Nutrition Can Strengthen the Immune System to Fight COVID-19

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  • Obesity, high blood pressure, and type two diabetes may raise the risk of hospitalization and death from COVID-19, research suggests.
  • Eating a whole foods diet and monitoring blood sugar may help maintain metabolic health.
  • Diet and metabolic health can strengthen the immune system to fight COVID-19 and other viral infections.
Kateryna Kon/123RF

Source: Kateryna Kon/123RF

No diet can reduce your risk of catching COVID-19. Viruses can’t reproduce without you, so if they find you, they’re going in. However, we are not passive Petri dishes. The human body is armed with a sophisticated security system for identifying and eliminating intruders of all kinds. Therefore it is largely the health of your immune system that ultimately determines your fate. So, is there a diet that strengthens your immune system?

Some advocates of Mediterranean, vegan, and low-carb lifestyles claim that following their diet of choice can help you fight off COVID-19, but no diet has been scientifically tested against this virus.

Yet even with a grand total of zero dietary studies available thus far, it would be a mistake to conclude that diet doesn’t matter in a pandemic. In fact, a pandemic should motivate all of us to double down on dietary quality, because the majority of people who suffer serious consequences from COVID infections have something in common: poor metabolic health. 

The Link Between Metabolic Health and Severe Cases of COVID-19

A new study of over 900,000 COVID-related hospitalizations in the U.S. confirms that people are at far higher risk for complications and death from this virus if they have obesity, high blood pressure, and/or type two diabetes. 

While these conditions may seem unrelated, often they are simply different tentacles of the same underlying beast: insulin resistance, aka pre-diabetes. The bad news is that at least one-third of American adults have pre-diabetes—and 80% of us don’t know it, because most doctors still don’t test for it.

In people with insulin resistance, insulin levels tend to run too high. The problem with high insulin levels is that insulin is not just a simple blood sugar regulator—it is a master metabolic hormone that orchestrates the behavior of every organ system in the body. High insulin levels shift us into growth and storage mode, making it easy to accumulate excess body fat. Insulin also plays a major role in controlling blood pressure, blood sugar, and the immune system—all three of which are intimately involved in how we respond to COVID-19 infections.

Blood Pressure. People with insulin resistance tend to have abnormally low levels of a cell surface enzyme called ACE-2, which is responsible for lowering blood pressure and protecting lung cells from injury. It just so happens that the only way COVID-19 can gain access to any human cell is by binding to ACE-2 first. Like a secret handshake, this crafty connection tricks the cell into letting its guard down and welcoming the virus inside. Because COVID-19 ties up ACE-2 molecules, people with insulin resistance who are infected with COVID-19 have even fewer ACE-2 enzymes available to keep blood pressure and lung damage under control than they usually do, leaving them more vulnerable to complications (Dalan et al. 2020).

Blood Sugar. Once inside, the virus hijacks the cell’s assembly lines to make copies of itself. It has long been known that respiratory viruses like influenza are particularly vicious in people with type two diabetes, with growing evidence suggesting that higher blood sugar levels encourage viruses to multiply faster (Drucker 2021).

Immune System. This elegant Stanford University study found that the immune systems of people with insulin resistance respond very sluggishly and abnormally to respiratory virus infections compared to metabolically healthy people, typically taking at least seven days to begin mounting a defense.

Dieting Practices to Reduce the Risk of COVID-19

Which diet might help stave off COVID-19? Any diet that keeps blood glucose and insulin levels in a healthy range.

Unfortunately, most popular home remedies believed to help ward off viruses such as orange juice, gummi vitamins, tea with honey, and elderberry syrup do exactly the opposite, because they are all high in sugar, which drives insulin levels up. What can you do instead?

1. Eat a nutritious whole foods diet. A whole food consists of a single ingredient, can be found in nature, and is perishable. Eggs, nuts, salmon, zucchini, steak, and blueberries are all examples of whole foods. Avoid factory foods and refined carbohydrates like sugar, flour, fruit juice, and cereal products that cause unnaturally steep spikes in blood sugar and insulin levels.

2. Find out whether you have insulin resistance. Anybody can have insulin resistance—even children, elite athletes, and people who are naturally thin. My post “How to Diagnose, Prevent and Treat Insulin Resistance” includes questions and tests you can use to find out where you stand on the insulin resistance spectrum, and an infographic to help you recognize sources of hidden sugar, boost your metabolism, and make healthier food choices.

3. Monitor your own blood sugar. People with insulin resistance don’t process carbohydrate normally, so blood sugar can run high between meals. Most doctors look for diabetes by testing morning fasting blood sugar and hemoglobin A1C (long-term average blood sugar); they don’t test for pre-diabetes, so your daily blood sugar could be on a dangerous invisible roller coaster without you or your doctor realizing it.

A previous post explains how to easily test your blood sugar at home to analyze your own metabolism. Buy or borrow a simple finger stick blood glucose meter, or wear a continuous glucose monitor (even for a couple of weeks) to observe how your food and beverage choices affect your blood sugar throughout the day. If your glucose ever rises to 140 mg/dl or higher, your current diet is a poor match for your metabolism. Keeping it under 125 mg/dL is an even healthier goal. 

4. If you have insulin resistance, take action. If eating a whole foods diet doesn’t control your blood sugar well enough, consider lowering its carbohydrate content. In human clinical studies, low-carbohydrate diets have the best track record of lowering blood sugar, treating type two diabetes and helping people reduce their diabetes medications:

“Reducing overall carbohydrate intake for individuals with diabetes has demonstrated the most evidence for improving glycemia [blood sugar]” (Evert et al. 2019). 

Low-carbohydrate diets can also lower blood pressure and help people lose weight.

Carbohydrate restriction is safe for almost everyone, but do not start a low-carbohydrate diet without learning more and discussing it with your doctor first, especially if you take prescription medications, have health problems, or are currently ill with COVID-19 or any other infection. The good news is that Mediterranean, paleo, vegan, and vegetarian diets can all be modified to be lower in carbohydrate, so you can tailor this approach to your personal dietary preferences.

You can take meaningful action to invest in your overall health and bolster your defenses not only against serious COVID-19 disease, but against other viruses as well—including those lurking around the corner which we have yet to meet. 

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