Commercially produced table sugar comes either from sugar cane or from sugar beet. Manufacturing and preparing food may involve other sugars, including palm sugar and fructose, generally obtained from corn (maize) or from fruit.
Excessive consumption of sugar has been associated with increased incidences of type 2 diabetes, obesity and tooth decay
The World Health Organisation and the Food and Agriculture Organization of the United Nations expert report (WHO Technical Report Series 916 Diet, Nutrition and the Prevention of Chronic Diseases) defines free sugars as all monosaccharides and disaccharides added to foods by the manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and fruit juices. The term distinguishes these forms from all other culinary sugars added in their natural form with no refining at all.
Natural sugars comprise all completely unrefined sugars: effectively all sugars not defined as free sugars. The WHO Technical Report Series 916 Diet, Nutrition and the Prevention of Chronic Diseases approves only natural sugars as carbohydrates for unrestricted consumption. Natural sugars come in fruit, grains and vegetables in their natural or cooked form.