How to Boost Your Immune System: Top 25 Immune System Boosters

Bone broth gives your gut lining the amino acids it needs, and that's where so much of your immune system works. Chicken broth's glycine and proline help heal the gut lining and support immune balance,7 and chicken broth in particular also carries glucosamine, chondroitin and hyaluronic acid, key parts of your gut lining.38 When I do get sick, I eat chicken broth or chicken vegetable soup at every meal.14

Warm soup also helps your body clear what it's fighting, and in a study of 15 healthy adults, sipping hot chicken soup sped the flow of nasal mucus from 6.9 to 9.2 mm a minute, while cold water slowed it.39 In a lab study, chicken soup also slowed the movement of neutrophils, a sign of a calming, anti-inflammatory effect.40

How to use it: Drink about 8 ounces most days.7 When you're sick, make a soup the way I make mine, with chicken bone broth, chicken, carrots, celery, onion and garlic, freshly grated ginger, and thyme, oregano, sage and a big tablespoon of yellow miso.14

Study takeaway: hot chicken soup sped nasal mucus from 6.9 to 9.2 mm a minute in 15 healthy adults.

Garlic and onions work as natural antimicrobials and immune modulators,7 and garlic's best-known compound, allicin, forms when you crush or chop a clove. In a placebo-controlled trial of 146 adults over 12 weeks from November to February, people taking one allicin-containing garlic capsule a day caught 24 colds against 65 on placebo, and they spent 1.52 days ill on average across everyone in the group, against 5.01 on placebo.41 A Cochrane review found it was the only garlic trial that met its standards.42 An aged garlic extract tested in 120 healthy adults for 90 days didn't change how many colds and flu they caught, but symptoms were 21% fewer and missed work or school days 58% fewer.43

How much: Other than in rare situations, every person on the planet should eat garlic, about 2 to 5 grams, or roughly one medium clove, a day.32 Crush it and let it rest for 10 minutes before you cook it.8

Study takeaway: a daily garlic capsule meant 24 colds against 65 on placebo over 12 winter weeks.

Ginger is a warming herb that helps strengthen the immune system through the digestive system, and it's used in Chinese medicine, Ayurvedic medicine and Western medicine alike.10 When I was sick as a kid, my mom gave me chicken noodle soup and ginger ale, and the ancient Chinese remedy when you're sick, or you have a child who's sick, is ginger tea and chicken bone broth soup.19

Lab research is starting to show why, and in one study, hot water extracts of fresh ginger kept respiratory syncytial virus (RSV), a common cause of colds, from attaching to and entering human airway cells, while dried ginger didn't show that effect.44

How to use it: Simmer 1 to 2 inches of sliced fresh ginger in water for 10 minutes for tea, and add it to soups, stir-fries and smoothies through the season.8

Study takeaway: fresh ginger kept RSV from attaching to human airway cells in a lab study.

Vitamin C stimulates both the production and the function of your white blood cells, and your body uses it up quickly while you're fighting an infection.177 I put vitamin C first among the immune nutrients, because it also helps strengthen and rebuild your gut lining, where the majority of your immune system lives.10 In a Cochrane review, taking at least 200 mg of vitamin C every day made colds 8% shorter in adults and 14% shorter in children, across 31 comparisons covering 9,745 colds.37 It didn't change how often most people caught a cold, but among marathon runners, skiers and soldiers training in subarctic conditions, regular vitamin C cut the risk of catching one by about half.37

A whole orange or red pepper provides far more cellular benefit than an ascorbic acid tablet,7 so build your plate around vitamin C foods such as citrus fruits (orange, lemon and grapefruit), black currants, guava, red and green bell peppers, pineapple, mango, honeydew, parsley, kiwi, papaya and broccoli.

How much: Eat vitamin C foods every day, and for extra immune support, take 500 to 2,000 mg a day in divided doses.7

Study takeaway: regular vitamin C made colds 8% shorter in adults and 14% shorter in children.

Your body turns beta-carotene into vitamin A, which keeps the skin and the mucous linings of your nose, throat and gut intact and helps your T and B cells find their way to those linings.17 These are the same orange foods Chinese medicine leans on to strengthen your defenses.10

The richest sources are yellow, orange and red fruits and vegetables and leafy greens: carrots and carrot juice, pumpkin, sweet potato, red bell peppers, apricots, kale, spinach and collard greens.

How to use it: Roast a tray of sweet potato and carrots, stir pumpkin or butternut squash into soup, and add a handful of leafy greens to your eggs or a smoothie most days.

Study takeaway: vitamin A from orange and green foods keeps the linings of your nose, throat and gut intact.

Fermented foods bring live cultures into your gut, where your immune cells get their training.16 Miso is a fermented food rich in probiotics that support the link between your gut and your immune system, and probiotic-rich yogurt provides live cultures that shape a youthful microbiome.7 The ones I'd start with are goat's or sheep's milk yogurt and kefir, coconut yogurt, miso, sauerkraut and kimchi.710 In a 10-week Stanford study of 36 healthy adults randomly assigned to a high-fiber or a high-fermented-food diet, the fermented-food group worked up to about six servings a day, and the variety of their gut microbes rose while 19 inflammatory proteins in their blood fell, IL-6 among them.45 The trials on respiratory infections are in the probiotics card below.

How to use it: Have a spoonful or two of sauerkraut or kimchi with meals, a cup of goat's milk kefir or probiotic yogurt, or a bowl of miso soup most days.

Study takeaway: in a 10-week trial of 36 adults, the fermented-food group showed decreases in 19 inflammatory proteins.

Green tea's main catechin, EGCG, enhances natural killer cell function and calms inflammation.7 In a placebo-controlled trial in healthy adults aged 18 to 70, capsules of a proprietary green tea formulation taken twice a day for 3 months meant 32.1% fewer people with cold and flu symptoms and 35.6% fewer days with symptoms, and the volunteers' gamma delta T cells, a type of T cell that reacts quickly to germs, multiplied 28% more.46

How to use it: Drink a cup or two of good-quality green tea a day, earlier in the day.

Study takeaway: green tea capsules meant 32.1% fewer people with cold and flu symptoms over 3 months.

Nuts and seeds supply vitamin E, which helps lymphocytes multiply and supports T-cell function, and selenium, which your body builds into antioxidant proteins that protect immune cells.17 An ounce of almonds carries about 7.3 mg of vitamin E, and an ounce of dried sunflower seeds about 10 mg, along with 15 micrograms of selenium.47

How to use it: Eat a small handful a day as a snack, scatter them over salads, or stir almond or sunflower seed butter into oatmeal or a smoothie.

Study takeaway: an ounce of sunflower seeds carries about 10 mg of vitamin E and 15 micrograms of selenium.

Your antibodies and immune cells are built from protein, and pasture-raised chicken supplies protein and zinc for antibody production.7 Too little protein is one of the ways an immune system gets worn down,48 and the Chinese medicine approach to immunity pairs organic meats such as chicken and salmon with plenty of cooked vegetables.10

Oysters top most zinc lists, but they're shellfish, so I leave them off, along with pork. I follow the fins-and-scales standard for seafood from the biblical diet.32

How to use it: Have pasture-raised chicken or turkey or wild salmon at your meals, and save the chicken bones for broth.

Study takeaway: pasture-raised chicken supplies the protein and zinc your body uses to make antibodies.

Medicinal mushrooms act primarily as adaptogens and immunomodulators, so they help your immune system respond in proportion.49 Culinary mushrooms count, too. In a randomized study of 52 healthy adults aged 21 to 41, with no placebo group, eating 5 or 10 grams of dried shiitake mushrooms a day for 4 weeks increased the growth of gamma delta T cells by 60% and of natural killer T cells twofold, raised secretory IgA, an antibody that guards the gut lining, and lowered CRP, a marker of inflammation.50

Reishi mushroom is calming, and it's one you can take every day of your life,38 while turkey tail mushroom also works as a prebiotic that feeds your gut bacteria.49

How to use it: Cook shiitake into soups and stir-fries a few times a week, and take reishi as a daily extract, about 1 to 3 grams.7

Study takeaway: 4 weeks of daily shiitake raised gamma delta T cell growth 60% in 52 adults.

Elderberry is one of the few immune herbs with solid trials behind it, and its deep purple anthocyanins help stop flu viruses from latching on to your cells.8 In a placebo-controlled trial of 60 adults in Norway who started elderberry syrup within 48 hours of their first flu symptoms, taking 15 mL four times a day for 5 days, symptoms eased about 4 days sooner, and they needed less rescue medicine.13

In a trial of 312 economy-class air travelers flying overseas from Australia, where neither the people nor the researchers knew who got what, people took 600 to 900 mg a day of elderberry extract capsules or a placebo, from 10 days before the flight until 4 to 5 days after arriving. The elderberry group's colds were shorter and milder, adding up to 57 days with a cold against 117 on placebo, even though the two groups caught a similar number of colds, 12 and 17.51 A 2019 analysis of 4 randomized trials with 180 people found elderberry substantially reduced upper respiratory symptoms.35

How much: Through cold season, 1 to 2 teaspoons of syrup or 300 to 600 mg of a standardized extract a day;7 at the first symptoms, 1 tablespoon of syrup four times a day for 3 to 5 days.8 It's also one of the easiest herbs to get kids to take, so use a children's product as labeled.8

Study takeaway: air travelers on elderberry had 57 total days with a cold, against 117 on placebo.

Echinacea, the purple coneflower, activates your innate immune cells, and timing is the key with it. Take it at the very first sign of a cold, or steadily through cold season to cut down how often you get sick, rather than all year round.78

In a placebo-controlled trial of 755 healthy adults over 4 winter months, an echinacea extract taken at 2,400 mg a day, raised to 4,000 mg a day during colds, meant 672 total days with a cold against 850 on placebo, about a fifth fewer, and fewer repeat infections, 65 against 100.4 A 2007 analysis of 14 studies found echinacea lowered the odds of catching a cold by 58% and shortened colds by about 1.4 days,36 and a 2014 Cochrane review of 24 trials, which mixed many different products, estimated a 10% to 20% lower risk of catching one.52

How much: At the first sign of a cold, 300 to 600 mg of extract two to three times a day.7 As a tincture, 2.5 mL three times a day, and as capsules, 300 to 500 mg three times a day; prevention has been studied for up to 4 months.8

Study takeaway: in a trial of 755 adults, the echinacea group had 672 total days with a cold over 4 months, against 850 on placebo.

Astragalus, called huang qi in Chinese medicine, is one of that tradition's most important tonics, and it's the number one herb I have for preventing the cold and flu.814 Rather than fighting an infection that is already here, it builds the body's defenses over weeks and months, and families in China simmer the dried root slices in soups and broths through the winter. It's best for people who tire easily, catch every cold and sweat easily.8

Most of its modern research comes from China. A Cochrane team found 44 studies of it in children with frequent respiratory infections, none of them with a placebo group,53 and a 2023 review of 19 studies with 1,094 people found astragalus lowered inflammatory cytokines and raised markers of T-cell immunity.54

How much: To prevent colds, around 1,000 mg a day through the season,14 or simmer a few slices of the dried root in your soups and broths.8

Study takeaway: taken daily through the season, astragalus builds your defenses before a virus arrives.

Ginseng is one of the classic Chinese herbs for the body's defense energy,10 and North American ginseng has a good human trial behind it. Researchers in Edmonton gave 323 adults who'd caught at least 2 colds the year before either a North American ginseng root extract or a placebo, 2 capsules a day for 4 months starting at the beginning of flu season. Among the 279 who started treatment, the ginseng group caught fewer colds, 0.68 per person against 0.93, only 10.0% had 2 or more colds against 22.8% on placebo, and they had 10.8 days of cold symptoms against 16.5.55

How to use it: Take a standardized North American ginseng extract as labeled through cold season.

Study takeaway: on North American ginseng, 10.0% had 2 or more colds over 4 months, against 22.8% on placebo.

Turmeric has been used in traditional medicine and in the kitchen for centuries, and in lab research its main compound, curcumin, calms inflammation by turning down the NF-kB pathway that switches on inflammatory messengers.56 About 3 grams of turmeric powder carries 30 to 90 mg of curcumin, and black pepper's piperine is one of the most effective boosters of how much curcumin your body takes up, especially when you take them with an oil rich in unsaturated fats.56

How to use it: Cook with half a teaspoon to a teaspoon of turmeric a day, with a pinch of black pepper and a little fat such as olive oil, in soups, curries, eggs and golden milk.5657

Study takeaway: curcumin calms inflammation by turning down the NF-kB pathway in lab research.

Zinc is the immune mineral, essential for T-cell development and antiviral defense, and running low on it makes illness last longer.107 Its best evidence is for colds once they start. Across 7 placebo-controlled trials with 575 people, zinc acetate or gluconate lozenges at more than 75 mg a day made colds 33% shorter, the same 33% seen in the 5 trials that used 80 to 92 mg a day.9 In a 2024 Cochrane review of 34 trials, zinc taken to treat a cold shortened it by about 2.37 days across the 8 trials with 972 people that measured it, though it did little to prevent colds.58 Pumpkin seeds are one of the best foods for it, at about 2.2 mg an ounce.1047

How much: Every day, 15 to 30 mg with food; for long-term use, I pair it with a little copper, because a zinc supplement that only has zinc almost always throws your copper out of balance.759 At the first sign of a cold, let zinc lozenges dissolve in your mouth through the day for the week of the cold, as the lozenge trials did.9

Study takeaway: zinc lozenges made colds 33% shorter across 7 placebo-controlled trials.

Probiotics work where most of your immune system lives. In a 2022 Cochrane review, people taking probiotics were about 24% less likely to come down with an upper respiratory infection, across 16 studies with 4,798 children, adults and older adults, and in the 6 studies with 2,406 people that tracked it, episodes ran about 1.22 days shorter, though the reviewers rated the certainty of that evidence as low.3

I once had a patient whose nutrient absorption was very poor. She was low in B vitamins and had been getting vitamin B12 shots because her numbers were so low, so I put her on a very, very high dose of probiotics and a probiotic diet, and 3 months later every single nutrient she'd been deficient in had normalized.60 My first choice is the soil-based organisms, such as Bacillus subtilis, Bacillus coagulans and Bacillus clausii, alongside probiotic foods.60

How much: A daily probiotic of 50 to 500 billion CFU, plus fermented foods most days.7

Study takeaway: probiotics lowered the risk of an upper respiratory infection by about 24% across 16 studies.

Bee propolis is the resin bees use to seal and protect their hive, and I always recommend propolis if somebody has a cold or flu, because it's a powerful immune booster.61 In a placebo-controlled trial of 122 adults with mild, uncomplicated upper respiratory infections, a propolis spray used three times a day for 5 days meant 83% had no symptoms by day 3, while 72% on placebo still had at least one, so recovery came about 2 days sooner.62 Raw honey helps too: across 14 studies, honey eased cough and overall symptoms of upper respiratory infections more than usual care.63

Propolis is gentle enough that in certain cases I recommend it for patients with autoimmune disease, too.61

How much: 1 teaspoon to 1 tablespoon of raw local honey a day, plus local bee pollen, in place of other sweeteners, and propolis as a throat spray at the first scratch in your throat, three times a day, as in that trial.62

Study takeaway: with a propolis spray, 83% of adults with mild colds had no symptoms by day 3.

Oregano oil is one of the best-known plant antimicrobials, and in a lab study, oregano's infusion and essential oil held back gram-positive bacteria from 23 species, staph among them.64 Myrrh oil has a long history of its own, since frankincense and myrrh were paired in Egypt's pharaonic medicine, and in the lab, combinations of the two oils worked together against microbes, most of them additively or synergistically.65

How to use them: Diffuse them, or dilute a few drops in a carrier oil before they touch your skin. Oregano oil can also be taken by mouth for short stretches, 2 to 4 drops twice a day for up to 10 days.32

Study takeaway: in a lab study, oregano held back gram-positive bacteria from 23 species.