In this episode, Leah and Aidan explore whether zinc can help prevent or reduce the duration and severity of the common cold and other upper respiratory tract infections.

How Zinc Works

zinc

Zinc supports immune cell development and function, including T cells and B cells, which are essential for fighting infections. Zinc deficiency weakens the immune system and increases infection risk—particularly in children and older adults.

This raises key questions:

  • Does zinc help if you’re not deficient?
  • How common is zinc deficiency?

How Common is Zinc Deficiency?

Accurate statistics are difficult to find, especially in Australia. Estimates suggest that 20–40% of people don’t meet the RDI, while 5–10% may be truly deficient. Those at higher risk include older adults and individuals following plant-based diets. Blood tests are currently the best way to check zinc status, though daily variability can reach 20%.

What the Research Shows

Part 1

A 2024 meta-analysis of 34 randomised controlled trials involving over 8,000 participants examined zinc’s effects on:

  1. Prevention
  2. Symptom severity
  3. Symptom duration

Most studies used zinc lozenges, with daily doses ranging from 45 mg to 276 mg—well above the RDI of 8 mg for women and 14 mg for men.

Part 2 — Outcomes

  • Prevention: No meaningful difference.
  • Symptom Duration: Zinc reduced illness duration by an average of 2 days, though outcomes varied.
  • Symptom Severity: No noticeable change, but shorter illness still makes it beneficial overall.

Key Takeaways

Start zinc supplements within 24 hours of noticing symptoms if you’re aiming to reduce illness duration. However, taking zinc year-round doesn’t make sense. Side effects like nausea and taste disturbances are common and worth considering. Since many studies were conducted in countries with different dietary patterns, effectiveness may depend on baseline zinc intake.

Food vs Supplements

Deficiency likely raises your risk of getting sick, so it’s best to aim for adequate zinc from food. While food alone won’t provide the high dosages used in studies, maintaining a nutrient-rich diet helps prevent deficiency. There’s no strong evidence that high food-based zinc intake helps once you’re already sick.

Why Lozenges?

Zinc Lozenges

Lozenges release zinc slowly in the mouth and upper respiratory tract—where cold viruses live and replicate. This localised delivery may explain why they’re commonly used in studies instead of food-based sources.

Dosage & How to Take Zinc

  • Aim for 50–75 mg per day
  • Use for 3–7 days
  • Split dosage across the day (e.g., 5–6 lozenges)
  • Avoid prolonged use, as excess zinc can affect copper absorption and cause nausea or taste issues

Summary

Zinc won’t prevent illness or reduce symptom severity, but it may slightly shorten the duration. Consider the side effects and weigh whether it’s worth trying during early symptoms. For overall health, focus on meeting your zinc needs through food and avoiding deficiency.

Relevant Studies

Relevant Blog Posts