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Restoring Digestive Vitality: Supporting a Healthy Gut as We Age

(by Jeremy Appleton, ND)
A well-functioning digestive tract is the key to good health. The digestive system provides the human body with the nutrients it requires to build itself and maintain all of its physiological and biochemical functions. Eating well is not necessarily enough, dietary components must also be effectively assimilated:
  • Motor functions of the gut must propel food and digestates through the digestive tract
  • Digestive secretion (e.g., of gastrin, gastric and pancreatic enzymes, hydrochloric acid, mucin, etc.) must be at appropriate levels; the integrity of intestinal lining itself must be maintained
  • Waste products, organisms and xenobiotics (substances foreign to the body) must be effectively eliminated
  • Normal intestinal flora (e.g., Lactobacilli and Bifidobacteria) must protect bacterial balance in the gut and support a balanced response from the gut-associated immune system.

Age-Related Digestive Changes

As we age, there is a natural decline in the Basal Metabolic Rate (BMR), and in many of the digestive structures and functions. Aging naturally involves some degree of decline in biological and physiological function. The organs at 60 can no longer do what they did at 30, or at least not as efficiently.

  • Decreased production of saliva, with attendant decrease in salivary amylase
  • Gastric acid secretion is reduced, which affects nutrient absorption
  • Gastric emptying is slowed, and the gastric mucosa loses some of its capacity to rebound from environmental, dietary and oxidative stress
  • Absorptive mucosal surface area is reduced; in the small and large intestines, the balance of bacterial flora can shift due to pH changes
  • Slowed digestion, responses and many other secondary effects can ensue from these changes.

We tend to view such changes as the herald of decline and, ultimately, of death. But although the aging body naturally undergoes a certain amount of decline in function, how much decline, and how fast we decline, is at least partly within our control.

How we age is determined by many factors: genetics the nutritional quality of our diet; inherited and acquired disease; the quality of health care we have access to; activity and exercise level; mental and physical stressors; exposure to sunshine, nature, and fresh air; love and physical touch; community and friendships; financial security; spiritual, religious or meditative practices; and our attitudes about and experiences with death and dying. [Editor note: our "Obesity" page within the research library has excellent related material to that discussed by Dr. Appleton herein]

Aging has been defined as the progressive, time-dependent deterioration in our capacity to respond adaptively to environmental changes, resulting in an increased vulnerability to death. The first visible signs of physical aging, of this deterioration, manifest at the cellular level. One of the first signs of aging in cells is a decline in mitochondrial function and density. Aging mitochondria have decreased ability to survive hypoxic insult. The energy production that occurs within mitochondria, oxidative phosphorylation, declines with age. DNA and RNA synthesis of structural enzyme proteins and membrane structures, like receptors, also declines. Senescent cells have decreased uptake of nutrients and a decreased ability to repair chromosomal damage that does occur. And aging cells accumulate lipofuscin, a brown, granular pigment that is the residue of lysosomal digestion. Considered an aging or wear-and-tear pigment, lipofuscin is found in the liver, kidney, heart muscle, adrenal and ganglion cells.

Morphologic abnormalities are also seen in cell organelles, including irregularly lobed nuclei, pleomorphic vacuolated mitochondria, decreased rough and vesicular smooth endoplasmic reticuli, and distorted Golgi apparatus.

As aging occurs on the cellular level, so are those changes expressed in alterations to organ function. Signs of cellular aging appear early in life. But cumulatively, they do not generally begin to manifest as visible decline in organ function until the 5th and 6th decades. Immune and neuroendocrine systems are considered aging “hot spots”. Organ level changes of aging are also seen in the cardiovascular system, kidney, lungs, and in overall body composition. The gastrointestinal tract has a close but often underappreciated connection to the so-called aging “hot spots”. Thus, age-related changes in the gastrointestinal tract are an often overlooked cause or contributor to chronic disease.

Age-Related Changes in the GI Tract

Aging brings many organ-level changes affecting the gastrointestinal tract: Decreased Basal metabolic Rate (BMR) means less conversion of food into energy (and less need for food). In the mouth, taste sensation decreases. Deterioration of dentition can lead to poor chewing, which affects the burden of digestive enzymes and HCl in the stomach. Decreased production of saliva and dentition issues, such as periodontal disease, may affect chewing and exacerbate reflux. In the stomach, reductions in basal and stimulated gastric acid secretion (hypochlorhydria) due to atrophic gastritis lead to nutrient malabsorption (vitamin B12 due to decreased Intrinsic Factor; calcium). Calcium absorption also diminishes due to decreased vitamin D intake and intestinal resistance to the action of 1,25-dihydroxyvitamin D. Aging also brings diminished capacity of the gastric mucosa to resist damage with an attendant increased need for protection.1

In the small intestine, mucosal surface area is reduced with age, though the main digestive and absorptive functions of the GI system do not decline substantially. The only purely age-related defect in intestinal absorption is that of calcium, which is likely due to decreased renal production of 1,25-dihydroxycholecalciferol and reduced intestinal response. Small-intestine motility appears to remain intact with age. However, small intestinal bacterial overgrowth (SIBO) is common in elderly who have predisposing conditions such as hypochlorhydria, small intestinal diverticula, and diabetes mellitus. This can lead to micronutrient malabsorption (e.g., of folate, iron, calcium, vitamin K and vitamin B6).1

In the large intestine, there are few morphologic changes associated with aging. However, fecal impaction and laxative use are common, affecting elimination, and potentially causing dysbiosis and increasing enterohepatic reabsorption of conjugated toxic metabolites and hormones.

Restore Digestive Vitality

The health of the gut is a good indicator of our overall health; restoring health of the gut is a good place to start in restoring overall health. By supporting the various functions of the gastrointestinal tract we can maintain and even restore a level of digestive function and vitality that is at once more youthful and supportive of healthy aging. To help maintain and restore digestive vitality, a four-step plan of nutritional therapies to support the function of the gastrointestinal tract can help surmount even the most entrenched and chronic problems.

    Step 1 – Optimize digestion
    Step 2 – Restore healthy intestinal mucosa
    Step 3 – Promote colon cleansing and healthy elimination
    Step 4 – Re-establish a healthy balance of intestinal microflora

Step 1: Optimize Digestion

There are many ways to optimize digestion. For fast and reliable results, the simple addition of digestive enzymes that are active and stable throughout a broad pH range is paramount. Many enzymes take part in the digestive process. The main types of digestive enzymes are involved in the digestion of macronutrients include:

  • Amylases break down carbohydrates such as starch
  • Proteases break down proteins into peptides and amino acids
  • Lipases break down lipids such as triglycerides, fats and oils
  • Sucrase acts on sucrose (a disaccharide) in food, breaking it down into the monosaccharides glucose and fructose
  • Lactase breaks down the dairy sugar, lactose, into glucose and galactose
  • Maltase breaks down the sugar maltose into glucose

The digestive tract has varying pH levels throughout the gut lumen. The stomach’s pH is highly acidic (usually in the range of 1.5–3.5), but the pH becomes more alkaline moving distally along the tract (to about pH 6 in the duodenum, and pH 7–8 in the jejunum and ileum). The enzymes involved in the digestion process are stable and optimally active at different pH levels, depending on where they are utilized. The following chart summarizes the optimum pH ranges in which the different enzymes are most active.

Acid 2 3 4 5 6 7 8 9 10 Alkaline
Protese I
Protese II
Protese III
Protese IV
Lipase I
Lipase II

Understanding Activity Units

As an example, consider the enzyme amylase, which has activity over a very wide pH range (pH 3 – pH 8). Because of this wide range of activity, it is often necessary to use different analytical methods to measure its enzyme activity at different pHs. Using the USP Method XXI that tests the enzyme activity at a pH of 6.8, the amylase had an activity of 16,000 USP units. Using the FCC Method IV that tests the enzyme activity at a pH of 4.8, the amylase had an activity of 11,900 DU (Dextrinizing units).

The amylase example applies to all different types of enzymes, such as proteases, lipases, etc. It illustrates how the same enzyme can have two different activity levels under different conditions, particularly different pHs. The amount of enzyme present is of far less importance, therefore, than the enzyme’s activity (i.e., how efficiently it breaks down the substrate within the given parameters of the test method, such as pH or temperature).

It is impossible to make direct comparisons between different activity units (such as the FIP unit, USP unit, and FCC unit). Different enzymes act upon different substrates and their enzyme activity is measured using different methods. Therefore, an enzyme product should be tested for potency and activity using the test method that is most validated and applicable to that type of enzyme.

Step 2: Restore healthy intestinal mucosa

Intestinal permeability issues can be identified by laboratory tests (such as the mannitol-lactulose test) or by clinical observation. If altered intestinal permeability is suspected, it is important to identify and eliminate, at least temporarily, foods to which the body is sensitive. This will reduce the inflammatory-immune load on the gut. As we age, our ability to bounce back and repair is not what it was so additional support may be needed. Nutrients that act as antioxidants or that positively influence cytokine metabolism can improve mucosal barrier function and support healthy intestinal permeability.

Antioxidants in the Gut

Intestinal antioxidant protection is critical to the integrity of intestinal mucosa. Several antioxidants have demonstrated activity specific to the intestinal mucosa. Quercetin, flavonoid found in apples and onions, been shown to enhance intestinal barrier functions in human intestinal cells by upregulating the tight junction protein claudin-4.3 Mast cells play an important role in the pathogenesis of intestinal mucosal inflammation and increased IP.4 Quercetin helps to control intestinal inflammation by inhibiting histamine release from human intestinal mast cells.5,6 It has also been shown to inhibit gene expression and production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL) 1-beta, IL-6, and IL-8 from human mast cells.7 The anti-allergic drug disodium cromoglycate is structurally related to quercetin.8 Isoquercetin is the naturally occurring form of quercetin, a quercetin-3-glucoside, that is much more bioavailable.9-11 It is also more stable in the gut than quercetin against oxidation.12

Ginkgo biloba extract has antioxidant and free radical–scavenging properties with cytoprotective effects on cells of the gastrointestinal mucosa.13,14 Oral supplementation with ginkgo extract has been shown to reduce macroscopic and histological damage to the colonic mucosa in vivo and to significantly decrease pro-inflammatory cytokines in experimentally induced intestinal inflammation.15 Ginkgo has also been shown to prevent increased intestinal permeability and mucosal damage associated with small intestinal ischemia in a dose-dependent manner in animal models.16

Vitamins C and E play essential roles in protecting intestinal mucosal cells from oxidative damage and free-radical pathology. In one clinical trial, oral supplementation with 300 mg of vitamin E resulted in evidence of decreased inflammation in the colonic mucosa.17 In a 1995 study, subjects in need of intestinal permeability support showed significantly decreased levels of vitamin C in mucosal tissues compared to controls.18

Nutrients for Barrier Function

Several other nutrients can help to maintain and restore healthy intestinal mucosa including glutamine, phosphatidylcholine, N-acetyl-D-glucosamine, and gamma-oryzanol. Glutamine is the preferred source of energy for epithelial cells of the small intestine. It is also a precursor for the biosynthesis of mucous glycoproteins. Glutamine maintains resistance across epithelial surfaces and has been shown to reduce permeability in intestinal cells. It has been shown to enhance intestinal barrier function in children, and several clinical studies have demonstrated beneficial effects of glutamine on intestinal permeability.20-22 Glutamine is presently the best known compound for modulating intestinal permeability.23–25

Step 3: Promote colon cleansing and healthy elimination

Toxic substances are everywhere: in the air we breathe, and in our food and drink. Our bodies and the bacteria that inhabit our gut produce endotoxins that must, as a normal part of digestive function, be eliminated. The food we consume is the most abundant source of xenobiotics, and our liver and intestines play a critical role in metabolizing and eliminating these substances. Detoxification regimens can become very complex, but the fundamental mechanisms already exist within our bodies, and can be gently promoted through healthy elimination.

Fiber is vitally important to elimination and digestive function for reasons well known to most practitioners. A combination of all-natural fibers and herbs that adsorb and eliminate toxins is a convenient method of supporting colonic health and optimal elimination. Components of such a formula could include such ingredients as flaxseed, psyllium, rice bran, dried plum, and fenugreek.

  • Flax seed, a rich source of omega-3 fatty acids and lignans. Flaxseed can absorb up to 8 times its weight in water and enhances intestinal peristalsis, thereby promoting healthy bowel function. Research suggests the essential fatty acids found in flaxseed also support the body’s natural anti-inflammatory response.26
  • Psyllium, a source of soluble fiber, supports healthy intestinal lubrication for ease in elimination. Psyllium has been shown to absorb up to 14 times its weight in water and has more reabsorption ability than any other bowel-supporting fiber. Psyllium husk supports healthy intestinal lubrication for ease in elimination. It also supports cardiovascular, endocrine, and immune health, additional health benefits that other detoxification fibers often lack.27
  • Rice bran is a rich source of gamma-oryzanol, which has been shown to have protective effects on stomach tissue.28-30
  • Dried plums (prunes) are a mainstay folk remedy for supporting healthy bowel elimination. They are a source of essential vitamins and minerals, dietary fibers, and a number of potent antioxidant compounds. In one study, dried plum was shown to provide protective effects for colon health.32 Fenugreek is a demulcent herb, meaning it soothes the mucous membranes. Its seeds contain approximately 40 percent of mucilage fibers.
  • Fenugreek has been studied for its protective effects on the gastrointestinal lining.33,34
  • Triphala, an ancient Ayurvedic herbal blend consisting of amla, belleric myrobalan, and chebulic myrobalan fruits is a combination that has long been used to promote healthy digestion, aid in detoxification, and improve immune response.35-38

Step 4: Re-establish a healthy balance of intestinal microflora

The interface between the gut and the immune system is complex and has evolved over millennia. The GALT (gut-associated lymphoid tissue) is the largest immune organ in the body, and communicates directly with the vast microbial entourage of our glut flora. This flora, sometimes called a microbiome, modulates epithelial inflammatory responses, antimicrobial protein expression, and critical tissue repair functions. 39

Our gut must accommodate large luminal bacterial populations without mounting an overzealous inflammatory response that could cause collateral damage to host tissues. On the other hand, the gut must be poised to trigger such responses if luminal microbes invade the epithelial barrier. It is a delicate balance, maintained by a complex network of interacting epithelial cells, immune cells, immunoglobulins, cytokines, interleukins, and other inflammatory mediators.40

As we age, there is a decline in the number of protective anaerobic bacteria (e.g., Bifidobacteria) in our intestines and an increase in anaerobes that are not protective41. Alterations of bacteria that dwell in the large intestine affect the digestion of fibers to produce short-chain fatty acids, the fuel for enterocytes that make up the intestinal lining. We depend on our gut bacteria to perform this function.

These changes in intestinal bacteria and changes in diet and digestive physiology may result in increased putrefaction and greater susceptibility to inflammation. There may also be declines in cellular immunity. Probiotics supplementation, for example to replenish bifidobacteria that decline with age, enhances immune function in older individuals.42 Probiotics also decrease intestinal inflammation and enhance mucosal integrity, which in turn normalizes gut permeability. Probiotics lessen systemic antigenic exposure and allergic exposure, and they increase both local and systemic immune activity.


Alterations in gut flora and intestinal permeability as the result of maldigestion and other digestive dysfunction can predispose individuals to chronic disease outside of the gastrointestinal system. Many challenging chronic health conditions will respond more effectively to specific treatment if digestive function is improved first. The protocol for restoring digestive vitality is simple to follow. Once appropriate dietary and lifestyle changes have been implemented, a four-step regimen can be followed with for most patients:

  1. Optimize digestion with the use of acid-stable fungal enzymes that are active across the pH range of the GI tract;
  2. Support intestinal mucosal integrity with targeted antioxidants and nutritional cofactors;
  3. Ensure proper elimination with fiber, alterative herbs and mild detoxifying supplements;
  4. Re-establish a beneficial balance of gut microflora using high-quality, protected probiotics with guaranteed viability through the manufacturer’s expiration date.


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This article was reprinted from Integrative Therapeutics practitioner information releases.

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