An Invisible Risk: Canned Foods

Cyprus International University (CIU) Faculty of Medicine members Assist. Prof. Dr. Nagat Balaman and Prof. Dr. Ayşegül Taylan Özkan evaluated the risk of botulinum toxin in canned foods, why this toxin particularly occurs in canned products, and its effects on human health. Drawing attention to food poisoning caused by the bacterium Clostridium botulinum, Prof. Dr. Özkan stated, “Clostridium botulinum is a spore-forming bacterium capable of producing toxic substances called botulinum toxin in oxygen-free environments such as canned foods.” Dr. Balaman emphasized that botulinum toxin targets the nervous system and can lead to “a severe clinical condition that may cause shortness of breath, muscle paralysis, and even death.”

1. What is Clostridium botulinum, which causes botulinum toxin, and what risks does this bacterium pose to human health?
Clostridium botulinum is a spore-forming bacterium that can produce toxic substances known as botulinum toxin in oxygen-free environments such as canned foods. When these toxins are ingested through food, they affect the nervous system and can cause a severe condition known as “botulism,” which may result in shortness of breath, muscle paralysis, and even death.

2. What are the symptoms observed in botulism cases, and what should the public know about the onset time of these symptoms?
The disease generally develops within one to two days after consuming contaminated food. In the early stage, symptoms similar to other types of food poisoning may appear. The occurrence of similar symptoms in individuals who consumed the same food, especially with a history of canned or fermented product consumption, increases suspicion.
The onset of symptoms varies depending on the type and dose of the toxin. Although it can range from a few hours to several days, symptoms typically appear 12 to 36 hours after consuming spoiled food (0–7 days for type A, 0–5 days for type B, and 0–2 days for type E). Early symptoms include nausea, pain, abdominal bloating, vomiting, diarrhea, and dry mouth. Since these are not specific to botulism, suspicion may not arise initially. After 12–36 hours, neurological symptoms develop, such as double vision, drooping eyelids, slowed or slurred speech due to weakened speech muscles, difficulty swallowing, and hoarseness. This is followed by paralysis in the limbs. Constipation may occur due to decreased bowel movements. As the disease progresses, respiratory failure may develop due to weakness of the respiratory muscles. Without timely diagnosis and treatment, the condition may progress to death. In infants, constipation is usually the first symptom. Additionally, lethargy and “floppiness” in the neck, arms, and legs indicate muscle weakness. Feeding difficulties and weak crying may also accompany the condition.

3.    What would you like to say about the importance of early awareness in botulinum toxin-related cases? What are the consequences of late detection? 
Early diagnosis and treatment are vital. Delayed treatment may lead to paralysis of the respiratory muscles and result in severe outcomes, including death. Therefore, preventing such cases by adhering to hygiene standards and safe procedural methods is the best approach.
 

4. What is the relationship between botulism and canned or fermented foods? Under what conditions does Clostridium botulinum pose a risk?
To survive harsh conditions, Clostridium botulinum bacteria transform into resistant forms called “spores.” These spores are naturally found worldwide in soil and on the surfaces of fruits, vegetables, and seafood. When conditions become favorable, the spores revert to bacterial form and produce deadly toxins.
Conditions that allow Clostridium bacteria to multiply and produce toxins include: low-oxygen or oxygen-free (anaerobic) environments, low acidity, low sugar, low salt, a specific temperature range, and some moisture.
Therefore, improperly canned, preserved, or fermented homemade foods prepared without proper hygiene provide an ideal environment for Clostridium spores to multiply and release toxins. Although rare, it should not be forgotten that store-bought foods may also contain botulinum toxin.

5. Why is the risk of botulinum toxin more frequently discussed in relation to homemade canned foods? What common mistakes are observed in society?
The risk of botulinum toxin in homemade canned foods is increasing because many people are either unaware of the safety precautions required during preparation or neglect hygiene rules even if they are aware. Even consuming a small amount of toxin-containing food can be fatal. Moreover, the toxin that causes botulism cannot be seen, smelled, or tasted. Therefore, it is extremely important that canned or fermented foods are prepared and stored under appropriate conditions.
There are many common mistakes people may make when preparing homemade canned foods, including inventing their own canning recipes, failing to maintain sterile conditions, using inappropriate canning methods according to the acidity level of processed foods, rushing the cooling process of the pressure canner, letting hot-packed foods cool in jars before processing, failing to vent the pressure canner, using thin jars not suitable for canning, reusing single-use lids, leaving air bubbles in jars, cooling jars too slowly or improperly, storing jars under unsuitable conditions.

6. Finally, considering these risks related to canned foods, what precautions would you particularly recommend for individuals to behave more safely in their daily lives?
1.    Do not purchase or consume the product if there are any signs of contamination in the container or the food inside:
•    The container is leaking, swollen, or bulging
•    The container appears damaged, cracked, or rusty
•    Liquid or foam spurts out when the container is opened
•    The food is discolored, moldy, or smells bad
2.    Avoid purchasing dusty cans or those with torn labels (They may be expired or improperly stored).
3.    Check the expiration dates of canned and jarred products before purchasing.
4.    Store filled cans and jars in a cool, dry place; do not keep them near heat sources such as stoves or ovens.
5.    After opening canned or pickled foods, transfer them to another container and store them in the refrigerator (for short-term storage).