by Dr. Gabe Mirkin, M.D.
Sugar is harmful when too much of it enters the bloodstream at one time. The difference between sugar IN fruit and all of the refined sugars is that fruit contains many other components that markedly delay the entrance of sugar into your bloodstream.
Refined sugars are extracted from various plant parts (sugar cane, sugar beets, corn, grapes, apples, flowers, maple trees) and concentrated so all of the fiber and most of the other nutrients in the plant are removed. Once sugar has been removed from its plant source, it can pass very quickly from the stomach into the intestines and cause a harmful high rise in blood sugar.
Definition of Sugars
All carbohydrates are made up of sugars alone, or in groups of twos, three and fours up to hundreds, thousands and millions. Before any carbohydrate can be absorbed from your intestines, it must be broken down into single sugars because only single sugars can be absorbed through your intestines. Of the many single sugars, only four can be absorbed through your intestines: glucose, fructose, galactose, and mannose. Glucose is the only sugar that is allowed to circulate in your bloodstream. The other three go from your intestines to your liver where they are removed from circulation and are not allowed to re-enter the bloodstream.
How High Rises in Blood Sugar Cause Damage
When blood sugar levels rise too high, sugar sticks to the outer surface of cell membranes to destroy the cells. That is why diabetes damages every cell in your body. It causes heart attacks, strokes, blindness, deafness, dementia, impotence, loss of blood flow to your legs, and so forth. A major key to preventing diabetes, heart attacks, strokes and even certain cancers is to prevent blood sugar levels from rising too high.
Why All Sugared Drinks Increase Risk for Diabetes, Weight Gain and Cell Damage
When solid food enters the stomach, the pyloric sphincter at the end of the stomach closes to prevent food from passing into the intestines until it is turned into a liquid soup. Only then does the liquified food pass into the intestines. Since sugar in liquid form passes immediately into the intestines, all sugared drinks cause a high rise in blood sugar (Adv Nutr, 2013 Mar 1;4(2):220-5). Many studies show that fruit juices increase risk for heart attacks, diabetes, and obesity, while eating fruit appears to help protect you from these diseases (Curr Opin Clin Nutr Metab Care, 2013 Jul;16(4):478-84).
Why Fruit Is Healthful and Refined Sugar can be Harmful
In whole fruit, the sugars are bound up with fiber that slows the absorption of sugar from the intestines and this reduces the rise in blood sugar when you eat it. Fruits are also loaded with antioxidants that help prevent the inflammation that causes insulin resistance. You need some sugar for energy, but unless you are exercising vigorously, you don’t need very much. Small amounts of sugar are stored as glycogen in your muscles and liver for future use, but then all left-over sugar is converted to triglycerides, fats that block insulin receptors and cause blood sugar levels to rise even higher.