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Does drinking water with a meal release lesser energy/glucose into the blood stream due to a diluted digestive mixture ?

For simplification : If a person eats 100 grams of cooked jasmine rice with no water in take, when digested in 90 minutes releases, say, a 100 calories. Then, if the person eats 100 grams of cooked jasmine rice and drinks 50 ml of water along with it (during/after) (basically, halving the power of the digestive juices) then will the energy released be 50 calories ?

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  • $\begingroup$ Cooked rice or dry rice? Cooked rice absorbs water, so even if you didn't 'drink' any water, you still would have ingested it. $\endgroup$ – XaNaX Aug 1 '16 at 14:16
  • $\begingroup$ @XaNaX edited question $\endgroup$ – happybuddha Aug 1 '16 at 22:32
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A moderate amount of water while eating will not dilute digestion

...according to Michael F. Picco, M.D. and the Mayo Clinic:

There's no concern that water will dilute the digestive juices or interfere with digestion. In fact, drinking water during or after a meal actually aids digestion.

Water and other liquids help break down food so that your body can absorb the nutrients. Water also softens stool, which helps prevent constipation.

Water, after all, is the "universal solvent" which should help break food and organic materials down further.

Effect of Stomach Acid Dilution

This is a total myth, especially if you consider it from totally a chemical perspective. Stomachs secrete about 400 to 700 mL of gastric acids per meal. Just to be conservative, let's say 500 mL. Also, the average stomach has a pH of about 2. Now let's look at the formula for pH and what the effects of adding water might be:

pH = log(1/(mols/volume))
2 = log(1/(mols/0.5L))

Now solve for mols, and we get mols = 0.005

Now let's assume our meal contains about a quarter of a liter of water in it. We'll also assume that our food is completely pH neutral. This is probably a little high on water concentration, but let's see its effect on our stomach's pH.

Since it has a neutral pH, the mols does not change, but our volume does (0.5L [previous contents] + 0.25L [from the food] = 0.75L).

pH = log(1/(0.005 mols/(0.5L + 0.25L)))

Now solve for pH and we get pH = 2.18. No problem here, since normal digestion occurs between a pH of 1.5 to 3.5.

Finally, let's say we drink a lot of neutral pH water with our meal now.

pH = log(1/(0.005 mols/(0.75L + 4.25L)))
pH = 3

So we are still within a normal pH of digestion, even though we just drank over 4.25 liters (~1.12 gallons) of water with our fairly liquid meal of 0.25L! We would need to drink about another 45 L of water to knock our gastic pH above 4. But don't worry, we would die of water intoxication well before that ever happens.

Furthermore, our stomachs (and digestive tract) are incredibly good at adapting their secretions to the consistency of a meal.

Water and Speed of Digestion

Perhaps another way that water may change caloric intake is to increase the speed at which solid foods exit the stomach.

This is thought to reduce the meal’s contact time with stomach acid and digestive enzymes, resulting in poorer digestion.

As logical as this statement may sound, no scientific research supports it.

A study that analyzed the stomach’s emptying speed observed that, although liquids do pass through the digestive system more quickly than solids, they have no effect on the overall solids’ digestion speed.

Bottom Line

Water during meals should not decrease the amount of calories absorbed. With all that being said, digestion is a very complex system, and there are still many unknowns as well as individual responses. Before making drastic changes concerning your health and digestion, you should consult a medical professional. This answer should in no means necessary replace any medical advice or treatments, but rather aid in your understanding of how digestion works.

A Final Word of Caution

I feel obligated to include that however you found this question/answer, staying hydrated to aid in digestion is a very healthy function, especially in considering weight loss and 'feeling full for longer.' However, obsessive water consumption aimed at decreasing food consumption/appetite ("fluid loading" or "water loading") is a common symptom of eating disorders. If this is a concern for you or someone you know, please, seek professional support and help.


Sources:

  1. NCBI - Adaptive Secretions

  2. NCBI - Digestion Speeds

  3. www.mayoclinic.org

  4. water.usgs.gov

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  • $\begingroup$ Thanks for answering. I am more interested in know if somehow (say by drinking half a litre of water) I am able to dilute digestion - will the process of digestion release only half the energy (carbs/fats/etc) from the food ? $\endgroup$ – happybuddha Aug 1 '16 at 22:34
  • $\begingroup$ @happybuddha no, drinking water will not decrease the amount of energy released from food by digestion. Any excess water will simply be absorbed by your body. There are no magic tricks. $\endgroup$ – MattDMo Aug 2 '16 at 21:21
  • $\begingroup$ I would suggest removing/rewording the last few sentences of your "Bottom Line" section - that's bordering on medical advice, which is off-limits on this site. If you are going to keep it, please add some supporting citations to show that the majority of acid reflux cases improve with more stomach acid. You also need to support your statement that one should delay drinking water until after a meal - neither one sounds scientifically accurate. $\endgroup$ – MattDMo Aug 2 '16 at 21:26
  • $\begingroup$ Now edited. I originally included that part as a way to indicate this answer should not be interpreted as medical advice and there is anecdotal evidence (albeit, no peer-reviewed articles from my cursory search) suggesting the contrary - that water during meals has impeded their digestion, such as perpetuating their acid reflux. Apparently this inclusion did the opposite of my intention. These edits now directly state that this answer is not medical advice. $\endgroup$ – Dave Gruenewald Aug 3 '16 at 14:52
  • $\begingroup$ @MattDMo I am not looking for magic tricks - just a definitive answer ! $\endgroup$ – happybuddha Aug 3 '16 at 22:36

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