Flu season is still going strong, not to mention there are a lot of other viruses and illnesses waiting in the wings to rear their ugly heads. And although you can get sick at any time, germs tend to spread more easily in winter and fall.
“Exposure to dry, indoor heat can dry out protective mucus membranes, making you more susceptible to microbes,” says Dr. Bill Rawls, M.D., medical director of Vital Plan. “People also spend more time indoors, in close quarters.” That makes it easier for germs to travel from person to person through the air or via contaminated surfaces.
Lack of vitamin D, which your body makes when exposed to sunlight, may also play a role. “You may not be getting as much sun exposure as you do in summer, which could cause vitamin D levels to be low, and vitamin D is essential for immunity,” says Dr. Rawls.
While you can’t control the weather, lengthen the shorter days, or even eradicate all the germs that lurk on doorknobs and desktops, that doesn’t mean you’re destined to get sick. There’s one major factor you can control (in addition to having a good hand-washing habit, of course): The state of your immune system.
A strong and healthy immune system can fend off pathogenic viruses and bacteria before they take hold and make you sick, says Dr. Rawls. And if you do happen to come down with something, a robust immune system can lessen the severity of symptoms or shorten their duration.
Getting at least 8 hours of sleep a night and keeping stress in check go a long way towards bolstering immunity against a virus. So does staying active. For example, adults who got at least some aerobic exercise five or more days a week experienced 43% fewer sick days during the cold and flu season compared to those who were mostly sedentary, according to a study in the British Journal of Sports Medicine.
But one of the most important strategies is to improve what goes into your body — as in, what you feed your immune system.
Why Plants Are Vital to Your Immune System
“Eating crappy food trashes your immune system, makes you susceptible to illness, and sets you up for a lot of problems,” Dr. Rawls says. Indeed, one study published in the Journal of Traditional Chinese Medical Sciences found that children who reported consuming a diet full of processed and high-sugar foods and with lots of meat and few vegetables were more likely to suffer from recurrent respiratory infections compared to those who ate healthier.
On the flip side, avoiding processed and fried food and increasing your intake of fresh vegetables, fruit, herbs, spices, and plant-based protein sources like beans and nuts can bolster your immune system. For starters, plants provide plenty of fiber, which helps feed the good bacteria in your gut and regularly flush your GI tract of harmful bacteria looking to gain a foothold. And, given that 70% of your immune system resides in your gut, a healthy microbiome is key to staying healthy overall, explains Dr. Rawls.
People who eat ample fiber also have better lung function than those who don’t eat as much, according to an analysis of nearly 2,000 adults published in the Annals of the American Thoracic Society. But plants’ immune-boosting power goes beyond fiber.
Vegetables, fruits, and herbs provide a veritable pharmacy of phytonutrients, natural plant chemicals that work directly to support your immune system so it can more effectively fend off and fight germs. While no one can say for sure how the phytonutrients in plants work, Dr. Rawls says, it’s likely that they support communication between different parts of your immune system.
“Immune cells have to communicate well in order for your entire system to function optimally,” Dr. Rawls says. These cells serve as messengers, sending information back and forth that helps the body dispatch the right white blood cells and launch the appropriate response to an attack or invader.
Like humans, plants also must deal with an onslaught of potentially harmful viruses and bacteria. What’s different, though, is how they’ve developed what Dr. Rawls calls a natural intelligence to fight them.
“Plants have created all these internal chemicals that counter the microbes — they have an innate ability to take care of themselves,” he says. Your immune system was made to likewise take care of your body, but plant phytonutrients give it a hand. “When you take in the natural intelligence of plants and herbs, it adds to your body’s own natural intelligence.”
You’ll reap the rewards by simply eating a lot of different plants, but certain foods and herbal supplements are particularly beneficial at targeting and supporting the human immune system. Here are the top 11 plants and herbs for immune support so you can stay well this cold and flu season.
11 Foods and Herbs for a Healthy Immune System
Long used for therapeutic benefits, garlic is known for its ability to help balance the good and bad microbes in the microbiome (the sum of all the microbes in your body). More recent research shows garlic also helps enhance the immune system by stimulating certain immune cells and regulating secretion of cytokines — natural chemicals produced by immune cells that help the immune system communicate and function.
In one double-blind, placebo-controlled study published in Advances in Therapy, participants took either a garlic supplement or a placebo for 12 weeks from November to February. During that time, only about a third of people in the garlic group got colds, while nearly all of the placebo group did. The placebo-takers were also more likely to catch more than one cold during the three-month period, and their symptoms persisted longer (5 days versus 1.5 for the garlic group).
You can’t go wrong adding garlic to food, especially in its raw form (try it in salads and salad dressings). But you’d need to eat three big cloves a day to to achieve the maximum benefit, says Dr. Rawls, so supplementing with garlic is a wise bet.
While alternative and Eastern medicine practitioners have relied on mushrooms to help fight illness for centuries, modern-day researchers are now starting to uncover how key fungi phytonutrients — particularly beta-glucans — work to support the immune system.
Beta-glucans are complex polysaccharides or sugars that live in the cell walls of mushrooms, and they seem to act on immune receptors and activate various immune cells, according to a paper in the Journal of Hematology and Oncology.
Among the mushrooms you might find at the grocery store or farmer’s market, “Any will do,” says Dr. Rawls. “But shiitake, maitake, oyster, lion’s mane, and turkey tail mushrooms have the highest immune benefits.”
Another powerful mushroom: Reishi. Preliminary studies suggest reishi mushrooms help modulate the immune system by increasing the activity of immune cells and the production of communication-enhancing cytokines, according to a research review in Integrative Medicine: A Clinician’s Journal. Reishi is one you won’t find in grocery stores and will need to get in supplement form; aim for 350 mg daily.
These sweet berries contain more antioxidants than all other commonly consumed fruit, including a high level of one type known as flavonoids. A review of 14 studies by researchers in New Zealand found that consuming flavonoids, either through food, juice, or supplements, reduced upper respiratory infections by 33% compared with controls, plus cut sick days by 40%.
One type of flavonoid in particular — quercetin, found in high levels in dark blue and red fruits — has been shown to have potent antiviral properties, even helping to stop the virus from replicating and reducing the viral load and lung inflammation.
Other foods rich in quercetin and other flavonoids include apples, onions, and green tea (see below for more on green tea’s benefits). To get your fill, add berries to smoothies, yogurt parfaits, and desserts, snack on apples, add onions to salads and sandwiches, and sip green tea.
Although not a plant you eat, this native to India has been used for centuries for a wide range of benefits, including its ability to support a healthy immune system. “For viral illnesses, I would rate andrographis as one of the best plants available,” Dr. Rawls says. (He recommends taking 250 mg to 500 mg of andrographis a day.)
Indeed, research shows supplementing with andrographis helps significantly reduce symptoms of the common cold. Patients taking andrographis extract reported greater relief from nasal secretions, tiredness, sore throat and sleeplessness after just two days than those taking a placebo, according to findings in the journal Phytomedicine. After four days, the andrographis group also reported a significant decrease in all symptoms, including cough and headache.
This species of flowering plant from the mint family is known as a “heat-clearing” and phlegm-removing herb in Traditional Chinese Medicine (TCM), an ancient practice for preventing and treating various diseases. Its reputation comes from its purported anti-inflammatory and antimicrobial effects.
For instance, in one study in the Journal of Ethnopharmacology, researchers suggest Chinese skullcap helps decrease the expression of pro-inflammatory cytokines that play an essential role in our inflammatory response and resistance to pathogens. Other research has shown Chinese skullcap to be helpful in inhibiting the growth of bacteria like Helicobacter pylori and coagulase-negative staphylococci, a staph bacteria commonly found on skin.
To get the immune supporting benefits of Chinese skullcap, Dr. Rawls recommends taking 450 mg once a day. Or, if you’re feeling run down or like your immune system is under more pressure than usual, up the amount to 450 mg twice daily.
While technically not an “herb,” this fungus is popular in TCM for treating fatigue, sickness, and more. It naturally grows on the backs of a certain species of caterpillar that lives in the mountains of Tibet, and historically, it was saved for the likes of emperors and royalty. More recently, research has shown that cordyceps helps boost immunity to the flu.
“Cordyceps offers properties of immunomodulation and resistance to any type of stress,” explains Dr. Rawls. More specifically, it works by stimulating natural killer (NK) cells and macrophage activity, and also by enhancing cellular immunity, he explains.
As with Chinese skullcap, you can double up on servings of cordyceps when you need an extra immune boost beyond everyday support: Start with 450 mg once a day, then move up to 900 mg daily as needed.
This Japanese native is a rich source of resveratrol, the chemical compound in wine that gives the adult beverage its healthy reputation. While resveratrol is probably best known for its antioxidant powers and heart health-promoting properties, Dr. Rawls also points to its antibacterial properties.
Japanese knotweed may help inhibit the growth of “bad” bacteria in your gut microbiome — again, where the bulk of your immune system exists — while increasing the growth of “good” gut bacteria, he explains. Dr. Rawls suggests taking 400 mg once or twice daily, depending on the level of immune support you need.
This spicy plant does more than tamp down nausea (a benefit it’s well known for). Ginger contains nearly a dozen antiviral compounds, including some that seem to be especially effective against a common cold-causing virus, according to a paper in the International Journal of Drug Development & Research.
Extracts from both the ginger plant and root were also found to be quite effective against two pathogenic staph strains, reports a study in the Journal of Microbiology and Antimicrobials. Supplements provide the most potent dose, but you can also use ginger to flavor stir-fry dishes, eat it pickled, or brew up some ginger tea.
This bright-yellow spice common in Indian cuisine has been used for medicinal purposes for ages. Curcumin, one of its main compounds, gives it its color and much of its immune-boosting potential.
Research suggests curcumin helps activate white blood cells and downregulate proinflammatory cytokines. It also may help enhance an antibody response and shows microbiome balancing activity.
As with ginger, eating turmeric-spiced foods is a great way to incorporate the plant into your diet, but supplements will deliver the biggest bang for your buck, Dr. Rawls says.
Sprouts from baby broccoli plants contain high levels of a phytonutrient called sulforaphane, which you can also get from cauliflower, Brussels sprouts, and other cruciferous vegetables. Early research showed that consuming the sprouts could increase inflammation-fighting enzymes in the upper respiratory system.
More recently, a study published in the journal PLoS One suggested that subjects who drank a daily shake containing sulforaphane-rich broccoli sprouts got a boost against the flu virus. The researchers noted several changes to subjects’ immune cells after administering a live flu vaccine in their nostrils. Later, those who had been drinking the broccoli-sprout shakes showed lower levels of the flu virus in their nasal fluids compared to people who drank a control shake with alfalfa sprouts.
While the sprouts blend well in green smoothies and shakes, they also make a tasty addition to salads.
Black and Green Tea
Sipping a hot cup of tea is always comforting when you’re under the weather, but it may actually do more than keep you warm. A study in the journal Proceedings of the National Academy of Sciences found that drinking five cups of black tea a day seems to supercharge T cells (a type of white blood cell that plays a key role in the immune response). After two weeks of drinking the tea, the cells produced 10 times more interferon, a chemical that actively fights viruses and helps stop them from replicating.
If you prefer green tea, that can help, too. Along with quercetin (the beneficial flavonoid in blueberries), green tea also contains theanine, an amino acid that research shows may work with other polyphenols to give your immune system a boost.
Making these foods and herbs a part of your daily routine — not just during cold and flu season, but year-round — can go a long way toward supporting a strong and healthy immune system. Don’t forget to add in ample sleep, regular exercise, stress management, and an overall healthy diet to optimize your odds of avoiding the sniffles (or worse!) altogether.
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