Medically reviewed by Onikepe Adegbola, MD, PhD
All that we now know about sugar is that it is not an ingredient of choice in an ideal diet. Most of the research and study is based on how a sugar-rich, high-fat, and low-fiber diet can cause diseases. However, these lifestyle diseases are a combination of many factors, and they cannot be attributed to only sugar intake. Many other body functions require and use the sugar consumed in our diet for various processes.
What is Sugar?
Sugar is not merely the white granules you may add daily to your tea, coffee, or juices.
It is much more than that. Sugar is available in many forms depending on its source and how it is processed. Some examples of sugar in daily diet are raw sugar, brown sugar, fruit sugar, corn sugar, milk sugar, and beet sugar. In addition, sugar alcohols and natural sugars are found in fruits, vegetables, milk products, and food grains. And lastly, the added sugar, which is refined sugar, ‘the table sugar,’ is usually available to us in the form of crystals, syrups, or powders.
Sugars are divided into monosaccharides and disaccharides. For example, sucrose is a disaccharide that splits into glucose and fructose. Glucose is the energy-building compound of a body. It is less sweet than other sugars. All carbohydrates are broken down into glucose.
Fructose is found in most fruits and vegetables and causes several adverse effects on your body in high quantities. The study “Effect of glucose, sucrose, and fructose on plasma glucose and insulin responses in normal humans: comparison with white bread,” published in the European Journal of Clinical Nutrition, enlists the adverse effects of fructose as compared to other sugars.
Sugar also means all types of carbohydrates that are a part of our diet, including sucrose that we add to our food and all-natural and artificial sweeteners. Sugars that occur in our diet are glucose, sucrose, and fructose. As glucose is the simplest product of carbohydrate breakdown, it is taken up by the blood and used for energy production.
This is termed blood sugar. Our body produces insulin to help transport glucose to the blood cells and tissues for energy production. It eliminates the excess unused glucose via the kidneys. Excess blood sugar is stored in the liver and muscles with the help of insulin. This stored sugar is released and utilized when blood sugar levels fall.
Added sugar is sucrose. It is a compound of glucose and fructose added to food and drinks to enhance their taste. It is a tiny chain compound that breaks down and releases glucose faster in the blood. This results in an instant burst of energy, but excess sucrose can lead to insulin and glucose resistance.
Most sugars are broken down and metabolized in the body in the small intestine. Some theories mention that sugar can pass on to the large intestine in the presence of large quantities, but this has not yet been proven. The bacterial colonies are occupied mainly in the large intestine; therefore, sugar influencing the regulation of body microflora is not very well supported in scientific studies.
Does Sugar Help Digestion?
Sugars are known to stimulate the digestive system to release water and electrolytes. This can loosen our bowel movements.
In a study published in Nature Neuroscience titled Sweet signals are relayed from the gut to the brain, it was reported that eating sugar activates the guard cells and signals them to release glutamate, which in turn stimulates the Vagus nerve. The Vagus nerve acts as a regulatory body in internal functions like digestion. So a moderate amount of sugar consumption may aid the smooth running of your gut (FDA describes it as 10% of your total daily calorie requirement).
What Harm Can Excess Sugar Cause?
Sugars require enzymes to be broken down. In the presence of excess sugars and fewer enzymes, sugar is not taken up by the body properly, and this causes uncomfortable digestive symptoms like pain, gas, constipation, diarrhea, and bloating. It also leads to malabsorption, which can lead to nutrient deficiencies and unexplained weight loss.
FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polysaccharides) sugars are primarily responsible for speeding up digestion, causing symptoms of gas bloating and diarrhea.
Sucrose increases movement in the gut in large quantities leading to diarrhea. Fructose present in fruits and added as an added sugar in fruit juices and soft drinks can be responsible for causing diarrhea. Artificial sweeteners like saccharin can also cause loose tools if taken in large amounts.
Normal sugar levels are known to help provide the energy required by the body for digestion. But excess sugar, especially fructose and sucrose, causes impaired digestion.
Fructose is broken down and metabolized only in the liver. Fructose overload can impair digestion, as digestion takes place because of enzymes released by the liver.
A large part of water absorption occurs in the large intestine. But it is seen that the presence of excess sugars causes the water to re-enter the large intestine or fluctuate its proper absorption.
So why do we crave sugars after eating our food? Why is it customary in so many traditions to eat desserts after meals? One of the answers is that digestion requires energy. Digesting heavy meals requires a higher amount of energy. Our primary source of energy comes from sugars. These consumed sugars provide the body with the instant supply of energy needed to digest the heaviest of meals.
All kinds of sugars are not harmful to the body when taken in small quantities. Sugars within dietary limits are beneficial for digestive processes. Excess sugar can cause irritable bowel syndrome, diarrhea, constipation, gas, and bloating. In addition, the high sugar, high-fat, and low fiber diet is responsible for the growth of harmful bacteria in the body rather than sugar alone. High sugar quantities can cause water re-entry into the large intestine, causing diarrhea.
Buchanan, K. L., Rupprecht, L. E., Kaelberer, M. M., Sahasrabudhe, A., Klein, M. E., Villalobos, J. A., Liu, W. W., Yang, A., Gelman, J., Park, S., Anikeeva, P., & Bohórquez, D. V. (2022). The preference for sugar over sweetener depends on a gut sensor cell. Nature Neuroscience, 25(2), 191–200. https://doi.org/10.1038/s41593-021-00982-7
Carbohydrates and blood sugar. (2013, August 5). The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/
Is something in your diet causing diarrhea? (2022, April 7). Harvard Health. https://www.health.harvard.edu/diseases-and-conditions/is-something-in-your-diet-causing-diarrhea
Lee, B. M., & Wolever, T. M. (1998). Effect of glucose, sucrose, and fructose on plasma glucose and insulin responses in normal humans: comparison with white bread. European Journal of Clinical Nutrition, 52(12), 924–928. https://doi.org/10.1038/sj.ejcn.1600666
Ochoa, M., Lallès, J.-P., Malbert, C.-H., & Val-Laillet, D. (2015). Dietary sugars: their detection by the gut-brain axis and their peripheral and central effects on health and diseases. European Journal of Nutrition, 54(1), 1–24. https://doi.org/10.1007/s00394-014-0776-y