Vitamin C is water-soluble and is not produced by the body itself – you obtain it through diet or supplementation. Vitamin C contributes to the normal functioning of the immune system and protects cells from oxidative stress (both EFSA-approved health claims).

Recommended daily allowance 

EFSA: 80 mg/day is the recommended reference intake. For increased demands or intensive physical exercise, 200-1000 mg/day is often used. High doses (above 2-3 g per day) can cause mild digestive issues in some people; in that case, divide into multiple intakes per day.

Which form? 

Ascorbic acid is the most common form – inexpensive and effective, but it can be harsh on sensitive stomachs. Ester-C (buffered form) or plant-based vitamin C complexes are then a more pleasant alternative. Plant-based complexes provide not only vitamin C but also natural bioflavonoids, which can support absorption.

Zinc – supporting white blood cells and mucous membranes 

Zinc is a mineral that plays a role in more than 300 enzymatic reactions – including many in the immune system. White blood cells need zinc for activation and cell division. In addition, zinc supports the integrity of mucous membranes (nose, throat, lungs) – the first line of defense against pathogens.

Recommended daily allowance 

EFSA: 9.4 mg/day for men, 7.5 mg/day for women(depending on phytate intake). In supplements, 10-25 mg/day is often used for maintenance, and briefly 30-50 mg for increased demands. Long-term high doses can cause copper deficiency – it is advisable to switch after a few weeks.

Which form? 

Zinc bisglycinate (bound to glycine) and zinc citrate have high bioavailability. Zinc oxide (often in inexpensive supplements) has lower absorption.

The three reinforce each other through different mechanisms of action — they do not compete for the same role but cover complementary parts of the immune system:

• Vitamin Dprovides for the regulation and activation of white blood cells.
• Vitamin Csupports white blood cell function and protects against oxidative stress.
• Zincactivates white blood cells and strengthens mucous membranes.

For most adults who want to get through winter well, a combination of the three — in basic dosages — is a logical start. In case of specific risk factors or increased strain, you can temporarily increase the dosage.

When to use which dosage? 

Maintenance (October-April) 

• Vit D: 25-50 µg/day (1000-2000 IU)
• Vit C: 200-500 mg/day
• Zinc: 10-15 mg/day

In case of increased strain (short-term, 3-7 days) 

• Vit C: 1000-2000 mg/day, divided into 2-3 intakes
• Zinc: 30 mg/day (short-term, max 1-2 weeks)
• Vit D remains at maintenance level

For risk groups (60+, dark skin, little time outdoors) 

• Vit D: 50-75 µg/day year-round (2000-3000 IU)
• Vit C: 500 mg/day maintenance
• Zinc: 15 mg/day maintenance

Vitamin D, vitamin C, and zinc are not just the classic immune trio. They all have EFSA-recognized claims for immune system function and cover complementary roles — regulation (D), antioxidant (C), and activation + mucous membrane (zinc). For most people who want to face winter strongly, a basic stack of these three is a logical start. In case of specific risk factors or increased strain, you can temporarily increase the dosage.

Disclaimer:This article is for informational purposes only and does not replace medical advice. A dietary supplement is not a substitute for a varied and balanced diet and a healthy lifestyle. In case of doubt or medication use: consult a doctor or pharmacist. Do not exceed the recommended daily dosage. Keep out of reach of young children.