Which of the following is a key symptom of foodborne illness?

Diarrhea is a key symptom of foodborne illness because it is a common way the body reacts to the presence of harmful pathogens, toxins, or irritants in the gastrointestinal tract. When food containing these harmful agents is consumed, the body often responds by expelling the contents of the intestines, leading to loose or watery stools. This is a protective mechanism to eliminate the offending substance from the body.

Recognizing diarrhea as a symptom is essential in the context of food safety, as it can indicate contamination or spoilage in food, which can lead to further complications if not addressed properly. It serves as a critical marker for both individuals experiencing it and food safety professionals monitoring public health.

Other options like high energy levels, improved appetite, or increased hydration do not typically correlate with foodborne illness symptoms. In fact, many individuals suffering from foodborne illnesses often experience low energy, reduced appetite, and dehydration due to fluid loss caused by diarrhea and vomiting.