Fructose is a form of simple sugar found in foods like fruits, honey and some vegetables. Common table sugar is a combination of equal parts of fructose and another sugar, called glucose. However, in pure form, fructose is about 1.5 times sweeter than sucrose.
One form of fructose is high fructose corn syrup, made from corn. It contains 55 percent fructose and 45 percent glucose and has about the same level of sweetness as sucrose (table sugar).
Fructose, especially high fructose corn syrup, is commonly used as a sweetener in foods. It doesn’t raise blood sugar levels to the same degree as sucrose. So, fructose is often used as the sweetener in foods for people with diabetes.
Fructose and Digestion
In some people, the small intestine is unable to efficiently break down fructose (and sometimes other forms of sugar). This problem is sometimes referred to as fructose intolerance. The undigested fructose passes into the large intestine, where it is broken down by bacteria. A by-product of this process is the creation of carbon dioxide and hydrogen. These two gases build up in the intestine, causing bloating, gas, pain and diarrhea. In some cases, the problem can affect absorption of important nutrients, like calcium and iron.
Diagnosing Fructose Intolerance
Researchers estimate about 33 percent of Americans have some level of sensitivity to sugar, most commonly to fructose, but the symptoms are often vague. Some people with fructose intolerance can eat small amounts of the sugar and not have any problems, making diagnosis even trickier.
Daniel Lustig, M.D., Pediatric Gastroenterologist at Mary Bridge Children’s Health Center in Tacoma, WA, says patients with chronic digestive problems should have a physician’s evaluation to rule out other possible causes of the symptoms, like Celiac disease or Crohn’s disease. Once those conditions have been ruled out, he recommends a diagnostic tool called the breath hydrogen test.
A patient is given a dose of fructose. Then, periodically, he/she breathes into an air collection bag. The gases from the bag are retrieved and analyzed for the presence of hydrogen (one of the gases given off when fructose is broken down in the large intestine). Patients whose hydrogen levels exceed 20 points beyond a baseline reading are likely to be fructose intolerant.
Dealing with Fructose Intolerance
Lustig explains the main treatment of fructose intolerance is avoidance of foods containing fructose. That includes fruits, fruit juices, sodas and processed foods and drinks with high fructose corn syrup. Since fructose is in so many foods, it can be tricky to find and hard to avoid.
Lustig recently performed a study to look at possible fructose intolerance in 245 children and adolescents (ages 2 to 18) with unexplained chronic abdominal pain, gas or bloating. The breath hydrogen test found that nearly 54 percent of the participants tested positive for fructose intolerance. Lustig says the problem appeared to be especially high among teen girls.
Those who were judged to be fructose intolerant were given advice on using a low-fructose diet. The investigators found that nearly 68 percent of those who followed the recommended diet had an improvement or resolution in their symptoms.
AUDIENCE INQUIRYFor general information on fructose and intolerance or absorption problems:
International Food and Information Council Foundation, http://www.foodinsight.org
BIBLIOGRAPHYBolin, Terry, “IBS or Intolerance?” Australian Family Physician, December 2009, Vol. 38, No. 17, pp. 962-965.
Choi, Y., et al., “Fructose Intolerance in IBS and Utility of Fructose-restricted Diet,” Journal of Clinical Gastroenterology, March 2008, Vol. 42, No. 3, pp. 233-238.
Fernandez-Banares, F., et al., “Fructose-sorbitol Malabsorption,” Current Gastroenterology Report, October 2009, Vol. 11, No. 5, pp. 368-369.
Gomara, R., et al., “Fructose Intolerance in Children Presenting with Abdominal Pain,” Journal of Pediatric and Gastroenterologic Nursing, September 2008, Vol. 47, No. 3, pp. 303-308.
Rao, Satish, et al., “The Ability of the Normal Human Small Intestine to Absorb Fructose,” Clinical Gastroenterology and Hepatology, August 2007, Vol. 5, No. 8, pp. 959-963.