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  • Omie Mills, M.D.

Covid 19 (Part 2): Optimize your immune system to prevent or minimize infection


Hopefully, COVID-19 is winding down for good. At the time of this writing, over 32 million people in the United States have had confirmed SARS-CoV-2 infections with over 580,000 deaths from COVID-19. (See the attached link for up-to-date statistics: Coronavirus Update: Maps And Charts For U.S. Cases And Deaths : Shots – Health News : NPR) Among the infected persons, some had no symptoms. Why are some people asymptomatic while infected, while others get severely ill, and still others die? If we can answer this question for COVID-19, we can theoretically learn some principles for avoiding similar infections in the future.

Asymptomatic Infections

Why are some people asymptomatic while infected with the coronavirus that causes COVID-19?

The World Health Organization (WHO) defines an asymptomatic person as a laboratory-confirmed infected person without overt symptoms (1).

Research early in the pandemic suggested the rate of asymptomatic infected individuals to be up to 81% (2). But a recent meta-analysis including 13 studies with 21,708 people followed for a minimum of 7 days after exposure (to help differentiate between pre-symptomatic and asymptomatic patients) suggests that the rate of asymptomatic presentation is 17% (3). This is an updated statistic from that presented in part 1 of this blog.

Recent studies (4, 5, 6, 7, 8, 9, 10) have shown asymptomatic individuals have the following characteristics:

  1. Younger age

  2. Female > male

  3. Exhibit normal laboratory values for liver function and proteins

  4. Inflammatory markers and indictors of tissue damage are within the normal range (ie. erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), procalcitonin (PCT), and lactate dehydrogenase (LDH))

  5. Possess adequate numbers of T and B cells and natural killer (NK) cells

  6. Fewer coexisting diseases.

While some of these risk factors cannot inherently be changed, many can be improved with simple lifestyle changes, discussed below.

Can I decrease the risk of severe COVID-19 infection associated with advanced age?

While chronological age (how old you are in years) increases at the same rate for everyone and is non-modifiable, the aging process of the cells of your body (biological age) can be modified.

How fast our cells age depends on many factors (11, 12). While genetics play a significant role, other factors include the following:

  • Diet and nutrition

  • Exercise

  • Stress

  • Sleep

  • Exposure to environmental and other toxins

  • Chronic conditions

Your body’s biological age can be measured. Researchers have found correlations between the aging of body tissues and a measurable process called DNA methylation, also known as “epigenetic clocks.” The extent to which your DNA contains methyl groups can be influenced by “not only age, but by a wide range of environmental and biological factors, including your diet, your physical health, your microbiome, your mental/emotional health, and environmental factors like exposure to tobacco smoke and other pollutants” (13).

Telomere length is another age- and health-associated biomarker. Telomeres are structures found on the end of chromosomes that are responsible for protecting DNA’s structure and function. Shorter telomeres are associated with increased biological age and poorer health. While telomeres will shorten with chronological age, some factors may speed up the process including:

  • Poor diet (14)

  • Obesity (15)

  • Smoking (16)

  • Less than adequate amounts of sleep (17)

  • Lack of exercise (18)

So, while an older chronological age may suggest a risk of more severe disease if infected with the coronavirus that causes COVID-19 or something similar, the good news is that biological age is modifiable which may allow for an asymptomatic or mild infection.

Does smoking increase my risk of severe COVID-19 infection and death?

In a scientific brief from the World Health Organization (19), the following statements are made:

“The harms of tobacco use are well-established. Tobacco causes 8 million deaths every year from cardiovascular diseases, lung disorders, cancers, diabetes, and hypertension. Smoking tobacco is also a known risk factor for severe disease and death from many respiratory infections.”

“…the available evidence suggests that smoking is associated with increased severity of disease and death in hospitalized COVID-19 patients.”

“Given the well-established harms associated with tobacco use and second-hand smoke exposure; WHO recommends that tobacco users stop using tobacco.”

Can drinking alcoholic beverages increase my risk of severe COVID-19 infection and death?

The World Health Organization makes the following recommendations regarding alcohol, and dispels myths regarding the use of alcoholic beverages and COVID-19 (20):

Avoid alcohol altogether so that you do not undermine your own immune system and health and do not risk the health of others. Stay sober so that you can remain vigilant, act quickly and make decisions with a clear head, for yourself and others in your family and community.”

General myths about alcohol and COVID-19:

Myth: Consuming alcohol destroys the virus that causes COVID-19.

Fact: Consuming alcohol will not destroy the virus, and its consumption is likely to increase the health risks if a person becomes infected with the virus. Alcohol (at a concentration of at least 60% by volume) works as a disinfectant on your skin, but it has no such effect within your system when ingested.

Myth: Drinking strong alcohol kills the virus in the inhaled air.

Fact: Consumption of alcohol will not kill the virus in the inhaled air; it will not disinfect your mouth and throat; and it will not give you any kind of protection against COVID-19.

Myth: Alcohol (beer, wine, distilled spirits or herbal alcohol) stimulates immunity and resistance to the virus.

Fact: Alcohol has a deleterious effect on your immune system and will not stimulate immunity and virus resistance.

What type of diet should I be eating to optimize my immune system to fight infection?

Eat a plant-based diet

According to The Permanente Journal, in a nutritional update for physicians to help their patients adopt healthier lifestyles, the following statement is made: “Healthy eating may be best achieved with a plant-based diet, which we define as a regimen that encourages whole, plant-based foods and discourages meats, dairy products, and eggs as well as all refined and processed foods.” “Research shows that plant-based diets are cost-effective, low-risk interventions that may lower body mass index, blood pressure, HbA1C, and cholesterol levels. They may also reduce the number of medications needed to treat chronic diseases and lower ischemic heart disease mortality rates. Physicians should consider recommending a plant-based diet to all their patients, especially those with high blood pressure, diabetes, cardiovascular disease, or obesity” (21).

Whole, plant-based foods include fruits and vegetables, whole grains, beans, nuts, and seeds. These foods contain many vitamins, minerals, fiber, and antioxidants that are needed for ultimate health, and their consumption can boost the immune system.

According to UK doctors, “Going vegan is one of the simplest, cheapest things Britons [or anyone] can do to slash the risk of becoming seriously ill with COVID-19. Now more than ever before it’s time to embrace the benefits of a plant-based diet before it’s too late.” “A healthy vegan diet can help you lose weight, reverse Type 2 diabetes and protect heart health, reducing your risk of severe COVID-19” (22).

Dr. Michael Gregor, M.D. FACLM, says “What we eat—or don’t eat—can affect our immune system” (23) and recommends using the produce isle to boost our immune system (24).

And, did you know 70 to 80% of your immune system resides in your gut (25)? A plant-based diet sustains a healthy gut microbiome (the microorganisms living in the gut that help to break down food, protect against pathogens, and effect mood and psychological processes) (26). “A strong microbiome empowers the neighboring immune cells for optimal function” (27).

In a recent article by T. Colin Campbell, PhD, who studied diet, lifestyle, and disease mortality in China and Taiwan as well as the hepatitis B virus (HBV) which causes primary liver cancer, Dr. Campbell relates finding that “HBV antibody prevalence was highly correlated with vegetable consumption, dietary fiber, and plant protein. In short, more plant food consumption was associated with more antibodies” (28). Given that the microorganism that causes COVID-19 is also a virus, he states, “I believe that this consistent interplay of nutrition, virus activity, and disease should apply to coronavirus (COVID-19) as well, especially for older individuals compromised by diseases arising from the same nutrition that decreases antibody formation. Switching to a whole-food, plant-based diet should lessen the severity of disease symptoms while simultaneously increasing COVID-19 antibodies, a win-win effect. Based on other studies, this effect may begin within days, possibly providing enough time for people not yet infected by COVID-19 to strengthen their immunity” (28).

In a randomized controlled trial of elderly patients (those generally at greatest risk of respiratory infections, patients increased their daily intake of fruits and vegetables to five portions per day (29). The control group continued with approximately 2 portions per day. Those who ate more fruits and vegetables showed an enhanced antibody response following vaccination. Researchers concluded that eating five fruits or vegetables per day improved immune function.

Eat less fat

In the American Society for Microbiology, increased dietary fats are postulated to affect the gut microbiome and intestinal permeability allowing for an increase in Gram-negative bacteria in the gut, and their product, endotoxin, into the circulation, thus contributing to and exacerbating the inflammatory response that contributes to the high mortality in coronavirus disease (COVID-19). “Shifting from a diet high in saturated fats to one with monosaturated fats will reduce the numbers of those bacteria that produce the most inflammatory endotoxin molecules and thereby reduce the severity of the inflammatory response to a COVID-19 infection in vulnerable individuals…” (30).

A recent study found that the virus that causes COVID-19 needs cholesterol in order to enter and infect cells (31). When cholesterol levels are low, there are very few entry points into cells (as in the case of most children). The higher a person’s cholesterol level, the more entry points are available for the virus to enter and infect cells. Dr. Kim Williams, former president of the American College of Cardiology, says, “Anything that you can do to lower your … cholesterol, even during an infection, seemed to be helpful” (32).

“People can reduce their cholesterol levels dramatically by changing the foods they eat. Diets high in saturated fats, trans fats, and cholesterol—found in meat, dairy products, and eggs—raise cholesterol levels, which increases heart attack risk [and increase the ability of the COVID-19 virus to infect cells]. Foods high in saturated fat are especially dangerous because they can trigger the body to produce extra cholesterol.

Plants do the opposite. They are very low in saturated fat and free of cholesterol. Plants are also rich in soluble fiber, which helps lower cholesterol. Soluble fiber slows the absorption of cholesterol and reduces the amount of cholesterol the liver produces. Oatmeal, barley, beans, and some fruits and vegetables are all good sources of soluble fiber” (33).

The ideal blood cholesterol level is below 150 milligrams per deciliter (mg/dL), based on the results of the Framingham Heart Study and other research (34). At that level, heart disease is very unlikely.

And, based on recent study findings noted above, this low cholesterol level has the potential to protect you from severe COVID-19 as well.

Eat less free sugar

Laura Schmidt, PhD, a sugar scientist and professor of health policy at the University of California at San Francisco, in an interview with Healthline stated, ““Many people will say there isn’t much that can be done about obesity rates within the context of an infectious disease pandemic, but just taking the sugar out of your diet can potentially lower your risk for severe outcomes if you do get the virus,” Schmidt said. “We know from controlled feeding trials, where we feed people a particular diet and look at their metabolic biomarkers, that within a couple of weeks of going on a no-sugar diet their insulin sensitivity and biomarkers for chronic metabolic disease actually get better” (35).

Sugar can also trigger inflammation in the body and contribute to obesity, diabetes, metabolic disease, and subsequently cardiovascular disease… all known risk factors for a more severe course of COVID-19 (36).

“Consuming too much sugar can affect the cells in your immune system that target bacteria. … Sugar affects the way your white blood cells attack bacteria.” explained board-certified internist and gastroenterologist Niket Sonpal (36).

Current American Heart Association recommends men should consume no more than 9 teaspoons (36 grams) of added sugar per day, while women should consume no more than 6 teaspoons (25 grams) per day (37).

The World Health Organization (WHO) recommends adults and children reduce their daily intake of free sugars to less than 10% of their to