The single most common reason people quit the Paleo Diet is digestive distress. Sometimes the gut just isn't ready for healthy food, especially vegetables and fruit that are high in fiber. Whether you have a chronic digestive issue or not, but especially if you do, it is important to prepare your digestive tract for healthy eating. The way to do this is by providing it with prebiotics so it can develop healthy probiotics.

Prebiotics and probiotics are especially necessary for people who have irritable bowel syndrome, inflammatory bowel disease, and Crohn's disease, but it's not venturing too far to say that no one can be really successful on a Paleo Diet, or any other diet, without the right microbial balance in the gut.

What Are Probiotics?

Probiotics are microorganisms that live inside the human body and assist it with its functions. Most probiotics are bacteria.

Probiotic bacteria exist in astonishing numbers in every human body. The body contains about 10 trillion (10,000,000,000,000) cells with human DNA. It contains about 100 trillion (100,000,000,000,000) bacteria.

At least 500 and possibly as many as 2,000 different species of bacteria live inside the human digestive tract. Some species are helpful, or probiotic, while others are harmful, or pathogenic (and some are just along for the ride).

The sheer number of probiotic bacteria helps keep pathogenic, disease-causing bacteria in check. Additionally, probiotic bacteria engage in cross-talk with cells of the immune system, letting the immune system know when they can handle the job of killing the “bad” bacteria so the immune system does not have to release inflammation. If you have a digestive condition fueled by chronic inflammation, probiotic bacteria can be very helpful to keeping symptoms at a minimum.

What Are Prebiotics?

Prebiotics are the food for the helpful bacteria we know as probiotics. If the prebiotics are not present when the probiotics are introduced to the intestinal tract, friendly bacteria can never grow and multiply.

Prebiotics are the complex carbohydrates in plant foods that our own bodies do not make the enzymes to digest. In the plants in which they are found, these complex carbohydrates, generally termed “fiber,” served as a “skeleton” for the plant's stems or leaves. These fibers may be oligosaccharides, fibers which can ferment while they are in the digestive tract, or fructooligosaccharides, fibers which pass through the digestive tract as “scrubbers” until they eventually meet fermenting bacteria which break them down into sugars with the release of gas.

Which Foods Provide the Prebiotic Nutrients That Probiotic Bacteria Need?

Certain foods are especially rich in fiber. You need to eat these foods before you take a probiotic supplement, and you need to emphasize these foods at the beginning of your Paleo Diet.

Ground (or at least well-chewed) almonds are great food for healthy bacteria. Clinical studies have found that it is the combination of fiber and essential fatty acids in the oil in the nut that give probiotics a boost.

Artichokes, chicory, and jicama are a great source of inulin (not to be confused with insulin), an indigestible starch the plant uses to store energy for itself. Inulin helps the small intestine absorb calcium and magnesium from other foods. It buffers the release of sugar from starchy foods, effectively lowering the glycemic index of other foods with which it is eaten.

Inulin is a major food for the Bifidobacteria, a group of probiotic bacteria that keep disease-causing bacteria from forming a biofilm that lines the small intestine, prevents the formation of some of the toxic byproducts of digestion linked to colon cancer, and helps the infant's digestive tract break down the sugars in milk.

Asparagus is a good source of oligosaccharides. It also provides folic acid, which helps the body reduce the production of artery-inflammatory homocysteine, and potassium, which helps  with energy and muscle tone.

Coffee, especially espresso, contains fibers that feed probiotic bacteria. Coffee is also the single greatest source of antioxidants in most North American diets.

Miso is a fermented food, but since it's usually cooked, it typically offers no probiotic value. Adding a small amount of miso as a condiment on fish or chicken, however, offers a few additional friendly bacteria. Small amounts of miso are not likely to upset your diet otherwise.

Garlic, leeks, and onions, apples, bananas, spinach, tomatoes, and especially Jerusalem artichokes (sunchokes) and the related vegetable yacón contain large amounts of fructooligosaccharides. They are naturally sweet, and they also feed Bifidobacteria. Because the fibers in these foods are fermentable, however, it is important to limit yourself to just 1 serving of no more than 2 of these foods per day (a little onion or garlic for flavor is OK) until your colon builds up the bacteria it needs to digest them. As your colon grows more Bifidobacteria, which digest fructooligosaccharides with a minimum of gas production, the probiotic bacteria will kill off the E. coli, Klebsiella, and yeast that release the especially smelly gases of flatulence.

Which Probiotics Address Specific Digestive Problems?

The probiotic Lactobacillus reuteri is especially helpful for women who are pregnant or nursing. Babies exposed to this probiotic are less likely to experience colic, and less likely to develop eczema, asthma, or hayfever, due to its cross-talk with the immune system. Lactobacillus reuteri is avaiable as a supplement by BioGaia.

Bifobacterium lactis Bb12 lowers the pH of the colon so that harmful bacteria are less likely to multiply. (While “acidity” is considered a bad thing inside the body, lowering pH inside the colon is healthy. What's bad for pathogenic bacteria is good for humans.) This probiotic also releases beneficial fatty acids that the lining of the small intestine and colon can use for food, and which protect against cancer. A good source of a bacterium very closely related to the probiotic mentioned in the medical literature is Immuprobio.

If you just have to indulge in dairy products, go for yogurt, and make sure you buy products that contain live, active strains of Streptococcus thermophilus (a good species of “strep”) and Lactobacillus delbrueckii subsp bulgaricus. These bacteria make their own lactase in the small intestine, breaking down the milk sugar so it does not ferment in the colon. The only way to be sure the yogurt you buy in the store has live cultures of these probiotic bacteria (heat-treated or pasteurized cultures not doing your body any good) is to look for the National Yogurt Association (NYA) seal on the product. However, be aware that the NYA seal only certifies that the production contains 100,000,000 live organisms per serving. Some supplements contain as many as 50,000,000,000 live organisms per capsule. Want to be sure you are getting the right probiotic bacteria in yogurt? Make your own, with a yogurt starter such as Natren Yogurt Starter.

And if you have irritable bowel syndrome, the product of choice is Align Probiotic Supplement, made by Procter and Gamble. We'll be discussing how to deal with irritable bowel syndrome while on the Paleo Diet in much more detail elsewhere on this site.