Opinion Review
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 21, 2020; 26(43): 6706-6709
Published online Nov 21, 2020. doi: 10.3748/wjg.v26.i43.6706
Gastric acid level of humans must decrease in the future
Shunji Fujimori
Shunji Fujimori, Department of Gastroenterology, Chiba Hokusoh Hospital, Nippon Medical School, Inzai 270-1694, Chiba, Japan
Author contributions: Fujimori S contributed to the writing this paper.
Conflict-of-interest statement: The author declares no conflict of interest.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Shunji Fujimori, MD, PhD, AGAF. Director, Department of Gastroenterology, Chiba Hokusoh Hospital, Nippon Medical School, 1715 Kamagari, Inzai 270-1694, Chiba, Japan. s-fujimori@nms.ac.jp
Received: August 2, 2020
Peer-review started: August 2, 2020
First decision: October 18, 2020
Revised: October 24, 2020
Accepted: November 2, 2020
Article in press: November 2, 2020
Published online: November 21, 2020
Abstract

Proton pump inhibitors strongly inhibit gastric acid production, but digestion problems do not generally arise. We can intake almost ordinary food even after total gastrectomy. Small intestine itself can digest and absorb food using various digestive enzymes without digestion in the stomach. The pH level of gastric acid in humans is much lower than that of most animals, and very close to that of carrion-eating animals called scavengers. It is assumed that ancient humans became bipedal approximately 4 million years ago. It was difficult for humans, who just started unstable bipedal locomotion, to catch quadrupedal-walking animals that can move faster, without special hunting tools. They may have eaten remaining carcasses, which is mainly the leftovers of carnivora species, as animal-derived food. The benefit to produce a volume of gastric acid for humans is carrion eating, in which disinfection by gastric acid is important. Humans produce a high concentration of gastric acid to enable consumption of a diet containing some bacteria and support this lifestyle by consuming significant energy to protect themselves from gastric acid. Now, the opportunity for strong deleterious bacteria to enter the gastrointestinal tract has decreased because of the organized clean environment. If this hygienic environment is maintained for a long time, our gastric acid level must be decreased gradually.

Keywords: Gastric acid, Proton pump inhibitor, Digestion, Scavenger, Carrion eating, Ancient humans

Core Tip: We can intake almost ordinary food even after total gastrectomy. Small intestine itself can digest and absorb food without digestion in the stomach. The pH level of gastric acid in humans is much lower than that of most animals, and very close to that of carrion-eating animals. The benefit to produce a volume of gastric acid for humans is carrion eating, in which disinfection by gastric acid is important. Now, we have decreased risk of food poisoning because of clean environment. If this hygienic environment is maintained for a long time, our gastric acid level must be decreased gradually.