Mardi Crane-Godreau, PhD

Vitamin D, what’s all the fuss?  Is it relevant to COVID-19? To read about new developments, click here.  But if you simply want to understand a little more about this fascinating hormone/vitamin, read on.

Vitamins are needed in small quantities to support normal life processes. Most can be obtained from food sources.   However, since diets vary, some need to be obtained from supplements.  Vitamin D is somewhat of a special case.  It’s actually a hormone, obtained from food or supplements, but also made by the body under favorable conditions.  We humans are able to make our own vitamin D when our skin is exposed to sunlight.  Exposing arms and legs for about 10 to 15 minutes per day, when the sun is at least halfway up from the horizon, can go a long way to provide what is needed by the body to make vitamin D.

A note of caution! Sunburn is dangerous and extended time in the sun does not mean that your body will make more vitamin D.   Our systems have a natural shut off mechanism.  After a certain point, the body stops making vitamin D, so this is one of those instances where too much can be worse than not enough.

In this time of COVID-19, many articles have been written about the possible benefits of vitamin D in reducing the impact of the disease.   Some have looked at evidence from patient records comparing their previously measured vitamin D levels with how sick they became with COVID-19.   Others have looked at established information about which groups of people tend to have adequate vitamin D levels and which groups tend to have low, deficient levels of vitamin D.   Many of these articles point to evidence that vitamin D has a protective benefit when fighting respiratory viral infections in general.  They also point to recent evidence that COVID-19 is less severe when vitamin D levels are adequate.

Sunlight to Vit D

As a hormone, vitamin D has a wide range of effects on the body.  It helps to regulate over a thousand genes, many of which are related to the immune system.  Vitamin D modulates immune responses allowing for a balanced response by the body to challenges from bacteria and viruses.  It plays a key role in making molecules that attack and destroy microbes.  It also supports cell to cell signaling, making it possible for the immune system to respond without excesses that can be as dangerous as the microbes.

How do you know if you are getting enough vitamin D?  Simple blood tests are available to determine if your level is sufficient to meet the needs of your body. Vitamin D deficiency and insufficiency are found widely in industrialized societies world wide, especially in areas more than 37 degrees latitude distant from the equator.   Deficiency is also common in older adults, in individuals with diabetes, heart disease, obesity, hypertension and some forms of cancer.  In the US,  vitamin D deficiency is documented to be common in those with African American genetic heritage.  Vitamin D deficiency is defined as having a level of 25-hydroxyvitamin D below 20 ng/ml (50 nmol/liter).  When vitamin D is between 21–29 ng/ml (52.5–72.5 nmol/liter) it is defined as insufficient.  If available, ask your medical provider for a test.

Sources differ on how much vitamin D individuals should take.  In 2011, The Endocrine Society, a prestigious group of professional endocrinologists who treat patients with hormonal disorders, recommends from 1,500 iu  (37.5 mcg) to 2,000 iu (50 mcg) for anyone over 19 years old to raise the blood level of 25(OH)D consistently above 30 ng/ml (75 nmol/liter).    For those 19 and under, they suggest that at least 1000 IU/d of vitamin D may be required to achieve and maintain a level consistently above 30 ng/ml (75 nmol/liter). They acknowledge that specific at-risk groups may need higher levels of vitamin D supplementation to achieve and maintain sufficient vitamin D.  The Endocrines Society also states that a maximum safe daily dose should not exceed 10,000 iu (250 mcg). Scientists conducting the VITAL (vitamin D and Omega 3) Trial also have chosen a dose of 2,000 iu/day dose for those in the study, who are receiving vitamin D supplements.  However this study is ongoing with results likely in 2021 or beyond.

Irrespective of these recommendations and studies, many physicians recommend higher doses. The safest and most effective way to determine your need for vitamin D and the correct dose, is to consult your medical provider for professional advice.

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