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High blood levels of vitamin D protect against COVID-19 and other respiratory infections

High blood levels of vitamin D protect against COVID-19 and other respiratory infectionsThe immune system cannot function without vitamin D. In fact, blood levels of the nutrient should ideally be higher than the official threshold values for optimal protection against COVID-19 and other respiratory infections, according to a new study from the University of Chicago Medicine that is published in JAMA. An estimated 50 percent or so of the world’s population is believed to lack vitamin D, and people with dark skin are particularly vulnerable. It has been shown in previous studies that the majority of people who test positive for COVID-19 lack vitamin D. Therefore, scientists plan to look at whether daily vitamin D supplementation can help prevent COVID-19 infections or reduce serious symptoms. The researchers mention that it often takes high-dosed supplements to optimize levels of vitamin D in the blood.

Exposing your skin to sunlight is best way to get vitamin D. People with dark skin and older people, however, do not synthesize the vitamin quite as effectively. Also, during the winter period, the sun sits too low in the sky at our latitudes to enable vitamin D synthesis. Then there is the fact that overweight people and diabetics have an increased need for the nutrient. Other factors that contribute to the widespread vitamin D deficiency are modern living and spending far too much time indoors, veiling in certain cultures, full beards, face masks, and the use of sun factor creams. According to the researchers behind the new study, around 50 percent of the global population is vitamin D-deficient with blood levels of the nutrient below 30 ng/ml. This can have broad implications for a person’s health.

Blood levels of vitamin D are important for our protection against COVID-19

As part of the new study from the University of Chicago Medicine, the scientists pitched blood levels of vitamin D against the tendency to test positive for COVID-19. In the United States and large parts of the world, having blood levels of 30 ng/ml or higher is regarded as sufficient. Nonetheless, the scientists observed that black people with levels of 30-40 ng/ml had a 2.65 times higher risk of testing positive compared with people that had 40 ng/ml or more. It appears that black or colored people are more exposed if they lack vitamin D.
According to the new study, having vitamin D levels well above the official threshold value protects against COVID-19, particularly among people of color.
The new study is published in the Journal of the American Medical Association and follows up on a study showing that lack of vitamin D (less than 20 ng/ml) increases the risk of testing positive with COVID-19. The scientists also referred to a study from 2020 showing that 80 percent of patients hospitalized with COVID-19 lacked vitamin D.

We need more vitamin D than the official recommendations

The scientists behind the new study claim that blood levels of vitamin D should be higher than the threshold values that are normally considered adequate, at least if you want to protect yourself against COVID-19. This is particularly true for people of color. The results of the study will be used to form the basis for new clinical studies to test if supplementing with vitamin D can minimize the risk of contracting COVID-19 or developing serious symptoms as a result of being infected.
Lead investigator David Meltzer, PhD, who is affiliated with the University of Chicago Medical Center, was inspired by an earlier study from the beginning of 2020. This study showed vitamin D-deficient participants who were supplemented with vitamin D had a much lower rate of respiratory infections than those not taking a supplement.
Meltzer also refers to the enormous amount of research showing that vitamin D strengthens the immune response and counteracts unwanted inflammation. Still, as he points out, there are conflicting results. It appears that in the studies where vitamin D has not had an effect on the immune system the doses have been too low. Meltzer also points out that the official recommendations for vitamin D are exclusively targeted at maintaining bone health – not immune health. The question is how much do we need?

Recommendations and actual requirements

In Denmark, health authorities recommend that white adults up to 70 years of age get 5-10 micrograms of vitamin D daily. In the United States, the recommendations call for 15 micrograms. The actual need for vitamin D varies from one person to another and depends on factors such as sun exposure, skin color, ageing processes, BMI, chronic diseases, genes, and many other things. The safe upper intake level for vitamin D is 100 micrograms per day according to EU’s Scientific Committee on Food and The National Academy of Medicine in the USA. In any case, it is a good idea to strive to have optimal blood levels of vitamin D if you want to strengthen the immune system against COVID-19 and other respiratory infections. In Denmark, the lower threshold value for vitamin D in the blood is 50 ng/ml. Leading scientists believe the optimal levels are somewhere around 75-100 ng/ml.

Other studies of vitamin D and the immune defense

Scientists from Queen Mary University of London have launched a study to see if vitamin D taken in different doses can lower the risk and severity of COVID-19 and other respiratory infections. The study includes around 6,000 people, all of whom had baseline levels of vitamin D below the threshold value.
The control group will be following the authorities’ recommendations of getting 10 micrograms per day. The scientist will not be looking at whether or not these participants take supplements. The remaining participants will be divided into two groups that will receive vitamin D in two different doses. For a period of six months, one group will be taking capsules with 20 micrograms per day, while the participants in the other group will be taking 80-microgram capsules. When the study has been completed vitamin D levels in the blood will be measured again. That way, the scientists will be able to see how the different vitamin D doses and blood levels of the nutrient have affected the COVID-19 infection rate and disease severity.


David O. Meltzer et al. Association of Vitamin D Levels, Race/Ethnicity, and Clinical Characteristics With COVID-19 Test Results. JAMA Network Open, 2021

University of Chicago Medical Center. High vitamin D levels may protect against COVID-19, especially for Black people, study suggest. ScienceDaily. March 22, 2021

José L Hernandez et al. Vitamin D Status in Hospitalized Patients with SARS-CoV2- Infection. The Journal of Clinical Endocrinology & Metabolism. 27 October 2020

Hutchings, N. et al. Patients hospitalized with COVID-19 have low levels of 25-hydroxyvitamin D. Endocrine. Interview mit Dr. Carlberg: Vitamin D, epigenetik und der respons-index. Hämtad. 2020-09-03

Trial of Vitamin D to reduce Risk and Severity of COVID-19 and other Acute respiratory Infections (CORONAVIT).

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