Supplements for autumn and immunity: what to take to survive winter without getting sick

Every autumn, millions of Poles reach for "immunity" supplements – echinacea, elderberry, vitamin C, zinc, probiotics – hoping that this season will be better. How many of these supplements actually have solid scientific backing, and how many are just marketing and tradition? We analyze five immunity-supporting supplements that have the best research documentation, with specific doses and starting times. Plus one important bonus: what you definitely should not buy.

KEY INFORMATION
• Cochrane Review (Hemilä et al., 2013) included 11,000 participants: vitamin C shortens colds by 8–14%, but does not prevent illness – the exception is very physically active individuals.
• Meta-analysis by Hemilä (Cochrane, 2015): zinc in lozenge form taken within 24 hours of symptoms shortens colds by about 33%.
• 70–80% of Poles have a vitamin D deficiency in the winter season – this is one of the most important immunomodulating factors.
• Elderberry (sambucus) has shown activity in inhibiting the neuraminidase of the influenza virus – it works most effectively at the first signs of infection.

Vitamin D3 – the foundation of immunity in winter

Vitamin D3 is not just the "sunshine vitamin" – it is an active modulator of the immune system. Its receptors (VDR) are present on dendritic cells, macrophages, T and B lymphocytes. A deficiency of vitamin D impairs both innate and acquired immune responses. Meta-analiza Martineau et al. (BMJ, 2017) It included 25 RCT studies with 11,321 participants and showed that vitamin D supplementation reduces the risk of acute respiratory infections by 12% overall, and by 70% in individuals with a deficiency (25-OH-D3 below 25 nmol/l).

In Poland, from October to March, the skin synthesis of vitamin D is virtually zero – the angle of sunlight is too low for UVB radiation to reach the skin in sufficient amounts. It is estimated that 70–80% of Poles have D3 levels below the recommended threshold of 30 ng/ml during this period. EFSA (2012) It recognized 4000 IU daily as a safe upper limit for adults without medical supervision.

Dosage: 2000–4000 IU of D3 daily from October to March, with a meal containing fats (absorption increases several times). Adding K2 MK-7 (100–200 µg) to D3 is justified – K2 activates osteocalcin and matrix GLA protein, directing calcium to the bones and preventing its deposition in blood vessels. In May, check the level of 25-OH-D3 in a blood test – this will allow you to adjust the dose for the next season.

The dose of vitamin D should be adjusted to body weight and the baseline level of 25-OH-D3. Individuals with obesity (BMI over 30) often require doses of 4000–6000 IU due to sequestration of D3 in fat tissue. With 25-OH-D3 above 50 ng/ml, the dose can be reduced to 1000–2000 IU for maintenance. Vitamin D toxicity is real, but it only occurs at very high doses (above 10,000 IU daily for many months) or in rare diseases that increase sensitivity to D (sarcoidosis, tuberculosis).

Our observations: Many people start supplementing D3 only at the first sign of a cold – in November or December. Meanwhile, D3 levels in the blood gradually decrease, and the effects of supplementation are visible after 4–8 weeks of regular use. It should start in mid-September, without waiting for deficiency symptoms.

Zinc – shorter cold duration if you know how to take it

Zinc is one of the few supplements for which Cochrane clearly confirms a clinically significant effect in colds. Meta-analiza Hemilä (Cochrane Database of Systematic Reviews, 2015) It showed that zinc taken within 24 hours of the onset of the first symptoms shortens the duration of a cold by about 33%. The mechanism is direct inhibition of rhinovirus replication and modulation of the inflammatory response by reducing the production of pro-inflammatory cytokines.

Key detail: the form of administration. Zinc in lozenge form (zinc acetate or zinc gluconate) works through direct contact with the mucous membranes of the mouth and throat – where rhinoviruses multiply. A swallowed zinc capsule goes to the stomach and does not contact the mucous membranes of the upper respiratory tract – the effect is significantly weaker. Minimum dose: 75 mg of elemental zinc daily during infection, divided into several lozenges every 2–3 hours. Do not use zinc lozenges for more than 7–10 consecutive days.

Preventive zinc: 15–30 mg/d during the autumn season reduces the risk of infection in case of deficiency. In Poland, zinc deficiency particularly affects older adults, vegetarians, and those on low-protein diets. Zinc from food includes red meat, seafood, pumpkin seeds, lentils. With prolonged zinc use (above 40 mg/d), always add copper (1–2 mg/d) – zinc blocks its absorption. Take zinc without iron and away from coffee and tea, which contain tannins and polyphenols that reduce zinc absorption by 40–50%.

Vitamin C – shortens colds but does not prevent them

Vitamin C is the king of the "immunity" supplement market – and at the same time an example of a well-researched ingredient whose effect is often miscommunicated. Cochrane Review (Hemilä et al., 2013) It included 29 trials with 11,000 participants. The results are clear: regular intake of at least 200 mg of vitamin C daily shortens the duration of a cold by about 8% in adults and 14% in children. However, it does not reduce the incidence of colds in the average person.

Exception: very physically active individuals (marathon runners, ski athletes, soldiers in the cold) – in them, vitamin C reduces the incidence of colds by about 50%. This phenomenon is related to extreme oxidative stress and exercise-induced immunodepression. Form: ascorbic acid and bioflavonoids from food have comparable bioavailability. Liposoluble "ester-C" did not show better effects than regular ascorbate in RCT. Dosage: 500–1000 mg/d divided into two doses. Doses above 2000 mg/d may cause osmotic diarrhea and increase the risk of kidney stones in predisposed individuals – for immunological purposes, there is no reason to exceed 1000 mg/d.

Magnesium and sleep – the foundation without which supplements won't work

No immunity supplement will work optimally if you sleep poorly and are chronically stressed. Cortisol (the stress hormone) inhibits the production of T lymphocytes and NK (natural killer) cells – this is why people under chronic stress get sick more often and severely. Magnesium glycinate taken in the evening improves sleep quality by activating GABA receptors and reducing nighttime cortisol. Dose: 200–400 mg of elemental magnesium 1–2 hours before sleep.

Sleeping less than 6 hours a day increases the risk of catching a cold nearly threefold – this was shown in a study Prather et al. (Sleep, 2015) using the rhinovirus exposure method. Even the best-chosen supplementation cannot replace 7–8 hours of sleep. Treat magnesium not only as an immunity supplement but as an investment in the regeneration of the nervous and immune systems. In autumn and winter, when D3 and melatonin levels drop and stress increases, magnesium is one of the cheapest and most important supplements to keep in mind.

Elderberry (sambucus) – works when you use it at the right time

Elderberry (Sambucus nigra) is one of the oldest medicinal plants used for respiratory infections. Modern science confirms the mechanism: anthocyanins in elderberry fruits, particularly cyanidin-3-glucoside and cyanidin-3-sambubioside, inhibit the neuraminidase of the influenza virus – the same enzyme that oseltamivir (Tamiflu) blocks. Randomizowane badanie Zakay-Rones et al. (Journal of International Medical Research, 2004) A study with 60 patients showed that elderberry syrup shortened the duration of the flu by about 4 days (from 7.1 to 3.1 days) compared to placebo.

Important practical note: sambucus works best at the early signs of infection, not as a constant preventive supplement throughout the winter. The data for its preventive role is weaker. Dosage: 15 ml of syrup 4 times a day during infection for 5 days. Note: raw elderberries and leaves contain cyanogenic glycosides (sambunigrin) and can cause nausea and vomiting – always use products made from thermally processed extract.

A controversial issue regarding sambucus: can it 'accelerate the cytokine storm' in more severe infections (like COVID-19)? This claim emerged in the media in 2020 and there is no solid clinical evidence confirming this mechanism in humans at typical doses. In vitro studies show cytokine modulation, but not a 'cytokine storm' in the clinical sense. Sambucus is safe for standard colds and flu.

Sambucus in capsule form (dry extract 175 mg = 875 mg of fruit) is more convenient than syrup, but syrup is the traditional form used in studies. If you choose capsules, look for extracts standardized to 3.2–3.6% anthocyanidins. There are also combined preparations available: sambucus + zinc + vitamin C – a logical combination, although not clinically studied as a whole.

Quercetin – promising, but more research is needed in humans.

Quercetin is a flavonoid found in onions, apples, capers, and green tea. It has documented antiviral activity in vitro – it inhibits the replication of rhinoviruses, coronaviruses, and influenza viruses by binding to capsid proteins and blocking the endosomal protease cathepsin L. In animal model studies, quercetin reduced mortality in viral infections.

U ludzi: badanie Nieman et al. (Medicine and Science in Sports and Exercise, 2007) Involving 40 physically active men showed that 1000 mg of quercetin daily for 3 weeks reduced the incidence of respiratory infections in athletes after intense training. For the average adult without intense physical exertion, the data is less conclusive. Quercetin has low bioavailability – the isoqercetin form or a combination with enzymes (Quercefit, Sophora japonica) is better absorbed. Dosage: 500–1000 mg/day. Safe for short-term use.

The combination of quercetin with zinc is particularly interesting from a mechanistic point of view: quercetin acts as a zinc ionophore – transporting zinc ions into cells, where zinc can directly inhibit viral RNA polymerases. This mechanism is being studied in the context of viral infections, although clinical evidence in humans for this specific synergy is still preliminary. If you are taking zinc in lozenge form during an infection and simultaneously drinking onion or apple tea (sources of quercetin), it is possible that several mechanisms are working simultaneously.

How to create a supplementation protocol for autumn and winter?

Instead of buying everything at once, create a simple, prioritized protocol. Priority 1 (September–March, daily): witamina D3 2000–4000 IU z K2 MK-7, magnez glicynian 200–300 mg wieczorem. Priorytet 2 (profilaktycznie przez sezon): cynk 15–20 mg/d i witamina C 500 mg/d. Priorytet 3 (przy pierwszych objawach infekcji): zinc in lozenge form (75 mg/day divided every 2–3 hours) and/or elderberry syrup 4 times a day for 5 days. Quercetin and probiotics – optional, if you have specific indications (physical activity, gut issues).

Budget for the season: D3+K2 costs about 20–30 PLN/month, zinc about 15–25 PLN/month, vitamin C about 10–15 PLN/month. Together, less than 80 PLN per month for solid, evidence-based immune protection. Magnesium is another 20–30 PLN. This is incomparably less than a typical "immune multivitamin set" from the pharmacy, which often contains low doses of all ingredients and a high marketing price.

What definitely does not work for colds: echinacea (research results are conflicting, Cochrane does not confirm it unequivocally), garlic in capsules (no evidence from RCT), high-dose "immune" multivitamin preparations (no evidence of an additional effect beyond covering deficiencies). Save your money for something that has proven efficacy.

A practical tip to conclude: eat a varied diet, sleep 7–8 hours, exercise moderately (30 minutes of walking daily significantly increases NK cell and T lymphocyte activity), and wash your hands. No supplement can replace these foundations. Supplements are an additional layer – correcting deficiencies (D3, zinc) and support during infection (zinc lozenge, sambucus). This is a realistic, evidence-based approach for winter 2026.

What absolutely not to buy as an immune supplement?

Several categories of products worth avoiding due to lack of evidence or cost-effectiveness:

Echinacea. Clinical data is inconsistent. The Cochrane Review from 2015 analyzed 24 RCT studies with over 4000 participants and found no clear confirmation of echinacea's effectiveness in preventing or treating colds. Some preparations (especially fresh juice from E. purpurea) showed marginal effects in one or two studies, but the effect was not reproducible. At a price higher than zinc and vitamin D3 combined – a poor value ratio.

Preparations "for immunity" with colostrum. Bovine colostrum has an interesting composition (immunoglobulins, lactoferrin, antibiotic peptides), but the proteins are digested by gastric and intestinal enzymes before reaching the lymphatic system. The absorption of biologically active immunoglobulin IgG through the digestive tract in adults is negligible. This differs from the situation in newborns, whose intestines are still permeable.

Megadawki witaminy C (5000–10 000 mg/d). At doses above 2000 mg/day, the body excretes the excess in urine, without improving the immune response. The only proven benefit of such doses is a reduction in the duration of a cold by a few hours – an insignificant clinical difference with the risk of osmotic diarrhea and oxalate stone formation with prolonged use.

A detailed discussion of probiotics – how to choose a strain, when to use it, and why the form matters – can be found in the article Probiotic for the intestines – how to choose a strain. You can read about supplements for vegetarians and vegans, where vitamin D and zinc are particularly important, in the article Supplements for vegetarians and vegans.

Frequently Asked Questions

When to start taking immunity supplements?

Start vitamin D3 and zinc in mid-September – before skin synthesis becomes insufficient. Vitamin C can be taken year-round or more intensively in autumn and winter. Use elderberry at the first signs, not prophylactically for several months.

How much vitamin D3 to take in winter?

Przy stwierdzonej niedoborze 2000–4000 IU dziennie. EFSA considers 4000 IU/day to be a safe upper limit for adults without medical supervision. Combine with K2 MK-7. Check your 25-OH-D3 level with a blood test once a year.

Does zinc shorten the duration of a cold?

Yes. Meta-analiza Hemilä (Cochrane, 2015) showed a reduction of about 33% with zinc in lozenge form taken within 24 hours of symptoms. Key: lozenge form (acetate/gluconate), not capsule. Minimum dose: 75 mg/day during infection.

Does elderberry (sambucus) really work?

The study by Zakay-Rones et al. (2004) showed a reduction of flu duration by 4 days with sambucus syrup. Anthocyanins inhibit the virus's neuraminidase. It works best at the first signs, not as a long-term prophylactic. Use processed extract, not raw fruit.

Does vitamin C prevent colds?

Not in the average person – but it shortens the duration by 8–14% with regular use of at least 200 mg/day. Cochrane Review (Hemilä, 2013) confirms. In very physically active individuals, it reduces the incidence of infections by 50%.

Do probiotics support immunity in winter?

Indirectly – by modulating gut microbiota and the gut-immune axis. A meta-analysis by King et al. (2014) showed a reduced risk of respiratory infections. The best-studied strains: Lactobacillus acidophilus NCFM and Bifidobacterium lactis. Use for at least 4 weeks before the season.

This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.

Author: Michał Waluk · Published: 2026-05-04 · Updated: 2026-05-04