October 2015 update: Scientists are continuing to identify various food sources of fermentable fiber, including sources of “pre-biotic” fermentable fiber–the kind that provides the healthy bacteria for your gut to ferment. I’ll be updating this list as new studies come out. If you haven’t read through it in a while, you might want to do so.
Just when you thought you could tell the differences among various kinds of fiber, scientists start dishing out a brand new term for our anti-cancer diets: fermentable fiber.
For years, researchers had us making distinctions between soluble fiber, the kind that forms a gel with water, slows your digestion and keeps your blood sugar even, and insoluble fiber, which bulks up your stool and prevents constipation. Now “fermentable “ is becoming the new buzz word (although scientists have known about it for a long while.)
Healthy bacteria in your gut feed on fermentable fiber and turn it into butyrate and other short chain fatty acids. In turn, those fatty acids control appetite and blood sugar, regulate inflammation and improve your immune system. Butyrate also helps quiet genes that drive cancer and heal the intestinal lining, often damaged by chemo.
Some types of fermentable fiber even stimulate the growth of those beneficial bacteria as well. You’ve heard of probiotics, no doubt? Meet prebiotics, the prequel.
Prebiotic fibers contain the raw material to produce good bugs. And your health is dependent on good bacteria in the gut overpowering the bad.
So what foods are sources of fermentable and prebiotic fiber? Fermentable fiber is in virtually all fruits, vegetables and legumes. It’s also present in grains, nuts and seeds.
Here’s a list of sources of fermentable fiber based on research compiled by Australia’s Monash University and dietitian Jo Anne Hattner, author of “Gut Insights.” Foods rich in prebiotic fiber are indicated in italics.
Although the allium family and Jerusalem artichoke are the traditional superstars of pre-biotic fiber, new research is showing that many foods rich in polyphenols may be pre-biotic. Think color.
And because polyphenols and fermentable fiber concentrate in the outer layers of plants, choose small versions of plants (wild blueberries over domestic ones, for example) and eat the peel.
● Vegetables: alliums, especially bulbs (garlic, leeks, onions, scallions, shallots), artichoke and Jerusalem artichoke, asparagus, bamboo shoot, beets, burdock root, savoy cabbage, cassava, cauliflower, celery, chicory and dandelion root, daikon, fennel bulb, greens (collards, dandelion, kale, mustard, salsify, spinach) , jicama, mushrooms, okra, butternut squash, sweet potato and yam.
● Fruits: apples, avocado, Ladyfinger bananas, berries, guava, kiwi, mango, pears, persimmons, pomegranate, stone fruits (apricots, cherries, peaches, white peaches, plums, nectarines), tomatoes, watermelon, some dried fruits
● Grains/pseudo-grains: amaranth, barley, buckwheat, corn, couscous, oats, quinoa, brown rice, spelt, teff, whole wheat
● Nuts and seeds:almonds, cashews, chestnuts, flaxseed, hazelnuts, pistachios
● Legumes: all dried beans and dried peas, including soybeans and lentils; fresh peas; hummus. Keep in mind that with canned legumes, much of the fermentable fiber ends up in the liquids.
● Other Foods: agave, green tea, honey, tomato sauce