If you look at the classics, the most frequently cited articles in the scientific nutrition literature, the original glycemic index paper comes out at #10, cited over a thousand times. Learning about fruit, vegetables, and cancer prevention was a hallmark. But hitting the top five, cited more than 2,000 times, “Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics.”
Prebiotics are the food components that feed and nourish the good bacteria in our gut, like fiber and resistant starch. In general, eating high-fiber plant foods is a good foundation for a prebiotic-rich diet.
Once upon a time, fiber was just thought of as just the undigested component of foods, known only for bulking up our stools and keeping our bowels regular. Then, we discovered an array of receptors in the body in which fiber breakdown products fit in like a lock-and-key. We feed our good bacteria with fiber, and they feed us right back, munching the fiber and creating short-chain fatty acids that get absorbed into our bloodstream and fit into these receptors that are expressed on immune cells, and generally mediate a direct anti-inflammatory effect.
So, the reason for lower systemic inflammation in plant-based eaters may not just be due to the abundance of anti-inflammatory molecules in plant foods, or the avoidance of pro-inflammatory molecules in animal foods, but from the production of anti-inflammatory molecules from scratch by our good gut bugs when we feed them fiber. Just to give you an idea how protective fiber-rich foods can be, those randomized to get advice to eat fiber-rich plant foods during radiation therapy for cancer didn’t just experience reduced toxicity during the treatments, but even a full year later.
Indeed, the benefits of fiber are supported by more than a century of research. Prospective studies show striking reductions in death from all causes put together, including “total cancer deaths, total cardiovascular disease deaths and incidence, stroke incidence, and incidence of colorectal, breast, and esophageal cancer.” And “dose-response relationships” suggest that the more the better, in terms of protecting against heart attacks and stroke, type 2 diabetes, and cancer. So, at a minimum, fiber intakes should be no less than 25–29 grams per day, with additional benefits likely to accrue with higher intakes. Yet, the average American only consumes about 16 grams of fiber per day.
We have co-evolved over millennia with gut bacteria to the point of reliance on our good gut bugs, a kind of symbiosis for fiber digestion and the production of short-chain fatty acids, and even certain vitamins. Yet, we’re not holding up our end of the bargain. We’re supposed to be providing up to 100 or so grams of fiber a day, and we are barely passing along a measly 16 grams. The simplest solution, the simplest approach to remedy this lack of dietary fiber, is to encourage consumption of whole food plant-based nutrition.
