Since news about the coronavirus broke, there is a good chance you have read or seen advice about how to “boost” your immune system — whether it is loading up on citrus fruit, sipping herbal or green tea, eating yogurt for the probiotics, or taking vitamin or zinc supplements. Unfortunately, there is no evidence any of these strategies will supercharge immunity. To understand why, let’s consider how the immune system works.

The immune system’s role is to defend your body against disease by fighting infection. It is “system” in the truest sense — it has many interconnected working parts: white blood cells, antibodies, bone marrow, the spleen, the thymus and lymphatic system. These cells and organs operate in concert to hunt down and destroy dangerous pathogens, such as viruses, that enter your body.

A “boost” in that process would not be a good thing. Scientifically, it would mean your immune system was overactive, and overactive immune systems lead to autoimmune disorders. You just want the immune system to function normally, so it helps prevent infection.

While it is true some parts of the system require vitamins and minerals (such as vitamins A, C and zinc) to function normally, higher doses have not been shown to make the system function better. In fact, scientists are still a long way from understanding the complex interplay of cells and organs that allows the immune system to perform at its optimum level.

As of early March, people have tested positive for the coronavirus in about 70 countries. Officials are taking "unprecedented" actions. (The Washington Post)

“The medical profession still doesn’t know exactly how to influence the immune system despite what supplement products may claim,” says Julie Stefanski, a registered dietitian nutritionist and spokeswoman for the Academy of Nutrition & Dietetics.

“Obviously good and balanced nutrition is important, but I actually do not think there is any strong scientific evidence for any specific type of food being linked to better immune function, and certainly there is no serious work on the area that I am aware of,” says Shiv Pillai, a professor of medicine at Harvard Medical School and director of the Harvard immunology program.

So, what can we do to keep the immune system — and our overall health — functioning optimally? The experts I spoke with all had the same suggestions, and this list probably will not surprise you. In addition to the balanced diet mentioned by Pillai, you should: aim to be physically active for at least 150 minutes per week; take steps to quit smoking; use strategies to reduce stress (exercise is great for that); and try to get adequate sleep — about seven or eight hours per night.

If you consume a diet filled with adequate protein, fiber, vitamins and minerals, you should not need any of the supplements being marketed around coronavirus. To get there, fill half of your plate with vegetables and fruit, and the remaining quarters are left for protein-rich foods (chicken, fish, beans, eggs, etc.) and some whole grains like oats or brown rice.

Vegetables and fruits are especially important; choosing a colorful array — perhaps carrots, peppers, oranges, leafy greens, berries or apples — will provide vitamins A and C, which both play important roles in immune function. It is also vital to get enough vitamin D, because vitamin D deficiency is linked to an increased susceptibility to infection. Since it is found in a limited number of foods, such as fortified milk and fatty fish, supplements are often recommended (the dose you need depends on age, gender and how much you get from food).

If you are not getting the range of vitamins and minerals you need from food, you can take a multivitamin. But be wary of unregulated supplement claims. “People should know that the FDA requires a lot of evidence that medications are safe and do what they say they will do” before they reach the market, says Ellen F. Foxman, an assistant professor in the Department of Laboratory Medicine at Yale University School of Medicine. “However, the same is not true for dietary supplements. Statements that appear on packaging often have not been approved by the FDA or any official organization — be skeptical!”

For example, probiotics are often touted as immune enhancers. But although there is some evidence that certain Lactobacillus and Bifidobacterium probiotic strains can help shorten the duration of a cold, it does not mean they will be effective for coronavirus. “Viruses mutate,” says Natasha Haskey, a research dietitian at the University of British Columbia. “To say that one particular probiotic is going to stop the coronavirus or influenza is just impossible.”

Still, if taking your vitamin C or some other supposed immune enhancer simply makes you feel good, go ahead. “Taking a supplement is an intervention a person can implement immediately,” Stefanski says. “This leads to feelings of control and may even have a placebo effect of enhancing their well-being even if the supplement isn’t actually enhancing the immune system.”

Just check with your doctor or pharmacist to ensure your dosage is safe and will not interfere with any prescription medications you take. For example, high doses of vitamin A may interfere with certain antibiotics (such as tetracycline).

Haskey, the co-author of “Gut Microbiota: Interactive Effects on Nutrition and Health,” also says each strain of probiotic has a particular use, and taking the wrong one can be problematic.

“The immune system is in place to fight infection,” says Haskey. “If you take a probiotic that acts on the wrong type of cell and suppresses the immune system, it can do more harm than good.” She suggests getting probiotics from food (such as a probiotic-filled yogurt) instead of taking a supplement.

In the past few weeks, my inbox has been inundated with pitches from publicists representing products such as juice cleanses, vitamins and homeopathic cures they claim can prevent the coronavirus. Of course, there is absolutely no research any product can do such a thing, and these unscrupulous marketers are looking to cash in on a vulnerable population during a crisis. Anyone claiming their product can prevent or cure the coronavirus is lying, because they could not possibly have that information in any scientific way.

Registered dietitian Cara Rosenbloom is president of Words to Eat By, specializing in writing, nutrition education and recipe development. She is the co-author of “Nourish: Whole Food Recipes Featuring Seeds, Nuts and Beans.”

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