In a prior post, I promised examples to illustrate the significance of the connection between microbiome and overall health. Those described below suggest that we can begin to use rational nutritional choices to modify the microbiome and provide new approaches to both avoid and treat chronic diseases.
Weight Management - It looks as if our microbiome is involved in the current obesity epidemic by modifying how efficiently we use our daily calories, and may also help explain why some of us can eat anything we want and not gain weight.
In one study bacteria from the large intestine (colon) of two twins, one lean and one overweight, were injected into the colon of genetically identical mice that had been raised in a germ free environment. They were then placed on an identical diet and after just two weeks the mouse that received bacteria from the heavier twin had 17% more body fat. It appears that the microbiome from an overweight person can signal the body to change how our cells use sugar for energy and store the rest as fat.
Have you changed to diet soda to lose a few pounds? Studies in mice compared artificial sweeteners (aspartame, sucralose or saccharin ) and natural sugars ( glucose and sucrose). The mice given the artificial sweeteners experienced a documented change in the bacterial composition of their microbiome, and that change caused them to extract more energy from their food as well as storing more of that energy as fat. The result was the paradoxical effect of taking in fewer daily calories but not losing weight.
Diabetes - Along with obesity, we are experiencing a diabetes epidemic in this country. The microbiome may be playing a role here as well. Mice given artificial sweeteners developed glucose intolerance (an abnormal glucose metabolism often referred to as pre-diabetes) compared to mice given the natural sugar glucose. When their feces were transplanted into germ free mice, these mice also developed glucose intolerance. Treating the newly prediabetic mice with antibiotics eliminated the glucose intolerance as the microbiome was altered.
This experiment was duplicated in human subjects. Seven healthy volunteers were given artificial sweeteners for a week and four of them also developed glucose intolerance which, just as in the mouse model, could be transmitted to germ free mice with a fecal transplant.
Not only is it possible that the microbiome is linked to the diabetes epidemic, it also offers us the possibility of a novel dietary treatment option. In a study of large populations, it was noticed that those that ate beans regularly had a lower incidence of diabetes. On further investigation it was found that the poorly absorbed carbohydrates in legumes are metabolized by colon bacteria into proprionate, a molecule which slowed stomach emptying and the rate at which dietary sugar is absorbed. Proprionate, given as a rectal suppository, produced the same effect.
But eating a half cup of beans a day and letting your colon bacteria do the work is more acceptable to most people.
Heart Disease - Bacteria in the colon modify a protein in red meat (L-carnitine) into trimethylamine oxide (TMAO) which rapidly accelerates atherosclerosis in mice. TMAO can be measured in the blood, and the more red meat one eats per meal, the higher the TMAO blood levels. Thus it may be TMAO, not cholesterol or fat, that is the smoking gun that explains the association (in large groups) of a high red meat diet with a higher rate of heart disease.
Interestingly TMAO is also formed from the metabolism of the amino acid choline. Choline is found in significant amounts in eggs and thus TMAO, not cholesterol, may also explain the link between egg consumption and heart disease.
What can you do to maintain a healthy microbiome?
- Avoiding unnecessary antibiotics for “possible” infections is important.
- It is harder to avoid second hand exposure to the antibiotics in meat from animals raised on antibiotics as a growth strategy (yes, via their effect on the animals microbiome).
- Most experts agree that increasing fiber in our diet is the most important, and relatively easy, step we can take.
- Your regular diet has such a pronounced effect on your microbiome that there is little impact from adding daily probiotics.
- Eat an extra serving of vegetables with dinner.
- Decrease the amount of red meat in your diet (try to incorporate a meatless dinner once a week)
- Add beans to your diet as often as seems reasonable for your personal tastes Take your daily flax meal.
Each of these will add their little bit to keeping your microbiome diverse and healthy.