Skip to content

In case you missed it, Michael Pollan wrote an article about the human microbiome (the community of microbes that live within us) that was published May 15, 2013. Much of the article was about how the modern western diet may not be good for the human microbiome and how we can eat for better gut health. From the NY Times:

Some of My Best Friends Are Germs 

 As part of a new citizen-science initiative called thAmerican Gut project, the lab sequenced my microbiome — that is, the genes not of “me,” exactly, but of the several hundred microbial species with whom I share this body. These bacteria, which number around 100 trillion, are living (and dying) right now on the surface of my skin, on my tongue and deep in the coils of my intestines, where the largest contingent of them will be found, a pound or two of microbes together forming a vast, largely uncharted interior wilderness that scientists are just beginning to map.

Few of the scientists I interviewed had much doubt that the Western diet was altering our gut microbiome in troubling ways. Some, like Blaser, are concerned about the antimicrobials we’re ingesting with our meals; others with the sterility of processed food. Most agreed that the lack of fiber in the Western diet was deleterious to the microbiome, and still others voiced concerns about the additives in processed foods, few of which have ever been studied for their specific effects on the microbiota.

So I gave up asking scientists for recommendations and began asking them instead how, in light of what they’ve learned about the microbiome, they have changed their own diets and lifestyles. Most of them have made changes. They were slower to take, or give their children, antibiotics. (I should emphasize that in no way is this an argument for the rejection of antibiotics when they are medically called for.) Some spoke of relaxing the sanitary regime in their homes, encouraging their children to play outside in the dirt and with animals — deliberately increasing their exposure to the great patina. Many researchers told me they had eliminated or cut back on processed foods, either because of its lack of fiber or out of concern about additives. In general they seemed to place less faith in probiotics (which few of them used) than in prebiotics — foods likely to encourage the growth of “good bacteria” already present. Several, including Justin Sonnenburg, said they had added fermented foods to their diet: yogurt, kimchi, sauerkraut. These foods can contain large numbers of probiotic bacteria, like L. plantarum and bifidobacteria, and while most probiotic bacteria don’t appear to take up permanent residence in the gut, there is evidence that they might leave their mark on the community, sometimes by changing the gene expression of the permanent residents — in effect turning on or off metabolic pathways within the cell — and sometimes by stimulating or calming the immune response.

...something a gastroenterologist at the University of Pittsburgh told me. “The big problem with the Western diet,” Stephen O’Keefe said, “is that it doesn’t feed the gut, only the upper G I. All the food has been processed to be readily absorbed, leaving nothing for the lower G I. But it turns out that one of the keys to health is fermentation in the large intestine.” And the key to feeding the fermentation in the large intestine is giving it lots of plants with their various types of fiber, including resistant starch (found in bananas, oats, beans); soluble fiber (in onions and other root vegetables, nuts); and insoluble fiber (in whole grains, especially bran, and avocados).

With our diet of swiftly absorbed sugars and fats, we’re eating for one and depriving the trillion of the food they like best: complex carbohydrates and fermentable plant fibers. The byproduct of fermentation is the short-chain fatty acids that nourish the gut barrier and help prevent inflammation. And there are studies suggesting that simply adding plants to a fast-food diet will mitigate its inflammatory effect.

...I began to see how you might begin to shop and cook with the microbiome in mind, the better to feed the fermentation in our guts. The less a food is processed, the more of it that gets safely through the gastrointestinal tract and into the eager clutches of the microbiota. Al dente pasta, for example, feeds the bugs better than soft pasta does; steel-cut oats better than rolled; raw or lightly cooked vegetables offer the bugs more to chomp on than overcooked, etc. This is at once a very old and a very new way of thinking about food: it suggests that all calories are not created equal and that the structure of a food and how it is prepared may matter as much as its nutrient composition.

Within the past few years there has been an explosion in human microbiome research - looking at the community of microorganisms that live in and on human beings. Within the body of a healthy adult, microbial cells are estimated to outnumber human cells ten to one! This community of microorganisms remains largely unstudied, and so their influence on human development, diseases, immunity, and health are almost entirely unknown.  Some of the latest research looks at the microbiomes of healthy people and those with diseases, seeing how they differ, and from that looking at possible treatments using bacteria.  This is a whole different mind-set from the one we've had for decades that viewed all bacteria as bad (pathogens) and needing to be eliminated. 

An introduction to this emerging area of human microbiome research was written by Gina Kolata in the NY Times, June 13, 2013:  

In Good Health? Thank Your 100 Trillion Bacteria

For years, bacteria have had a bad name. They are the cause of infections, of diseases. They are something to be scrubbed away, things to be avoided. But now researchers have taken a detailed look at another set of bacteria that may play even bigger roles in health and disease: the 100 trillion good bacteria that live in or on the human body.

No one really knew much about them. They are essential for human life, needed to digest food, to synthesize certain vitamins, to form a barricade against disease-causing bacteria. But what do they look like in healthy people, and how much do they vary from person to person?

In a new five-year federal endeavor, the Human Microbiome Project, which has been compared to the Human Genome Project, 200 scientists at 80 institutions sequenced the genetic material of bacteria taken from nearly 250 healthy people. They discovered more strains than they had ever imagined — as many as a thousand bacterial strains on each person. And each person’s collection of microbes, the microbiome, was different from the next person’s. To the scientists’ surprise, they also found genetic signatures of disease-causing bacteria lurking in everyone’s microbiome. But instead of making people ill, or even infectious, these disease-causing microbes simply live peacefully among their neighbors.

"Until recently, Dr. Bassler added, the bacteria in the microbiome were thought to be just “passive riders.” They were barely studied, microbiologists explained, because it was hard to know much about them. 

The work also helps establish criteria for a healthy microbiome, which can help in studies of how antibiotics perturb a person’s microbiome and how long it takes the microbiome to recover.

In recent years, as investigators began to probe the microbiome in small studies, they began to appreciate its importance. Not only do the bacteria help keep people healthy, but they also are thought to help explain why individuals react differently to various drugs and why some are susceptible to certain infectious diseases while others are impervious. When they go awry they are thought to contribute to chronic diseases and conditions like irritable bowel syndromeasthma, even, possibly, obesity.

"The microbiome starts to grow at birth, said Lita Proctor, program director for the Human Microbiome Project. As babies pass through the birth canal, they pick up bacteria from the mother’s vaginal microbiome.

Babies born by Caesarean section, Dr. Proctor added, start out with different microbiomes, but it is not yet known whether their microbiomes remain different after they mature.In adults, the body carries two to five pounds of bacteria, even though these cells are minuscule — one-tenth to one-hundredth the size of a human cell. The gut, in particular, is stuffed with them.

“The gut is not jam-packed with food; it is jam-packed with microbes,” Dr. Proctor said. “Half of your stool is not leftover food. It is microbial biomass.” But bacteria multiply so quickly that they replenish their numbers as fast as they are excreted.

Including the microbiome as part of an individual is, some researchers said, a new way to look at human beings. The next step, he said, is to better understand how the microbiome affects health and disease and to try to improve health by deliberately altering the microbiome. But, Dr. Relman said, “we are scratching at the surface now.”

-----------------------------------------------------

FOR THOSE WHO WOULD LIKE TO SEE A VIDEO ON THIS TOPIC, this TED talk given by Dr. Jonathan Eisen  is an excellent introduction to the human microbiome and how we should view ourselves as being covered in a microbial cloud.  And that this microbial community within and on us should be viewed as an organ, and thus should be treated carefully and with respect.

Who are “Me, Myself and Us?”

2012Jonathan Eisen