Health: Good carbohydrates! Understanding resistant starches and soluble fibers
One time I was checking the nutrition facts of chia seeds and noticed something very strange: although 100 grams of chia seeds have 41.2 grams of carbohydrates, it’s glycemic index is just 1 (one!) with a glycemic load of also one. This is much lower than lettuce, that has a GI of 15 or even kale, that has a GI of 4.
At first I thought it must be a mistake, but after checking other sources I saw it was actually correct information. How can this be? The answer, I found out, resides in the difference between starches (and other types of carbs) and soluble fibers. Although counted as carbohydrates in the nutrition tables, soluble fibers are a completely different animal.
Different from insoluble fibers (like the ones present in wheat bran and in the skin of fruits and vegetables, for example) that are just a type of bulk that is not absorbed by the body at all, soluble fibers do get digested and converted into energy, generating about two calories per gram.
However, instead of being converted into glucose, like in the case of simple starches, soluble fibers are complex starches that our bodies can’t directly digest: they can only be digested by the bacteria living in the gut. They slowly convert the soluble fibers into short-chain fatty acids, a very healthy compound that reduces the risk of inflammatory diseases, type 2 diabetes, obesity, heart disease and other conditions. Not only that, but they can be very easily absorbed by the body and converted into energy. In other words, the soluble fibers feed the good bacteria in the gut (that’s why they are also called prebiotics), and they reciprocate by giving us a lot of different health benefits and also a stable supply of energy in the form of these fatty acids.
Due to this particularity, soluble fibers don’t raise the blood sugar and don’t provoke the release of insulin at all. Quite the opposite: they make the absorption of sugars and staches much slower, and therefore contribute to reduce the glycemic index and glycemic load of other foods that you may eat alongside it.
From the 42.6 grams of carbs present in 100 grams of chia seeds, 34.4 are soluble fibers. Therefore, although they also have 8.2 grams of starches, the presence of the fiber makes it be absorbed so slowly that they don’t raise the blood sugar at all.
One of the secrets of good health is to minimize the ingestion of simple starches (like rice, wheat, corn, etc.) and to increase the ingestion of foods rich in soluble fibers, like most vegetables, berries, nuts, barley, oats, lentils, avocados, etc. and to always combine high glycemic foods (like rice or potatoes, for example) with ingredients that are rich in soluble fibers.
It's difficult to overstate the importance of good gut bacteria for our health. Not only do they help with the digestion process and protect us from the proliferation of bad gut bacteria, but they produce a good chunk of the vitamins and other important nutrients that the body needs. In the Ayurveda it is mentioned how vitamins are created by the fire of digestion. It may seem hard to believe at first, but it's actually scientifically correct, and the only reason this happens is because of good gut bacteria. One that has his population of good bacteria destroyed due to a bad diet or the use of antibiotics can have all kinds of problems, not only related with digestion. An imbalance in the gut bacteria will affect even our mood, ability to focus and productivity. That's yet another reason why soluble fibers are so important.
Finally, there are the resistant starches. It can be considered a third type of fiber. The main characteristic of this type of starch is that it’s resistant to digestion. As a result, it’s digested slowly, also not contributing much to raise the blood sugar. Resistant starches are found in legumes, certain grains (like barley and oats), seeds, roots, etc.
The problem with resistant starches is that they can be easily converted into simple starches if they are heated for long enough. The higher the temperature, and the longer the cooking, the more they break down, resulting in a progressively higher GI and GL.
Potatoes, for example, are normally accepted as a starchy food. However, raw potatoes are actually very rich in resistant starches. If one would eat raw potatoes, it would not raise the blood sugar at all, almost like chia seeds. When potatoes are boiled, the GI rises to 59 (or 78 if mashed), but if they are baked, it rises to 85! Cooked sweet potatoes have a GI of 44 (lower than white potatoes) but when baked their GI skyrockets to 94, almost as high as pure glucose.
From this we can see that not just the individual ingredients, but also the way they are combined and prepared, should be taken into consideration. In general, the more food is cooked and crushed into small particles, the higher their GI becomes. That's why, as far as possible, we should try to take grains and tubers as close to their natural state as possible, cooking for a shorter time and preferring whole grains instead of polished or refined ones.