Fructose is a form of carbohydrate, or sugar, found in fruits, vegetables and honey. It is often added to commercially prepared foods as a preservative and flavor enhancer. Fructose has been of much interest in recent years due to its possible role in contributing to the obesity epidemic in the United States and has been identified as factor in some gastrointestinal conditions.
Fructose Intake and Metabolic Disease
Scientists and public health officials have been searching for the causes of increased numbers of overweight and obese observed in the American population over the past four decades. Studies have made an association between the intake of added sugars and weight gain; however, fructose consumed from fruit is not included in the category of added sugars. Much evidence exists showing the positive effects of fruit intake with regard to chronic disease prevention, and diets high in fruit consumption have lower rates of cardiovascular disease, cancer and neurological disease. Despite this evidence, Americans do not meet recommended fruit intake goals of 1.5 to 2 cups per day, and popular diet culture intensifies the problem through the promotion of fruitless dieting for weight loss.
Fructose and Diabetes
It is a myth that people with diabetes cannot eat fruit. Fructose from fruit is not harmful to people with diabetes when consumed in moderate amounts. The American Diabetes Association recommends having a piece of fruit for dessert or eating fruit in exchange for other sources of carbohydrate in the diet. One study in a 2013 issue of the "Nutrition Journal" found that decreased fruit intake for diabetic patients did not show an effect on weight loss, waist circumference or blood glucose levels. In fact, antioxidants contained in fruits may actually help to improve insulin resistance.
For some people with gastrointestinal discomfort, fructose may be the culprit due to an inability to completely absorb the sugar. In the case of malabsorption, too much fructose from fruit is not harmful, but it can be irritating. Fructose malabsorption is a fairly normal occurrence, not a disease. Fructose is absorbed most easily when it is paired with glucose in a 1-to-1 ratio. Many fruits are not made with equal parts of fructose and glucose, so fructose goes unabsorbed in the small intestine and makes its way into the large intestine. There, it is fermented by bacteria producing the uncomfortable symptoms of bloating, gas, abdominal pain and diarrhea. The low FODMAP diet has shown some benefit in helping reduce the symptoms associated with fructose malabsorption.
In order to maximize performance, athletes need to consume carbohydrates. The timing, type and amount of carbohydrate is important. For example, consuming a piece of fruit 30 to 60 minutes before most workouts provides the right amount of carbohydrate in the form of fructose sugar. Preworkout fruit intake should be limited to one serving, as the fructose and fiber in fruit can have an osmotic effect in the gastrointestinal tract and cause diarrhea and cramping. A fruit smoothie or a glass of 100 percent fruit juice within 15 minutes to an hour after exercise is beneficial for postexercise recovery and glycogen repletion.