Why You’re Probably Not Eating Enough Fiber

Fail to feed your bacteria properly and they’ll start eating you.

I don't want to frighten you, but right now there are around 100 trillion bacteria chomping away in your gut. It's a hungry job being a microbe.

There's something like three pounds of bacteria lining your intestinal tract, probably made up of about 500 different species. I say probably, because everyone's different. Although you and I share around 99.5% of the same DNA, our microbiomes almost certainly vary widely, one of the reasons it's so fascinating to explore yours with a uBiome test.

The thing is, a lot of your bacteria keep you healthy – they're helping you digest food and synthesize vitamins, for instance. Doesn't it therefore make sense, in return, to keep them healthy too? One way to do that is to ensure they're properly fed, and here's where things get interesting and actually pretty serious.

You see, a prime source of bacterial nutrition comes from fiber, but most people's diets are vastly underrepresented in this respect. An average individual in the West gets roughly 15 grams of fiber a day, which is nowhere near enough. In fact, The Institute of Medicine recommends women should get 25 grams per day, while men should consume 38 grams.

Well, yes. Actually it matters enough for the U.S. government's dietary guidelines to label dietary fiber as a “nutrient of concern”. A public health issue, no less. It's long been accepted that having enough fiber in your diet can contribute to a feeling of fullness (so you know when to stop eating) and what gastroenterologists politely call “healthy laxation” (regularity in the bowel movement department).

More seriously, a low fiber diet may also be associated with the risk of developing various conditions, including heart disease, diabetes, diverticular disease, and constipation. But now studies are showing that failing to provide enough fiber to the gut's bacteria may lead to them feeding on the gut itself. Researchers at the University of Michigan Medical School found that when mice were placed on a fiber-free diet, their microbes began to eat away at the gut's protective mucus lining, potentially triggering inflammation and disease.

So fiber's important. How easy is it to get enough, then?

Test your gut to see if you're getting enough fiber.

Well since most of us are only getting around half as much as we should, clearly not very. Eating a salad every night, for instance, would only provide two or three grams of fiber. Dieticians say it's best to get fiber as part of your regular diet, but supplements can help. In a small study at the University of Illinois at Urbana Champaign, adults ate a fiber-enriched snack bar containing 21 grams of fiber once a day for three weeks.

The good news?

Their gut bacteria composition shifted from a profile similar to that found in obese individuals to one which was more like the microbial make-up of lean people.

The bad news?

The minute the experiment was over, participants' microbiomes returned to the way they'd been before the experiment began. So to keep your gut healthy, it's vital to eat a high fiber diet every day. Whole grains, legumes, vegetables, and fruits. Raspberries, bran, split peas, artichokes. Whatever roughage you like.

Your bacteria will thank you for it. Split peas for dinner tonight, anyone?

Fiber-Famished Gut Microbes Linked to Poor Health

Shift in gut bacteria observed in fiber supplement study may offer good news for weight loss

Fiber supplementation influences phylogenetic structure and functional capacity of the human intestinal microbiome: follow-up of a randomized controlled trial

Think Globally, Act Locally: Regulated Deployment of Polysaccharide Degradation Abilities by our Symbiotic Gut Bacteria