Blood sugar is a term used to refer to levels of glucose in the blood. Blood sugar concentration, or serum glucose level, is tightly regulated in the human body. Glucose, transported via the bloodstream, is the primary source of energy for the body's cells.

Normally, blood glucose levels stay within narrow limits throughout the day: 4 to 8 mmol/L (70 to 150 mg/dL), thus the total amount of glucose in the bloodstream is 3.3 to 7g (5L blood estimated). Levels rise after meals and are usually lowest in the morning, before the first meal of the day.
In diabetes the blood sugar level moves outside these limits until treated. Even with good control of diabetes, the blood sugar level will still at times drift outside this normal range.
Low blood sugar, or hypoglycemia is a commonly perceived problem. In actuality, while some or many of the symptoms may be present, it is rarely documented. The presence of true, documented hypoglycemia in the absence ofdiabetestreatment is cause for a comprehensive evaluation by an endocrinologist. It usually affects those at the extremes of age, such as small babies and the elderly, but may happen at any age. Generally, low blood sugar is defined as a serum glucose level (the amount of sugar or glucose in your blood) below 60 mg/dL. However, hypoglycemia as a medical problem is diagnosed by the presence of 3 key features, also known as the Whipple triad. The Whipple triad consists of the following: (1) symptoms consistent with hypoglycemia, (2) a low plasma glucose concentration, and (3) relief of symptoms after the plasma glucose level is raised. Symptoms of low blood sugar, however, usually begin at a level below 60 mg/dL. Some people may feel symptoms before this level. A level of 50 mg/dL is thought to affect brain function.

• The body regulates its level of glucose, a primary source of energy for the brain, muscles, and other cells, by the actions of different hormones such as insulin insulin,glucagon , and epinephrine.
• Both insulin and glucagon are manufactured in the pancreas, an organ that assists the digestive tract. Special cells in the pancreas called beta cells make insulin and alpha cells make glucagon.
• The role of insulin is to help in the absorption of glucose in the blood by causing it to be stored in the liver or used by other cells in the body.
• Glucagon increases the amount of glucose in the blood by breaking down stored glucose called glycogen and releasing it into the bloodstream.
• Insulin and glucagon are usually correctly balanced if the liver and pancreas are healthy.
• Epinephrine (or adrenalin), traditionally referred to as a stress hormone, is made in the adrenal gland and in certain cells in the central nervous system. It also elevates blood glucose levels by making glucose available for the body during a time of stress. When this mechanism is not working properly, low blood sugar can result. Other hormones, like cortisol made by the adrenal gland and growth hormone made by the pituitary gland, also help in raising the level of blood glucose.

It’s recommended than you keep it lower than 100mg/dl. The excess sugar in the blood that’s caused by diabetes damages the arteries by inactivating a specific phosphokinase, a substance that makes it possible for your arteries to smoothly dilate and contract. Without that phosphokinase, the risk of holes or cracks appearing at junctions in the arterial walls increase dramatically. So we should avoid foods that are high in simple sugars and saturated trans fats.

Carbohydrates supply the body with the energy it needs to function. They are found almost exclusively in plant foods, such as fruits, vegetables, peas, and beans. Milk and milk products are the only foods derived from animals that contain a significant amount of carbohydrates.
Carbohydrates are divided into two groups-simple carbohydrates and complex carbohydrates. Simple carbohydrates, sometimes called simple sugars, include fructose (fruit sugar), sucrose (table sugar), and lactose (milk sugar), as well as several other sugars. Fruits are one of the richest natural sources of simple carbohydrates. Complex carbohydrates are also made up of sugars, but the sugar molecules are strung together to form longer, more complex chains. Complex carbohydrates include fiber and starches. Foods rich in complex carbohydrates include vegetables, whole grains, peas, and beans.
Carbohydrates are the main source of blood glucose, which is a major fuel for all of the body's cells and the only source of energy for the brain and red blood cells. Except for fiber, which cannot be digested, both simple and complex carbohydrates are converted into glucose. The glucose is then either used directly to provide energy for the body, or stored in the liver for future use. When a person consumes more calories than the body is using, a portion of the carbohydrates consumed may also be stored in the body as fat.
When choosing carbohydrate-rich foods for your diet, always select unrefined foods such as fruits, vegetables, peas, beans, and whole-grain products, as opposed to refined, processed foods such as soft drinks, desserts, candy, and sugar. Refined foods offer few, if any, of the vitamins and minerals that are important to your health. In addition, if eaten in excess, especially over a period of many years, the large amounts of simple carbohydrates found in refined foods can lead to a number of disorders, including diabetes and hypoglycemia (low blood sugar). Yet another problem is that foods high in refined simple sugars often are also high in fats, which should be limited in a healthy diet. This is why such foods-which include most cookies and cakes, as well as many snack foods-are usually loaded with calories.
Dietary fiber is the part of a plant that is resistant to the body's digestive enzymes. Only a relatively small amount of fiber is digested or metabolized in the stomach or intestines. Most of it moves through the gastrointestinal tract and ends up in the stool.
Although most fiber is not digested, it delivers several important health benefits. First, fiber retains water, resulting in softer and bulkier stools that prevent constipation and hemorrhoids. A high-fiber diet also reduces the risk of colon cancer, perhaps by speeding the rate at which stool passes through the intestine and by keeping the digestive tract clean. In addition, fiber binds with certain substances that would normally result in the production of cholesterol, and eliminates these substances from the body. In this way, a high-fiber diet helps lower blood cholesterol levels, reducing the risk of heart disease.
It is recommended that about 60 percent of your total daily calories come from carbohydrates. If much of your diet consists of healthy complex carbohydrates, you should easily fulfill the recommended daily minimum of 25 grams of fiber.

 More References:

MayoClinic

Webmd.com

Familydoctor.org

The connection between your blood sugar, Diabetes, and Soft Drinks