TL;DR
According to EFSA authorization, Vitamin D, zinc, and Vitamin C contribute to the normal function of the immune system – but not all forms of intake are equally effective. Data from the RKI, BfR, and DGE indicate that nearly 60% of adults in Germany do not reach the recommended Vitamin D status, with the sharpest decline occurring in late winter. Zinc shows a proven effect on cold duration only in high-dose lozenge form (at least 75 mg daily), while Vitamin C does not reduce the frequency of colds for most people – though it does for those under intense physical stress.
When looking for nutrients to support the immune system in the fall, you usually get three answers: Vitamin D, zinc, and Vitamin C. The data on all three micronutrients is now well-researched – and it is more nuanced than packaging labels might suggest. This article breaks down what is actually supported by EFSA authorizations, RKI surveys, and Cochrane analyses.
Why the immune system is under more pressure in the fall
As UV radiation decreases, the body's own vitamin D production through the skin drops noticeably from September onwards, while the start of the school year, indoor living, and lower humidity favor the transmission of cold viruses. This combination—less vitamin D replenishment alongside a higher pathogen load—is the main reason why doctors and nutrition societies recommend beginning targeted supplementation in early autumn at the latest, rather than waiting until you have your first scratchy throat.
This does not change the fact that sleep, exercise in the fresh air, and a balanced diet remain the foundation. Dietary supplements can bridge real nutritional gaps, but they do not replace these fundamentals.
Another often overlooked factor: Dry heating air indoors causes the mucous membranes in the nose and throat to dry out, making it easier for viruses to attach. This effect occurs regardless of nutritional status and explains why even well-nourished individuals catch more colds in the fall than in the summer. The German market for dietary supplements is accordingly seasonal: according to industry figures from the German Food Association, sales of vitamins and minerals continued to grow in 2025, with a clear surge in demand at the start of the cold season.
Vitamin D in the fall: What the data in Germany shows
According to EFSA authorization (Regulation (EU) No. 432/2012), Vitamin D contributes to the normal function of the immune system. However, a significant portion of the German population does not reach the recommended status—and this varies markedly by season.
According to a joint statement by the Robert Koch Institute (RKI), the Federal Institute for Risk Assessment (BfR), and the German Nutrition Society (DGE), nearly 60% of adults in Germany do not reach the desirable blood concentration of 50 nmol/l 25-hydroxyvitamin D. Evaluations of RKI data also show that in late winter and early spring—the period with the least endogenous production—around 70 to 80% of the population fall below this target value.
For daily baseline support, for example, Veyt™ D3 High-Potency Depot is a suitable choice; we have compiled detailed dosage recommendations based on body weight and baseline values in our separate Vitamin D3 dosage guide.
Practical Tip
Vitamin D is fat-soluble—taking it with a meal containing some fat noticeably improves absorption compared to taking it on an empty stomach.
Zinc: Daily baseline support is not the same as cold treatment
According to the EFSA, zinc also contributes to the normal function of the immune system—this authorization refers to daily nutritional intake, not acute treatment. This is exactly where the greatest confusion in public perception arises.
A meta-analysis by Hemilä (2017, Open Forum Infectious Diseases / JRSM Open) on zinc lozenges shows: studies using zinc acetate in daily doses of 75 mg or more shortened the duration of colds by an average of about 42%. Studies with doses under 75 mg per day, however, consistently found no effect. The current Cochrane review (Nault et al., 2024) confirms a possible shortening of cold duration but also points to a likely higher rate of mild side effects such as nausea or mouth irritation at this high therapeutic dosage—and notes methodological weaknesses in some of the included studies.
| Use Case | Typical Dosage | What the Data Shows |
|---|---|---|
| Daily baseline support | up to 25 mg/day (EFSA maximum for supplements) | EFSA claim "normal immune function" applies to this range |
| Lozenges at first symptoms | from 75 mg/day zinc acetate, short-term | approx. 42% shorter cold duration per Hemilä 2017; more mild side effects per Cochrane 2024 |
Important to know
The EFSA maximum limit for zinc in dietary supplements is 25 mg per day. The high-dose lozenges (75 mg+) used in studies go significantly beyond this and should be understood as a short-term, symptom-oriented application—not for long-term supplementation. Consult a doctor regarding pre-existing conditions or concurrent medication.
For daily baseline support within the EFSA-compliant range, Veyt™ Zinc High-Potency Shield is suitable, providing 25 mg of zinc bisglycinate per serving. Read more about the effects, forms, and side effects of zinc in our in-depth Zinc Effects Study Check.
Vitamin C: What the Cochrane data really shows
For most people, Vitamin C does not reduce the frequency of colds. This is shown by a Cochrane review by Hemilä and Chalker, which evaluated 29 comparisons with a total of 11,306 participants from the general population and found no reduction in cold risk through regular Vitamin C intake.
However, in individuals subjected to short-term, intense physical stress—such as marathon runners, skiers, and soldiers during exercises in subarctic cold—five studies with 598 participants showed a halved risk of colds (relative risk 0.48). Regular intake had a moderate effect on cold duration across all groups: minus 8% in adults and minus 14% in children.
Regardless of cold prevention, Vitamin C contributes to a normal function of the immune system according to EFSA authorization and supports cellular protection against oxidative stress. For those seeking an uncomplicated daily combination, it can be found in Veyt™ Immune Power C or in the Veyt™ Immune Defence Liquid, which combines Vitamin C, Vitamin D3, and zinc in a single serving. In the original guide on this topic, we introduced Veyt™ Elderberry Vitamin C Gummies as a chewable-friendly alternative—they remain suitable for anyone wishing to avoid capsules or drops. Details on daily requirements and upper intake limits can be found in the Vitamin C Dosage Guide.
The Fall Routine: How to meaningfully combine the three nutrients
A sensible fall routine separates daily prevention from short-term reactions to initial symptoms. For daily baseline support, Vitamin D3 at an appropriate dosage, zinc within the EFSA limit of 25 mg, and Vitamin C as part of a balanced diet or supplement are entirely sufficient.
- Starting in September: Keep an eye on your Vitamin D status, especially with limited sun exposure, and begin with your baseline dose instead of waiting to react to the first symptoms.
- Year-round, including fall: Zinc within the recommended daily intake, not in lozenge dosages.
- At the first sign of a cold: Temporarily switching to higher-dose zinc lozenges is an option that should be discussed with a pharmacy or doctor if in doubt—not a long-term solution.
For those who wish to compare the four featured products directly, the most important key data is provided here at a glance:
| Product | Format & Nutrient | Scope of Application | Price |
|---|---|---|---|
| D3 High-Potency Depot | 180 Softgels, Vitamin D3 | Daily baseline support | €27.00 |
| Zinc High-Potency Shield | 500 Tablets, 25 mg Zinc Bisglycinate | Daily baseline support | €27.00 |
| Immune Power C | 240 Capsules, 500 mg buffered Vitamin C | Daily baseline support | €25.00 |
| Immune Defence Liquid | 500 ml liquid, Vitamin C + D3 + Zinc | Combined basic supply in one product | €16.50 |
For whom is a combination product worthwhile?
Anyone who does not want to coordinate three individual supplements in their everyday life can opt for a combined product like the Veyt™ Immune Defence Liquid. The advantage lies in the simplicity, not in a stronger effect compared to individual supplements in comparable dosages.
What you should keep in mind when taking them
In higher doses, zinc can impair the absorption of certain antibiotics, such as tetracyclines and gyrase inhibitors, as well as the active ingredient penicillamine. Anyone taking such medications should take zinc supplements at a different time, with a gap of at least two hours, and consult a doctor or pharmacist. A permanently excessive intake of zinc can also disrupt the body's copper balance, which is why the EFSA maximum limit of 25 mg per day for over-the-counter dietary supplements should not be exceeded without medical advice.
Very high doses of Vitamin C in the gram range are suspected of increasing the risk of kidney stones in predisposed individuals; people with a known tendency for kidney stones or impaired kidney function should consult a doctor about high-dose Vitamin C supplements in advance. Vitamin D, on the other hand, is fat-soluble and can accumulate in the body – long-term intake significantly above the recommended daily dose without prior blood level checks is not recommended by the DGE (German Nutrition Society). Pregnant women, breastfeeding mothers, and people with pre-existing conditions should generally seek medical advice before beginning targeted supplementation.
Other nutrients related to the immune system
Vitamin D, zinc, and Vitamin C are the best-studied micronutrients for normal immune function, but they are not the only ones with EFSA approval in this area. According to the EFSA, selenium also contributes to the normal function of the immune system; we explain how a deficiency manifests itself and which groups of people are particularly affected in our Selenium Effects & Studies Check. Those who prefer to use a single product for several micronutrients simultaneously can find an evaluation in the article Multivitamin: Who really benefits and when it is superfluous.
Limits of the available research
The evidence is not a guarantee against colds for any of the three nutrients. The EFSA claim "contributes to the normal function of the immune system" describes a physiological contribution to the maintenance of normal functions, not the prevention or treatment of diseases. The data on zinc lozenges comes from a limited number of smaller studies with varying methodological quality, which the 2024 Cochrane review also expressly points out. The effects of Vitamin C during extreme physical exertion cannot simply be transferred to the everyday life of people without comparable physical demands.
Frequently asked questions
When should I start taking supplements in the autumn?
Since the body's own production of Vitamin D via the skin decreases noticeably from September onwards, early autumn is a sensible time to start with a needs-based basic supply rather than waiting until the first symptoms appear.
Can I take Vitamin D, zinc, and Vitamin C at the same time?
Yes, all three micronutrients can be combined within the framework of the recommended daily intake. If you have existing illnesses, are pregnant, or are taking medication, a medical consultation is recommended in advance.
Do high-dose zinc lozenges help with every cold?
The available evidence refers to use at the onset of the first symptoms and to zinc acetate lozenges with at least 75 mg per day. Lower doses showed no effect on the duration of colds in studies.
For the average frequency of colds, the data show no measurable benefit for people without intense physical exertion. The contribution to normal immune function according to the EFSA approval remains independent of this.
Is sunlight still enough for sufficient Vitamin D in autumn?
In Germany, from about October until early spring, the position of the sun is no longer sufficient to produce relevant amounts of Vitamin D via the skin. This exact period coincides with the lows in supply shown by RKI (Robert Koch Institute) data.
What is the difference between zinc bisglycinate and zinc acetate?
Both are zinc compounds, but they differ in bioavailability and the available research. The cited lozenge studies on cold duration predominantly used zinc acetate and zinc gluconate in high doses; zinc bisglycinate is often preferred for daily basic supply due to its good tolerance and absorption, but it was not investigated in the same way in the cold duration studies cited here.
Conclusion
Vitamin D, zinc, and Vitamin C are relevant for a functioning immune system, but they do not act as a general shield against colds. Those who ensure a basic supply from early autumn onwards and specifically use higher-dose zinc lozenges at the first symptoms are using the nutrients according to the actual state of research – not according to the marketing promises on the packaging.
Read more:
Vitamin D3 dosage: How many IU per day really make sense
Zinc effects: What studies really show about the immune system, hair, skin, and nails
Vitamin C dosage: How many mg per day really make sense
Selenium effects: What studies really show about the thyroid, immune system, and cell protection
Multivitamin: Who really benefits and when it is superfluous
Sources:
Commission Regulation (EU) No 432/2012 of 16 May 2012 – List of permitted health claims made on foods
Robert Koch Institute, German Federal Institute for Risk Assessment, German Nutrition Society – joint statement on Vitamin D supply in Germany (2012)
Hemilä H. (2017): Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate. JRSM Open.
Nault D. et al. (2024): Zinc for the prevention and treatment of the common cold. Cochrane Database of Systematic Reviews.
Hemilä H., Chalker E. (2013): Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews.
