Your gut is the site of constant turf wars:

Hundreds of bacterial species—along with fungi, archaea and viruses—do battle daily, competing for resources. Some companies advocate for consuming more probiotics, live beneficial bacteria, to improve microbial communities in our gut, but more and more research supports the idea that the most powerful approach might be to better feed the good bacteria we already harbor. Their meal of choice? Fiber.  

Fiber has long been linked to better health, but new research shows how the gut microbiota might play a role in this pattern. One investigation discovered that adding more fiber to the diet can trigger a shift from a microbial profile linked to obesity to one correlated with a leaner physique. Another recent study shows that when microbes are starved of fiber, they can start to feed on the protective mucus lining of the gut, possibly triggering inflammation and disease.

"Diet is one of the most powerful tools we have for changing the microbiota," Justin Sonnenburg, a biologist at Stanford University, said earlier this month at a Keystone Symposia conference on the gut microbiome. "Dietary fiber and diversity of the microbiota complement each other for better health outcomes." In particular, beneficial microbes feast on fermentable fibers—which can come from various vegetables, whole grains and other foods—that resist digestion by human-made enzymes as they travel down the digestive tract. These fibers arrive in the large intestine relatively intact, ready to be devoured by our microbial multitudes. Microbes can extract the fiber's extra energy, nutrients, vitamins and other compounds for us. Short-chain fatty acids obtained from fiber are of particular interest, as they have been linked to improved immune function, decreased inflammation and protection against obesity.

Today's Western diet, however, is exceedingly fiber-poor by historical standards. It contains roughly 15 grams of fiber daily, Sonnenburg noted. For most of our early history as hunter-gatherers, we were likely eating close to 10 times that amount of fiber each day. "Imagine the effect that has on our microbiota over the course of our evolution," he said.

Your bugs are what you eat

Not all helpful fiber, however, needs to come from the roots and roughage for which our ancestors foraged, new research suggests. Kelly Swanson, a professor of comparative nutrition at the University of Illinois at Urbana-Champaign, and his team found that simply adding a fiber-enriched snack bar to subjects' daily diets could swing microbial profiles in a matter of weeks. In a small study of 21 healthy adults with average U.S. fiber intake, one daily fiber snack bar (containing 21 grams of fiber) for three weeks significantly increased the number of Bacteroidetes bacteria and decreased the number of Firmicutes compared with levels before the study or after three weeks of eating fiber-free bars. Such a ratio—of more Bacteroidetes to fewer Firmicutes—is correlated with lower BMI. The findings were published in the January issue of the American Journal of Clinical Nutrition.

"We've known forever that if you eat a lot of fiber, you lose weight," Swanson says. His and other recent studies suggest that our gut microbes are a key player in this relationship. In addition to identifying groups of bacteria, a genome scan revealed a shifting pattern of genes active in the gut microbes. As fiber consumption increased, the activity of genes associated with protein metabolism declined, a finding that researchers hope will help them understand the complicated puzzle of diet and weight loss. "We're getting closer to what is actually cause and effect," Swanson says. 

Feed the microbes so they don't feed on you

As gut microbes are starved of fermentable fiber, some do die off. Others, however, are able to switch to another food source in the gut: the mucus lining that helps keep the gut wall intact and free from infection.

In a recent study presented at the Keystone meeting, Eric Martens of the University of Michigan Medical School, postdoctoral researcher Mahesh Desai and their colleagues found that this fuel switch had striking consequences in rodents. A group of mice fed a high-fiber diet had healthy gut lining, but for mice on a fiber-free diet, "the mucus layer becomes dramatically diminished," he explained at the meeting. This shift might sometimes have severe health consequences. Research by a Swedish team, published last year in the journal Gut, showed a link between bacteria penetrating the mucus layer and ulcerative colitis, a painful chronic bowel disease.

A third group of mice received high-fiber chow and fiber-free chow on alternating days—"like what we would do if we were being bad and eating McDonald's one day and eating our whole grains the next," Martens joked. Even the part-time high-fiber diet was not enough to keep guts healthy: these mice had a mucus layer about half the thickness of mice on the consistently high-fiber diet. If we can extend these results to humans, he said, it "tells us that even eating your whole fiber foods every other day is still not enough to protect you. You need to eat a high-fiber diet every day to keep a healthy gut." Along the same lines, Swanson's group found that the gut microbiomes of his adult subjects reverted back to initial profiles as soon as the high-fiber bars were discontinued.

Martens and his colleagues also observed that mice on the consistently high-fiber diet consumed fewer calories and were slimmer than those on the fiber-free diet, showing that fiber benefits the body in multiple ways. "Studies like this are great because it's getting at the mechanisms to explain why fiber is beneficial," Swanson says.

As all this work underscores, the gut microbiome is exceptionally plastic. Such rapid, diet-influenced changes likely served us well over the course of our evolutionary history—shifting faster than our own physiology could, wrote Justin Sonnenburg and Erica Sonnenburg in a November 2014 article in Cell. "In delegating part of our digestion and calorie harvest to our gut residents, the microbial part of our biology could easily adjust to day-to-day or season-to-season variation in available food," they noted. New studies continue to demonstrate that microbial changes due to diet are "largely reversible on short time scales." But the question remains as to how chronic low-fiber intake—over a lifetime or generations—might permanently alter our guts and our health.

This bears focus:  Another recent study shows that when microbes are starved of fiber, they can start to feed on the protective mucus lining of the gut, possibly triggering inflammation and disease.

Holy smokes, thanks for repeating that!

So inflammation could result from not enough fiber in one's diet!

Get your fiber from vegetables, not snack bars:

http://reddit.com/r/science/comments/30lvih/fiberfamished_gut_microbes_linked_to_poor_health/

We are but substrate for all others...

...

...and all others expect us to eat raw-ly, train simply and rest deeply.

My mind is reading science, but my heart is yelling: Beer is a surprisingly healthy alcoholic beverage. Despite being high in both carbohydrates and calories, it contains large amounts of B vitamins and some minerals. Beers that contain a lot of hops -- for example, India pale ales -- are rich in kidney health-promoting phytochemicals. Beer is also a source of dietary fiber, with different varieties contributing different amounts to your daily intake. Although you shouldn't rely on beer for its nutritional benefits, one or two beers per day can be part of a healthy diet.

I've heard that Guinness Beer is high in fiber.

Extracted from The Natural Testosterone Plan by Stephen Harrod Buhner

Hops is best known for its use in beer. (...and this is NOT a good thing, read on).

The majority of physicians and men overlook its potent chemicals and do not realize that beer itself can significantly alter the male androgen levels. German beer makers noticed long ago that the young women who picked hops in the fields commonly experienced early menstrual periods. Eventually, researchers discovered the reason – hops is perhaps one of the most powerfully estrogenic plants on Earth. Just 100 grams of hops (about 3.5 ounces) contains anywhere from thirty thousand to three hundred thousand IUs of estrogen, depending on the type of hops. Most of it is the very potent estrogen estradiol. 

Estradiol, as it is taken into the male body, causes a direct lowering of testosterone levels in the testes and an increase in SHBG levels, which then binds up even more free testosterone in the bloodstream. The estradiol in hops has also been found to directly interfere with the ability of the testes Leydig cells to produce testosterone. The presence of this highly estrogenic substance in beer is not an accident.

Prior to the German Beer Purity Act of 1516, beer almost never contained hops. In fact, more than one hundred different plants were used in brewing beer for at least ten thousand years prior to the introduction of hops in the middle ages. For the last thousand years of that period, the most dominant form of “beer” was called gruit, which contained a mixture of yarrow, bog myrtle, and marsh rosemary. These herbs, especially in beer, are sexually and mentally stimulating. (It is rare to become sleepy when drinking un-hopped beers.) The Catholic Church had a monopoly on the production of gruit, but competing merchants and the Protestants worked together to break their monopoly and force the removal of all sexually stimulating herbs from beer. They replaced them with an herb that puts the drinker to sleep and dulls sexual drive in the male. The legislative arguments of the day all hinged on the issue of the stimulating effects of other herbs that were used in beer. A pilsner, for example, was originally a henbane beer (pilsen means “henbane”), which is an incredibly strong, psychoactive beer, used earlier in history by German berserkers before battle. 

The German Beer Purity Act was, in effect, the first drug control law ever enacted. Beer, so highly touted as sexy in television commercials, in actuality can powerfully inhibit sexual strength in men. There is a well known condition in England – Brewer’s Droop – that occurs from middle-aged brewers’ extensive handling of hops plants. The plant chemistries readily transmit through the men’s skin just as they did in the young women in the fields. Very few physicians have looked at any correlation between beer drinking and androgen levels or erectile dysfunction problems in their patients. (How many men on Viagra are heavy beer drinkers?) 

However, the physician Eugene Shippen in The Testosterone Syndrome comments that one of his patients undergoing pharmaceutical testosterone replacement therapy, showed no response to the testosterone until he reduced his beer intake to one or two beers a night from six to seven. Hops is extremely potent and its consumption should be limited if not completely excluded during all androgen replacement therapy. These effects can be exacerbated if the beers you buy also contain licorice (see Licorice section at beginning of chapter), a fact that will not be noted the beer label.It is possible to buy beer that does not interfere with androgen levels, although it can be somewhat hard to find. Some microbreweries and brew pubs are now making traditional gruits. Check the brew pubs in your town.

However, the best source is Bruce Williams, a Scottish Brewer who is bringing back the traditional ales of Europe and especially Scotland (i.e., pre-hopped European beers). He has five in production and they can often be found in larger American cities at any store that carries a wide selection of unusual beers. The heather ale is excellent but perhaps more useful would be the traditional pine ale made from the Scotch pine, Pinus sylvestris, whose pollen contains testosterone.It is also best to buy beers that are bottle-conditioned. Bottle-conditioned beers are carbonated in the bottle and as such contain live yeasts. These yeasts (most commonly Saccharomyces cerevisiae) are highly nutritive. They are extremely high in protein, glucose tolerance factor, and B vitamins – especially niacin and B1. Glucose tolerance factor, because it helps regulate blood sugar levels, can help with many of the problems associated with diabetes. Brewer’s yeast contains the highest levels of glucose tolerance factor of any food. It also has been found to reduce serum cholesterol and triglyceride levels and newer research has indicated that S. cerevisiae yeasts may have direct enhancement impacts on androgen activity in the body.

Yikes, you just made me scared of beer with hops!

Most beer is also really high in purines, which can be a problem if you are metabolically prone to gout.

It is interesting that hops is such a problem, particularly given the trend in ultra-hoppy beer. I wonder how it's affecting all the hipsters who obsess over and consume all that ultra-hoppy beer?

Hipsters don't mind. They're also into bread lately and that's about as pro-carb as possible. 

Young males with overabundant testosterone probably don't even feel it.  Older fellas, or those intensively exposed to hops will have more symptoms:  

Go into any home brewing store and check out the veteran employees that handle all the grains and inventory of hops... man boobs every one of them.

!!!

Something to look for if ever I go to a home brewing store.