Food choices matter when aiming for a gut microbiota that is in good shape. Can the same be said for water choices?

The effect of food, nutrients and overall diet on human gut microbiota composition and functions have been widely studied. For instance, what you eat can not only alter gut microbial composition within just 24 hours of initiation, but it can also shape its functions and intestinal inflammation.

When looking for the best advice for a healthier gut microbiota and maintaining health, focusing on diet quality is better than concentrating on specific nutrients. However, beyond food choices, little is known about the impact of water choices (in terms of water source and intake) on gut microbiota composition. That is explained in part by the fact that drinking water is not always considered part of the diet and some scientists have even referred to it as “the forgotten nutrient”.


A link is revealed between drinking water origin and amount and differences in gut microbiota composition

New findings in over 3,000 mostly healthy participants from the US and UK showed how drinking different types of water led to differences in gut microbiota composition.

Compared to bottled, tap or filtered water, drinking well water was associated with higher fecal microbiota diversity, which, broadly speaking, is a hallmark of gut microbiome health (with the exceptions of higher diversity linked to constipation and lower diversity in breast-fed infants). To put this data into the context of other known factors that affect the gut microbiota, the effect of drinking water source on fecal microbiota diversity within the same individual was lower compared to age, body mass index and diet type.

The amount of water consumed also matters. High water drinkers (consuming daily or regularly) vs low water drinkers (consuming never, rarely or occasionally) showed different fecal microbiota compositions. For instance, high water drinkers had a lower abundance of Campylobacter bacteria, which has been linked to gastrointestinal infection.

So what could be the factors affecting the way water impacts the gut microbiota composition? In that regard, the authors hypothesized that the physicochemical properties, mineral content or microbial composition of water may influence the participants’ microbiota.

It should be acknowledged that the study did not report participants’ health outcomes in relation to their water choices, so the impact of drinking water on maintaining health or managing gut issues remains to be seen.

As expected, oral microbes did not vary with drinking water source, supporting the idea that the oral microbiota is pretty stable and resistant to change in response to modifications in diet.


Water intake may be considered a novel factor that influences the gut microbiota

The findings are the first to explore the link between drinking water sources and amount and changes in gut microbiota composition in a large population. Although it is too early to conclude that changes in gut microbiota composition are the main drivers of the health benefits that come with staying well hydrated, the study highlights the importance of considering water intake as a significant variable that may shape gut microbes as part of the overall diet.



David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014; 505(7484):559-563. doi: 10.1038/nature12820.

Vanhaecke T, Bretin O, Poirel M, et al. Drinking water source and intake are associated with distinct gut microbiota signatures in US and UK populations. J Nutr. 2021. doi: 10.1093/jn/nxab312.