In short: According to the EFSA, zinc, Vitamin C, and Vitamin D contribute to the normal function of the immune system – which is not the same as proven protection against colds. The actual body of evidence shows that for most people, Vitamin C does not noticeably reduce the frequency or severity of colds, though it can slightly shorten their duration. Zinc lozenges show a similar, small effect on cold duration if taken early enough. For elderberry extract, the evidence is promising but still too thin for a definitive recommendation. This evidence review provides a sober assessment of the state of research, including its limitations.
TL;DR
Why cold season starts in autumn of all times
The common belief that cold temperatures alone make you sick is only part of the explanation. The seasonal spike in colds in autumn and winter has several causes: people spend more time in closed, poorly ventilated rooms, which promotes the transmission of viruses via droplets and aerosols. Humidity drops with falling outdoor temperatures and additional heating, which dries out the mucous membranes of the respiratory tract and weakens their barrier function against viruses. At the same time, shorter days reduce the body's own Vitamin D production via the skin, as UVB radiation in Germany is usually no longer sufficient for adequate synthesis from October to March. Combined, these three factors explain why cold and flu viruses spread much more easily in autumn and winter than in summer – regardless of nutritional supplements.
What the immune system actually needs according to the EFSA and current science
For three micronutrients, there is an officially reviewed and approved health claim by the EFSA regarding the "normal function of the immune system": Vitamin C, Vitamin D, and zinc. Selenium and copper also have such a claim, but play a subordinate role in the context of VEYT products. Important for the interpretation of these statements: They refer to maintaining normal function when the supply is already adequate – not to boosting defenses beyond normal levels or to proven protective effects against specific infections. This distinction is not a nuance, but the central point where many marketing claims for immune boosters overstretch the actual body of research.
Vitamin C for colds: What the evidence shows
Regarding the question of whether Vitamin C prevents or shortens colds, one of the most comprehensive summaries of randomized studies in nutritional research exists. Finnish Vitamin C researcher Harri Hemilä from the University of Helsinki, together with Australian public health researcher Elizabeth Chalker, evaluated all available randomized, placebo-controlled studies on Vitamin C and colds in their Cochrane review. Their core finding: In the general population, regular Vitamin C intake does not relevantly reduce the number of colds per year. An exception was found in individuals under short-term, intensive physical stress and cold stress, such as marathon runners, skiers, or soldiers in winter training – in this specific group, the risk of colds was approximately halved in several studies with regular Vitamin C intake. For the duration and severity of an existing cold, regular, preventative intake showed a small but statistically measurable shortening effect of an average of about eight percent in adults and 14 percent in children in the overall evaluation. If, however, Vitamin C is only started after the first symptoms appear, most studies show no relevant benefit.
Assessment
Zinc for colds: What studies show
For zinc, the body of research is somewhat more nuanced, even though reliable, current meta-analyses with exact daily data on shortening duration are rarer and less consistent than for Vitamin C. Several randomized studies suggest that zinc lozenges – taken in sufficient doses within the first 24 hours of symptom onset – can shorten the duration of a cold. The formulation and timing are crucial: zinc must be in a form that releases free zinc ions in the throat, and intake must begin early to show an effect. For preventative long-term use to avoid colds, the evidence is significantly weaker. The German Consumer Association (Verbraucherzentrale) also points out that the zinc supply situation in Germany is generally good and a true deficiency is rare – additional intake when the supply is already adequate usually brings no additional benefit and, in high doses with long-term use, can interfere with copper balance.
Elderberry (Sambucus nigra): Promising, but not yet sufficiently proven
Elderberry extract is one of the plant substances traditionally used for cold symptoms and has gained attention in recent years through several smaller clinical studies. A research team led by Hawkins summarized the available evidence on Sambucus nigra for upper respiratory symptoms in a meta-analysis of randomized, controlled trials with a total of around 180 participants and reported a shortened duration of symptoms and a milder course in study participants who took elderberry extract at the first signs of a cold compared to a placebo.
However, the current body of research is still too limited for a safe, generally valid recommendation: most available studies work with small participant numbers, sometimes inconsistent elderberry preparations and dosages, and some of the research was co-financed by manufacturers of elderberry preparations, which increases the risk of biased results. Larger, independent studies with standardized extracts are still pending. The honest assessment is therefore: promising potential, but not yet established evidence at the level of Vitamin C or zinc.
Vitamin D and the immune system in autumn and winter
In addition to its better-known role for bones, Vitamin D also contributes to the normal function of the immune system, according to an EFSA opinion. Observational studies regularly find a correlation between low Vitamin D levels in winter and a higher susceptibility to respiratory infections. A major meta-analysis of randomized studies found a moderate protective effect of Vitamin D supplementation against acute respiratory infections, with this effect being more pronounced in people with a previously low baseline level than in people with an already good supply.
This is consistent with the general observation that the body's own Vitamin D production in Germany is severely limited from October to March, which is why many professional societies list supplementation as a useful option during this time, especially for those who spend little time outdoors.
| Nutrient | Studied Population | Observed Effect | Evidence Quality | Practical Assessment |
|---|---|---|---|---|
| Vitamin C | General population vs. people under extreme physical/cold stress | No effect on frequency in the general population; approx. 8% shorter duration with regular intake; halved risk under extreme stress | High (Cochrane review, Hemilä & Chalker) | No cold protection for most people; relevant for those under heavy physical strain |
| Zinc (lozenges) | Adults with emerging cold, taken within 24 hrs. | Shortened cold duration with early intake | Moderate (inconsistent formulations between studies) | Early timing crucial; no good data for long-term prevention |
| Elderberry extract | Small groups of adults with acute cold/flu (Hawkins et al., n≈180) | Tending towards shorter, milder symptoms in individual studies | Low to moderate (small sample sizes, potential conflicts of interest) | Promising, but no safe recommendation yet possible |
| Vitamin D | Adults, especially with low baseline levels in winter | Moderately lower risk for acute respiratory infections | Moderate to high (meta-analysis of randomized studies) | Particularly relevant with little sunlight and confirmed low levels |
Cold or real flu: an important difference for the assessment
A common misunderstanding in the autumn and winter season is equating a cold with influenza (real flu). A cold usually develops gradually over one to two days, primarily causing a runny nose, scratchy throat, and mild cough, and is rarely accompanied by a high fever. Real flu, on the other hand, typically begins abruptly, with high fever, pronounced muscle aches, and severe exhaustion that forces the affected person to stay in bed. This distinction is relevant for the classification of nutrients: the evidence discussed in this article on Vitamin C, zinc, and elderberry refers primarily to classic colds caused by rhinoviruses and related pathogens, not to influenza. If you suspect real flu, especially in risk groups, a medical assessment is advisable, as different treatment options and precautions apply here than for an ordinary cold.
The role of the gut for immune function – a brief overview
A large part of the body's immune system is closely linked to the gut and its microbiome, as the intestinal mucosa represents the body's largest contact surface with the outside world. A balanced, high-fiber diet that supports the diversity of gut bacteria is considered by research to be a relevant but long-term acting factor for a functioning immune response – unlike the short-term intake of individual micronutrients for existing cold symptoms. Those interested in more detail on the state of research regarding probiotics and gut health can find a detailed assessment in our separate article on gut health. This evidence review deliberately focuses on the nutrients directly relevant to colds: Vitamin C, zinc, Vitamin D, and elderberry, in order to avoid overlaps with the existing gut health article.
Special caution for children, pregnant women, and the chronically ill
The studies and dosages discussed in this article refer, unless otherwise stated, to healthy adults. Different reference values and sometimes different safety limits apply to children, especially for zinc and Vitamin D, which is why supplementation in children should only take place after consultation with a pediatrician. Pregnant and breastfeeding women should coordinate any nutritional supplement, even seemingly harmless vitamins, in advance with their gynecologist, as needs and upper limits change during this life phase. People with chronic illnesses, such as kidney or autoimmune diseases, or those taking regular medication should also seek medical advice before higher-dose supplementation, as interactions are possible.
What nutrients cannot replace
Even the best nutrient supply cannot replace basic hygiene and behavioral measures. Regular and thorough hand washing remains one of the best-proven single measures for reducing the transmission of cold viruses, as they are often transmitted via hand contact with surfaces and subsequent contact with the eyes, nose, or mouth. Adequate, regular sleep is another well-documented factor: studies on sleep duration show that people with chronically shortened sleep are significantly more likely to actually get sick after experimental virus exposure than people with sufficient sleep. Regular, moderate exercise is also linked to a lower cold frequency, while very intensive, inadequately regenerated training loads can actually increase the risk of infection in the short term. For risk groups, the annual flu vaccination is also a measure whose effectiveness against influenza is not comparable to nutritional supplements – the family doctor can provide individual advice on this.
Suitable VEYT products for the autumn and winter season
Practical tip
Elderberry Immune Guard
Combines elderberry extract with Vitamin C, which, according to the EFSA, contributes to the normal function of the immune system.
Immune Defence Liquid
A liquid combination of Vitamin C, Zinc, and D3 for practical daily foundational support.
Immune Power C
Buffered, stomach-friendly Vitamin C for individuals with sensitive stomachs.
Vegan D3 Vitality Depot
Particularly relevant from October to March, when the body's own vitamin D production is limited.
Practical classification for everyday life
A realistic look at your own situation helps more than randomly trying several supplements at the same time. Someone who spends a lot of time in the office or on public transport, rarely gets outside, and has an irregular diet has a fundamentally different risk profile than someone who regularly exercises in the fresh air and eats a balanced diet. For the first group, vitamin D and general nutritional optimization may be the greatest lever, while for endurance athletes under winter cold stress, vitamin C may play a comparatively greater role according to the current state of research. A blanket “one supplement for all” recommendation does not do justice to the different starting positions.
If you are wondering what the most sensible approach is in autumn, keep the order of effectiveness in mind: First place goes to sleep, hand hygiene, and an overall balanced diet with plenty of fruit and vegetables. Second place is targeted vitamin D supplementation in the low-sun months, for which the evidence is comparatively solid. Third place is zinc, preferably as a response to the first signs of a cold rather than as long-term prophylaxis. Vitamin C and elderberry extract can be useful additions, but they should be viewed realistically: small, supporting building blocks rather than a reliable protective shield against colds.
When a doctor's visit is necessary
Most colds resolve on their own within seven to ten days. A visit to the doctor is advisable for fever above 39 degrees Celsius that lasts longer than three days, for breathing difficulties or pain while breathing, for severe, one-sided head or sinus pain, for symptoms that worsen again after initial improvement, as well as for risk groups such as the elderly, the chronically ill, or people with a weakened immune system, for whom even milder symptoms should be clarified at an early stage.
Expert Perspectives & Protocol Breakdown
Well-known health voices express very different opinions on the subject of the immune system and cold prevention – from scientifically sound to not supported by evidence. We deliberately include a non-medically qualified voice because it is very visible online in the immune system field, and we contrast all positions with the actual state of research.
Dr. Rhonda Patrick
What she recommends: Dr. Rhonda Patrick has written extensively about the role of vitamin D in immune function, referencing the same category of randomized and observational studies summarized in this article. She generally recommends having your vitamin D levels tested and specifically correcting a proven deficiency, rather than taking high doses across the board.
→ Source: foundmyfitness.com
Dr. Andrew Weil
What he recommends: The pioneer of integrative medicine, Dr. Andrew Weil, has long recommended a generally anti-inflammatory diet as well as echinacea and elderberry in moderate dosages at the first signs of a cold, along with sufficient sleep and stress management. He explicitly emphasizes that herbal remedies have a supporting, not a curative effect.
→ Source: drweil.com
Anthony William ("Medical Medium")
What he claims: Anthony William promotes celery juice and specific “detox” protocols as central measures for the immune system. Important context that VEYT makes transparent here: William has no medical or scientific qualifications and describes his source of information himself as spiritual or intuitive, not as clinically or scientifically grounded. There is no peer-reviewed scientific evidence for the concrete mechanisms of action of celery juice on the immune system described by him.
→ Source: medicalmedium.com
Dr. Joseph Mercola
What he recommends: Dr. Joseph Mercola advocates vitamin D, zinc, and general “natural” immune support, in terms of content similar to recommendations from integrative medicine. Important context: In 2022, Mercola had to account for a settlement with the US Federal Trade Commission (FTC) specifically regarding the marketing of vitamin D and zinc supplements with unsubstantiated COVID-19 treatment promises – directly relevant to the classification of his statements in this exact nutritional category.
→ Source: US Federal Trade Commission, press release on settlement with Dr. Joseph Mercola/Mercola.com (2022)
Where They Differ
Patrick and Weil base their recommendations on quotable clinical research and explicitly name the limits of the evidence – coinciding with the cautious classification in this article. William's protocol, on the other hand, is not derived from clinical evidence and is not presented as such by him. While Mercola's general nutritional recommendations overlap with the mainstream of integrative medicine, his documented history of promoting the same nutrients during the corona pandemic with unsubstantiated healing promises is, however, a factual reason for additional caution regarding his product-related statements.
What the Evidence Says
The state of research presented in this article supports vitamin D most clearly in the case of a proven deficiency, followed by zinc when taken early, and a small but measurable effect of vitamin C under high physical stress. There is no scientific evidence for celery juice or comparable “detox” protocols. VEYT does not adopt any of the expert statements presented here without verification and explicitly recommends aligning nutritional supplements with the actual state of research rather than the popularity of individual persons.
Frequently asked questions about immune system support in autumn
Can I completely avoid colds with nutritional supplements?
No. No nutrient offers reliable, complete protection against cold viruses. Nutritional supplements can at best moderately influence the frequency, duration, or severity in certain groups of people.
Should I only take vitamin C when I already have a cold?
The state of research speaks rather against a relevant benefit if you start taking it after the onset of symptoms. An effect is primarily seen with regular, preventive intake.
When should I start with vitamin D during the year?
In Germany, the body's own synthesis via the skin becomes insufficient starting around October. Many professional societies mention the period from October to March as a sensible window for supplementation, especially if you spend little time outdoors.
How high should zinc be dosed if I use it for the onset of a cold?
Studies on zinc lozenges usually work with daily doses in the range of official reference values, distributed throughout the day. Long-term overdosing should be avoided, as it can disrupt the copper balance.
Is elderberry a safe alternative to classic cold remedies?
For most healthy adults, elderberry extract is considered well-tolerated, but does not replace medically prescribed treatment for severe or unusual courses. The state of research on its effectiveness is promising, but not yet sufficiently validated.
How do I distinguish the beginning of a cold from an allergic reaction?
A cold usually develops over one to two days and is often accompanied by slight sore throats or fatigue, while allergic symptoms (e.g., from house dust or residual pollen in early autumn) occur suddenly, often with itching in the eyes or nose, and can remain constant for weeks instead of subsiding after a few days. In case of doubt, a doctor or pharmacist can make the classification easier.
Why do I get sick every autumn despite a “healthy” diet?
Nutrition is only one factor among several. Lack of sleep, chronic stress, little exercise in the fresh air, and frequent contact in indoor spaces (office, public transport, school) often influence the risk of catching a cold more strongly than individual nutrients.
Are high-dose vitamin C supplements better than low-dose ones?
No, from a certain dose, excess vitamin C is largely excreted unchanged via the urine. Very high single doses provide no additional benefit and can strain the stomach in sensitive individuals. A uniform distribution of intake throughout the day is more sensible than a single mega-dose.
Does hot tea with honey help against cold symptoms?
Warm liquid can moisten the mucous membranes and improve subjective well-being, but has no proven effect on the duration of the cold itself. Honey can relieve symptoms of a cough, but is unsuitable for infants under one year old.
Does cold air alone make you sick, as is often claimed?
Not directly. Cold itself does not transmit viruses. However, it promotes behaviors and conditions – more time indoors, drier mucous membranes, less humidity – that make transmission more likely. Some studies also indicate that lower temperatures can slightly weaken the local immune defense in the nasal mucous membrane.
Is a combination of nutrients from several supplements at the same time worthwhile?
A sensibly coordinated combination, such as vitamin C, zinc, and vitamin D at the level of the reference values, is unproblematic. We advise against an uncoordinated combination of several high-dose individual supplements, as the risk of overdosing, particularly with zinc, can add up without a proven additional benefit.
Conclusion
References & Scientific Citations
- Hemilä, H., Chalker, E. (2013). Vitamin C for Preventing and Treating the Common Cold, Cochrane Database of Systematic Reviews
- Hawkins, J. et al. (2019). Black Elderberry (Sambucus nigra) Supplementation Effectively Treats Upper Respiratory Symptoms: A Meta-Analysis of Randomized, Controlled Clinical Trials, Complementary Therapies in Medicine
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2015). Scientific Opinion on Vitamin D and Normal Function of the Immune System, EFSA Journal 13(5):4096
- Regulation (EU) No. 432/2012 of the European Commission, List of authorized health claims (vitamin C, zinc: normal function of the immune system). EUR-Lex 32012R0432
- German Nutrition Society (DGE), Reference values for vitamin C (110 mg/day men, 95 mg/day women) and zinc — dge.de/wissenschaft/referenzwerte
- Consumer Association (Verbraucherzentrale), Classification of zinc for colds — verbraucherzentrale.de
- US Federal Trade Commission (FTC), press release on settlement with Dr. Joseph Mercola/Mercola.com (2022) — ftc.gov
- Dr. Rhonda Patrick — foundmyfitness.com
- Dr. Andrew Weil — drweil.com
- Anthony William (Medical Medium) — medicalmedium.com (not medically/scientifically qualified)
- Dr. Joseph Mercola — mercola.com
