Dr. Michael Greger is a well-known doctor and author, whose bestselling books, How Not to Die, and How Not to Diet are each a veritable tome and guide to healthy living. Dr. Greger, who launched NutritionFacts.org, guide to living a healthy plant-based life, makes no secret that he believes in the power of plant-based foods like fruits, vegetables, whole grains, legumes, nuts, and seeds to boost immunity, fight inflammation, reverse heart disease and help dial back diabetes symptoms and pre-diabetes. If you read his books you know the exhaustive research that goes into each of his chapters in How Not to Die from .... Alzheimer's, Lung Cancer, Heart Disease, you name it. Here, he explains exactly what we all need to be doing, right now, to boost our immune systems. The body's own defenses are our best bets in fighting off the virus that causes COVID-19, the flu, and every other possible infection that could be coming your way. Boost it now, while you are healthy enough to be able to fight back when the virus is making its way to your door.

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  1. What should we do to avoid the virus — or any virus and can a plant-based diet help?

Dr. Michael Greger: There are amazing studies showing that simple foods can boost your immune system, like randomized double-blind trials showing that eating broccoli sprouts can reduce viral loads for influenza, decrease virus-induced inflammation, and boost our antiviral natural killer cell activity—all from just eating broccoli, but COVID-19 isn’t the flu.

Unlike other common viruses, coronaviruses have not been shown to cause a more severe disease in immunosuppressed patients. Why? Because your own immune response appears the main driver of lung tissue damage during infection.

Starting around the second week of symptoms, the virus can trigger what’s called a cytokine storm, an autoimmune reaction where your body over-reacts. In attacking coronavirus, your lungs get caught in the crossfire. In burning down the village in order to save it, we may not survive the process.

I certainly support general, commonsense advice to stay healthy during the crisis—getting sufficient sleep, keeping active, reducing stress, staying connected (albeit remotely) to friends and family, and eating a healthful diet—but I would not go out of your way to take supplements or eat foods to boost elements of your immune system until we understand more about this virus.

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  1. What do you eat in a day — and how much Vitamin C or D or A do you strive for?

Dr. Michael Greger: Whole-food, plant-based nutrition. Pretty self-explanatory, right? But aren’t some plant foods better than others? You can apparently live extended periods eating practically nothing but potatoes, which would, by definition, be a whole-food, plant-based diet—but not a very healthy one. All plant foods are not created equal.

The more I’ve researched over the years, the more I’ve come to realize that healthy foods are not necessarily interchangeable. Some foods and food groups have special nutrients not found in abundance elsewhere. As the list of foods I tried to fit into my daily diet grew, I made a checklist, which evolved into the Daily Dozen.

Each day, I recommend a minimum of three servings of beans (legumes), two servings of berries, three servings of other fruits, one serving of cruciferous vegetables, two servings of greens, two servings of other veggies, one serving of flaxseeds, one serving of nuts and seeds, one serving of herbs and spices, three servings of whole grains, five servings of beverages, and one serving of exercise (90 minutes at moderate intensity or 40 minutes of vigorous activity).

This may sound like a lot of boxes to check, but it’s easy to knock off several at once. With one peanut butter and banana sandwich, you’ve just checked off four boxes. Sit down to a big salad of two cups of spinach, a handful of arugula, a handful of walnuts, a half cup of chickpeas, a half cup of red bell pepper, and a small tomato, and seven boxes can be ticked in one dish. Sprinkle on your flax, add a handful of goji berries, and enjoy it with a glass of water and fruit for dessert, and you could wipe out nearly half your daily check boxes in one meal. And then if you ate it on a treadmill…(kidding!).

Regarding vitamin D, we evolved to make all the vitamin D we need from the sun, but most of us are no longer running around naked in equatorial Africa. It shouldn’t come as a surprise that many of us modern humans may be deficient in vitamin D, also known as the “sunshine vitamin,” if we live, for example, in Northern climes covered up over the winter months.

If you don’t get adequate sun exposure, I recommend daily supplementation with 2,000 IU of vitamin D, ideally with the largest meal of the day.

Regarding vitamins C and A, just eat your fruits and veggies, and these vitamins will take care of themselves.

The only other vitamin I’m zealous about is B12, which is not made by plants or animals but by microbes that blanket the earth. In today’s sanitized, modern world, the water supply is commonly chlorinated to kill off any bacteria. So, while we don’t get much B12 in the water anymore, we don’t get much cholera, either, which is a good thing!

A regular, reliable source of vitamin B12 is critical for anyone eating a plant-based diet. Though deficiency for those starting out with adequate stores may take years to develop, the results of B12 deficiency can be devastating, with cases reported of paralysis, psychosis, blindness, and even death. Newborn infants of mothers who eat a plant-based diet and who fail to supplement may develop deficiency much more rapidly, with disastrous results. Getting enough vitamin B12 is absolutely nonnegotiable for those centering their diets around plant-based foods.

For adults under age 65, the easiest way to get B12 is to take at least one 2,500 mcg supplement each week or a daily dose of 250 mcg. Note that these doses are specific to cyanocobalamin, the preferred supplemental form of vitamin B12, as there is insufficient evidence to support the efficacy of the other forms, like methylcobalamin.

As we age, our ability to absorb vitamin B12 may decline. For those over 65 who eat plant-based diets, the supplementation should probably be increased up to 1,000 mcg of cyanocobalamin each day.

Instead of taking B12 supplements, it is possible to get sufficient amounts from B12-fortified foods, but we would have to eat three servings a day of foods each providing at least 25 percent of the Daily Value (on the Nutrition Facts label), with each serving eaten at least four to six hours after the last. For B12-fortified nutritional yeast, for example, two teaspoons three times a day would suffice. For most of us, though, it would probably be cheaper and more convenient to just take a supplement. Our fellow great apes get all the B12 they need eating bugs, dirt, and feces, but I’d suggest supplements instead!

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  1. Do you think Zinc is helpful and if so how much should we try to get?

Researchers have found that zinc is beneficial in reducing both the duration and the severity of the common cold when taken within the first 24 hours of symptom onset. Zinc lozenges appear to shorten colds by about three days with significant reductions in nasal discharge, congestion, hoarseness, and cough.

The common cold results for zinc are often described as mixed, but that appears to be because some studies used zinc lozenges containing added ingredients like citric acid that strongly sequester zinc, so little or no free zinc is actually released. They taste better, but what’s the point if you don’t actually get the zinc?

What’s the best way to take zinc for the common cold? Lozenges containing around 10 to 15 milligrams of zinc taken every two waking hours for a few days, starting immediately upon symptom onset, as either zinc acetate or zinc gluconate without zinc binders, such as citric acid, tartaric acid, glycine, sorbitol, or mannitol may work best.

I’m skeptical it would be helpful in well-nourished individuals, but, if taken as directed, it shouldn’t hurt, though zinc supplements and lozenges can cause nausea, especially when taken on an empty stomach, and some other gastrointestinal symptoms. And one should never put zinc in their nose. In the drug store, you’ll find all sorts of intranasal zinc gels, sprays, and swabs that have been linked to the potentially permanent loss of one’s sense of smell.

Because the zinc in plant foods isn’t absorbed as well as the zinc in flesh foods, a study published earlier this year found relatively low blood zinc levels in vegetarians. So, anyone eating plant-based diets—men or women—should make sure they eat whole grains, beans, and nuts every day. But some men might just require more than others.

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  1. What are other things that lower our chances of infection and boost immunity? Turmeric? Anything else?

Researchers have shown that a more plant-based diet may help prevent, treat, or reverse some of our leading causes of death, including heart disease, type 2 diabetes, and high blood pressure. Interventional studies of plant-based diets have shown, for example, 90 percent reductions in angina attacks within just a few weeks.

Plant-based diet intervention groups have reported greater diet satisfaction than control groups, as well as improved digestion, increased energy, and better sleep, and significant improvement in their physical functioning, general health, vitality, and mental health. Studies have shown plant-based eating can improve not only body weight, blood sugar levels, and ability to control cholesterol, but also emotional states, including depression, anxiety, fatigue, sense of well-being, and daily functioning.

Only one way of eating has ever been proven to reverse heart disease in the majority of patients: a diet centered around whole plant foods. If that’s all a whole-food, plant-based diet could do—reverse our number-one killer—shouldn’t that be the default diet until proven otherwise? The fact it may also be effective in preventing, treating, and arresting other leading killers seems to make the case for plant-based eating simply overwhelming.

So, give yourself the best advantage by boosting your immunity with whole plant foods brimming with antioxidants and phytonutrients, such as berries, cruciferous vegetables, whole grains, and legumes.

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  1. What is the ONE thing you want people to eat every day?

Dark-green, leafy vegetables are the healthiest foods on the planet, which is why I recommend two servings each day. As whole foods go, they offer the most nutrition per calorie. Of all the food groups analyzed by a team of Harvard University researchers, greens turned out to be associated with the strongest protection against major chronic diseases, including up to about a 20 percent reduction in risk for both heart attacks and strokes for every additional daily serving.

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