PrintThe Fructose Question: Once More With Feeling

Fruits and vegetables supply fructose and glucose at naturally healthy levels, but sugar-sweetened beverages can increase consumption drastically.

by Michael Colgan, Ph.D.

There are a few folk out there who are still missing the scientific picture on sugar, because I get the same questions repeated at least once a week. Sugars form a natural part of the human diet and mechanisms to deal with them have been built into our DNA for millions of years.

If you eat vegetables, you eat naturally occurring fructose and glucose every day. If you eat fruit, you eat naturally occurring fructose and glucose every day. If you do not eat fruit & vegetables, you will suffer a lot of illness. If you like self-torture, avoiding all fructose and glucose in your diet will suit you very well.

All tree, bush, and vine fruits, and all berries that folk eat as fruits, contain fructose and glucose, as do most vegetables. In plants, fructose may be present as fructose, and glucose as glucose, or both as components of sucrose. Sucrose is composed of a molecule of glucose and a molecule of fructose bonded together.

Here are some very conservative figures of fructose and total sugars content from the US Department of Agriculture, which always leans a fair way to support commerce. Note that the figures are for 3.5 ounces. A good-sized apple, the size I would consider to still be an apple, is 6 to 7 ounces. The Belle de Boskoop eating apples I can see right now on the tree outside my study window average about 10 ounces each. They are about 26 grams fructose each.

Sugar content of common plant foods (g/100g)(1)

Fruits Total Carbohydrate (grams) Total Sugar (grams) Free Fructose (grams)
Apples 13.8 10.4 5.9
Apricots 11.1 9.2 0.9
Bananas 22.8 12.2 4.9
Figs, dried 63.9 47.9 22.9
Grapes 18.1 15.5 8.1
Peaches 9.5 8.4 1.5
Pears 15.5 9.8 6.2
Pineapple 13.1 9.9 2.1
Plums 11.4 9.9 3.1
Beets 9.6 6.8 0.1
Carrots 9.6 4.7 0.6
Corn, sweet 18.7 6.3 1.9
Red pepper, sweet 6.0 4.2 2.3
Onion, sweet 7.6 5.0 2.0
Sweet potato 20.1 4.2 0.7

Too Much Sugar

Sugar-sweetened sodas contain anywhere from 20 to 80 grams of sugar per serving.

One problem with the American diet today is too much sugar supplied in the form of sugary desserts and soft drinks. With the invention of high-fructose corn syrup (HFCS), which was brought into the food chain in 1970, sugar consumption has increased substantially.

Since about 2000, numerous reviews link high consumption of HFCS to the current epidemics of obesity, adult-onset-diabetes, and other metabolic syndrome disorders in the US today. The largest source of HFCS in the American diet is sodas (the typical amount of sugar in soda ranges from 20 to 80 grams per can or bottle) (1-5). My book Nutrition for Champions tells you how to avoid most of it (6).

Non-caloric Sweeteners

Can you get around the sugar problem by drinking “diet” sodas and soft drinks, and eating “diet” foods sweetened with sucralose or other synthetic “no-calorie” (hypocaloric) sweeteners? No way! They fail utterly to satisfy the genetically mandated appetitive arousal of the brain and the gut. Consequently, users typically eat more calories elsewhere. You have a diet coke and 15 minutes later that piece of pumpkin pie in the fridge is hollering, “Eat me now!”

The latest, just published, review of hundreds of studies of these sweeteners concluded: “Despite tremendous interest in hypocaloric sweeteners as a potential tool to prevent obesity and its complications, we found little evidence to support their health benefits as compared to caloric alternatives” (7).

Nature spent millions of years developing our genes to respond with a precision that makes cell phone technology look quaint and cumbrous. Any time you try to fool them with lo-cal, no-cal synthetic foods, they will make you suffer down the road.


1.USDA National Database for Standard Reference. Available at:
2. Malik VS, Schulze MB, Hu FB. Intake of sugar-sweetened beverages and weight gain: a systematic review. Am J Clin Nutr. 2006 Aug;84(2):274-88.
3. Vermunt SH, Pasman WJ, Schaafsma G, Kardinaal AF: Effects of sugar intake on body weight: a review. Obes Rev 2003, 4:91-99.
4. Tuomilehto J, et al. Finnish Diabetes Prevention Study Group: Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 2001, 344:1343-1350.
5. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Nathan DM: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002, 346:393-403
6. Colgan M. Nutrition for Champions. Vancouver: Science Books, 2007.
7. Natasha Wiebe, Raj Padwal, Catherine Field, Seth Marks, Rene Jacobs and Marcello Tonelli A systematic review on the effect of sweeteners on glycemic response and clinically relevant outcomes. BMC Medicine 2011, 9:123 doi: 10.1186/1741-7015-9-123 Published: 17 November 2011.

About Dr. Colgan

Dr. Michael Colgan is a world-renowned research scientist, leading expert in the inhibition of aging, and a member of the Isagenix Science Advisory Board. Dr. Colgan has provided nutrition, training and anti-aging programs to more than 11,000 athletes, including many Olympians. He is director of his eponymous Colgan Institute, a consulting, educational and research facility concerned with the effects of nutrition and exercise on athletic performance, along with prevention of chronic degenerative disease, and prevention of degeneration of the brain.