Can not simply think that cancer patients can not eat sugar, sugar is a general term, belongs to carbohydrates, is one of the three functional nutrients, the main role is to provide energy. Sugar can be divided into monosaccharides, disaccharides, oligosaccharides and polysaccharides according to the degree of polymerization. Monosaccharides include glucose, fructose and galactose, and glucose, which is also commonly known as dextrose, is the basic unit that constitutes a variety of oligosaccharides and polysaccharides in food. Some sugars, such as starch, are composed entirely of glucose, while others are formed by chemically combining glucose with other sugars, such as sucrose. Glucose has a D-type and an L-type, and the human body can only metabolize this D-type glucose and cannot utilize the L-type glucose, so some use the L-type glucose as a sweetener to achieve the purpose of increasing the sweetness of food without increasing energy intake. Fructose is usually found in fruits and honey along with sucrose. After absorption, fructose is converted to glucose by the liver and utilized by the body, while some of it is converted to glycogen, lactic acid and fat. Galactose is an important component of lactose, which needs to be converted to glucose in the body before it can be utilized. Disaccharides include sucrose, lactose, maltose, alginate and sugar alcohols. Sucrose is commonly known as white sugar, granulated sugar also, brown sugar, in sugar cane, sugar beet and honey content is relatively large. Oligosaccharides in oligofructose, difficult to be digested and absorbed by the human body this, is considered a water-soluble dietary fiber, mainly found in fruits and vegetables like onions, garlic, bananas and so on. Polysaccharides are made up of more than 10 monosaccharide units, and this carbohydrate exists in the form of starch or cellulose in whole grains as well as potatoes. There are three forms of sugar present in the body such as glucose, glycogen and glycoconjugates, and the various sugars have different health effects related to the form in which they are present. Refined sugars, also known as monosaccharides, may promote the development of certain tumors when eaten in excess, and this high-sugar diet may promote the development of certain tumors. The American Institute for Cancer Research issued recommendations in 2009 should limit the intake of refined sugars to no more than 25g per day for women and no more than 38g per day for men.Refined sugars, also known as added sugars, and functional oligosaccharides, dietary fiber-active polysaccharides, are tumor-protecting factors, which can prevent or curb the development of tumors.