In most parts of the world, sugar is a vital part of the human diet, making food more palatable and providing food energy. After cereals and vegetable oils, sugar derived from sugar cane and beet provide more kilocalories. According to the FAO, an average of 24 kilograms (53 lb) of sugar, equivalent to over 260 food calories per day, was consumed annually per person of all ages in the world in 1999. Even with rising human populations, sugar consumption is expected to increase to 25.1 kilograms (55 lb) per person per year by 2015.

It has been questioned whether a diet high in sugars, especially refined sugars, is good for human health. Sugar has been linked to obesity, and suspected of, or fully associated as a causal agent in the occurrence of diabetes, dementia, cardiovascular disease, macular degeneration, tooth decay and various other health hazards.
Added sugar is the single worst ingredient in the modern diet. It can have harmful effects on metabolism and can contribute to all sorts of diseases. Here are various reasons why you should avoid adding sugar.

Added sugar contain no essential nutrients
Added sugars like sucrose and high fructose corn syrup (HFCS) contain bunch of calories with NO essential nutrients. Therefore, they are called “empty” calories. There are no proteins, essential fats, vitamins or minerals in sugar, except pure energy. When people eat up-to 10-20% of calories in the form of sugar, this could be a big problem and contribute to nutrient deficiencies.

Added Sugar High in Fructose, Can Overload Your Liver
In order to understand what is so bad about sugar, you need to understand what it is made of. Before sugar enters the bloodstream from the digestive tract, it is broken down into two simple sugar sub-units (glucose and fructose).

• Glucose is found in every living cell on the planet. If we don’t get it from the diet, our bodies produce it.
• Fructose is different. Our bodies do not produce it in any significant amount and there is no physiological need for it.

Fructose is only metabolized by the liver in any significant amounts. If we eat a little bit (such as from fruit), that’s not the problem, fructose will be turned into glycogen and stored in the liver until we need it. However, if the liver is full of glycogen, eating a lot of fructose overloads the liver, forcing it to turn the fructose into fat. When repeatedly eating large amounts of sugar, this process can lead to fatty liver and all sorts of serious problems
When fructose gets turned into fat in the liver, it is shipped out as VLDL cholesterol particles. However, not all of the fat gets out, some of it can lodge in the liver. This can lead to Non-Alcoholic Fatty liver disease (NAFLD), a growing problem in Western countries that is strongly associated with metabolic diseases.

Sugar is bad for teeth
Sugar is also very bad for the teeth, because it provides easily digestible energy for bacteria in the mouth and bacteria grow in favorable condition and causes tooth-decay.

Sugar Can Cause Insulin Resistance and Diabetes
Insulin allows glucose (blood sugar) to enter cells from the bloodstream and tells the cells to start burning glucose instead of fat. Having too much glucose in the blood is highly toxic and one of the reasons for complications of diabetes.
One feature of the metabolic dysfunction that is caused by the Western diet, is that insulin stops working as it should. The cells become “resistant” to it. Eventually, as insulin resistance becomes progressively worse, the pancreas can’t keep up with the demand of producing enough insulin to keep blood sugar levels down. At this point, blood sugar levels skyrocket and a diagnosis of type II diabetes is made.

Excess of Sugar can cause cancer
Many scientists believe that having constantly elevated insulin levels (a consequence of sugar consumption) can contribute to cancer. In addition, the metabolic problems associated with sugar consumption are a known driver of inflammation, another potential cause of cancer.

Because it causes Massive Dopamine Release in The Brain, Sugar is Highly Addictive
Sugar can be addictive for a lot of people. Like abusive drugs, sugar causes a release of dopamine in the reward center of the brain. The problem with sugar is that it can cause massive dopamine release, much more than we were ever exposed to from foods found in nature. For this reason, people who have a susceptibility to addiction can become strongly addicted to sugar.

Sugar is a Leading Contributor to Obesity
Not surprisingly, people who consume the most sugar are by far the most likely to become overweight or obese. This applies to all age groups. This is especially strong in children, where each daily serving of sugar-sweetened beverages is associated with a whopping 60% increased risk of obesity. One of the most important things you can do if you need to lose weight is to significantly cut back on sugar consumption.

Diet Rich in Sugar Can Hurt Your Heart
A study published in the Journal of the American Medical Association (JAMA) found that people who got 25% or more of their calories from added sugars were more than 3 times more likely to have low levels of HDL (the good cholesterol that helps prevent plaque buildup by carrying cholesterol from your arteries to your liver where it is then excreted) than those whose diets included less than 5% sugar. Both high triglycerides and low HDL levels contribute to atherosclerosis, hardening of your arteries, a condition that increases your risk of heart disease, stroke, and heart attack.

Brown sugar & white sugar
Although many people are of the opinion that brown sugar is a healthier option than white sugar, the truth is that they only have marginally different nutritional values. White sugar is actually 99.9% pure sucrose, while brown sugar is 97% sucrose, 2% water and 1% other substances. A teaspoon of white sugar contains 16 kilocalories, whereas one teaspoon of brown sugar has 17 kilocalories. The molasses in brown sugar contains a number of minerals, which include calcium, potassium, magnesium and iron, but since only very small amounts of these minerals are present in brown sugar, they do not bring any health benefit to the body. But this is not true; both are equally harmful in large quantities.