Boosting your immune system against coronavirus is less complicated than you think

My friend and I have been talking weekly since the COVID-19 pandemic began. She mentioned that her mother has been wondering about what supplements she should be taking to avoid an infection. I’ve met her mother several times over the course of our 20 plus year friendship. She is in her 70s and lives in California. She has a PhD in chemistry. I was surprised that she was confused. Wasn’t the internet providing plenty of information on what to take?

I typed supplements for COVID in the search box. Among the first items that appeared were:

  • 20 Vitamins and Supplements to Boost Immune Health
  • Don’t Rely on Supplements to Treat or Prevent COVID-19
  • The 15 Best Supplements to Boost Your Immune System Right Now

I see why her mother is confused. The messaging out there is so mixed. And who wants to start taking 20 plus pills per day? The idea makes my stomach hurt!

In the spirit of big picture learning, I want to share some information about three natural immune system boosters that can decrease the chances of a serious coronavirus infection. Before we get there, let’s take a look at two ways our body prevents infections.

The literal layers of protection that boost your immune system against coronavirus

A virus has to overcome obstacles to cause an infection in your body. The first ones are so obvious that we often forget about them. I am referring to physical barriers – your skin, your GI tract, and your respiratory tract. GI tract refers to the long tube that starts in your mouth and finishes in your buttocks. Respiratory tract refers to your nose, throat and airway passages, large and small. These are THE gateways to your body, and we have some control over how well they work.

Each of these barriers is made of epithelial cells. You can picture them as a protective cover like plastic wrap-thin, flexible, strong yet fragile at the same time. The GI tract and respiratory tract have an additional coating in the form of mucus. The connections between epithelial cells are tight junctions. The name is misleading. The junctions can be tight OR loose. Think about a sliding door. It can be:

  1. closed
  2. partway open
  3. completely open

The more open the door is, the more people can come inside.

It is a similar situation with the connections between epithelial cells. We need those sliding doors to remain closed in the presence of bacteria or viruses as much as possible. We also need our epithelial cells to turn over efficiently, and on a regular basis. This process maintains good tight junction functioning. The SARS-COV-2 virus primarily enters our body through the respiratory tract. If we can strengthen the protective lining of the tract, we can boost our immune system against coronavirus. We can prevent large amounts of the virus from getting inside. That means a milder infection, or no infection at all.

In the case of COVID-19, the epithelial cells that line the GI tract are also essential. A healthy gut lining can mean the difference between a mild case of COVID-19 or a severe one. That may seem strange. Why should the lining of your gut have anything to do with an infection that causes damage to your lungs? It turns out that most of our immune system lives in the lining of the intestines, just under that epithelial cell layer. The cells respond to signals locally in the gut and signals from distant areas to become more or less active. When the epithelial lining is leaky and malfunctioning, this causes problems.

  1. Pathogens, food bits and other materials come through because the tight junction sliding doors are inappropriately open
  2. Your vigilant immune system is confused by the mix of innocent food fragments, helpful bacteria and harmful organisms
  3. The immune system creates an inflammatory response to deal with all the potential invaders

Over time, the immune system is overactive but less effective. The inflammation becomes chronic and dangerous. It contributes to the development of health conditions like hypertension, diabetes and dementia. It is not a coincidence that people with these illnesses have a higher chance of hospitalization if they get the coronavirus. They are living with a high level of body inflammation at baseline. This means when their body attempts to fight a COVID-19 infection, they are more likely to develop the dreaded “cytokine storm” that can lead to lung failure and death. When the lining of the GI tract is functioning well, it is a natural immune system booster. We can focus on supporting its function with targeted supplementation.

The first responders: innate immune cells that fight coronavirus

If a virus gets past any of our physical barriers, it faces the first responders of the immune system. There are many of them. For simplicity we focus on four important ones. Dendritic cells recognize foreign fragments in the body, such as parts of a virus. They are the sentinels of the immune system. I think of them as a combination of the neighborhood watch and the town crier that show up in stories from the past. Dendritic cells find anything that is possibly dangerous. Then they tell everyone else about it.

These cells exist to locate what is unfamiliar and to present their findings to other immune cells. These other cells, called natural killer cells, T helper cells, and macrophages, make decisions about what to do next. Sometimes they decide that what the dendritic cell is presenting is not a threat at all. Other times, they shift into killing mode. Macrophages actually eat the invaders by sucking them up like vacuum cleaners. Then they make enzymes that are like acid. The virus dies.

Natural killer cells and T helper cells make interferon. This is a powerful alarm signal for other immune cells. In the case of viruses like SARS-COV-2, interferon is essential.

  • It makes the macrophages eat the viruses more quickly
  • It brings more macrophages, natural killer cells and T cells into the battle
  • It gets the adaptive immune system involved to make antibodies

Antibodies make the killing response even stronger. They also stay with us for a while. If a virus recurs, our body recognizes it and kills it faster. We want to support the function of all these cells to boost our immune system against the coronavirus. This prevents a serious infection.

Enter vitamin A, vitamin D, and zinc: natural immune system boosters

Fortunately, there are many natural compounds that can strengthen both our physical barriers and our immune cell activity. I focus on these particular ones because all three perform multiple roles. Immunity is a complicated orchestra. Orchestras involve a conductor and sections of instruments composed of individual players. Each of those sections has its a leader. We can think of vitamin A, vitamin D and zinc as co-conductors who also lead smaller sections AND play several instruments. That’s how vital they are. All of them boost the immune system against coronavirus.

Sadly, a large percentage of adults are deficient in all three nutrients. The elderly are most at risk for deficiency. I advise getting these nutrients from whole foods as well as from supplements. It is safer to buy supplements directly from reputable manufacturers than from a site such as Amazon with many third party sellers. Jarrow Formulas has a good track record for supplement quality, and prices are reasonable.

Vitamin A

This vitamin helps the epithelial lining of the GI and respiratory tracts to form properly. Remember that the cells in these linings need to replace themselves constantly. When someone is deficient in vitamin A, the cells dry out. Picture a grape versus a raisin. They are the same raw material, but the grape takes up a lot more space. The smaller, shriveled epithelial cells are not a very effective barrier. They don’t do as good job of protecting us from infections. Vitamin A keeps the cells healthy and strong. It supports the production of protective mucus. It helps the tight junctions between the cells to maintain the right amount of closure. The dendritic cells also rely on vitamin A to guide them to the right places in the body. We want to have enough of those watchdogs in the intestines and the lungs. Vitamin A also makes the dendritic cells in the gut smarter – they are less likely to overreact to harmless materials like food bits. That means lower levels of chronic inflammation and a lower chance of a severe COVID-19 infectionResearch studies show that vitamin A levels correlate with lower frequency and severity of respiratory illnesses.

Food sources: liver, egg yolks, cod liver oil (I personally use the formulation from Nordic Naturals)

Supplementation considerations: you want to focus on actual vitamin A as opposed to beta carotene. The conversion from beta carotene to active vitamin A, called retinol, is inefficient in a large portion of the population. 10,000-15,000 international units, or IU, per day is a safe dose. To maintain appropriate balance, vitamin A is taken with both vitamin D and vitamin K2.

Vitamin D

Vitamin D Rich Foods

Vitamin D is more like a hormone because of its essential role in many processes throughout the body. Like vitamin A, it improves the functionality of those tight junctions between epithelial cells and trains the dendritic cells to recognize actual threats more effectively. This reduces total body inflammation. Vitamin D has a special role in respiratory infections. The cells lining the respiratory tract have many receptors for vitamin D, which suggests that these cells NEED vitamin D to work well. This vitamin makes macrophages more efficient in killings viruses by increasing production of antiviral proteins. **Vitamin D likely interacts with natural killer cells and T helper cells to increase the level of interferon in the lung. This is the immune system alarm signal mentioned above. This boosts the immune system against coronavirus.**Previous research suggests that lower vitamin D levels in the winter may relate to the higher number of respiratory infections during those months. This is probably because we have lower vitamin D levels due to less sun exposure. That can lead to a less robust immune response to viruses. More recent data from China shows that lower vitamin D levels at baseline may predict higher rates of death in patients hospitalized with COVID-19. Given what we know about vitamin D’s role in fighting respiratory infections, this makes sense.

Food sources: cod liver oil, shellfish (oysters, clams, shrimp, etc), fatty fish like tuna, sardines, salmon and mackerel

Supplement considerations: don’t forget about sunshine! This is actually the best way to improve vitamin D levels. A safe dose is 5000 IU per day. Vitamin D absorbs best when you take it after a meal containing fat. You should work with a clinician to monitor your vitamin D levels if you want to consider higher supplement doses. An optimal level is 35-60 ng/ml. Many functional medicine practitioners prefer higher levels, especially for patients with autoimmune diseases.


Foods high in Zinc

Zinc is an essential trace mineral. Approximately 10% of our genes make proteins that have to partner with zinc to work well. One example is that zinc increases the production of tight junction proteins. Without it, there are fewer sliding doors and more unguarded spaces between epithelial cells. That leads to many substances coming in through the GI tract. You now know that this leads to a higher inflammation level in the body and worse outcomes with coronavirus infections. In the respiratory tract, zinc has a protective role. It makes the epithelial cells more resilient and less likely to die when they face a lung infection. A 2017 study of patients in the intensive care unit found that lower zinc levels correlate with developing lung failure from acute respiratory distress syndrome, or ARDS. ARDS means that the epithelial lining in the lungs is not working. Small airways clog up because of the leaky lining, and the person cannot breathe. This syndrome is similar to what happens in those with severe COVID-19 infections. Zinc also interacts with our innate immune cells through the hormone thymulin. This hormone boosts the immune system against coronavirus. It is dependent on zinc for normal activity. Studies on the first SARS virus show that zinc interferes with the virus’s ability to copy itself. Preliminary data suggest that this is also the case for SARS-COV-2. Fewer copies equals a milder infection.

Food sources: oysters, crab, beef, lamb, crimini mushrooms, broccoli rabe

Supplement considerations: look for the zinc glycinate formulation, which has high absorption and minimal GI side effects. A dose of 15-30 mg per day is safe. You should work with a clinician to monitor your levels if you want to consider higher doses. Long term zinc supplementation can reduce copper levels. Partnering with a clinician can help you maintain a good balance of these two minerals.

You can’t out-supplement a destructive lifestyle with natural immune system boosters

I appreciate that my friend’s mother wants to do everything she can to prevent a coronavirus infection. It’s a scary disease. Taking pills makes us feel more in control of illness. I understand that is why so many people are seeking information about supplements. Still, I want to emphasize that your underlying lifestyle habits are by far more important than supplements in boosting the immune system against coronavirus. Our bodies crave nutritious food, enough sleep, appropriate exercise and stress management. In times of fear we eat more junk food, sit a lot and sleep less. If we continue living our lives this way, we are more likely to get sick.

This pandemic makes it clear that many of us need a mind/body reboot to build resilience in our immune system. Targeted supplementation is a useful accessory for health. It’s not a replacement for good habits. If you want to better understand your health issues and why you have them, consider seeking out a qualified practitioner in functional medicine. We focus on diagnosing the root causes of your illness and correcting imbalances as much as possible. We do this through tailored nutrition, lifestyle changes and treatment regimens. Ultimately, this is the best way to boost your immune system against coronavirus.

Woman wearing mask in supermarket shopping for tomatoes


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