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The One Vitamin That Could Reduce Your Coronavirus Risk

Here's why to consider taking vitamin D in the age of COVID-19.
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COVID-19 has shaken us all to the very core. Our lives have been changed beyond recognition. We all live in fear of contracting the virus, both ourselves and our families and friends. As a doctor, I'm sure I'm not alone—scratching my head and thinking hard about what on earth we can do to help ourselves to beat this.

I'm not making sensationalist claims here, but I would like to make sure everyone knows the facts about one possible step we can all take—it's all about vitamin D. And I'm not alone on this—former CDC director Tom Frieden himself has said "as we race to develop effective treatments and a vaccine against COVID-19, people are looking to reduce their risk of getting sick. One thing that might help is as obvious as the sun in the sky and as close as your medicine cabinet—Vitamin D." The New York Times also reports that "the notion that vitamin D levels could influence the risk of COVID-19 has sparked debate among experts and prompted researchers at Harvard and other universities to start randomized trials examining whether there is a link. Some scientists believe that people with vitamin D deficiencies have weak or abnormal immune responses that make them more susceptible to developing COVID-19 and experiencing severe symptoms. "

Have you thought about vitamin D? Up to 60% of the US population are estimated to have low levels of vitamin D. Could you be one of them? Why does this matter? Should you consider a vitamin D supplement? 

Read on and find out. Let's start with the basics. 

What is Vitamin D? 

Vitamin D is an essential vitamin—essential because our bodies can't exist without it. There are two forms of vitamin D: D2 and D3.

  • Vitamin D2 comes from the diet—it's found in oily fish, egg yolks, red meat, liver, some fat spreads, and fortified cereals. Dietary intake of vitamin D2 is vital because we cannot synthesize this in our bodies. Many people just don't like eating these foods, and do not take in enough vitamin D2.
  • Vitamin D3 is made in the skin in response to sunlight—UVB radiation. However, many of us are also deficient in this too. This occurs especially in the winter, when the days are short and dark. Also, using SPF factor 30 sunscreen—imperative for skin cancer protection—reduces skin absorption of UVB by 95%.

It may not be a coincidence that seasonal flu and other respiratory infections peak in the winter months. 

There are many other reasons/risk factors for low vitamin D levels, listed below.

How Common is a Vitamin D Deficiency?

50% of the world are vitamin D deficient. It affects one billion people around the globe. How could this be? Here's a list of reasons:

  • Social/cultural – Fewer people work outdoors these days for long periods. Plus peoples' eating habits have changed.
  • Skin color –The increased amounts of melanin in darker skin absorb greater quantities of UVB. Darker-skinned people need more UVB exposure than fairer skinned people to achieve adequate vitamin D levels. 
  • Older people – In the US, 60% of people in nursing homes and 57% in the hospital are vitamin D deficient. They may only go outside infrequently, tend to wear long-sleeved clothes, and cover up more—plus they may have a small appetite, or eat a poor diet.
  • Babies, children, pregnant and breastfeeding women – They all have increased vitamin D requirements and intake may not match demand.
  • Young adults – In a study in Boston, 36% of young healthy adults aged 18-29 were vitamin D deficient by the end of the winter. The authors suggested this was because young people don't like eating oily fish or eggs, and use more sunscreen to protect from skin cancer.
  • Obesity – Being obese significantly impairs our body's ability to produce vitamin D3 in sunlight. 42% of the US population is now obese.
  • Medical conditions – Some medical conditions reduce your absorption of vitamins from the gut, for example, coeliac disease, lactose intolerance, or Crohn's Disease. Bariatric surgery has the same outcome.
  • Kidney disease – Vitamin D levels are lowered with kidney disease because vitamin D is converted to its active form in the kidney. 
  • Lymphoma – Vitamin D levels are lowered in people suffering from lymphoma.
  • Primary hyperparathyroidism – This is a condition in which there is an increased breakdown of vitamin D.
  • Autoimmune disease – Vitamin D deficiency is more common in people with a range of autoimmune diseases such as rheumatoid arthritis, diabetes, multiple sclerosis and systemic lupus erythematosus (SLE).
  • Medications – Some medication interferes with vitamin D such as anticonvulsants, benzodiazepines, and some anti-HIV drugs.
  • Special dietsVegans, for example, avoid eggs, meat or fish.

What Does Vitamin D Do?

Vitamin D has two important roles:

1. Calcium and Phosphorus Metabolism

Vitamin D increases blood levels of calcium and phosphorus. It also regulates osteoblastic (bone-building) and osteoclastic (bone-clearing) activity. It is used to prevent and treat osteoporosis. However, mega-doses of vitamin D are not advised. It should be used within the recommended dosage.

2. Supporting the Body's Defense Mechanism Against Infection

Vitamin D has many complex effects on the body's defense mechanisms. It plays a role in maintaining the barrier function of the skin and at other epithelial cell surfaces. It is also involved in innate immunity – this is your body's ability to recognise and destroy an invading organism. Vitamin D also plays a role in adaptive immunity – the way your body produces an antibody response.

Why Does Vitamin D Deficiency Matter?

Evidence is accumulating of the potential health risks associated with low levels of vitamin D. It must be stressed that these are observational studies—studies which report data that have been collected in specific populations/situations—and that just because these statistics have been observed, that does not prove causation. More research is needed. However, the links between low levels of vitamin D, and many different diseases are still relevant, and of great public health interest.

In 2017, the journal PLOS One, reported a meta-analysis of 26,916 participants, regarding vitamin D and mortality. The authors concluded that people with low blood levels of vitamin D —less than 30 nmol/L—had significantly higher mortality than those with recommended levels of 75-99.9 nmol/L.

In a 2017 review in the journal Vitamin D and Chronic Diseases, the authors reported the following—see the list below. The authors defined vitamin D deficiency as a blood level of vitamin D of less than, or equal to, 20 ng/ml.

Vitamin D deficiency has been reported:

  • To increase the risk of cancer of the breast, prostate and bowel, by 30-50%.
  • To increase the risk of cardiovascular disease. Vitamin D stimulates the production of nitric oxide and helps prevent oxidative stress. There appears to be a link between low levels of vitamin D and high blood pressure. Vitamin D may have an anticoagulant effect. It may also have a role in reversing atherosclerosis.
  • To increase the risk of the onset of diabetes. Vitamin D deficiency is associated with insulin resistance, and with pancreatic cell function.
  • To effect brain function. Vitamin D works a neurotransmitter and also has a protective role for brain tissue. Vitamin D deficiency has been linked to a higher risk of depression, Alzheimer's disease and epilepsy.

Of note, other studies have reported reduced mortality in people taking vitamin D supplements.

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How to Increase Your Vitamin D Levels

  1. Eat foods rich in vitamin D, like fatty fish (tuna, salmon); foods fortified with vitamin D, like some dairy and cereals; cheese; eggs (the yolks); beef liver and any of these.
  2. Expose your skin to sunlight, without sunscreen. For fair-skinned people 15-20 minutes per day. For darker-skinned people 20-40 minutes per day.
  3. Consider taking a vitamin D supplement.

How Much Vitamin D Supplement to Take?

The Mayo Clinic "recommends that adults get at least the RDA of 600 IU. However, 1,000 to 2,000 IU per day of vitamin D from a supplement is generally safe, should help people achieve an adequate blood level of vitamin D, and may have additional health benefits."

Are vitamin D supplements safe?

For the vast majority of people, if you take vitamin D supplements within the recommended levels, it is safe. However, as with any new regular medication/supplement, if you have any medical conditions or take any other medicines, you are strongly recommended to discuss this with your doctor in advance. It is possible to have a blood test to check your vitamin D levels—however, this is rarely felt to be necessary. 

What are the Side Effects of Vitamin D?

Vitamin D is well tolerated and side effects are uncommon. The most common side effects are skin rashes or urticaria, aka hives. The most serious side effect is hypercalcaemia—a raised calcium level—but this is only possible when you take high levels of vitamin D for long periods and is very rare. If you know you have high calcium levels already, do not start vitamin D supplements.

Signs/symptoms of vitamin D toxicity include

  • Anorexia
  • Vomiting
  • Fatigue
  • Weakness
  • Thirst
  • Frequently passing urine
  • Constipation

If you take vitamin D supplements and develop these symptoms, you must see your doctor without delay.

Who Should Not Take Vitamin D Supplements?

Do not take vitamin D supplements if you have:

  • Hypercalcaemia
  • Severe kidney disease
  • Kidney stones
  • Heart disease – and/or take digoxin
  • Sarcoidosis
  • Allergy to vitamin D, or any vitamin D products
  • Other allergies —some vitamin D drops contain peanut oil, aspartame, and other substances, such as food colorings and dyes. Check the product ingredients carefully.
  • Check with your doctor before taking any supplements.

Are There Any Drug Interactions With Vitamin D?

  • Anticonvulsants – enzyme-inducing e.g. carbamazepine, phenytoin, topiramate, and non-enzyme inducing e.g. gabapentin, lamotrigine
  • Benzodiazepines – e.g. diazepam, nitrazepam
  • Steroids – e.g. prednisolone taken by mouth
  • Digoxin – there is a risk of digoxin toxicity
  • Cholestyramine – this prevents vitamin D absorption
  • Actinomycin –this possibly inhibits vitamin D absorption from the gut
  • Imidazole – this inhibits activation of vitamin D in the kidney

This list is not exhaustive. If you take regular medication, always check with your doctor or pharmacist before you start to take any additional medicines.

How to Take Vitamin D Supplements

  • Vitamin D is available as a tablet, capsule, soft gel, or as drops.
  • Choose the preparation/brand which suits you best and the appropriate recommended dosage. There is no benefit from taking large doses of vitamin D and this may be harmful, so do not be tempted to exceed the recommended dose.
  • Take care because not all vitamin D products contain the same amount of vitamin D – cholecalciferol. In one 2013 study, published in the Journal of the American Medical Association, researchers tested various vitamin D brands and found the potency of cholecalciferol varied from 9 – 146% of the stated dose. Only one manufacturer supplied a product within 90 – 120% of the expected potency. 

When choosing a vitamin D product, always look at the back of the packaging and check the product is USP verified. This means the products have been rigorously tested and the ingredients have been verified. 

  • Vitamin D options are available for vegans.
  • Take vitamin D just before a meal. This is a fat-soluble vitamin and if you take it on an empty stomach is unlikely to be absorbed.
  • You generally take vitamin D once a day—either in the morning or at night. If you don't eat breakfast, take in the evening, just before your evening meal.
  • There is a suggestion that vitamin D may interfere with melatonin production, although there is no evidence it affects sleep, however you may prefer to take it in the early evening.
  • Make sure you always drink plenty of fluids.
  • If you forget your daily dose, miss it out that day, and take it on time the next day.

Vitamin D, Respiratory Infections, and COVID-19

UK scientists have warned that you should not take high levels of vitamin D for the purpose of preventing or treating COVID-19. However, some experts are suggesting the reverse. 

In a publication from March 2020 in the journal Nutrients, the authors reviewed the current medical evidence and suggested that vitamin D supplementation might reduce the risk of influenza, COVID-19, and deaths.

They presented evidence to suggest that higher levels of vitamin D in the population would reduce the risk of acute respiratory tract infections including influenza, COVID-19, and pneumonia. They also suggested that additional vitamin D should be started now, to raise levels before the onset of the winter.

But on the contrary, UK scientists warn that caution is needed. The currently available evidence comes from observational studies only which do not prove causation. Furthermore, high levels of vitamin D can be harmful. 

Final Thoughts From the Doctor

The issue of vitamin D deficiency and the threat of COVID-19 was recently discussed in the New York Times. They reached a sensible conclusion—that those who cannot obtain enough vitamin D from their diet should consider a supplement of 1000-2000 IU/day.

It seems to me that vitamin D deficiency is so common, supplementation is safe, and may indeed have numerous understandable benefits for our overall health. This is something relatively easy we can do, which is likely to be beneficial and not harmful for ourselves and those we love. Whether or not it will help protect us from COVID-19 is unknown—but maybe … just maybe? Furthermore, to get through this pandemic at your healthiest, don't miss these Things You Should Never Do During the Coronavirus Pandemic.

Dr. Deborah Lee is a medical writer for Dr Fox Online Pharmacy.

Eat This, Not That! is constantly monitoring the latest food news as it relates to COVID-19 in order to keep you healthy, safe, and informed (and answer your most urgent questions). Here are the precautions you should be taking at the grocery store, the foods you should have on hand, the meal delivery services and restaurant chains offering takeout you need to know about, and ways you can help support those in need. We will continue to update these as new information develops. Click here for all of our COVID-19 coverage, and sign up for our newsletter to stay up-to-date.

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