Unlike food infection which requires the presence of living pathogens, food intoxication is caused by chemicals in food, independent of pathogens. These chemicals may be natural, such as toxins produced by bacteria and mold, or toxins in plant foods, e.g. solanine in potatoes and cyanide in cassava. They may alternately be synthetic, such as agricultural fertilizers and pesticides intentionally added to food, and industrial waste chemicals that unintentionally get into the food supply.
While food infections cause a delayed effect (8 hours to days), food intoxication symptoms present much sooner (a few minutes to a few hours). Acute effects are similar to foodborne infections such as vomiting, diarrhea, cramps, fever and fatigue. Neurological symptoms may also result in cases where toxin interferes with the nervous system. For example toxin produced by Clostridium botulinum can cause difficulty speaking, difficulty swallowing, facial muscle weakness, paralysis, shortness of breath and slow reflexes.
The effect of toxins will vary widely depending on the site of action. Common sites of action include the GI tract, brain, heart, kidney, liver, lungs, skeletal system, and skin. Chronic outcomes of food intoxication such as cancer may occur after repeated ingestion of the chemical over a long time.
For toxins to cause health problems they must be able to maintain their toxicity through storage, preservation and food preparation. After ingestion they must be able to withstand the digestive process and have the ability to cross the GI lining and access their site of action. In addition, they must be at a concentration that is high enough to overcome the body’s ability to detoxify it.
We possess a number of defense mechanisms that can reduce the effect of toxins and hence lower risk of foodborne injury. These include:
- Vomiting, which expels toxin from the GI tract
- Internal microflora in the gut which helps to detoxify toxins
- Structural barrier of the GI tract which acts as a wall against toxin absorption. Damage results in increased absorption
- Detoxification of toxins with the help of intestinal enzymes
- Internal motility of the gut, reducing the residence time toxins
- Consumption of fiber. Fiber binds and helps to remove toxins from the body
- Antibodies produced by B cells in the immune system which are able to bind proteinaciaus toxins
Reference: Taylor, S. L. (2017). Disease processes in foodborne illness. In C. E. R. Dodd et al. (Eds.), Foodborne diseases (3rd ed.). Philadelphia, PA: J.B. Lippincott.