Gastric acid
The highest concentration that gastric acid reaches in the stomach is 160 mM in the canaliculi. This is about 3 million times that of arterial blood, but almost exactly isotonic with other bodily fluids. The lowest pH of the secreted acid is 0.8, but the acid is diluted in the stomach lumen to a pH between 1 and 3.
Alkaline diet
Alkaline diet (also known as the alkaline ash diet, alkaline acid diet, acid ash diet, and acid alkaline diet) describes a group of loosely related diets based on the misconception that different types of food can have an effect on the pH balance of the body. It originated from the acid ash hypothesis, which primarily related to osteoporosis research. Proponents of the diet believe that certain foods can affect the acidity (pH) of the body and that the change in pH can therefore be used to treat or prevent disease. Due to the lack of credible evidence supporting the claimed mechanism of this diet, it is not recommended by dietitians or other health professionals, though some have noted that eating unprocessed foods as this diet recommends may have incidental health benefits unrelated to bodily pH.