Although we have evolved a symbiosis with good gut bacteria, we do not continue to make the final bargain.
Looking at the most frequently cited classic papers in the scientific nutrition literature, the original glycemic index paper ranks 10th and has been cited more than 1,000 times. Learning about fruits, vegetables, and cancer prevention ranks 7th. However, in the top four is “Dietary Regulation of the Human Colonic Microbiome: Introducing the Prebiotic Concept,” which has been cited more than 2,000 times.
As I explain in my video “How to Keep Your Microbiome Healthy with Prebiotic Foods,” prebiotics are food ingredients, such as fiber and resistant starch, that feed and nourish the good bacteria in your gut. In general, eating fiber-rich plant foods is a “good foundation for a prebiotic-rich diet.”
Fiber was once thought to be the undigested portion of food and was only known to increase stool volume and regulate bowel movements. Researchers then discovered a series of receptors in the body to which fiber breakdown products fit like a lock and key. When we feed fiber to our good bacteria, they immediately feed us, munching on the fiber and producing short-chain fatty acids. These fatty acids are absorbed into the bloodstream, match receptors expressed on immune cells, and generally have a direct anti-inflammatory effect.
Therefore, the reason plant-based eaters have less systemic inflammation may be due not only to anti-inflammatory molecules rich in plant foods and avoidance of pro-inflammatory molecules found in animal foods, but also because when fed fiber, our good gut bugs produce anti-inflammatory molecules from scratch. To explain how fiber-rich foods can have a protective effect on the body, people who were randomly selected to receive advice about eating fiber-rich plant foods during radiation treatment for cancer not only experienced reduced toxicity during treatment, but the benefits persisted a full year later.
In fact, the benefits of fiber are backed by more than a century of research. Prospective studies have shown “striking reductions” in deaths from all causes, including “total cancer deaths, total cardiovascular disease deaths and incidence, stroke incidence, colorectal cancer, breast cancer, and esophageal cancer incidence.” And when it comes to protection against heart attacks, strokes, type 2 diabetes, and cancer, dose-response relationships suggest that the more fiber you have, the better. Therefore, your fiber intake should be at least 25-29 grams per day. Taking more may provide additional benefits. However, the average American only consumes about 16 grams of fiber each day.
We have co-evolved with our gut bacteria over thousands of years and have come to rely on them in a sort of symbiotic relationship to digest fiber, short-chain fatty acids, and even produce certain vitamins. But we are not following the final stages of negotiations. We’re supposed to be consuming up to 100 grams of fiber a day, but we’re only consuming just 16 grams. The simplest solution to this fiber deficiency is to encourage a fiber-rich plant-based diet.
doctor’s note
100 grams of dietary fiber a day?! Check out “Paleopoo: What we can learn from fossilized feces.”
For more information on prebiotics, see Prebiotics: Taking Care of Our Inner Garden.
