Vitamin D Deficiency, Exercise, and COVID-19

As the rules around the pandemic begin to change and our connection with family, friends, and strangers slowly returns, it is best to keep in mind that this virus, as well as the common cold and flu, are still prevalent. You can still become infected and potentially sick. Fortunately, there are several ways to boost your immune system and bolster your body’s ability to fight off and prevent COVID-19 as well as other respiratory illnesses. Here, we are going to talk about two items that almost anyone can start optimizing and utilizing right now: Vitamin D and exercise!

Based on the nickname given to Vitamin D, the sunshine vitamin, it should theoretically be abundant in the state of California. However, Dr. Samar Singh, a UCI health endocrinologist, stated that about 50% of her patients have low levels. She proposed that this could be linked to spending more time indoors and the use of sunscreen. Another factor is the complexion of our skin. In the USA, 42% of the population is deficient. The rate of deficiency increases with people of darker skin, with 69% for Latinos and 82% of African Americans [1]. Lastly our age and fat cells heavily affect our body’s ability to create vitamin D. Vitamin D is synthesized from the cholesterol within our skin. As the sun’s ultraviolet B (UVB) rays make contact with skin cells, it provides the energy needed to convert the cholesterol in our skin into Vitamin D [2]. As we age, our bodies become less efficient at converting cholesterol into Vitamin D and our fat cells sequester it. So how does all of this tie back to our immune system?

A study of 489 patients published in JAMA Network Open found that “the relative risk of testing positive for COVID-19 was 1.77 times greater” for patients who were likely vitamin D deficient compared with those with sufficient levels. Vitamin D has several functions within the body and has been long known for its important role in bone health however, there is a building body of evidence that shows it plays a critical role in our immune system [3]. Vitamin D deficiency impairs the ability of macrophages (a form of white blood cells that fight off infection) to mature and may explain the significant and negative crude relationship seen in Europe between vitamin D levels and the number of COVID-19 cases, especially the mortality caused by this infection [4]. It may also explain the similar situation seen in the United States. Thankfully, there are several things we can do to boost our levels, and no, it doesn’t require expensive supplements.

While food sources that naturally provide vitamin D such as swordfish, salmon, tuna, sardines, egg yolks, and mushrooms, are fairly limited, we can also get it from fortified sources as well, such as dairy products, orange juice, soy milk, and cereals. Another great source can come from going outside and doing a level of exercise you feel comfortable with. This will help your vitamin D levels in two ways. First, the sunlight will synthesis it within your body via the mechanisms mentioned earlier. Secondly, the continual act of increased physical activity will result in the shrinking of fat cells which will ultimately sequester less vitamin D consequently, and will therefore allow your body to use more of it towards immune and other vital functions. So go outside, take a walk in your neighborhood, or a stroll on the beach. Take advantage of the ample vitamin D producing sunlight we are fortunate to have here on California’s Central Coast!

– By Johnathon Primmer, Dietetic Intern, California Department of State Hospitals, Atascadero