Glucose & Fructose in Plants

Updated February 21, 2017

Glucose and fructose are the products of photosynthesis. When plants convert sunlight into energy, they are producing the simple sugars fructose and glucose. Those sugars are then converted to sucrose for storage until the energy is needed. Plant sugars are stored in seeds, roots, leaves and the fruit of the plant. The plants that make the most sucrose are sugar beets and sugar cane and those are commonly used to make table sugar. Fructose is consumed via fresh fruits, fruit juices and honey and in manufactured products like high fructose corn syrup, which is actually a fructose-glucose blend.


Fructose, or fruit sugar, is the sweetest sugar and is obtained mainly from fruits and honey. It has the exact same molecular formula as glucose but, unlike glucose, fructose acts as a ketone in the body. Ketones are acidic byproducts of fat burning. An excess of ketones in the blood can lead to a dangerous condition called ketoacidosis, a complication of diabetes. Consumption of fruit is part of a healthy diet, providing important vitamins, minerals and fibre. The sugar content is only a problem when it is isolated from the whole fruit and consumed in excess.


Glucose is stored in plants as starch. It comes from beans, rice, potatoes, corn, and wheat and is found primarily in plant sap. Enzymes in the human body break down starches when they are eaten and release their sugar into the bloodstream. There it can be used as instant energy or stored in the form of glycogen in the liver and the muscle tissues. Glucose is not as sweet to the taste buds as fructose so it is not as widely used in food preparations. It does, however, convert to energy in the body more efficiently and glucose releases beneficial hormones that affect hunger sensations and body weight.

Sucrose and HFCS

Sucrose is table sugar. It is primarily obtained from sugar beets and sugar cane. After fructose, it is the sweetest sugar and was once the main sweetener in the American diet. Due to the rising cost of sugar, food manufacturers developed a method for extracting the sugar from corn, creating a mix that is 55 per cent fructose and 45 per cent glucose, hence the name, high fructose corn syrup or HFCS. HFCS is now the most widely-used sweetener and has been implicated in the increasing incidence of obesity in American adults and children.

Sweets to Eat

Overconsumption of any sweets leads to weight gain and dental caries or cavities. Too much sugar in the diet can lead to diabetes and a host of medical conditions that are related to it -- all serious health concerns. Eating fresh fruits and vegetables and natural foods that contain fructose and glucose is not a problem in a balanced diet for a healthy person. But sugar additives, in low-nutrient products like sweetened soft drinks, may be contributing to America's explosive obesity epidemic and a rise in diabetes. A University of California study using human subjects found that those who consumed drinks sweetened with fructose and with glucose gained similar amounts of weight over 12 weeks but showed different health effects. Fructose sweeteners resulted in altered liver function, insensitivity to insulin and high risk conditions for developing diabetes, atherosclerosis and heart attack.

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About the Author

Benna Crawford has been a journalist and New York-based writer since 1997. Her work has appeared in USA Today, the San Francisco Chronicle, The New York Times, and in professional journals and trade publications. Crawford has a degree in theater, is a certified Prana Yoga instructor, and writes about fitness, performing and decorative arts, culture, sports, business and education .