Vitamin D "sunshine vitamin" is a fat-soluble secosteroid provided by food and produced in the form of vitamin D3 in the skin after exposure to ultraviolet rays (UVB), it is then transformed into its active form in the liver and the kidneys. Vitamin D production starts from acetyl-CoA following the cholesterol production pathway until 7-dehydrocholesterol is synthesized. Statins act through the reversible block of hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR), thereby reducing cholesterol synthesis and the production of 7- dehydrocholesterol and vitamin D. Statins do not prevent your body from absorbing cholesterol from your food, but instead prevent your liver from making it by blocking an enzyme in the mevalonate pathway called HMG-CoA reductase, which is used to make cholesterol in the liver. Cholesterol is found in almost every cell in your body. This waxy substance is vital for optimal functioning of cell membranes, regulation of protein pathways, and support of brain health, hormone levels, and reduction of heart disease risk. Image 1

The increased emphasis on protecting the skin against sun damage (fear of cancer) and the shift from an outdoor to an indoor and restricted lifestyle in recent generations has led to a serious vitamin D deficiency problem in many developed parts of the world. Added to this are recommendations to limit the consumption of animal fat wrongly accused of the emergence of cardiovascular diseases.

Vitamin D deficiency is a global public health problem in developed and developing countries.

Low levels of vitamin D are associated with upper and lower respiratory tract infections, heart disease, asthma, cancers, diabetes, multiple sclerosis, HIV, hypertension, inflammatory diseases of the intestine, Alzheimer's disease and other autoimmune diseases.

People with naturally dark skin tones benefit from natural sun protection and require at least three to five times longer exposure to produce the same amount of vitamin D as someone with fair skin tones. Image 2

Vitamin D being fat soluble can be stored in fatty tissues. Accordingly, experimental and human studies suggest that greater storage of vitamin D in body fat decreases its bioavailability, hence the need for obese people to dissolve their body fat stores by fasting or exercising to benefit from it.

Vitamin D deficiency has been found to contribute to acute respiratory distress syndrome; and…case fatality rates increase with age and with comorbidity of chronic diseases, both of which are associated with lower 25(OH)D concentration.

Vitamin D supplementation causes at least 1.5-fold change in expression of genes involved in apoptosis, immune function, transcriptional regulation, epigenetic modification, stress response, cell cycle activity and differentiation. This finding is consistent with previous in vitro studies which have shown that 1,25(OH)2D3 directly or indirectly controls more than 200 genes, including genes responsible for regulating cell proliferation, differentiation, angiogenesis and immunomodulatory activities on innate and adaptive immune responses.

Researchers have shown that vitamin D has a "significant protective effect" and reduces the risk of acute respiratory infection from 60% to 32% of patients as well as it may help prevent respiratory infections and reduce the use of antibiotics.

According to research done by GrassrootsHealth's group of 48 vitamin D researchers, 40 ng/ml is the lower edge of the optimum, with 60 ng/ml to 80 ng/ml being ideal for health and disease prevention.

There is strong scientific evidence that vitamin D plays a central role in your immune response and your ability to fight infections. Recent studies supporting higher vitamin D levels may lower your risk against COVID-19 and its complications.

Mounting evidence suggests that your vitamin D status may also play an important role in the development of COVID-19, as well as the severity of the disease.

Vitamin D plays an important role in reducing the risk of respiratory tract infections, knowledge about the epidemiology of influenza and COVID-19, and how vitamin D supplementation might be a useful measure to reduce the risk. Through several mechanisms, vitamin D can reduce the risk of infections.

These mechanisms include the induction of cathelicidins and defensins which can lower viral replication rates and the reduction of proinflammatory cytokine levels which produce the inflammation that damages the lining of the lungs, leading to pneumonia, as well as the increase in concentrations of anti-inflammatory cytokines…

Evidence supporting the role of vitamin D in reducing the risk of COVID-19 includes that the outbreak occurred in winter, when 25-hydroxyvitamin D (25(OH)D) concentrations are the weaker; that the number of cases in the southern hemisphere towards the end of the summer is low.

Diabetic patients with liver or kidney problems are at high risk of deficiency, as are patients with gastrointestinal disorders such as celiac disease, pancreatitis, low bile levels, thus worsening their health status with respect to live with Covid-19.

There are many things we can do to improve our resistance to infections. These include getting regular physical activity, enjoying a healthy diet and getting plenty of sun exposure to replenish vitamin D, getting enough sleep, and quitting smoking. Taking multivitamin combinations that include vitamin D, or a vitamin D supplement, probably can't hurt, and it might help. Image 3

One thing to keep in mind is that our bodies can store vitamin D in liver and fatty tissue, so there are plenty of opportunities to make vitamin D in the spring and summer. Preparing for winter with a good reserve of vitamin D remains as vital as necessary to possibly help our immunity to face the threats of covid-19 just in case?