Hydration and Digestive Health

You may always hear or repeat the phrase “drink plenty of water.”  Why? Because water is the most plentiful substance in the body, comprising roughly 50-65 percent of body composition in the average adult.  And, because fat tissue does not contain as much water as lean tissue, people with higher amounts of body fat have less total body water.

Fluid recommendations vary based on age, activity, medical and physical conditions. A simple method to estimate your fluid requirements is to divide your weight in pounds by two, which provides how many ounces of fluid you should consume daily. For example, if you weigh 150 pounds, dividing by two, this equals 75 ounces. Divide this by eight (eight ounces per cup), you would need to consume about 9-10 cups of fluid per day.

You can then gauge if your fluid intake is adequate based on the color of your urine, which should be a pale yellow. There are several symptoms of inadequate fluid intake including dark urine, dry mouth, lips, mucous membranes; headache; dry or sunken eyes; weight loss; and constipation.

Adequate hydration is important for optimal digestive health.   Tweet This! The gastrointestinal tract is the major site of water absorption. The small intestine, which has the surface area of a doubles tennis court, is designed to absorb high volumes of fluid, around 7-12 liters per day.

The large intestine, or colon, is the distal part of the gastrointestinal tract and absorbs about 1½ liter of fluid per day.  The fluid absorbed in the digestive tract is comprised of those consumed by mouth, as well as fluids in the body that are secreted into the gut and assist with digestion, such as salivary, gastric and biliary juices and digestive enzymes.

When the intestine absorbs water, it also functions to co-absorb other important molecules that help keep our metabolic pathways and cells happy and functioning properly, such as glucose and electrolytes such as sodium, potassium and magnesium.

Optimal intestinal contraction, or peristalsis, requires adequate hydration. Peristalsis is the involuntary contraction of the smooth muscles in the intestinal tract that causes foods we eat to move though the digestive tract. When peristalsis goes awry, bowel cramps, constipation, diarrhea, or abdominal pain can result.

A diet rich in fiber, the non-digestible carbohydrate in plant foods, assists with adding “bulk” and improving bowel regularity.   Tweet This! Soluble fiber dissolves in the intestinal fluids and forms a gel in the colon; insoluble fiber does not dissolve, but also adds bulk and can assist with moving intestinal material along. Consuming fluids with fiber to increase fecal bulk is very important, otherwise stools can harden and be difficult to pass. Eating whole fruits and vegetables accomplishes both consuming fiber and water as many types of fresh produce are rich in fiber and 85-96 percent water (e.g., watermelon, cucumbers, strawberries, pineapple, tomatoes).

So, as we approach warmer summer months, let’s maintain a focus on supporting our healthy lifestyle by consuming adequate hydration necessary for optional digestion as well as other essential functions in the body.


Scientific and Medical Advisory Board Members are compensated for their role on the Scientific and Medical Advisory Board.