By Sabrina Petersen
Contagious—this word might best describe the new viruses that have surfaced in the past couple of decades. Think SARS, the H1N1 swine flu, Ebola, and COVID-19, to name a few. In the case of COVID-19, the exceptionally long 14-day incubation period and ease of transmission have left many worried about contracting this sickness. With the onslaught of one new virus after another, is there anything we can do to protect ourselves?
During the Spanish flu of 1918, people wondered the same. No cure or treatment was available, leading to nearly 50 million deaths with a fatality rate as high as 10%. But the way in which the Hutchinson Theological Seminary of Minnesota combated the flu stands out above all others, despite the fact that 120 of its teachers and students lived in the same dormitory—not ideal for social distancing. In the wake of the epidemic, a newspaper article shouted the astounding headline: “120 Exposed, 90 Patients, No Deaths, None Very Sick”—a record!1 What was their secret? It was simple: a vegetarian diet, hydrotherapy (treatments using water), and bed rest.2 Disclaimer: the teachers and students did not smoke or drink and were already following a vegetarian diet and other health principles that gave them better immune health than the general population.
Let’s explore these principles and others for boosting your immunity—the body’s ability to both defend itself against foreign “invaders” and to heal.
Nutrition, particularly from fruits and vegetables, plays a key role in the effectiveness of the immune system. A study of people aged 65 to 85 who were vaccinated against pneumonia compared the antibody response of those who ate five servings of fruits and vegetables to those who ate only two. Those who ate more plant foods produced twice as many antibodies!3
Why are plant foods so effective for raising immunity? They provide a whole array of vitamins, minerals, and phytonutrients, substances that have an anti-inflammatory effect upon the body and subsequently balance the immune response. Inflammation is like stress: Some stress is healthy, motivating us to meet a deadline or accomplish a task. However, constant stress can be disastrous, leading to both mental and physical breakdowns. In the same way, some inflammation is needed for a healthy immune response, but too much will put the immune system in overdrive. And that’s where plant foods come in. Nearly all plant foods are anti-inflammatory, including berries, dark leafy greens, and omega-3-rich flaxseed, chia, and walnuts. In contrast, dairy, meat, refined sugar, and fatty or fried foods are inflammatory.4
A plant-based diet can improve and even reverse chronic diseases that compromise the immune system. This is relevant, considering that in February 2020 the case mortality rate of COVID-19 among the Chinese, for example, was only 0.9% in those without pre-existing conditions, but was 6%, 7.3%, and 10.5% in those with hypertension, diabetes, and cardiovascular disease, respectively.5
Though we need a varied diet, certain components deserve special recognition for immune-boosting benefits. One is nitric oxide (NO), found to be antimicrobial, particularly against the SARS coronavirus.6 NO comes from nitrates in plants, such as the green “leafies.” Think arugula, spinach, lettuce, and beetroot greens, as well as garlic, citrus, nuts, and seeds.7 In addition, legumes are high in arginine, which the body converts to NO.
Cruciferous vegetables are powerful in stimulating the immune system. Researchers found that dripping kale juice on a blood sample increased the production of white blood cells.8 Make kale or one of its relatives—cabbage, cauliflower, broccoli, and brussels sprouts—a part of your daily diet.
Also worthy of note are foods high in antioxidants and vitamins A and C. Citrus, sweet potatoes, bell peppers, and dark greens contain vitamin C and carotenoids that convert to vitamin A. Berries with their bright red, blue, and purple colors have high levels of antioxidants. One study even found that eating berries directly increases the body’s number of natural killer (NK) cells—key players in the body’s first line of defense against invaders.9
The mineral zinc, taken in moderation,10 balances the immune response by lowering inflammation and directly inhibiting virus growth.11 Two other powerful immunostimulants are echinacea and elderberry syrup.12
A final note on nutrition: skip the sugar and the alcohol. Due to their inflammatory nature, both have been found to suppress the immune system.13
Colds and flus tend to emerge during the winter months when our exposure to sunlight is low. The skin turns sunlight into vitamin D, a hormone that regulates the function of the immune system. One specific role of vitamin D is to increase the development of antibodies, which help the body to resist bacteria and viruses when exposed to them. Furthermore, according to a study out of the University of Copenhagen, important killer T cells that fight off infections remain inactive without the stimulation from vitamin D in the bloodstream.14
If you’re not able to get much sunshine, taking vitamin D supplements can help. In one clinical study, children who were given daily doses of vitamin D3 had lower incidences of influenza.15 A review of 25 randomized clinical trials of over 11,000 people found that taking vitamin D daily or weekly helped protect participants against acute respiratory tract infections.16
Some daily moderate exercise can go a long way in boosting your immune system. When children spent just an hour in active play, their immune cell numbers shot up 50%!17 Adults also experienced the benefits. Immunoglobulin A (IgA) acts as a barrier to viruses that try to enter the eyes, nose, and mouth. In a 12-week study, individuals who exercised just 30 minutes three times a week increased IgA levels in their saliva by 50% and had fewer symptoms of respiratory tract infections compared to their sedentary counterparts.18
So go for a brisk walk or work actively in your garden. Your immune system will thank you!
Most of us have heard of the importance of drinking water. And indeed, water is vital to the body’s proper function—and immune health! Water helps the body to detoxify and promotes a healthy blood circulation for the transport of immune cells. It’s also vital for many body fluids involved in defending the body, such as saliva, mucus, and lymph.
External water use assists the immune system more than we realize. In fact, it was one of the measures taken by the Hutchinson Seminary during the 1918 influenza. Records show that the sick students were treated with fomentations—hot towels applied to the chest and the back. Why was this method so effective? When being attacked by microorganisms, the body uses various mechanisms, such as fever, sweating, or chills, in its attempts to maintain an internal balance. Water therapy encourages these processes by improving blood circulation, increasing antibody production, or raising body temperature to kill viruses and bacteria.19 Those hot towel applications gave the flu patients an extra boost in their body’s natural defense.20
One of the easiest forms of hydrotherapy is to simply turn your shower knob to cold for a few seconds at the end of a hot shower. You can also alternate with 3 minutes of hot water and 1 minute of cold, finishing with cold. A review of the literature on hydrotherapy shows that the “daily brief cold stress can increase both numbers and activity” of various immune cells.21
Sleep is truly a long-lost friend. Few people realize its great benefits for the immune system, but during the 1918 Spanish flu, bed rest was a vital contributor to the recovery of students and teachers at the Hutchinson Seminary. More recently, a study of 153 healthy men and women analyzed their sleep duration and efficiency (the percentage of time in bed that they actually slept) for 14 days. Then, the participants agreed to have cold virus drops put in their nostrils. Sleeping less than 7 hours a night resulted in a three times greater likelihood of becoming sick as opposed to those who slept more than 8 hours. And those with a lower sleep efficiency (92%) were 5.5 times more likely to catch the virus than those with high efficiency (98%)!22
The hormone melatonin, produced at night to help promote a healthy sleep cycle, plays an important part in the body’s ability to fight infections. It is also anti-inflammatory.23 What are some ways to improve sleep quality and increase your melatonin levels? Consistency is key. Develop a nighttime routine with a specific bedtime, avoiding bright light exposure close to that time. Make sure your environment is quiet, dark, and a comfortable temperature. Sweet dreams may be just what your immune system needs to stay strong!
Convinced that you would like to make some changes to improve your immune health? Great! But let me warn you of the side effects. Being proactive with your lifestyle will not only help prevent you from contracting a pandemic virus; it may also lower your blood pressure and cholesterol levels, reduce your risk of stroke, heart attack, and cancer, and help you lose weight! Beyond merely avoiding sickness, you will find yourself enjoying a higher quality of life—all from simple lifestyle principles.
For further study, we suggest the following resources: Fighting Disease with Food and The Ministry of Healing.
H. Kahleova, “Lessons from the 1918 Pandemic,” Physicians Committee for Responsible Medicine. Presentation. Apr. 1, 2020.
Gibson, et al., “Effect of Fruit and Vegetable Consumption,” Am J Clin Nutr, Vol. 96(6), 2012, pp. 1429–36.
“Take Back Your Power,” Center for Nutrition Studies, March 21, 2020.
“Age, Sex, Existing Conditions of COVID-19 Cases and Deaths,” Worldometer, Feb. 29, 2020.
Åkerström, et al., “Nitric Oxide Inhibits the Replication Cycle,” Journal of Virology, Vol. 79(3), 2005, pp. 1966–1969.
D. Kwon, “Top 5 Foods That Help You Fight Coronavirus,” Life and Health Network, lifeandhealth.org.
M. Greger, “Kale & the Immune System,” NutritionFacts.org, March 7, 2012.
Due to risk of zinc toxicity, do not take more than 40 mg per day—the tolerable upper intake level set by the FDA for adults—unless under the supervision of a medical professional. A maximum of five days is recommended.
Molina, et al., “Focus On: Alcohol and the Immune System,” Alcohol Res Health, Vol. 33(1–2), 2010, pp. 97–98.
“Vitamin D Crucial to Activating Immune Defense,” ScienceDaily, Mar 8, 2010.
Gunville, et al., “The Role of Vitamin D,” Inflamm Allergy Drug Targets, Vol. 12(4), 2013, pp. 239–245.
“Vitamin D Supplementation,” BMJ, 2017; 356:i6583.
Mooventhan and Nivethitha, “Scientific Evidence-Based Effects of Hydrotherapy,” N Am J Med Sci, Vol. 6(5), 2014, pp. 199–209.
Cohen, et al., “Sleep Habits and Susceptibility,” Arch Intern Med, Vol. 169(1), Jan. 12, 2009, pp. 62–67.
Vielma, et al., “Effects of melatonin,” Acta Tropica, Vol. 137, 2014, pp. 31–38.
Sabrina Petersen is the associate editor of Last Generation magazine. Passionate about healthful living, she is a certified plant-based nutritionist with the American Fitness Professionals Association.