Based on the existing data, the World Health Organization (as well as the USDA, AHA, etc.) recommends that added sugars be limited to no more than 10% of total calories and suggests that reducing sugar to 5% of calories may confer additional risk reduction.
http://nutritionovereasy.com/2015/05/is-sugar-nutritionally-necessary/
Hypoglycemia (low blood sugar). Sometimes blood sugar levels fall too low. This is called hypoglycemia. Hypoglycemia can happen when a person eats too little food, takes too much insulin or diabetes medicine, or is more physically active than usual. Often hypoglycemia happens suddenly and sometimes there is no explanation for why it occurs.
https://www.health.ny.gov/diseases/conditions/diabetes/controlling_blood_sugar_importance.htm
Soda, for example, contains a lot of added sugar, which might give you short-term energy, but it also provides nothing in the way of essential nutrients such as protein, fiber, calcium and vitamin C. Further, most foods with added sugars are high in calories.
http://www.livestrong.com/article/409694-importance-of-sugar-in-the-human-body/
For most people with diabetes, a healthy range is between 90 and 130 mg/dl before meals and less than 180 mg/dl at one to two hours after a meal (see chart below). A doctor or health care provider can tell a person with diabetes about how and when to test blood sugar.
https://www.health.ny.gov/diseases/conditions/diabetes/controlling_blood_sugar_importance.htm
The only scenario that I can think of where concentrated sugar might have an actual nutritional function is for endurance athletes. If you’re exercising hard for more than 60 minutes at a time, consuming simple sugars is the most efficient way to provide fuel for depleted muscles.
http://nutritionovereasy.com/2015/05/is-sugar-nutritionally-necessary/
Of course, almost 100% of the calories in vegetables are from sugars and we wouldn’t want to eliminate them because they include so many essential nutrients! I think what you (and they) are really talking about is added or concentrated sweeteners, like white sugar, honey, molasses, etc.
http://nutritionovereasy.com/2015/05/is-sugar-nutritionally-necessary/
Very high blood glucose may also make you feel sick to your stomach. If your blood glucose is high much of the time, or if you have symptoms of high blood glucose, call your doctor. You may need a change in your diabetes medicines, or a change in your meal plan. It's important to treat hyperglycemia as soon as you detect it.
https://www.health.ny.gov/diseases/conditions/diabetes/controlling_blood_sugar_importance.htm
Sugar provides energy to your muscles and acts as a source of energy for your brain and nervous system. You also need sugar because it helps metabolize fats and prevents your body from using protein as energy. Glucose, for example, gets broken down in a series of chemical reactions that give off energy, which fuels your cells. A hormone called insulin is involved in the process, too -- it's released when you eat sugar and tells your cells to absorb the glucose so they can use it as a source of energy.
http://www.livestrong.com/article/409694-importance-of-sugar-in-the-human-body/
Sugar cane — native to Southeast Asia — first made its way to the New World with Christopher Columbus during his 1492 voyage to the Dominican Republic, where it grew well in the tropical environment.
http://www.livescience.com/4949-sugar-changed-world.html
Q. I work with girls with eating disorders and the topic of sugar keeps coming up. There is a lot of info in the media targeting sugar, and diets that encourage you to “quit” sugar completely. I’d really like to be able to give the girls I work with an evidence-based explanation for why cutting out sugar completely isn’t a good idea.
http://nutritionovereasy.com/2015/05/is-sugar-nutritionally-necessary/
why was the sugar necessary?
Sugar is necessary because it helps metabolize fats and prevents your body from using protein as energy. Suger is necessary because it helps metabolize fats and prevents your body from using protein as energy.