Saturday, July 7, 2012

Sievenpiper: Fructose should not "worry" in diabetes

As the fructose debate rages on, one serious concern has been what the message should be for people who have diabetes. There's no question that the alarming media headlines, articles, and YouTube videos have confused many with prediabetes and both type 1 and type 2 diabetes.

Even health professionals and organizations like the American Diabetes Association have taken a cautious approach by recommending avoidance of fructose as a sweetening agent. That is, for fear it may raise plasma lipids. They stop short of recommending people avoid fructose from fruit.

There is also the extreme arguments of Internet marketers like Joe Mercola blasting out articles about the supposed danger of fructose including that of which comes from fruit. (I've had more questions than I can count about Mercola's unreasonably scary headlines and viral copy. He makes baseless recommendations that those with diabetes should cut fructose from all sources to amounts of less than 15g per day.)

In my prior interview with John Sievenpiper, M.D., of St. Michael's Hospital, University of Toronto,  we talked of the controversies surrounding fructose, as well as rhetoric used by scientists like Dr. Robert Lustig and others, which he said could lead people to reduce intake of fruits. "That's the danger," Dr. Sievenpiper said, "that people will say that fruit is a source of fructose and won't consume fruit because it may induce obesity, metabolic syndrome, and so on. It's not just the lay public that may take this message to heart, but health professionals."

As the lead author of three systematic reviews and meta-analyses evaluating fructose's effects in randomized controlled feeding trials, Dr. Sievenpiper offered some perspective to the metabolic fate of this simple sugar in humans (versus animals). In short, these analyses found fructose had no significant effect on body weight or blood pressure in humans (as it does in rats, for example). In fact, fructose in amounts similar to that found in fruit improved glycemic control in humans.

Now, Dr. Sievenpiper and his colleagues -- including Dr. David Jenkins (who first introduced the concept of a low-glycemic index) -- has released yet another meta-analysis and systematic review to evaluate the effect on fructose on long-term glycemic control in diabetes.

The new study, published in Diabetes Care, included 18 controlled feeding trials that included 209 individuals with type 1 and type 2 diabetes. The study's results: The isocaloric exchange of fructose improves long-term glycemic control as determined by significantly reduced glycated proteins, namely hemoglobin (HbA1c) and glycated albumin.

Moreover, the isocaloric exchange of fructose reduced HbA1c by an average of 0.53 percent, which is the equivalent to taking a hypoglycemic or anti-hyperglycemic agent like glucophage (Metformin). The fructose also didn't significantly affect fasting glucose or insulin.

When I asked Dr. Sievenpiper what people with diabetes should take away from the results of the study, what they should make of fructose's contribution to total carbohydrates, and its use as a substitute for other carbohydrates in the diet, he wrote:
In the context of a healthy, nutritionally balanced, weight-maintaining diet, people with type 2 diabetes do not need to worry about avoiding sources of fructose.  
Provided weight management goals are being met, no one dietary pattern has shown itself to be best for the nutritional management of diabetes. A number of dietary patterns have shown benefit in people with diabetes. These include a low-glycemic index, Mediterranean, or vegetarian dietary patterns, as well as those which emphasize specific foods such as dietary pulses or nuts or allow for a range of macronutrient distributions. The range of possibilities allows for the individualization of diets based on treatment goals and the values and preferences of the individual. 
Within this context, using small to moderate amounts of fructose in place of other sugars and starch may offer added benefit. This would be expected to be especially true where the sources are low-glycemic index fruits and cereal grain products, both of which have shown metabolic benefit.  
That being said, we need larger, longer, and higher quality trials to clarify the benefit of fructose in people with diabetes. We are currently planning such trials. 
Fructose, far from being "toxic," may be a uniquely beneficial carbohydrate in diabetes when given in amounts equivalent to what's found in fruits, according to the evidence. Once again, the study drives home the point further that dose matters, as it does with most nutrients and bioactive compounds, and that fructose can be healthy when eating as part of a well-balanced diet.

With the virtues of a low-glycemic diet extolled recently in the media for healthy weight loss (mainly after Dr. David Ludwig and colleagues published an impressive three-way crossover study in the Journal of American Medical Association evaluating low-fat, low-glycemic index, and very low-carb diets) it's odd that more attention hasn't been given to the value of fructose as a source of low-glycemic carbohydrate.

The most likely reason, perhaps, as addressed in my previous posts, is the continuing fears people have about high-fructose corn syrup. Despite the fact that it's chemical makeup being almost identical to plain sucrose, the ingredient is still often singled out as somehow uniquely problematic. Greater intake of all foods, especially all carbohydrate sources, is what is most likely what has led us down the road of the obesity epidemic.

Bottom line? Fruit is still healthy. Fructose is most likely good for folks in amounts equivalent to what's found in fruit. Moderation in the diet needs to be the key message as it comes to any nutrient. Plus, more focus could be put on the intake of low-glycemic carbohydrates along with balanced amounts of proteins and good fats as part of a reduced-calorie diet for weight management.


Cozma AI et al. Effect of Fructose on Glycemic Control in Diabetes: A Systematic Review and Meta-analysis of Controlled Feeding Trials. Diabetes Care 2012;35:1-10.doi: 10.2337/dc12-0073