Healthy Digestion: The Key to a Healthy You

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Healthy Digestion: The Key to a Healthy You

The proper digestion of the foods you eat and the beverages you drink requires the integrated cooperation of vastly complex chemical and physical machinery. Only when every component is operating efficiently can your food be converted into your good health. It’s amazing how integral proper digestive function is to health overall. Optimizing digestive function impacts the health of so many other systems throughout the body. We all know the saying, “You are what you eat!” This is indeed true as digestive health is the key to overall wellness.

As one thinks about this link, it makes sense. After all, the digestive tract, stretching from the mouth to the rectum, is a major site of contact with the outside world. Our food, toxins, microbes and other environmental substances all enter our system through the digestive tract. This system plays a critical role as an immune barrier in two major ways. Firstly, it acts as a structural barrier simply by keeping bad things out and good things in, only allowing things to pass through for particular reasons. Second, it’s a major component of our immune system and the first line of defense for our bodies. Major immune structures and immunoglobulins reside in the digestive tract or are manufactured there. These factors play an important role in maintaining our overall immune defenses. Thus the dual role played by the digestive tract, by acting as a physical barrier and an immunological barrier, is critical to our health. Given this crucial function, it’s easy to see how the health of the digestive tract can impact so many other areas throughout the body.

Now that we understand the importance of digestive health, let’s look at how we can best maintain it. In order to do that, we need to explore the function of the various components of this system. Digestion literally begins with the sight and smell of food. These senses initiate the production of enzymes in the mouth that prepare for the arrival of food and to begin the process of breaking foods down. Of course, chewing is a critically important step as this allows the salivary enzymes to begin acting on the food. From here, the food moves down through the esophagus and into the stomach.


The stomach mixes food with the acid and enzymes it adds to what you’ve eaten; the acid partially dissolves big food particles into much smaller ones and the enzymes begin the digestion of those smaller fat and protein particles. Along with stomach acid, pepsin plays an important role by breaking down proteins into smaller particles known as peptides.

Small Intestine

The small intestine is where most food digestion and nutrient absorption occur. Most food digestion occurs in the upper small intestine and most of the absorption of the individual nutrients occurs in its lower regions. Anything remaining after traveling down the length of the small intestine goes into the large intestine for a different kind of processing before being expelled in the stool.

Pancreatic Enzymes

Food leaving the stomach stimulates the pancreas to send a package of digestive enzymes to the small intestine where they join the bile from the gallbladder. Together these enzymes can digest just about anything we’re likely to eat except fiber. They serve to further break down fats, carbohydrates and proteins into their components and nutrients for assimilation. But there’s a catch – all of the digesting compounds sent to the small intestine could digest our pancreas and gall bladder, so they are initially sent in inactive forms. Once they arrive, the small intestine releases a “master enzyme” that activates all of the others and gets digestion really rolling.


There’s another catch – all that stomach acid could deactivate the enzymes. To prevent this, the pancreas sends along with its enzymes some bicarbonate. This neutralizes the excess acidity and serves to protect the enzymes and lining of the small intestine from stomach acids. The small intestine itself does its part by covering its inner lining with a layer of bicarbonate-rich mucus.


In order for the digestive process to function smoothly, water is a necessary cofactor. Copious amounts of water are needed to keep everything dissolved. This water comes from the beverages we drink during meals and snacks and from your blood. Several cups of water are moved from your circulation into your digestive tract with each meal or snack. While in younger people the hydration of the circulation is maintained by the entry of water from other parts of the body, studies published recently in the American Journal of Clinical Nutrition and the Journal of Applied Physiology found that in older adults the body surrenders less of its total water to the circulation, increasing the risk for bouts of dehydration after meals.1,2

The Colon

Your large intestine, or colon, is required to perform one major and essential task above all others – retrieve back into the body the water that has been added to your food by your saliva and digestive secretions. This water was taken from your bloodstream (about 1 to 2 cups per meal) and added to the material in your alimentary tract (the “digesta”) to help your body digest food and absorb its nutrients relatively rapidly and, for the most part, extremely efficiently. However, if that water is simply lost through your stool you would dehydrate very rapidly a few hours after every meal – certainly not a healthy outcome!

The cells lining the colon are responsible for recapturing the water and restoring it to your blood. Normally they are very efficient. And, like anybody else, these hard workers need to be fed. Here’s something you probably don’t know: Unlike just about every other cell in our body, the cells lining our colon are not fed through the bloodstream. They get their nutrition directly from whatever gets to them from the small intestine – the leftovers of the digestive process. If they are undernourished, they cannot operate effectively. This leads to abnormal stools and inefficient digestive function.

Recently, the colon has also been recognized as a major immune organ. It contributes to overall immunity by functioning as the reservoir for healthy (and unfortunately, unhealthy) bacteria and yeast. Numerous studies shine light on the positive health benefits associated with healthy gut ecology and adequate numbers and strains of probiotic organisms. Likewise, the chronic presence of unhealthy bacteria and yeast lead to unhealthy digestive function and detrimental effects on immune functioning. Maintaining healthy gut ecology by supporting colon health is necessary for our well-being.

Our colon depends on two major factors to keep it healthy:

  1. A healthy balance of probiotic organisms, as the intestines, particularly the colon, are where the majority of these beneficial organisms reside, and
  2. Sufficient amounts of fiber in the diet. This should be in the form of both soluble and insoluble fibers.

Changes with Age

Research suggests that this entire process may work less and less well as we get older. And of course there’s no justice – this age effect doesn’t mean we can eat more without gaining as much weight; it means that as we age the balance between what we eat, what we absorb and what our body needs grows increasingly out of whack. Thus, with age it becomes more necessary to ensure that our digestive tracts function at an optimal level. This often requires nutritional support.

Next Best Kept Secrets to Healthy Aging topic:
Optimize Your Digestion: Stomach Acid

1. Bossingham MJ, Carnell NS, Campbell WW. Water balance, hydration status, and fat-free mass hydration in younger and older adults. Am J Clin Nutr 2005;81:1342-1350.
2. Silva AM, Wang J, Pierson RN Jr, Wang Z, Heymsfield SB, Sardinha LB, Heshka S. Extracellular water: Greater expansion with age in African Americans. J Appl Physiol 2005;99:261-267.

One Comment

  1. Joseph Campbell

    Outstanding article…..I gained a lot of useful information out of this one….Thanks…..Joe

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