Vitamin D and COVID-19 - Can Vitamin D Protect You During this Coronavirus Pandemic?
Can vitamin D help against COVID-19? 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 and COVID-19.
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.
What Does It Do in Your Body?
First, it is converted to calcidiol, or 25(OH)D, in your liver. This is the storage form of the vitamin.
Second, it is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D.
When the active form of vitamin D binds to this receptor, it turns genes on or off, leading to changes in your cells. This is similar to how most other steroid hormones work (Trusted Source, Trusted Source).
Vitamin D and COVID-19: The Evidence
Of those with a vitamin D level below 20 ng/ml (deficiency), 12.5% tested positive for SARS-CoV-2, compared to 8.1% of those who had a vitamin D level between 30 and 34 ng/ml (adequacy) and 5.9% of those who had an optimal vitamin D level of 55 ng/ml or higher.
Another study, published in JAMA (JAMA Netw Open - Sep 2020) found that persons who are likely to have deficient vitamin D levels at the time of COVID-19 testing were at substantially higher risk of testing positive for COVID-19 than were persons who were likely to have sufficient levels.
The same team above, has also published a preprint article: A study at the University of Chicago of over 4,000 patients that found that untreated vitamin D deficiency was associated with an increased risk for COVID-19 infection.
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.
Frequently Asked Questions
Best Food Sources of Vitamin D
Here is the vitamin D3 content of a few of the best food sources (nih.gov):
Cod liver oil, 1 tablespoon (15 ml)
1,360 IU / 34 mcg
Salmon, cooked, 3 ounces (85 grams)
447 IU / 11 mcg
Tuna, canned in water, 3 ounces (85 grams)
154 IU / 4 mcg
Beef liver, cooked, 3 ounces (85 grams)
42 IU / 1 mcg
1 large whole egg (D is found in yolk)
41 IU / 1 mcg
1 sardine, canned in oil, drained
23 IU / 0.6 mcg
Although fatty fish like salmon, mackerel, swordfish, trout, tuna, and sardines are decent sources, you would have to eat them almost every day to get enough.
The only excellent dietary source of vitamin D is fish liver oil — such as cod liver oil — which contains upwards of two times the Reference Daily Intake (RDI) in a single tablespoon (15 ml).
Keep in mind that dairy products and cereals are often fortified with vitamin D (Trusted Source).
Some rare mushrooms also harbor vitamin D, and egg yolks contain small amounts.
Symptoms of 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).
That said, it’s unclear whether deficiency contributes to these diseases or whether people with low levels are just more likely to get them.
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.
The RDI for vitamin D is as follows (nih.gov):
- 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 (Trusted Source).
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, as well as online.
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.
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.
Do we have large randomised controlled trials to prove that vitamin D can combat COVID-19. Not at the moment.
Of course, the most important thing you can do to avoid infection with coronavirus is to prevent exposure by following the latest recommendations of the CDC and World Health Organization such as wearing face mask, social distancing and hand sanitisation. Also take steps to stay healthy, including getting adequate sleep and exercise and eating a healthful diet that includes adequate (but not excessive) intakes of essential nutrients, such as vitamins C and D.
For those with hypertension, please take steps to control your blood pressure as high blood pressure is associated with more severe outcome if infected.
Your own immune system, works best when fed right. As long as you are taking supplements under medical supervision and within a safe range, the risk is low but the potential benefit is high? What have you got to lose?