Drinking Water Dilutes Stomach Acid

With all of the information available right at our fingertips, the potential to stumble upon diet myths is fairly high. During the age of information-overload, how do you know you’re getting accurate facts rather than hyped-up hyperbole?

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This is part three of a ten part mythbusters series on acid reflux relief. Part one explores if acidic foods cause acid reflux.  Part two dives into myths surrounding a high fat diet and reflux. Today’s article divulges if drinking water dilutes stomach acid, a common question by those aiming to optimize digestive health.

Let’s explore why this myth became popular and what the current research has to say about it. I use the mythbuster-scaling system of totally true, a little bit true, or not true at all.

So, fact or fiction: does drinking water dilute stomach acid? 

Let’s Breakdown this Myth-

There is much confusion around this myth because to get the answer, we must uncover 3 distinct parts. The first area to address is, “Does drinking fluid/water impact stomach acid?” The next concept to explore is, “Should we drink or not drink fluid/water with a meal to optimize digestion?”And then the final part is, “Does any of this matter?”

While researching this topic, I hit some roadblocks, realizing that there are many theoretical discussions based on human physiology, but little to no actual studies. Therefore, allow me to explain the theory behind this myth, and then we’ll jump right into some of the research findings. 

My Explanation-

People drink water both with meals and between meals. This means that sometimes water enters an empty stomach and other times enters a stomach with food inside. Let’s breakdown both of these scenarios…

Drinking Water on an Empty Stomach:

On an empty stomach, water is pretty much absorbed within about 5-minutes. Digestive cues (the release of stomach acid) do not occur when water alone passes through the stomach to the small intestine. The journey of water into an empty stomach is pretty straight forward. 

Conclusion: Drinking water on an empty stomach does not dilute stomach acid because it was never released in the first place.

Drinking Water with a Meal:

However, when water is consumed with a meal, a very different stream of events occurs. Water during a meal is used to help lubricate the food we swallow, especially when eating quickly with little chewing/saliva mixing. As water and food simultaneously enter the stomach, this adds volume and expansion of the stomach walls, stimulating the release of digestive juices (i.e. stomach acid, digestive enzymes). 

The stomach releases anywhere from 400 to 700 ml of stomach acid (also referred to as hydrochloric acid or HCl for short) to help digest a meal. HCl creates a highly acidic environment in the stomach, with the average pH level of 2

A few things to keep in mind:

  • Most drinking water has a pH level of ~7 (neutral)
  • Most foods (plant-based especially), naturally contain a certain level of water. For instance, most fresh fruits and vegetables are made up of >90% water!

Okay, so knowing these facts, the theorized change in the stomach’s pH with consuming “extra” water (e.g. an 8oz glass) with a meal is pretty minimal, almost discretionary! I stumbled upon this mathematical calculation of the change of pH on a paleo-blog that may bring more light to the topic. 

I also found this cross-over study on 12 healthy subjects that showed drinking water increased the stomach’s pH to >4 in less than one minute. This alkalizing effect (higher pH= more alkaline, less acidic) of water dissipated by 3 minutes.

You can read the abstract below: 

Is this where people got the idea that water diluted stomach acid?

After hours of searching, I was unable to find any other studies directly testing the impact of water on stomach acid (in humans). 

I did however find this newspaper article from the Washington Post published in 1926 that somewhat tries to answer this question. The headline read, “HEARTBURN IS LAID TO MUSCLE SPASM, NOT ACID STOMACH: Warm and Cold Water, Alkali and Other Substances Have Same Effect.” 

HEARTBURN IS LAID TO MUSCLE SPASM, NOT ACID STOMACH: Warm and Cold Water, Alkali and Other Substan- ces Have Same Effect. RATE OF BLOOD'S FLOW ACCURATELY MEASURED Tracing Radium Injection Is Described Before Clinical Research Body.

The article basically says that many factors impact those with chronic heartburn, but the common denominator was actually stomach muscle spasms. Maybe I’m getting off track here!

Now, if the stomach’s pH is minimally impacted by drinking water with a meal, we still have not answered the question, “Should we drink or not drink fluid/water with a meal to optimize digestion?”

To Drink, Or Not To Drink?

Ideally, we all have plenty of time to sit in a comfortable, relaxed state and thoroughly chew and digest our home cooked, healthy meals. Wouldn’t that be nice?

However, we know this is not typically the case. Often, we eat on the run, while simultaneously completing other tasks and don’t have enough time to chew and digest the packaged food we picked up from the Drive Thru line!

Maybe I’m exaggerating a bit, and your scenario may fall somewhere in between those two descriptions. Either way, we are all seeking better digestion and want to know the truth…to drink or not to drink?

Boiling it down (no pun intended), water or other fluids consumed with meals may be detrimental to digestion. But, this is not because they “dilute stomach acid” or drastically change the pH of the stomach (as stated above).

Fluids simply do 2 things:

  1. Take Up Space

    • Food and fluid takes up more space than food alone. Therefore, you may fill up the stomach faster, pushing undigested food closer to the lower esophageal sphincter (LES). The LES is the gateway that separates stomach content from the esophagus. This mechanism may be responsible for the feeling of acid reflux when drinking water with your meal. LES opening causing GERD
  2. Cheats On Chewing

    • Drinking fluid with a meal can be a “cheat” to not chewing thoroughly. Chewing not only creates mechanical breakdown of food, but also allows enough time for the mouth to mix food with saliva and start the digestion process. By allowing yourself to drink (lubricate) with a meal, you may be cheating yourself of proper chewing.

Conclusion: Theoretically speaking, drinking with a meal may impair optimal digestion. Drinking between meals helps you meet your fluid needs without potentially impacting the digestive process. 

So What’s the Verdict?

Mythbuster rating: a little bit true

Water can mildly and temporarily increase the pH of stomach, however, this response probably doesn’t really matter when it comes to heartburn. Rather, drinking water with a meal may cause heartburn/reflux because it makes the stomach fill up faster. This potentially relaxes the LES, allowing content to enter the esophagus. Additionally, it may prevent proper chewing, the first step in the digestion process. 

I recommend that you sip water with a meal only as needed and instead consume most of your daily water needs between meals.