There has always been a lot of talk–and commerce–about immune system boosters in wellness circles, but attention to the notion of enhancing the immune system is even greater since the onslaught of the COVID-19 pandemic. People understandably want to know if there are things beyond social distancing and handwashing they can do to lower their risks of contracting the virus that causes COVID-19.
As will be detailed below, there are some steps we can take to enhance our immune systems’ ability to fight off infectious agents. When it comes to supplements, however, the immediate answer to the question of whether it is possible to take something that will strengthen the immune system’s ability to fight off the novel coronavirus is, unfortunately, no. As we will explain, no over-the-counter pills have ever been shown definitively to have that ability for any type of infection, be it bacterial, viral, fungal, or parasitic.
Immune System 101
There are some supplements, however, for which limited data suggest a possibility of enhancing some parts of the immune system that might be relevant to dealing with a viral infection. Before detailing them, however, it is necessary to give a brief overview of the human immune system. You can read other, informative overviews of the immune system in this posting from the NIH and here.
After the central nervous system (i.e. brain and spinal cord), our immune systems are the most complex we have. It is designed to recognize and destroy abnormal cells, examples of which are bacteria, viruses, and cancer cells. The immune system is divided into two separate but interrelated systems, innate and adaptive. The innate immune system is hardwired into our genes and responds to proteins called antigens that are common to abnormal cells but generally not present on the surface of our own body’s cells. Examples of cells that make up the innate immune system are neutrophils, which are very important in the response to viral infection, and eosinophils, which respond to parasitic and fungal infections and also increase during allergic reactions. Cells of the innate system also continuously destroy malignant cells as they crop up, helping to prevent many cancers. These are our first line of immune defense, but because they are generalists, they often fall short of the job of eliminating specific abnormal cells.
The adaptive immune system, by contrast, learns to recognize specific abnormal or pathogenic cells that can cause disease. We are constantly bombarded by abnormal cells every time we touch something or take a breath. Immune cells called lymphocytes are the primary weapons of the adaptive immune system. After a first exposure to an antigen-presenting pathogenic (i.e. disease-causing) cell, lymphocytes called T and B cells express new proteins that are targeted at specific antigens on a single type of invading pathogen. Then, if we are exposed to the same abnormal cell again, specific T and B cells can rapidly emerge to knock it out. B cells make antibodies, which is one way they can react swiftly to infectious agents. For many illnesses, B and T lymphocyte memory is long-lived, sometimes for a lifetime. That is why before the measles vaccine was available, it was observed that no one could get measles twice.
Vaccination works by stimulating the creation of a reservoir of immune cells that remember proteins (antigens) from a disease-causing organism like a virus or bacteria. When we receive an immunization, we are given an inactivated form of a bacteria or virus, which cannot cause disease but does stimulate an adaptive immune system response. Then, if we are exposed to those abnormal cells again by nature in their active form, specific T and B cells are ready to recognize and neutralize them. Vaccines are right now the only proven pharmaceutical method of “boosting” the immune system. Unfortunately, some viruses, like the flu virus, mutate so quickly that it has been very difficult to find proteins on them that are stable enough to permit development of a vaccine. Every year we have to come up with a new flu vaccine to account for new strains of the flu virus, although there is some hope that common proteins to all strains of the flu virus are coming to light that will allow a universal vaccine.
We don’t know yet whether SARS-CoV-2 provokes an immune response that is long-lived enough to prevent a person who has been infected from getting re-infected. It is known that this virus mutates very slowly, which is good news for vaccine development.
In the last 50 years, immunologists have identified hundreds of different types of immune cells and thousands of genes and proteins in and on those cells that are involved in fighting off infection. This is the reason that boosting the entire immune system is hard to conceive. No single pharmaceutical agent—or even combinations of several medications–could seemingly influence the thousands of disparate proteins and genes involved in the human immune system. And even if there is a pill or pills that could do that, it wouldn’t necessarily be a good thing; autoimmune diseases like lupus and type I diabetes occur when our immune system is tricked into making cells that recognize some of our own cells as dangerous and attack them, causing serious disease. An overabundance of immune system activity could cause more harm than good.
Weak Evidence for Immune Boosting Supplements
What about all the supplements that are said to boost or support the immune system? Because these are not advertised as treating any specific disease, the FDA by law has limited authority to regulate them. Most importantly, no “immune boosting” supplement has ever been subjected to the kind of rigorous clinical trials that are required before FDA approves a new medication for an illness. Consequently, we simply do not know if any supplements are really effective.
There are a few for which preliminary evidence suggests a benefit. These include:
· Statins, prescription medications used to lower elevated cholesterol levels. These do seem to have some positive effects on the immune system, but also have important potential adverse side effects.
· Vitamin E, but only in small doses, because higher doses cause toxicities
· Vitamin D, again with caution because high doses can be dangerous
· Zinc, which may have antiviral effects but at higher doses may actually increase the risk for viral infection.
· Probiotics, because we are gaining increasing information that there are beneficial bacteria in the human intestines that may have important benefits for immune system health.
· Restricting calories, such as what is accomplished by intermittent fasting (but see our previous commentary on that topic).
We stress, however, that for each one of these, the evidence in favor of an immune system benefit is very weak and the possibility exists that long-term use, especially at higher doses, can have toxic consequences. At the present time, it is inappropriate to tout any supplement as having an immune system boosting effect. We simply do not have the evidence to support such a claim.
There are a few things that we know are safe and beneficial for health in general, including the immune system. They include:
- Don’t Smoke
- Avoid High Stress
- Vaccinations, including those recommended by CDC for adults.
- Sufficient sleep
Although children and young adults clearly can get infected with SARS-CoV-2, unless they have a preexisting illness that compromises the immune system they are much less likely to get severely ill than elderly people. That is in part because the immune system’s ability to fight infection declines with age, although at different speeds for different people. Exercise and stress reduction may slow this “immunosenescence” and vaccinations can prevent some forms of pneumonia that sometimes occur on top of COVID-19 and increase the risks for severe illness and death.
To reduce your risk for COVID-19 the best advice remains social distancing and self-quarantine, frequent handwashing, don’t touch your face, stay as calm as possible, stop smoking if you smoke, and exercise. You can be sure that as soon as any medication, prescription or over-the-counter, musters enough evidence for scientists to say it works to further decrease risk for COVID-19, the news will be quickly broadcast by responsible sources.