Helpful Immune Booster Supplements + Immunity Foods to Eat

Best Immune Booster Supplements: A Registered Dietitian’s Evidence-Based Guide

Healthy Immune System Basics: Start in the Gut

Your immune system is not just in your blood — it’s primarily housed in your digestive tract. This is one of the most important facts in all of functional medicine, and it fundamentally changes how we approach immune support. A few key points:

• Over 70% of your immune cells live in your gut as gut-associated lymphoid tissue (GALT).
• Certain strains of viruses are actually contracted through the gut lining.
• Research shows the ratio of beneficial to harmful bacteria predicts the presence of illness during cold season.
• HIV patients who spontaneously control the virus have healthier gut-associated lymphoid tissue.
• Probiotics stimulate interferon production and activation of innate immunity against viruses.

Food Sensitivities: The Hidden Immune Drain You Need to Know About

Here’s something that doesn’t get nearly enough attention in mainstream discussions of immune health: your immune system is one of the largest sources of inflammation in your body, and food sensitivities are a major — and often entirely overlooked — root cause of immune dysfunction.

Unlike true food allergies (IgE-mediated), food sensitivities involve a delayed immune response where white blood cells — neutrophils, monocytes, lymphocytes, and eosinophils — release inflammatory mediators (cytokines, histamine, leukotrienes, prostaglandins) in response to specific foods or food chemicals. This process can take up to 72 hours to manifest as symptoms, making it nearly impossible to identify through diet observation alone.

When your immune system is constantly being activated by the foods you eat every day, it becomes exhausted, dysregulated, and far less capable of fighting actual infections. Chronic low-grade immune activation from food sensitivities contributes to:

• Persistent fatigue and brain fog
• Digestive issues, bloating, and IBS-type symptoms
• Recurrent infections
• Headaches, migraines, and joint pain
• Skin problems like eczema and hives
• Autoimmune flares

If you’re doing everything “right” nutritionally but still getting sick frequently, feeling inflamed, or struggling with immune dysregulation, hidden food sensitivities may be the missing piece. I strongly encourage working with a CLT-certified practitioner to investigate this. Learn more about why MRT food sensitivity testing changes the approach to immune health.

Medicinal Mushrooms as Immune Booster Supplements

All edible mushrooms are packed with beta-glucans, polysaccharides, and other compounds that directly support immune function. Research published in Nutrients links mushroom intake to improved immune response including improved T-cell counts and immune compound activity.

Medicinal mushrooms are among the most time-tested immune modulators in traditional medicine and are increasingly validated by modern research. Reishi in particular has deep roots as a longevity and immune tonic in traditional Asian medicine, and the science continues to support this reputation. The best for immunity include:

• Chaga — rich in antioxidants and beta-glucans
• Reishi — renowned as an adaptogen and immune modulator
• Turkey Tail — contains PSK and PSP, studied in cancer immune support

Zinc and Natural Zinc Ionophores as Immune Booster Supplements

Zinc supplement options to support immune health

Long known to support both immune and gut health, zinc remains one of the most important nutrients for fighting infections. WebMD rates zinc as “possibly effective” for the common cold, as well as for acne, depression, and diarrhea.

An important nuance with zinc is its cellular transport. Zinc needs to get inside cells to do its job — and certain natural compounds called zinc ionophores dramatically improve that transport.

Natural zinc ionophores help zinc enter cells where it stops viruses from replicating

The best natural zinc ionophores to pair with your zinc supplement include:

• Quercetin — a plant polyphenol from apples and onions; among the most researched zinc ionophores
• EGCG (green tea extract) — epigallocatechin gallate enhances zinc’s cellular uptake
• Resveratrol — found in grapes and red wine; also acts as a zinc ionophore

If you want a food-first source of zinc with a broad spectrum of immune-supporting nutrients, try adding MK Supplements Grassfed Beef Liver capsules to your regimen.

Vitamin C as an Immune Booster Supplement

Vitamin C is perhaps the most recognized immune nutrient — and for good reason. Deficiency is directly linked to compromised immune response. Here’s what the clinical evidence shows:

I recommend liposomal vitamin C for optimal absorption — standard ascorbic acid is partially degraded during digestion, while liposomal forms dramatically improve bioavailability. One important caution: if you have a history of kidney stones, use vitamin C carefully and consult your doctor first.

Related post: The Kidney Cleanse Diet: 15 Easy Diet Swaps to Improve Kidney Health

Selenium as an Immune Booster Supplement

Selenium is a trace mineral that functions as a critical antioxidant in the body. Selenium deficiency may amplify viral infection severity, and many people are unknowingly low due to selenium-depleted soils in agricultural regions.

• Short-term supplementation at 100 mcg per day is safe and effective for most adults.
• Higher doses are not better — selenium toxicity (selenosis) can occur above 400 mcg/day long-term.
• Men’s multivitamins typically contain more selenium than women’s versions; men may benefit from a standard multivitamin, while women may want to supplement separately.

Vitamin A as an Immune Booster Supplement

Vitamin A plays regulatory roles throughout the immune system and directly protects the gut lining — making it doubly important for immune function. It also supports healthy aging by reducing oxidative stress.

• Approximately 30% of people carry genetic variants that limit their ability to convert plant-based beta-carotene to the active retinol form — meaning they need preformed vitamin A from animal sources or supplements.
• Experts recommend short-term dosing of preformed vitamin A (retinol) during acute illness, not prolonged high-dose supplementation.
• Always pair vitamin A with adequate vitamin D for best results — these two nutrients work synergistically in immune regulation.

Vitamin D3 — Not D2 — for Immune Support

Vitamin D is arguably the most critical immune supplement of all. It improves both innate and adaptive immune responses, and deficiency is extraordinarily common — especially in northern climates like Montana, in people with limited sun exposure, or those taking medications that deplete vitamin D.

I recommend having your blood vitamin D levels tested by your doctor at least once a year. If you’re taking blood-thinning medications, always check with your doctor before adding vitamin K2 alongside vitamin D. Also see my post on the remarkable effects of vitamin D on joint health as another reason to keep your levels optimized.

L-Carnitine: The Immune Supplement You’re Probably Missing

L-carnitine is best known for its role in fat metabolism and energy production — but its immunomodulatory effects are equally compelling and dramatically underappreciated. As someone who has covered L-carnitine extensively in my clinical writing, I want to highlight this nutrient specifically in the context of immune health because the 2024–2025 research is impressive.

For immune applications, both L-carnitine tartrate (well-studied for immune and athletic recovery applications) and acetyl-L-carnitine (ALCAR) (which crosses the blood-brain barrier and has additional cognitive benefits) are worth considering. Read my full breakdown of the best L-carnitine supplement brands and their benefits, as well as the vast health benefits of L-carnitine for brain health, heart health, and energy.

Probiotics and Fermented Foods as Immune Booster Supplements

Probiotics directly support gut-based immune function. Research confirms some strains actively combat viral infections by stimulating interferon production and natural killer cell activity. The best way to get probiotics naturally is through fermented foods:

• Sauerkraut — rich in Lactobacillus strains and vitamin C
• Apple cider vinegar with the mother
• Kimchi, yogurt, kefir, kombucha
• Fermented teas like oolong or Pu-erh

Pair fermented foods with prebiotic fiber from vegetables, seeds, nuts, and fruits to feed beneficial bacteria. If you dislike fermented foods, a high-quality probiotic supplement is a good starting point.

Protein as a Foundation for Immune Cell Repair

Protein is the critical building block for both immune cells and intestinal cells. Without adequate protein, your body simply cannot manufacture the antibodies, cytokines, and white blood cells needed to fight infection effectively. Amino acids from protein are also precursors to key immune-regulating compounds — for example, tryptophan supports serotonin production and immune modulation far beyond its association with turkey.

Aim for approximately 1 gram of protein per kilogram of body weight per day (roughly 0.5 g per pound). For a 150-pound person, that means at least 75 grams daily. Best protein sources for immune support:

• Wild-caught salmon and wild sardines (omega-3s also modulate immune response)
• Grass-fed meats (also a natural source of L-carnitine and zinc)
• Pasture-raised chicken and turkey
• Nuts, fermented legumes, and seeds
• Grass-fed whey protein or collagen protein

Immune-Boosting Spices and Herbs

Spices and herbs have served as immune tonics across nearly every traditional medicine system for thousands of years — and science is validating their use. Compounds in garlic, peppermint oil, and thyme oil have been shown to reduce viruses that cause bronchitis. More broadly, herbs play a meaningful role in reducing viral infections. Lemon is another underrated immune herb — its active compound limonene has anti-inflammatory and gut-supportive properties; learn more about the digestion and immunity benefits of lemon and limonene.

Daily use of culinary herbs — garlic, turmeric, oregano, ginger, thyme — provides a consistent low-dose immune benefit. Make it easy to use immune-supportive spices every day with a healthy southwest spice blend or try this espresso chipotle marinade — both pack multiple immune-supportive spices into easy everyday meals. Explore the immune and health benefits of peppermint oil, more essential oils for immune system support, and keep a selection of soothing herbal teas on hand for daily immune support and stress management.

Elderberry as an Immune Booster Supplement

Elderberry (Sambucus nigra) is one of the most well-studied botanicals for respiratory immune support. A review of research on 160 people found that elderberry supplements significantly reduce symptoms of upper respiratory infections in both duration and severity.

Elderberry is safe for daily use, and you can even harvest your own berries and make syrup using a simple elderberry syrup recipe. Standardized extracts are also widely available in capsule and gummy forms.

Supporting Gut Health for Lifelong Immune Function

Nourishing your gut means nourishing your immune system directly. The liver also plays a key supporting role — a healthy liver processes immune mediators and filters pathogens from the blood. Milk thistle supports both liver and gut health, making it a valuable addition to any immune-supportive protocol. Comprehensive gut health for immunity requires:

• Probiotics and fermented foods (see above)
• Prebiotic fiber from diverse plant foods
• All key vitamins and minerals (D3, A, C, zinc, selenium, B vitamins)
• Adequate protein
• Healthy fats — especially omega-3s and olive oil
• Antioxidant-rich foods — berries, leafy greens, colorful vegetables

Research published in Scientific American confirms that dietary changes can shift gut bacteria in as little as a few days. You don’t have to wait months to see immune benefits from improving your diet — the response is faster than most people realize. Cooking whole, real foods from scratch is one of the most powerful ways to support this — even something as simple as making homemade jam from whole fruit builds the habit of using real, unprocessed ingredients that feed a healthy microbiome.

Ingredients That Sabotage Your Immune Health

Ironically, many packaged products marketed for immune health contain additives that may actually undermine gut immunity. Always read labels carefully. Common ingredients shown to disrupt the gut and immune function include [R]:

• Sucralose and artificial sweeteners
• Titanium dioxide
• Added sugar and fructose
• Sodium nitrite
• Sodium benzoate
• Polysorbate-80
• Carrageenan

The best course of action is to eat primarily unprocessed foods — vegetables, fruits, wild fish, grass-fed meats, organic nuts, seeds, and eggs. See my comprehensive guide on risky chemicals in foods to avoid.

Frequently Asked Questions About Immune Booster Supplements

Immune Booster Supplements Summary

Building a robust immune system requires a whole-body, root-cause approach. The foundation is always the gut — and that means addressing diet quality, probiotic support, fiber intake, and, critically, identifying hidden food sensitivities through MRT testing if chronic inflammation or recurrent illness is a concern.

On top of that foundation, evidence-based supplementation with vitamin D3, zinc (with ionophores), liposomal vitamin C, selenium, medicinal mushrooms, L-carnitine, and elderberry can meaningfully support your immune resilience year-round.

Remember: many viruses and pathogens don’t thrive in a well-nourished, gut-healthy host. Your best immune defense is built from the inside out — starting with what you put on your plate and ending with carefully chosen, research-backed supplements.

Heidi Moretti, MS, RD, CLT

Heidi Moretti is a registered dietitian with over 25 years of clinical experience specializing in functional nutrition and natural medicine. She is the author of Cortisol Fix, Period Fix, Gut Fix, and The Whole Body Guide to Gut Health. As a Certified LEAP Therapist, she specializes in identifying food sensitivity-driven inflammation and creating individualized nutrition protocols. Follow her at @HeidiHmoretti or on LinkedIn.