Your gastrointestinal system breaks down the food you eat into minute molecules that pass into your bloodstream and nourish your body. The acid produced by your stomach aids in the physical breakdown of food and the digestion of protein. Several factors stimulate stomach acid secretion, including the nutritional composition of the food you eat. Although stomach acid secretion occurs with all types of food, high-protein foods are more potent stimulants than foods that contain high concentrations of starches, sugars or fats.
The hormone gastrin is the primary controller of acid secretion in your stomach. Specialized cells in your stomach, known as G cells, produce gastrin in response to the presence of food. Gastrin release from your G cells stimulates acid production by another type of stomach cell called the parietal cell. Foods containing protein are potent stimulants of gastrin production, which leads to vigorous secretion of stomach acid. Alcohol and caffeine increase stomach acid secretion by directly stimulating your parietal cells, bypassing the gastrin control mechanism.
Nervous System Control
Your nervous system exerts intricate control over your digestive system, including the secretion of stomach acid. When you see, smell or imagine delectable food, your nervous system signals your stomach to secrete acid in anticipation of a meal. Stomach stretching that occurs as you eat also induces acid secretion by stimulating nervous system receptors. Unlike gastrin-related control, nervous system stimulation of stomach acid secretion is not specific to the nutritional content of a meal.
Stomach Acid and Protein Digestion
The fact that protein proves a strong stimulant for stomach acid secretion relates to its importance in the digestion of this nutrient. Stomach acid breaks some of the chemical bonds that hold proteins together, a process known as denaturation. As food proteins become denatured, they transition from a solid to a liquid form, making them more accessible for breakdown by protein-digesting enzymes. In addition to protein denaturation, stomach acid activates the protein-digesting enzyme pepsin produced by your stomach. Without stomach acid, pepsin remains inactive and cannot digest dietary protein. In contrast to protein digestion, which begins in your stomach and continues in your small intestine, the breakdown of starches does not begin in earnest until food reaches your small bowel. Stomach acid secretion, therefore, has less effect on starch digestion than on protein digestion.
A Matter of Degree
Stomach acid secretion occurs in response to all types of food, unless you take medication to block this normal digestive response. Although the volume of acid your stomach produces typically proves greater with high-protein meals, acid secretion also occurs with starchy and high-fat meals. Therefore, diet alone is usually ineffective for significantly reducing stomach acid secretion for the treatment of medical conditions such as ulcers or acid reflux disease.