Final answer:
Oral feeding cannot be tolerated due to issues with swallowing, digestive system changes with age, chemical contamination, food intolerances, and diseases affecting appetite or digestion. Modern diet adaptations also contribute to the difficulty as human bodies are not fully adapted to drastic dietary changes from historical diets.
Step-by-step explanation:
There are numerous occasions where oral feeding cannot be tolerated, which may require alternate feeding methods. Individuals with certain health issues that affect their swallowing or digestive systems can face challenges. For example, exposure to chemicals can impair the ingestion process, leading to the necessity of avoiding contaminated food. In other cases, age-related changes in the digestive system, including appetite suppression, difficulty swallowing, and slower digestive transit can make oral feeding problematic. In these instances, food is not only less appealing but can be practically difficult to consume.
Apart food intolerances such as lactose intolerance can prevent individuals from consuming dairy without experiencing discomfort, as their bodies do not produce enough of the enzyme lactase. Similarly, diseases like cancer or inflammatory bowel syndrome can result in a lack of appetite or an inability to properly digest food, which can lead to undernutrition or necessitate specialized dietary adjustments.
Adaptation to modern diets has also presented challenges for oral feeding. The drastic change in diet from what humans evolved to consume as hunter-gatherers to contemporary agriculture-based diets has contributed to the prevalence of conditions like lactose intolerance and dental caries, indicating that our bodies may not be fully adapted to the modern diet.