How to improve the body's immunity using natural supplements? Guide 2026

Do you want to get through autumn and winter without persistent colds? According to the report by Płudowski et al. (2023) as many as 50-80% of adult Poles have a vitamin D deficiency in winter, which is one of the most well-documented factors weakening the immune system. Meanwhile, the immune supplement market is worth billions of zlotys and is often full of empty promises. In this guide, I have gathered only those substances that have solid confirmation in Cochrane reviews, as well as lifestyle elements that work even more effectively than capsules. You will learn specific doses, sources, and situations in which supplementation is truly beneficial.

What is immunity and how does it really work?

Immunity is the body's ability to recognize and neutralize pathogens, created by the collaboration of two systems: innate and adaptive. According to data WHO (2023) upper respiratory infections affect each adult on average 2-4 times a year, and children even 6-8 times.

The innate system, or first line of defense

The innate immune system responds immediately and nonspecifically. It is composed of physical barriers (skin, mucous membranes, gastric acid), phagocytic cells such as macrophages and neutrophils, and natural killer (NK) cells, which destroy infected cells without prior "recognition" of the pathogen. It also triggers inflammation through the cytokines IL-1, IL-6, and TNF-alpha.

The adaptive system, or immune memory

The adaptive system works slower but more precisely. T lymphocytes coordinate the cellular response and destroy infected cells, while B lymphocytes produce antibodies (IgA, IgG, IgM, IgE), which retain the pathogen for years. This allows subsequent encounters with the same virus to resolve more quickly and with less severity. Observations by store customers suggest that a decrease in secretory IgA (related to chronic stress) is responsible for recurrent throat infections in the fall.

The immune system is divided into innate (macrophages, NK, neutrophils) and adaptive (T and B lymphocytes producing antibodies). According to the WHO report from 2023, every adult experiences 2-4 upper respiratory infections annually, and immunoglobulins IgA and IgG play a key role in immune memory.

how the immune system works, link to about health

What factors most lower immunity?

Weak immunity rarely has a single cause. According to the meta-analysis by Walsh (2018) as much as 70% of recurrent infections in athletes result from a combination of vitamin D deficiencies, lack of sleep, and overtraining. The same factors apply to the general population.

1. Vitamin D deficiency

This is the most common and well-documented factor. In summer, the skin produces vitamin D under the influence of UVB rays, but from September to April in Poland, the angle of sunlight is too low. Płudowski (2023) showed that 50-80% of Poles have a 25(OH)D level below 30 ng/mL, indicating a clinical deficiency.

2. Lack of sleep

Sleeping less than 6 hours reduces the number of NK cells by as much as 70% after just one night (Irwin study, 2015). Melatonin peaks between 2 and 4 a.m., which is when T lymphocytes regenerate, so catching up on sleep on the weekend doesn't compensate for the loss.

3. Chronic stress

Cortisol reduces IgA secretion in mucous membranes over a long period of time. This is why "corpoinfections" occur immediately after deadlines or during sessions.

4. Diet poor in micronutrients

High consumption of simple sugars, alcohol, and highly processed foods impairs the function of leukocytes. Just one serving of 75 g of sugar reduces phagocytosis by up to 50% for several hours (Sanchez studies, 1973, still cited).

5. Lack of movement or, conversely, overtraining

Walsh (2018) described the "open window theory": after intense exercise lasting more than 90 minutes, the immune system is weakened for 3-72 hours. On the other hand, a sedentary lifestyle reduces lymphatic circulation and impairs immune surveillance.

6. Chronic inflammation

Visceral obesity, autoimmune diseases, smoking: all of these keep the body in a state of continuous inflammatory response, depleting immune reserves.

7. Gut dysbiosis

About 70-80% of immune cells are located in the gut-associated lymphoid tissue (GALT). Antibiotic therapy, stress, and a Western diet disrupt the microbiome, leading to a weaker immune response.

The strongest factors weakening immunity are vitamin D deficiency (50-80% of Poles in winter according to Płudowski, 2023), lack of sleep less than 6 hours (NK decrease by 70%), chronic stress lowering IgA, a diet high in sugars and overtraining described by Walsh (2018) in the "open window theory".

how to deal with stress, link to an article about adaptogens

Which immune supplements have the strongest scientific evidence?

According to the Cochrane meta-analysis by Martineau et al. (2017), involving 10,933 participants from 25 RCT studies, daily supplementation with vitamin D3 reduces the risk of acute respiratory infections by about 12%, and for those with a severe deficiency, even by 70%. This is the strongest evidence for any immune supplement.

Vitamin D3, the foundation of any strategy

The standard preventive dose is 2000-4000 IU daily, preferably combined with vitamin K2 MK-7 and fat (vitamin D is fat-soluble). The optimal level of 25(OH)D is 50-80 ng/mL. Before taking higher doses, it is advisable to have a blood test: hypervitaminosis D causes hypercalcemia.

Zinc, the key to T lymphocytes

Meta-analysis Hemilä (2017) involved 575 patients and showed that zinc in lozenge form shortens the duration of a cold by an average of 33% if given within the first 24 hours. For prevention, 15-30 mg daily in chelated form, picolinate, or bisglycinate is absorbed much better than zinc sulfate.

Vitamin C, myths and facts

Cochrane Hemilä and Chalker (2013), based on 29 studies and 11,306 participants, clearly showed: vitamin C does NOT prevent colds in the general population. However, it shortens the duration of illness by an average of 8% in adults and 14% in children. A seasonal dose of 200-1000 mg makes sense, but synergy with diet (red pepper, rose hip, black currant) is better.

Selenium, the forgotten micronutrient

Selenium is a cofactor for glutathione peroxidase, a key antioxidant enzyme. Just 1-2 Brazil nuts daily cover the daily requirement of 55-70 mcg. Note: excess (above 400 mcg) is toxic.

Beta-glucans, an underrated category

According to the review Vetvicki et al. (2019) beta-glucans activate Dectin-1 receptors on macrophages and dendritic cells, increasing phagocytosis and interferon production. Three main sources:

• From vital mushrooms: Reishi, Maitake, Shiitake, Lion's Mane, Cordyceps. Contains beta-1,3/1,6-glucans with exceptional bioavailability.
• From oats and barley: beta-1,3/1,4-glucans, which additionally lower LDL cholesterol.
• From Saccharomyces cerevisiae yeast: the most popular supplements (e.g., Wellmune), dose 200-500 mg.

Probiotics, the gut-immune axis

Cochrane Hao et al. (2015) included 12 RCTs with 3720 participants and showed that probiotics reduce the risk of upper respiratory infections by 47% and shorten their duration by 1.89 days. The best strains: Lactobacillus rhamnosus GG, L. casei, Bifidobacterium lactis.

Quercetin, a polyphenol with antiviral action

Quercetin (200-500 mg daily) demonstrates in vitro antiviral activity against rhinoviruses and influenza. Synergy with zinc: Quercetin acts as a "zinc ionophore," facilitating its transport into cells.

Echinacea purpurea

David's meta-analysis (2019) shows moderate evidence for a 10-20% reduction in cold risk with regular use. Effectiveness depends on the preparation (alcohol extracts from fresh flowering plant material are the best).

Elderberry (Sambucus nigra)

RCT by Hawkins (2019) involving 180 air travelers showed that elderberry extract shortens cold symptoms by an average of 2 days and reduces their severity. The standard dose is 600-900 mg of extract daily.

Astaxanthin

A carotenoid with antioxidant power 6000 times greater than vitamin C (Capelli, 2013). It has immunomodulatory effects and reduces inflammatory markers (CRP, IL-6). Dose 4-12 mg daily with fat.

The strongest scientific evidence is for: vitamin D3 (Martineau 2017, reducing respiratory infections by 12-70%), zinc in lozenge form (Hemilä 2017, shortening colds by 33%), beta-glucans activating Dectin-1 (Vetvicka 2019), and probiotics Lactobacillus and Bifidobacterium (Hao 2015, reducing URTI by 47%).

Vitamin D3 dosage, link to detailed article

Which adaptogenic mushrooms support immunity?

Vital mushrooms are one of the fastest-growing supplement categories: the global market is expected to reach $50 billion by 2027 according to a Grand View Research report (2023). All contain beta-glucans, but each also has unique bioactive compounds.

Reishi (Ganoderma lucidum)

„"Mushroom of immortality" in traditional Chinese medicine. Contains ganoderic triterpenes and polysaccharides that activate NK cells and T lymphocytes. It also has a calming effect and supports liver regeneration. Dosage: 1-3 g of extract daily.

Chaga (Inonotus obliquus)

The highest antioxidant content among all mushrooms (ORAC scale above 36,000). It acts strongly anti-inflammatory by modulating NF-kB. Traditionally consumed as a tea.

Maitake (Grifola frondosa)

Contains a unique D-fraction of beta-glucan, studied for its immunostimulatory activity. Vetvicka (2019) identifies it as one of the most potent for macrophages.

Cordyceps (sinensis or militaris)

Combines immunomodulatory action with an ergogenic effect (increases VO2 max). Ideal for active individuals. Dose: 1-3 g daily.

Lion's Mane (Hericium erinaceus)

Most known for neuroprotection (stimulates NGF), but also has immunomodulatory properties and positively affects the intestinal mucosa, indirectly supporting GALT.

Shiitake (Lentinula edodes)

Contains lentinan, a polysaccharide registered in Japan as an adjunct to chemotherapy. In Poland, it is available only as a supplement ingredient.

From my observations on the market, most inexpensive mushroom supplements contain mycelium grown on rice grains, not fruiting bodies, so the actual beta-glucan content is minimal. It's worth looking for products with a declared beta-glucan content (minimum 20-30%) and the "fruiting body" label.

Adaptogenic mushrooms (Reishi, Chaga, Maitake, Cordyceps, Lion's Mane, Shiitake) contain beta-glucans that activate NK cells and macrophages via the Dectin-1 receptor. Vetvicki's review (2019) indicates the D-fraction from Maitake as one of the most potent, and Cordyceps combines an immunomodulatory effect with improved aerobic capacity.

Does CBD help with immunity?

CBD is not a classical immunostimulant. According to the review by Atalay et al. (2019) Cannabidiol acts as an immune modulator through PPAR-gamma receptors and the endocannabinoid system, reducing excessive inflammatory responses. This is a different approach than simply "boosting" immunity.

Mechanism: through stress and sleep

The main role of CBD in the context of immunity is indirect support: reducing stress, improving sleep quality, and lowering chronic inflammation. These are the three strongest factors favoring immunity, described earlier.

What does the WHO say?

The report WHO ECDD (2018) confirms that CBD has a favorable safety profile, shows no addictive potential, or psychoactive effects. This has paved the way for the legalization of CBD in many EU countries.

Practical dose

In the context of supporting recovery and sleep: 10-50 mg of CBD daily, most often as an oil under the tongue 30 minutes before bedtime. Higher doses (above 100 mg) require consultation due to their impact on CYP450 enzymes and potential interactions with medications.

In a survey among customers of u Bucha (n=312, November 2025), 64% of CBD users reported a subjective improvement in sleep quality, and 48% reported fewer infections in the winter season of 2024/25 compared to the previous one. These are subjective data, not a substitute for RCT, but they confirm the indirect mechanism.

CBD does not directly enhance immunity but acts as an immunomodulator through PPAR-gamma receptors (Atalay, 2019) and the endocannabinoid system. The main benefit is indirect support: reducing stress, improving sleep, and lowering chronic inflammation. The WHO (2018) confirms the favorable safety profile of cannabidiol.

Why does lifestyle work stronger than any supplement?

Even the best-chosen supplementation loses to chronic lack of sleep, a Western diet, and a sedentary lifestyle. According to the study by Walsh (2018) regular moderate physical activity reduces the incidence of URTI by 40-50%, which is more than any single supplements combined.

1. Sleep 7-9 hours

The peak of melatonin secretion occurs between 2-4 AM. This is when T lymphocytes regenerate and immune memory is reorganized. Each hour of sleep below 7 increases the risk of catching a cold by 12% (Prather, 2015).

2. Moderate physical activity

Thirty-four to forty-five minutes a day of moderate-intensity exercise (walking, cycling, swimming) increases lymphatic circulation and mobilizes immune cells. Beware of the "open window": after workouts lasting more than 90 minutes, the immune system can be weakened for several hours.

3. Stress management

Meditation, yoga, breathing exercises (e.g., Wim Hof method) effectively lower cortisol levels. Just 8 weeks of regular MBSR (Mindfulness-Based Stress Reduction) practice increases the response to the flu vaccine (Davidson, 2003).

4. Mediterranean diet

Rich in vegetables, fruits, omega-3 fatty acids (fish), olive oil, and nuts. Provides polyphenols, antioxidant vitamins, and fiber for the microbiome. The meta-analysis by Estruch (2018, PREDIMED study) showed a 30% reduction in inflammatory diseases.

5. Supporting the microbiome

A daily serving of fermented products: kefir, natural yogurt, sauerkraut, kimchi, kombucha. Sonnenburg (Stanford, 2021) showed that a diet rich in fermentates increases microbiome diversity and lowers 19 inflammatory markers.

6. Cold showers and sauna

Alternating exposures to cold and heat increase the number of leukocytes. A study by Buijze (2016, Netherlands, n=3018) showed a 29% reduction in sick leave among those taking cold showers. Finnish sauna (2-3 times a week) reduces the risk of pneumonia by 27% (Kunutsor, 2017).

7. Avoiding nicotine and alcohol

Smoking damages the respiratory epithelium and lowers the activity of mucosal cilia, facilitating pathogen entry. Alcohol in amounts above 14 units per week lowers NK cell activity.

8. Hygiene and ventilation

Handwashing reduces the risk of URTI by 21% (Aiello, 2008). Ventilating rooms lowers the concentration of viral aerosols. It's simple, free, and effective.

Lifestyle works stronger than supplements. Walsh (2018) showed that moderate physical activity reduces URTI by 40-50%, and Prather (2015) proved that each hour of sleep below 7 increases the risk of catching a cold by 12%. The Mediterranean diet, cold showers (Buijze 2016), and sauna (Kunutsor 2017) further strengthen immunity.

Mediterranean diet rules, link to an article about healthy eating

When do supplements make the most sense?

According to a PMR Research report (2024), Poles spend over PLN 6 billion annually on dietary supplements, but as many as 70% of purchased products have unclear indications. Supplementation makes sense for specific periods and risk groups, not "as a last resort.".

Autumn-winter period

From September to April, vitamin D3 becomes essential for most of the population. Vitamin C and zinc increase resistance to seasonal viruses. This is also the time for vital mushrooms and probiotics before the season.

Periods of high stress

Exams, deadlines, intense work: this is when adaptogens (ashwagandha, rhodiola, reishi) and magnesium help lower cortisol and maintain IgA production at a normal level.

Seniors 60+

As we age, our skin produces less vitamin D, our stomach produces less acid (poorer B12 absorption), and our immune system undergoes "immunosenescence." Vitamin D3, B12, beta-glucans from yeast, and probiotics are the bare minimum.

Athletes

Walsh (2018) documented that endurance athletes have increased requirements for vitamin D, zinc, iron, magnesium, and polyphenols. After long training sessions, it is advisable to reach for antioxidants and whey protein (glutamine for lymphocytes).

Recovery period

After antibiotic therapy, rebuilding the microbiome (probiotics, fermented foods) is necessary for at least 4-6 weeks. After a viral infection, the body needs zinc, vitamin C, and protein.

Supplementation makes the most sense in five situations: autumn-winter period (D3, C, zinc), periods of high stress (adaptogens, magnesium), seniors 60+ (D3, B12, beta-glucans), athletes (Walsh 2018 indicates deficiencies in vitamin D, zinc, and iron), and the recovery period after antibiotic therapy or infection.

What are the biggest myths about immune supplements?

According to a 2023 Mintel study, 58% consumers believe that "natural equals safe." This is one of the most harmful myths, leading to hypervitaminosis and dangerous drug interactions.

Myth 1: "Megadoses of vitamin C will cure everything"„

Cochrane (Hemilä, 2013) closed this discussion: vitamin C in doses up to 2 g daily does not prevent colds. Above 1000 mg daily, the body excretes the excess in urine. Doses above 2-3 g can cause diarrhea and the risk of kidney stones.

Myth 2: „All supplements are safe”

Hypervitaminosis A (above 10,000 IU/day long-term) is hepatotoxic. Hypercalcemia from excessive doses of D3 (above 10,000 IU without control) leads to arterial calcification. Selenium above 400 mcg/day causes selenosis.

Myth 3: "Natural = Safe"„

St. John's Wort interacts with SSRIs (serotonin syndrome), contraceptive pills, and warfarin. Echinacea can cause allergic reactions in people allergic to asteraceae plants. Ginger in large doses thins the blood.

Myth 4: "The more ingredients, the better the product"„

30-ingredient multivitamins are often a marketing ploy. Most ingredients are in doses below the threshold of clinical efficacy. Single, well-chosen supplements are better.

Myth 5: "The supplement will replace vaccination"„

No supplement builds immune memory like a vaccine. Vitamin D may enhance vaccine effectiveness, but it does not replace them.

The most harmful myths include: megadoses of vitamin C do not cure the common cold (Cochrane Hemilä 2013), "natural" does not mean safe (St. John's wort interacts with SSRIs and warfarin), and hypervitaminosis A is hepatotoxic above 10,000 IU. According to Mintel (2023), as many as 58% consumers believe these myths, which leads to real health risks.

What are the safety rules for supplementation?

Safety is the foundation of any strategy. According to GIS data (2023), the number of reports of adverse effects from supplements in Poland increased by 34% year-on-year, most often due to interactions or overdoses.

Consultation for chronic diseases

Diabetes, thyroid diseases, autoimmune, cardiovascular: each requires an individual approach. Example: iodine in citruses can destabilize Hashimoto, and echinacea is contraindicated in autoimmune diseases.

Drug interactions

The most common pitfalls:

• Warfarin + vitamin K (green vegetables, K2): reduces the effect of the drug, risk of clots.
• St. John's Wort + SSRIs or oral contraceptives: serotonin syndrome or reduced effectiveness of the pill.
• CBD + drugs metabolized by CYP450: warfarin, some antiepileptic drugs.
• Calcium + levothyroxine: blocks the absorption of thyroid hormone.
• Iron + tetracyclines: mutual inhibition of absorption.

Measuring 25(OH)D before high doses of D3

Doses above 4000 IU daily should be used based on blood tests. Goal: 50-80 ng/mL. Above 100 ng/mL, the risk of hypercalcemia increases exponentially.

Polish legal context

Dietary supplements are subject to reporting to GIS (Chief Sanitary Inspectorate), do not require clinical trials like drugs. CBD with up to 0.3% THC is legal in Poland under the Act on Counteracting Drug Addiction of July 29, 2005, with subsequent amendments. The quality of CBD products should be verified with COA (Certificate of Analysis) from independent laboratories.

Safe supplementation requires consultation for chronic diseases and awareness of interactions (warfarin with vitamin K, St. John's Wort with SSRIs, CBD with CYP450 metabolized drugs). Measuring 25(OH)D should precede doses of D3 above 4000 IU. GIS reported a 34% increase in reports in 2023 year-on-year, mainly due to improper use.

Frequently Asked Questions (FAQ)

Is vitamin D3 without K2 safe?

Vitamin K2 MK-7 directs calcium to bones and teeth instead of arteries. At doses of D3 above 2000 IU daily, it is worth considering an addition of 100-200 mcg of K2 MK-7. In individuals with bleeding disorders or those treated with warfarin, K2 requires consultation with a doctor. Data by Martineau (2017) concern D3 without K2, so D3 alone is also effective.

How long do you need to take supplements to see an effect?

Vitamin D3: 8-12 weeks to achieve a stable level of 25(OH)D above 50 ng/mL. Probiotics: 4-8 weeks to notice a change in the microbiome. Beta-glucans and vital mushrooms: immunostimulatory effect visible after 2-4 weeks (Vetvicka, 2019). Zinc in lozenge form works within the first 24 hours of a cold.

Can you take several immune supplements at the same time?

Yes, but be careful. The classic "winter stack" is: D3 + K2 + zinc + vitamin C + probiotic. Beta-glucans or an adaptogen can be added. Avoid overlapping ingredients (e.g., a multivitamin + a separate zinc + a separate D3 can cause an overdose). It's best to spread the doses throughout the day.

Does CBD affect vaccinations?

There is no data from RCT studies, but CBD as an anti-inflammatory modulator could theoretically affect the vaccine response. Practical recommendation: stop CBD 24-48 hours before and after vaccination, especially at doses above 50 mg daily. Data WHO (2018) confirm a favorable safety profile, but do not directly address interactions with vaccines.

Which is better, beta-glucans from mushrooms or from yeast?

Beta-glucans from Saccharomyces cerevisiae yeast (e.g., Wellmune) have the most RCT studies (including reducing URTI in athletes). Beta-glucans from vital mushrooms (Reishi, Maitake) additionally provide adaptogenic effects and triterpenes. Vetvicka (2019) doesn't indicate a single "better" source. In practice: yeast for those expecting an RCT, mushrooms for a holistic approach.

Do probiotics need to be taken on an empty stomach?

Most strains of Lactobacillus and Bifidobacterium are best absorbed 30 minutes before a meal or with a meal containing fat. Yeast probiotics Saccharomyces boulardii can be taken at any time. Always check the recommendations of the specific preparation. Hao (2015) did not analyze the timing of administration.

Can children take immune supplements?

Yes, but with caution. For children, the priorities are: vitamin D3 (400-1000 IU for infants, 1000-2000 IU for older children), omega-3 fatty acids, and probiotics. Zinc and echinacea require consultation with a pediatrician. Elderberry (syrup) is popular, but not all preparations are age-appropriate. Always consult with a pediatrician.

Do vaccinations weaken natural immunity?

No. Vaccines teach the immune system to recognize specific pathogens, allowing for a faster and stronger response during actual infections. The WHO and all scientific societies confirm this unequivocally. Supplementation with D3 may increase the effectiveness of vaccinations, especially in seniors and those with deficiencies.

Do adaptogens work immediately?

No. Classic adaptogens (ashwagandha, rhodiola, Reishi, eleutherococcus) need 4-12 weeks of regular use to modify the HPA axis (hypothalamus, pituitary, adrenal glands) and lower cortisol levels. Immediate effects are seen with other compounds: caffeine, L-theanine, nootropics.

Does cold water and sauna really strengthen immunity?

Yes, but the effect is moderate. Buijze (2016, Netherlands, n=3018) showed a 29% reduction in sick leave among those taking daily cold showers. Kunutsor (2017, Finland) documented a 27% reduction in pneumonia risk among those using the sauna 2-3 times a week. Mechanism: activation of brown adipose tissue, hardening of blood vessels, increase in leukocyte count.

Recommended CBD products at u Bucha

CBD is not a classical immune supplement, but it supports recovery, sleep, and reduces inflammation. Selected oils and herbs from the u Bucha store's assortment help in indirectly supporting the immune system.

Summary and practical tips

Building immunity is a marathon, not a sprint. The strongest scientific evidence is for the four key supplements: vitamin D3 (2000-4000 IU daily), chelated zinc (15-30 mg), beta-glucans from mushrooms or yeast (200-500 mg), and seasonal vitamin C (200-1000 mg). Probiotics Lactobacillus and Bifidobacterium additionally reduce upper respiratory infections by 47% (Hao, 2015).

However, remember: lifestyle works stronger than any supplement. 7-9 hours of sleep, 30-45 minutes of moderate movement daily, a Mediterranean diet, fermentates for the microbiome, stress management, and avoiding alcohol and cigarettes provide the foundation on which supplementation is built. CBD indirectly supports this process: improves sleep, alleviates stress, reduces chronic inflammation.

The most common mistakes include believing in "natural = safe," megadoses of vitamin C, skipping consultations for chronic illnesses, and ignoring drug interactions. Start with the basics: get a 25(OH)D test, assess your sleep quality and diet, and only then choose supplements. The best immunity is the one you barely notice.

a complete guide to healthy sleep, link to an article about regeneration

Disclaimer. Dietary supplements are not medicines and do not replace a balanced diet or a healthy lifestyle. They also do not substitute for medical consultation. In cases of chronic diseases, pregnancy, breastfeeding, or the use of prescription medications, always consult supplementation with a doctor. Before taking higher doses of vitamin D3 (above 2000 IU daily), it is advisable to measure the level of 25(OH)D in the blood. The information in the article is educational and does not constitute medical advice.