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

Nausea and vomiting are among the most common symptoms of foodborne illness. These symptoms typically arise as the body responds to ingesting harmful pathogens or toxins present in contaminated food or beverages. The gastrointestinal system becomes irritated, leading to discomfort and the body's natural reaction to expel the harmful substances.

In comparison, increased energy levels and improved appetite are generally contrary to the typical responses seen in foodborne illnesses. Those affected usually experience a decrease in energy due to the body's effort to fight off the illness, which often leads to a lack of appetite. A persistent headache can occur in some cases but is less specific to foodborne illnesses than gastrointestinal symptoms like nausea and vomiting. Hence, nausea and vomiting are considered key indicators of foodborne illness and play a crucial role in identifying and addressing potential outbreaks.