The Coffee Conundrum: A Proposed Life-Lengthening Mechanism
A growing body of research demonstrates an association between coffee drinking and a host of health benefits. Just this week, a new study showed premature death decreased by as much as 16% in those who consume 6 to 7 daily cups of coffee. (1) In 2017, the American Heart Association presented preliminary research showing a lowered risk of stroke and heart failure in coffee consumers (2), while decrease in risk of dementia, by as much as 65% in late age, has been well-established. (3,4)
Relying mainly on observational studies, there are many proposed mechanisms by which coffee may increase longevity and protect against cognitive decline, such as antioxidant capacity, increased insulin sensitivity, and the anti-inflammatory effects of blocking adenosine receptors in the brain. (5,6) This article will explore a potential mechanism which is little talked about, accounting for the gut-brain axis which links emotional and cognitive areas of the brain with intestinal functions.
Coffee Increases Gastric Acid (HCl) Secretion in the Gut
Coffee, both caffeinated and decaffeinated (7,8), increases the production of the hormone gastrin in the gut (9), the prime regulator of gastric acid (HCl) secretion. Specialized endocrine cells (G cells) release gastrin into circulation after a meal.
The G cells are tightly regulated by two hormones: gastrin releasing peptide (GRP), which exerts stimulatory effects in the gut and is countered by the inhibitory effects of somatostatin. The release of gastrin is controlled by a negative feedback loop whereby fasting and increased stomach acid will inhibit it and a high gastric pH will stimulate its secretion.
This may partially explain why long-term proton pump inhibitor (PPI) takers often have chronically elevated serum gastrin levels. PPIs inhibit the H+/K+-ATPase system found in gastric parietal cells, thereby suppressing gastrin levels, which will eventually cause the body to respond to stimulate the release of gastrin to maintain homeostasis.
The hormone gastrin increases stomach motility and gastric emptying. Nutrient absorption is only possible when stomach acid levels are at their proper levels. One study indicates that bitter taste signaling occurring in the gastric parietal cells plays a role in the release of gastrin. (10)
Coffee May Help Optimize Digestion and Nutrient Absorption, Especially as We Age
Low stomach acid (hypochlorhydria) is more common in the elderly (11). Is it possible that coffee’s life-lengthening health benefits are in part due to its effect on gastric parietal cells, helping to maintain optimal pH levels and a healthy microbiome, as well as optimize digestion and nutrient absorption. This may very well be the main reason that coffee consumption, no matter in what form, increases longevity. Unfortunately, more observational studies will not give us the answer.
- Loftfield E, Cornelis MC, Caporaso N, Yu K, Sinha R, Freedman N. Association of Coffee Drinking With Mortality by Genetic Variation in Caffeine MetabolismFindings From the UK Biobank. JAMA Intern Med. Published online July 02, 2018. doi:10.1001/jamainternmed.2018.2425
- Drinking coffee may be associated with reduced risk of heart failure and stroke. Late-onset asthma linked to increased heart disease, stroke risk | American Heart Association. https://newsroom.heart.org/news/drinking-coffee-may-be-associated-with-reduced-risk-of-heart-failure-and-stroke. Accessed July 3, 2018.
- Santos C, Costa J, Santos J, Vaz-Carneiro A, Lunet N. Caffeine Intake and Dementia: Systematic Review and Meta-Analysis. Journal of Alzheimers Disease. 2010;20(s1). doi:10.3233/jad-2010-091387.
- Panza F, Solfrizzi V, Barulli MR, et al. Coffee, tea, and caffeine consumption and prevention of late-life cognitive decline and dementia: A systematic review. The journal of nutrition, health & aging. 2014;19(3):313-328. doi:10.1007/s12603-014-0563-8.
- Eskelinen MH, Kivipelto M. Caffeine as a Protective Factor in Dementia and Alzheimers Disease. Journal of Alzheimers Disease. 2010;20(s1). doi:10.3233/jad-2010-1404.
- Chiu GS, Chatterjee D, Darmody PT, et al. Hypoxia/Reoxygenation Impairs Memory Formation via Adenosine-Dependent Activation of Caspase 1. Journal of Neuroscience. 2012;32(40):13945-13955. doi:10.1523/jneurosci.0704-12.2012.
- Feldman EJ. Gastric Acid and Gastrin Response to Decaffeinated Coffee and a Peptone Meal. JAMA: The Journal of the American Medical Association. 1981;246(3):248. doi:10.1001/jama.1981.03320030040027.
- Deventer GV, Kamemoto E, Kuznicki JT, Heckert DC, Schulte MC. Lower esophageal sphincter pressure, acid secretion, and blood gastrin after coffee consumption. Digestive Diseases and Sciences. 1992;37(4):558-569. doi:10.1007/bf01307580.
- P. J. Boekema, M. Samsom, G. P. Van Be. Coffee and Gastrointestinal Function: Facts and Fiction: A Review. Scandinavian Journal of Gastroenterology. 1999;34(230):35-39. doi:10.1080/003655299750025525.
- Liszt KI, Ley JP, Lieder B, et al. Caffeine induces gastric acid secretion via bitter taste signaling in gastric parietal cells. Proceedings of the National Academy of Sciences. 2017;114(30). doi:10.1073/pnas.1703728114.
- Russell RM. Gastric hypochlorhydria and achlorhydria in older adults. JAMA: The Journal of the American Medical Association. 1997;278(20):1659-1660. doi:10.1001/jama.278.20.1659.