An example of unconditionally reflex regulation of the digestive process is the excretion of gastric juice during irritation of the walls of the stomach with food, and conditioned reflex regulation is excretion of saliva when you see, smell or talk about food.
It is not recommended to read with food because it is distracting and you can choke. For normal digestion, blood must rush to the stomach, and when you read it, blood rushes to the head.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.