If you are dehydrated you will typically see a change of stools. Seeing hard pebbles and dry stools is a logical consequence of the body rationing water. Recently, we got a new smart scale ($30 on Amazon) that comes with a smart phone app and does multiple measures, including hydration. I have been running below the desired range, so I am busy hydrating with Gerolsteiner Mineral Water (from Traders Joe) etc.
Conceptually, the availability of water should impact the microbiome. So tonight I started to search out studies to confirm my speculation.
Effect of Increased Daily Water Intake and Hydration on Health in Japanese Adults, 2020
There were five out of the 108 types of intestinal bacterium at the genus level that showed significant differences within and between groups due to water supplementation, and 17 out of 564 species identified by the homology search of OTU representative sequences in the DDBJ 16S database showed the same behavior… Of these, a slight correlation was seen in the intervention group between changes in blood pressure and changes in the Psudoflavonifractor capillosus bacterial count (R = 0.42) Kineothrix sp. (R = 0.36), Feacalibacterium prausnitzii (R = 0.38), and Ruminococcaceae (R = 0.34) showed weak correlations between changes in body temperature and changes in bacterial count
Some related studies that implies impact on the microbiome but failed to do microbiome analysis with the study
- Mild dehydration affects mood in healthy young women, 2011
- Mild dehydration impairs cognitive performance and mood of men. 
- Influence of progressive fluid restriction on mood and physiological markers of dehydration in women. 
- The effect of the consumption of water on the memory and attention of children. 
Dehydration is often reported as a contributor to various conditions
- Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Diagnosis and Management in Young People: A Primer 
Hydration is an often overlooked aspect of improving the microbiome. It has impacts on blood pressure, body temperature, mood and cognitive ability. While we have few studies on it’s microbiome impact, we can likely assume safely that improved hydration will improve the microbiome. It should not be left to a “I drink enough water, I do not feel dehydrated”, but with actual measurements. Improving it is actually a slow process — my goal is to shift from my current level below, to at least 55%.
6 thoughts on “Hydration and the Microbiome”
I wonder if there’s also much known about the impact of salt intake on the microbiome, as salt and hydration are connected to some degree.
I mention this because salt supplementation is a common treatment for POTS, which also affects a substantial minority of CFS sufferers.
Yes, there are over 500 impacts listed here: https://microbiomeprescription.com/library/modifier?mid2=480
Ah, great! Thanks
Hi Ken[edited], this article is great timing for me – I have a question, what if you are showing the signs of dehydration, in stool & skin etc, but are drinking buckets of water? This is a recent phenomenon for me, I have recently started MSM & Creatine, I don’t know if they would cause this? Thanks 🙂
Please review https://www.ncbi.nlm.nih.gov/books/NBK231133/ Some things to consider: Potassium intake (KCL is cited)
Also pH of the water is an significant factor “Thirst is not always quenched by drinking pure water, but depends upon the composition of the water (osmotic concentration) and the ability of the body to hold water.”