Friday, April 30, 2010
Diet selects for the bacteria that grow in the GI track and control the development of the immune system. Diet-based inflammation produces aging symptoms.
I want to return to the subject of aging. A year and a half ago I wrote, “You don’t wear out, you flame out.” I still think that is true, but I need to update that idea of inflammation and aging to include diet, gut flora and immune system development. So here is my old article with a new focus on the gut.
Wearing Out Only Happens with Inflammation
I don’t think that aging happens -- most symptoms associated with aging are just medically mismanaged chronic inflammation. The major observations are that older people have more degenerative/autoimmune diseases and they suffer from fewer infectious diseases. The typical explanation is that the bodies of older people have figured out infections with an experienced immune system and that mechanical damage takes its toll over time -- joints wear out. I think that there may be a minor amount of truth in this cultural perspective, but there is something more profound at work, sarcopenia combined with a compromised gut flora.
Replacing Muscle with Visceral Fat Is Inflammatory
Sarcopenia (muscle loss) is the gradual loss of muscle and replacement by fat. Thus, by age fifty most people are physically less active and even if they appear to have the same weight and shape as in their active youth, the muscle of their abdomens and limbs has been partially replaced with fat. This fat, as in those who are obese, releases inflammatory cytokines into the circulation and the body reacts as if it has a low grade infection.
Chronic Inflammation Taxes Immune System
Senior citizens are constantly expending energy and taxing their immune system by chronic inflammation. As a result they get fewer infections, but the chronic inflammation provides the foundation for cancer and autoimmune diseases. Their bodies aren’t mechanically wearing out, but they are wearing out by over use of the immune system.
Aging Symptoms Are Inflammation Symptoms
Those seniors who are physically active and eat an anti-inflammatory diet, do not appear to age as fast as those who are sedentary, obese and display the typical symptoms of chronic inflammation, the metabolic syndrome. Most of the characteristics associated with advancing years are merely symptoms of poorly managed chronic inflammation that can be reversed by an anti-inflammatory diet and exercise.
Diet Determines Gut Flora
Diet also contributes to aging, because diet controls development of gut flora and gut flora control development of the immune system. The gut flora of an individual reflect the bacteria that have entered the GI tract, nutrients available to the bacteria in previous meals, bacterial growth regulators released by the gut, exposure to antibiotics, exposure to phytochemicals and gut transit time.
Gut Flora Is Diverse and Adaptable
Gut flora appears to be amazingly diverse from individual to individual with thousands of bacterial species inhabiting humans worldwide and about 150 species in each individual. The same species remain in an individual for long periods of time regardless of diet. The dominance of particular species depends on recent diet. Major changes can result from antibiotics or gut diseases, e.g. Crohn’s.
Constipation Means Dysfunctional Gut Flora
Bowel stools are made up predominantly of bacteria and not undigested plant parts, i.e. fiber. Fiber is made up of plant polysaccharides that are not digested by salivary, stomach or pancreatic enzymes, e.g. proteases and amylases that degrade proteins and starch. Fiber polysaccharides pass into the colon where they are digested by gut flora. People with constipation usually have disrupted gut flora, e.g. wiped out by antibiotics, and so the minimal volume of remaining undigested fiber is all that passes out in compact, dehydrated lumps. If gut flora have been exposed to a particular type of fiber and bacteria having the needed enzymes have been brought into the gut previously, then the fiber is digested to sugars that feed the gut bacteria. The increased population of bacteria is what makes up normal, hydrated bowel stools.
Gut Flora Changes Slowly to New Foods (Polysaccharides)
Bacteria grow quickly and with ample nutrients gut bacteria can double in number in about an hour. Bacterial species are usually defined by the ability to utilize various carbohydrates or polysaccharides as nutrients. Depending on the food eaten, nutrients favor the growth of particular bacterial species and the gut flora population changes dynamically. New species are incorporated into the gut flora only if they find their way into the gut on food, e.g. riding on fresh, uncooked vegetables, and food provides nutrients that can permit the new bacteria to grow. It will take several meals for new bacteria to reach appreciable numbers. In the mean time the new fiber may be partially degraded and produce chemicals that disrupt other gut flora and cause bloating symptoms of food intolerance. This is not an allergic reaction of the immune system. It just takes time and persistence to permit the gut flora to adapt. Most people systematically make themselves intolerant to particular foods by over-reacting to initial maladaption of their gut flora to the new food. If they persisted with progressive exposure to diverse foods, their gut flora would adapt.
Simplified Aging Gut Flora Contributes to Inflammation
People of increasing age who maintain a diverse, anti-inflammatory diet and maintain muscle mass by weight-bearing exercise, avoid age-related inflammation and disease, i.e. they age more slowly. Conversely, those who simplify their diets by eating processed foods high in starch and vegetable oils, show symptoms normally associated with advanced age, even when young. The aging diet is inflammatory and it also produces a gut flora which is different from the youthful.
Aging Gut Flora Contributes to Disease
Constipation is an extreme example of dysfunctional gut flora and since gut bacteria are needed for the normal development of the immune system that is located in the lining of the small intestines, constipation is also an indicator of a compromised immune system. Aging is frequently accompanied by digestive problems with one extreme being constipation. It should not be surprising that individuals with compromised immune systems also develop numerous degenerative diseases indicative of a lack in the immunological tolerance systems that develop in the gut in response to normal gut flora. Constipation and digestive problems are not normal signs of aging.
Eliminate Symptoms of Aging by Cultivating Gut Flora
A healthy diet, healthy gut flora, and a competent immune system are all tightly connected. The typical symptoms of aging merely reflect an unhealthy diet and lifestyle that leads to chronic inflammation, a compromised immune system and disease. The process of aging can be slowed by attention to the next meal. Most people who fail to be healthy and active well into their 80’s are simply victims of bad choices (or of bad medical advice.)