7 Mistakes That Can Weaken Your Immune System (and How to Fix Them)

With the coronavirus surging and cold and flu season still in full swing, having a hardy immune system is more vital than ever. But it turns out, some everyday habits might be putting you at greater risk of infection.

We've got the scoop on common mistakes you could be making — and what you can do to strengthen your immunity instead.

Mental and emotional stress have a direct affect on immune function. In fact, an April 2012 study in the journal ‌Proceedings of the National Academy of Sciences‌ discovered that people who had experienced chronic stress during the previous year were more likely to develop a cold after being exposed to viruses, a finding the same team of researchers confirmed in a July 2020 article in ‌Perspectives on Psychological Science‌.

"When you are stressed, your body releases cortisol and adrenaline, hormones that lower your levels of lymphocytes and phagocytes," says immunologist Kathleen Dass, MD, assistant clinical professor at Oakland University William Beaumont School of Medicine and founder of the Michigan Allergy, Asthma & Immunology Center. "With decreased amounts of these white blood cells, your body has a harder time combatting bacterial and viral antigens."

On top of that are the unhealthy side effects associated with stress. See: drinking, smoking, insomnia and seeking out comfort food — all of which can further weaken your immune system (more on those later).

If you feel overwhelmed, the single best thing you can do is remove yourself from anxiety-inducing situations whenever possible.

"End the unhealthy relationship, switch jobs if you're in a toxic workplace or putting in too many hours, get a babysitter for short times to recover from parenting-related stress," says rheumatologist Aly Cohen, MD, author of ‌Non-Toxic: Guide to Living Healthy in a Chemical World‌. "In the event you do find yourself in a stressful circumstance, deep breathing exercises can reset and quiet down your body, and are easy to do anytime, anywhere."

What's more, several studies, including research published February 2019 in ‌Clinical Psychological Science‌, have linked a positive mindset and self-compassion to a stronger immune system.

Three ways to boost your self-love: Meditate, express gratitude and set aside time each day for an activity that brings you joy.

A diet high in refined carbs, added sugar, sugar substitutes and salt might make it tougher for your immune system to do its job.

"Processed foods attack the good bacteria in your gut, leaving room for bad bacteria to come in, and weakening your intestinal immune system," Dr. Dass says.

A series of studies done in humans and mice have shown that many chemical additives in processed foods may disrupt the gut microbiome — from stabilizers to emulsifiers to thickeners to sweeteners like saccharine, sucralose and stevia. The research is still in the preliminary stages, but the evidence is compelling.

"A single cup of coffee with stevia in the morning or an occasional can of soda won't increase your risk of catching a cold or the flu," Dr. Dass says, "But if you're having several a day, it can take a toll."

Processed foods (think fast food burgers, fries and deli meats) are bigtime sodium culprits, too. An additional six grams of salt per day (which comes out to 2,400 milligrams of sodium) is associated with pronounced immune deficiencies in humans, according to a March 2020 study in ‌Science Translational Medicine.‌ The researchers explain that eating a high-salt diet can impair neutrophils' ability to kill bacteria in the body.

Pile your plate with immune-boosting foods.

"Soluble fiber increases levels of the protein interleukin 4, stimulating your body to make T cells, which then lock onto infected cells and destroy them," Dr. Dass says. "Aim for 28 grams of soluble fiber a day for women and 36 grams a day for men. Good sources are apples, barley, oats, nuts, seeds and lentils."

Vitamin D is also essential. "It helps activate those infection-fighting T cells," Dr. Dass says. "You can find it in egg yolks, fortified milk and breakfast cereal, and fatty fish like salmon."

And don't skimp on vitamin C. According to the July 2020 ‌Perspectives on Psychological Science‌ report, people who got less than 85 milligrams a day — about the amount in a large orange, according to the USDA — were twice as likely to develop a cold after being exposed to a virus.

Finally, throw plenty of onions, garlic and ginger into your meals. Reviews published in ‌Critical Reviews in Food Science and Nutrition‌ in 2015, ‌Avicenna Journal of Phytomedicine‌ in February 2014 and the ‌Journal of Ethnopharmacology‌ in November 2012 confirmed these foods' immune-boosting properties.

If you're not getting the recommended seven to eight hours of quality shuteye each night, you could find yourself laid up. In the July 2020 ‌Perspectives on Psychological Science‌ report, sleeping less than 6 hours a night was linked with a greater risk of developing a cold compared to getting more than 7 hours of rest.

"When you're sleeping, your body releases cytokines, proteins that protect you against inflammation and infection," Dr. Dass says. "Without adequate rest, you can't produce as many cytokines and will have a harder time fighting viral and bacterial illness."

Prioritize your zzzs.

Since you probably don't pass out the second your head hits the pillow, "aim for an eight- to 10-hour stretch in bed to account for the time it takes to fall asleep," Dr. Cohen recommends. "And remove technology an hour before bedtime."

According to the National Sleep Foundation, using electronics before bed can disrupt your circadian rhythm, suppress the sleep-inducing hormone melatonin and make it more difficult to fall asleep.

Whether you knock back a few cold ones after work on the reg or occasionally overdo it when you're partying with friends, booze wreaks havoc on your immune system.

First, it disrupts your gut microbiome, the ecosystem of microorganisms living in our intestines that plays a key role in immune function. "Alcohol unhinges the balance between healthy and unhealthy bacteria in your gut," Dr. Dass says. "It strips the healthy bacteria, and as a result more bad bacteria pass into your bloodstream, which leads to inflammation in your liver."

When your liver is inflamed, it has trouble cleansing your body of environmental toxins — including antigens that can make you sick.

According to Dr. Dass, drinking suppresses production of both T cells and B cells, which help make antibodies that destroy viruses and bacteria. "In addition, it impairs immunoglobulins — antibodies that protect immune function in your gut and saliva," she says.

Getting buzzed also impairs the epithelial cells lining your intestines, which have a host of immune-supporting properties. "They send signals to your immune cells to keep out harmful substances or allow absorption of good substances," Dr. Dass says. "They also secrete antimicrobial proteins, help deliver antigens and regulate T and B cells in the gut. If you damage the intestinal epithelial cells, you are damaging all these functions."

Although any amount of alcohol has the potential to harm your immune system, Dr. Dass says you should be safe if you drink in moderation: That means up to one drink a day for women and up to two drinks a day for men, according to the U.S. Department of Health and Human Services.

5. You Light Up

Smoking is kryptonite to your immune system.

"The chemical compounds in tobacco affect the mucosal lining of your respiratory tract, from your nose to your lungs," Dr. Dass says. "When you smoke, your body produces excessive mucous, which narrows your airways and makes it harder for your lungs to clear out toxins, thus increasing your susceptibility to infection."

The authors of the July 2020 ‌Perspectives on Psychological Science‌ report note that smokers were three times more likely to develop colds when exposed to a virus than nonsmokers in their research.

What's more, since your body is working double time to remove the chemicals released by the tobacco, its ability to fight off infection is compromised. "Smoking also lowers the levels of protective antioxidants in your blood," Dr. Dass says. "This heightens your risk of everything from pneumonia to bronchitis."

Ready to kick your nicotine habit? According to Harvard Health Publishing, setting a specific quit date and going cold turkey (as opposed to gradually cutting back) can increase your chances of success. Counseling or support groups help, too. Or ask your doctor about available medications.

Getting vaccinated slashes your influenza risk by about half, according to the Centers for Disease Control and Prevention (CDC). So if you pass up the shot, you're putting yourself at risk.

"The flu shot builds your antibodies to the influenza virus so that if you're exposed, you either won't contract it at all or your symptoms will be very mild," Dr. Dass says. "It's especially important for pregnant women, children under 5, adults over 50 and people with lung issues like asthma."

The good news: It's not too late. "Contact your primary care doctor's office to find out if they still have it," Dr. Dass says. "You can also get it at your local pharmacy or health department."

Then, set a reminder in your calendar right now for next September or October (the optimal time to get immunized, per the CDC).

Been slacking on fitness? Don't be surprised if you end up sniffling and sneezing. According to a review published April 2018 in ‌Frontiers of Immunology‌, working out on a regular basis — whether at a moderate or vigorous level — enhances immunity.

"Exercise increases both antibodies and white blood cells, which allows your body to target infection earlier and fight it off more effectively," Dr. Dass says. "Plus, your body temperature increases during exercise, which can help prevent bacteria from growing and kill infection."

Hitting the gym is also a great way to kick harmful stress hormones to the curb. "Exercise slows the release of cortisol and adrenaline in your body, protecting you against bacterial and viral illness," Dr. Dass says.

The CDC suggests adults aim for at least 150 minutes of moderate aerobic activity or 75 minutes of intense activity a week, plus two or more strength-training sessions.

Try for at least three weekly sessions. The July 2020 ‌Perspectives on Psychological Science‌ review linked exercising less than twice a week to higher chances of coming down with a bug.