Vitamin D is an essential nutrient that is important for health. Unfortunately about 40% of the United States population is deficient in this vitamin. What effect does this have on overall health and also on Covid-19 severity?
The main health benefit of Vitamin D is its effect on bone health. Vitamin D is needed to regulate the absorption of calcium and phosphorous. Low vitamin D levels in children lead to Rickets, a disease where the bones don’t properly mineralize resulting in soft bones and skeletal abnormalities. In adults, low vitamin D leads to osteomalacia, which is weakening of the bones. This leads to an increase in the incidence of fractures, which decreases quality of life and increases mortality.
Vitamin D is important in facilitating normal immune system function. This leads to a decrease in risk of developing upper respiratory tract infections and the flu, as well as a lower risk of developing MS. Other suspected beneficial effects from vitamin D include a lowered risk of heart disease and beneficial effects in type 1 and 2 diabetes, glucose intolerance, hypertension and regulating mood and warding off depression. Lastly, an adequate level of vitamin D is associated with a lowered risk of colon, breast and prostate cancer.
Food sources of vitamin D are not very common. It is found in the flesh of fatty fish and fish liver oils, and there is a small amount in beef liver, cheese, egg yolks and some mushrooms. You can also find vitamin D in fortified foods such as milk (100iu/cup), ready to eat cereals, orange juice, yogurt and margarine. The biggest source of vitamin D for most people is the sun, it is estimated you need 15 minutes of sun exposure without sunscreen on your face, arms and hands at least twice a week to maintain an adequate level. This is just an estimation however, actual exposure time will be influenced by things such as the season, time of day, cloud cover, presence of smog and other factors. Sunscreen with an SPF greater than 8 will block vitamin D absorption, and sun exposure though glass (like a window) is not a source of vitamin D.
Vitamin D supplements are available as both vitamin D2 and D3, with D3 being preferable at higher dosages. Since Vitamin D is a fat soluble vitamin it takes about 6 weeks of supplementation to see an effect. Supplements should be taken with the biggest meal of the day because absorption may be increased by as much as 50% in the presence of fats and oils.
A blood level of greater than 20n g/dl is sufficient for optimal health for over 95% of the population, do not take vitamin D supplements if your level is over this. A level of over 50ng/dl would be considered too high. Risk groups for low vitamin D include older adults, those with limited sun exposure, those with dark skin, people who suffer from inflammatory bowel disease, obese individuals and those that have undergone gastric bypass surgery. These populations should have their vitamin D level checked periodically.
Preliminary studies are showing an association between vitamin D status and Covid-19, with those patients that have a lower level of vitamin D being more likely to test positive for the virus and showing more severe symptoms. Patients with a lower vitamin D level are also more likely to need intensive care. In a retrospective Indonesian study of 780 patients with Covid-19 the majority of deaths occurred in patients that had a low level of Vitamin D. When we examine the number of cases of Covid-19 in Europe there is a lower incidence of Covid-19 in Scandinavian nations where they consume lots of cod liver oil and vitamin D supplements compared with the rest of Europe. Vitamin D modulates white blood cells and keeps them from releasing too many inflammatory cytokines. This decreases the severity of the Covid-19 related cytokine storm which is what causes the most lung injuries.
To sum it all up, people with adequate Vitamin D levels of over 20 ng/ml have an increased resistance to Covid-19. One of the best ways to get your vitamin D is to spend some time in the sun a few days a week. There is no evidence to support the taking of mega doses of vitamin D supplements and I would not recommend this because Vitamin D is a fat soluble vitamin and can lead to toxicity in high doses. If you fall in to one of the high risk groups for low vitamin D levels have your practitioner check it with your next bloodwork and follow their recommendation for supplementation. Otherwise, just schedule a nice walk in the sun for 20 minutes 3 times a week, this will help you keep your blood level of this important vitamin optimal and will also boost your mood and help with cardiovascular fitness!