urine start to crystallize in your kidneys.

Choose food over pills. If possible, it's better to get your vitamin D from food sources rather than supplements. To find a good source, check the nutrition labels on packaged foods to see how much vitamin D they contain.


Buy Vitamin D supplement in Malaysia: Vitamin D3 supplements appear to be more effective at raising vitamin D levels than D2 supplements. D3 capsules are available in most supermarkets and health food stores such as Guardian and Watsons, as well as online.

Do take note that you can also get good amounts of vitamins C and D, zinc, and other essential vitamins and minerals from a basic multivitamin.


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