I previously discussed how galacto-oligosaccharides, or GOS, may provide unique or outsized benefits in cultivating healthy bowel flora, particularly bifidobacteria. Enriching bowel flora in bifidobacteria has been associated with a wide array of health benefits ranging from decreases in insulin to improved mental health. If you are interested in GOS and obtaining the beneficial effects of prebiotic fibers, note that these are strategies that should only be pursued if you are wheat/grain-free, have been taking a high-potency probiotic (e.g., 50 billion CFUs per day), and do not have dysbiosis. (Prebiotic fibers will make dysbiosis worse, signaled by abdominal pain, excessive bloating and gas, and diarrhea, since they feed undesirable microbial species as well as desirable.)
How do we go about increasing our intake of GOS? While there are nutritional supplements you can buy (though mostly also contain beta glucan sourced from oats, thereby risking exposure to oat proteins such as avenin that can cross-react with other grain prolamin proteins, such as gliadin of wheat), in the Wheat Belly lifestyle we try to obtain our nutrients from real, whole foods. (The supplement powders are also very expensive, while food sources are inexpensive.)
The food sources of GOS also tend to be digestible carbohydrate-rich: eating too large a portion size, while providing greater quantities of GOS, also can send blood sugar and insulin excessively high and can result in stalled weight loss or weight gain, insulin resistance if repeated many times, and all the phenomena of glycation over time, such as hypertension, heart disease, cataracts, senile dementia, and skin aging. So the key is small portion size. For every food listed, a safe quantity is no more than 1/4 to 1/2 cup cooked per meal. You will also see that the GOS-rich foods listed are all legumes and that, beyond their amylopectin content responsible for potential blood sugar havoc, also contain lectins (indigestible and potentially inflammatory in some people) and phytates (that bind calcium, magnesium, iron, and zinc and make them unavailable for absorption). Once again, the key here is small serving sizes. (Some people also advocate extended soaking to reduce phytate content, but this also reduces the GOS content by around 25%, as well.)
Among the foods rich in GOS to include in your dietary habits are:
- Green peas
- Lima beans
- Kidney beans
Of the 6 to 7 grams of total prebiotic fiber in each 1/2 cup serving of the above legumes, around 3 to 4 grams, or approximately half, are in the GOS form (Tosh 2013; Johnson 2013). From our previous GOS discussion, we know that maximum benefits and tolerability of GOS fibers occurs at an intake in the neighborhood of 5 grams per day, maximum total (GOS, FOS, etc., all summed up) prebiotic fiber benefits at 20 grams per day.
Given the lectin and phytate content of legumes, are we on balance better off by getting this quantity of GOS while staying low in serving size? I believe we are, particularly on the background of having eliminated the far worse effects of wheat and grains. I also believe it is important that, should you add GOS-rich foods to your regimen, it also occurs alongside other sources of prebiotic fibers, such as inulin, FOS, raw potatoes/raw potato starch, green bananas, etc. Is it important to obtain GOS every day if other such prebiotics have been incorporated into the diet? Unclear, but my gut sense (ha ha!) is that, as human habits over the millennia were characterized not by dietary monotony, but by variety, I suspect it is most important that you include varied sources of prebiotic fibers every day and that GOS-rich sources are just one ingredient in the overall effort but does not necessarily have to be a daily habit.
While I highlight the exceptional effects of GOS for bowel flora here, it is important to bear in mind that no single prebiotic fiber will suffice to fully cultivate a collection of healthy bowel flora because different microbial species “prefer” different fibers, depending on their genetic capacity to metabolize such fibers. While some prefer GOS, others prefer FOS, inulin, or other fibers. Variety is the key, as we are also trying to cultivate wide species diversity. In every study of the bowel flora of primitive people, such as the Hadza of sub-Saharan Africa, largely unexposed to antibiotics, plastics, pesticides, herbicides, grains and all the other factors that disrupt bowel flora composition, the one feature that stands out is a wide diversity of species, as compared to the narrower range of species in modern people. One way to cultivate species diversity is to vary your prebiotic fiber routine; GOS is simply another prebiotic fiber to add to the list, though one that may have special importance.
In coming weeks, I shall be posting some Wheat Belly recipes tweaked to include some of these fibers sources with portion sizes controlled in order to avoid all the adverse consequences of excessive carbohydrate exposure.