Natamycin in food and the risk of fungal resistance
What it found
Adding natamycin to drinks or yoghurt may expose gut fungi to high amounts, which could encourage drug resistance.
Surface use on cheese and sausages keeps exposure well below daily limits.
What they found
Studies in people
Gut fungi lose sensitivity
In 356 patients given natamycin pills for gut infections, fewer fungi stayed sensitive during treatment. Sensitivity returned to normal months later. Lab tests also showed vaginal fungi needed higher doses to be stopped after treatment.
Animal and lab studies
Resistance genes can spread
Fungi can swap genes with each other. This gene sharing has helped spread resistance to polyene drugs among Candida species and within Aspergillus fumigatus.
Studies in people and animals
Factory fungi stayed sensitive
Surveys in cheese warehouses and sausage factories using natamycin for up to 9 years found no change in local fungi. In lab tests, moving fungi to stronger natamycin 25 to 30 times did not make them less sensitive.
Other findings
Cheese and sausage surfaces
When sprayed on the outside of cheese and sausages, natamycin breaks down under shop lights. Estimated intake stays ten times lower than the daily limit set by health experts.
Drinks raise exposure sharply
Natamycin does not dissolve well in water, so scientists pair it with cyclodextrin to keep it dissolved in drinks. Drinking one litre of a beverage made this way could exceed the daily limit by 27.8-fold for a 60 kg adult.
What the authors conclude
- They say that spraying natamycin on solid foods like cheese keeps intake far below the daily limit.
- They warn that mixing natamycin into yoghurt or drinks exposes gut fungi to high levels that could drive resistance.
- They call for new studies to measure how much natamycin reaches the gut and whether it changes resident fungi over time.
How it was done
Natamycin is used to stop mould on foods like cheese and sausages. The authors wanted to know if mixing it into drinks or yoghurt might make gut fungi resistant to life-saving antifungal medicines.
The authors gathered published research on how natamycin works, how much people consume from different foods, and whether fungi become less sensitive after exposure. They looked at studies in people, lab tests, and surveys of food factories.
What it can’t tell you
- This paper gathers older research rather than running a new trial, so it cannot prove that eating natamycin causes resistance in people.
- Estimates of gut exposure rely on calculations, not direct measurements in shoppers who eat these foods.
- Lab findings about fungi swapping genes do not show how often this happens in a human gut after eating preserved food.
Who paid
- Authors work at
- University Medical Center Schleswig-Holstein, Germany; Tufts University School of Medicine, USA
The paper
- Title
- Does use of the polyene natamycin as a food preservative jeopardise the clinical efficacy of amphotericin B? A word of concern
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Dalhoff AA, Levy SB (2015). Does use of the polyene natamycin as a food preservative jeopardise the clinical efficacy of amphotericin B? A word of concern. International journal of antimicrobial agents. doi:10.1016/j.ijantimicag.2015.02.011Free full textPubMed 25862309DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error