It’s common knowledge that fiber helps with digestion and lowers the risk of certain diseases, but there are many types of indigestible or poorly digestible carbohydrates. The two big ones are cellulose and lignin, the most abundant organic polymers on Earth. Some other examples you might have heard of are waxes, chitins (the hard shells on the outside of shellfish and insects), pectins (a common food additive in jelly, usually from citrus fruit), and some starches.
In a study this month in the Nutrition Journal, researchers sought to find out what other health benefits indigestible carbohydrates might have besides the ones commonly known. In particular the researchers looked at the ingestion of barley kernels, which are high in fibrous materials and digestion-resistant starches. They speculated that the promotion of digestion, especially the boon to the intestinal microflora, would have further-reaching and longer-lasting effects than we previously knew.
Researchers had the subjects in the study consume barley kernels versus a control. They tested the blood of the participants and had them come back for a few more meals in the following day. They did this a few times with the barley and the control for every person being tested.
What the researchers discovered was substantial. The indigestible carbohydrates improved glucose regulation, meaning blood sugar was more stable for up to sixteen hours after eating the barley kernels. There was also a decrease in the indicators of inflammation, fewer circulating free fatty acids, and less hunger the following day. Participants actually ate less at lunch the next day. They ate a little less at breakfast too, but not significantly.
Interestingly the barley kernel also stimulated the release of a substance called GLP-1. This peptide often stimulates the release of insulin. Since the release of GLP-1 continued into the next day, higher insulin in a fasted state would normally be a bad thing because it would cause low blood sugar, reduce insulin sensetivity, and possibly increase hunger. However, researchers in this study discovered that although GLP-1 was elevated the following day, it did not have it’s normal insulin stimulating property, and actually helped to restore glucose sensetivity. This means the indigestable carbs helped return the body to homeostasis faster than without.
Now it’s not clear if all of these effects are solely attributed to the types of fibers and starches in barley, but it would be weird to me if this were true. In fact, I suspect that similar benefits would have been noted with other fiber and starch combos, and indeed, other forms of indigestible carbs as well. But I would like to see similar studies that focus on vegetable-based indigestible carbs, which I believe are healthier for other reasons.
What is clear is that fiber and other indigestible carbohydrates are a very important part of nutrition. Because healthy glucose metabolism and dietary control are cornerstones of health and fitness, the inclusion of fiber should be at the forefront of your meal planning.
1. Elin V Johansson, et. al., “Effects of indigestible carbohydrates in barley on glucose metabolism, appetite and voluntary food intake over 16 h in healthy adults,” Nutrition Journal 2013, 12:46
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