Jill A. Poole, MD
Jill A. Poole, MD, chief of allergy and immunology, professor of internal medicine, University of Nebraska Medical Center, Omaha.
When a foreign invader like the coronavirus or the flu enters the cells of your body, your immune system is your first line of defense. It is always on guard to prevent or limit infections.
When it identifies a threat, it sends out T cells, a type of white blood cell called a lymphocyte. These killer cells attack and destroy infected cells, and signal other lymphocytes called B cells to make antibodies. Once you have antibodies, which can take a few weeks, you have developed immunity to that particular virus. Your immune system has you covered.
This is how vaccines work: They activate the immune system and produce antibodies without the discomfort and the risk of an actual infection. People with weak immune systems, however, are less likely to respond to vaccines. Obviously, in the age of pandemics, like corona and flu viruses, you want your immune system to be as strong and effective as possible. Here’s how you can make that happen.
Chronic stress wears down your immune system. When you are physically or emotionally stressed, your body produces the stress hormone cortisol. Cortisol can boost your immunity in the short run, but long-term, chronic stress increases inflammation and decreases your immune system’s ability to produce the lymphocytes you need to fight infections. Avoiding stressful situations and using strategies for stress reduction like deep breathing, meditation, or mind-body exercises like yoga or tai chi are good ways to manage chronic stress. If you struggle with stress or anxiety, you should talk to your health-care provider.
Your internal body clock controls the daily cycles of body functions. These rhythms are essential for a healthy immune system. Circadian rhythms in your brain are controlled by the cycles of light and dark and sleep. Circadian rhythms in the rest of your body are controlled by when you eat.
When these body rhythms are out of sync, your immune system is out of balance, and your ability to fight or resist an infection is reduced. To maintain your circadian rhythms—and immune system—get outside in daylight for 30 minutes or more every day to help set your brain clock.
Go to bed and get up at about the same time every day to further support your circadian rhythms. Strive for eight hours of sleep every night. Getting enough sleep is also important because immune proteins called cytokines are produced and released during sleep. You need these proteins for T-cell functions. If you aren’t getting seven to eight hours of sleep at night, try to add two 30-minute naps to maintain immune health.
To maintain a healthy rhythm for eating, limit the times that you eat to about an eight- to 12-hour window. That means if you have breakfast at 8 in the morning, your last food intake should be at around 6 p.m. Studies show that these lifestyle patterns reduce infection rates.
One thing you can’t control is aging. As you get older, your immune system weakens, resulting in fewer T and B cells. That may be why respiratory infections like COVID-19, pneumonia, or the flu become a leading cause of death in people over age 65. Micronutrient malnutrition, or the loss of some essential nutrients that occurs with age, may be to blame.
Vitamin D. The most important nutrient to replace is vitamin D. Studies show that this vitamin is low in people with chronic disease and obesity. Vitamin D deficiency is more common in northern parts of the world during winter, which may partly explain why colds and other viruses are more common in winter.
While whole foods are the best sources of most vitamins, vitamin D is an exception. Although it is found in fatty fish and in fortified foods like milk, orange juice, and cereal, it is hard to absorb from foods for many people. The good news is that it is easy to boost with a supplement. For an otherwise healthy adult, 4,000 units of vitamin D each day is safe and effective. If routine blood work shows that you have very low levels of vitamin D, your doctor may recommend more.
Vitamin-rich foods. Other vitamins that may boost immune health can be easily absorbed from foods. Vitamins C, E, and A are abundant in leafy green vegetables, colorful vegetables, citrus fruits, nuts, and seeds.
Zinc. The mineral zinc is highly important for immune health, and many older people are deficient. It may help keep inflammation in check and prevent damage that can occur in inflammatory diseases. Zinc can interfere with viral replication when taken early in a cold. Zinc is found in crab, oysters, lean meat, poultry, beans, chickpeas, and yogurt. It can also be taken as a supplement.
Herbal supplements that claim to support immune health are less safe and have no evidence to support their use. Since they are not regulated, they may also have fillers that can cause an allergic reaction. It is always a good idea to check with your health-care provider before adding any supplement. Echinacea, a popular remedy, may shorten colds, but the effect is generally minor.
A healthy lifestyle is probably the best thing you can do to maintain a healthy immune system. This means not smoking, including marijuana, or vaping. Drink alcohol only in moderation, and maintain a healthy weight with a balanced diet and exercise. Eat lots of fruits and vegetables, reduce your stress, and get enough sleep. If you take better care of your immune system, it will take better care of you.
