The review article, “The emerging role of dietary fructose in obesity and cognitive decline”1 by Lakhan and Kirchgessner has serious limitations. Although the authors concluded that fructose is associated with cognitive decline and potentially contributes to “lower academic performance in adolescents”, these conclusions are not warranted.
The review had some serious flaws, including:
- Fructose is not associated with lower academic performance in children and adolescents. Although the authors stated that fructose might lead to poorer academic performance in children and adolescents, the studies cited did not actually support that conclusion. In the studies referenced, other factors like educational attainment had more of an impact on academic performance. Finally, most of the paper focused on cognitive decline later in life, so it was a stretch for the authors to suddenly bring up academic performance in children.
- Studies showing the association between fructose and cognitive decline were conducted with animals.The authors reference animal studies that have found a relationship between fructose intake and cognitive decline. There are differences between rodent and human bodily processes and it cannot be assumed that the reported results of these studies would apply in humans. Further, in one of the referenced studies that concluded that fructose intake was associated with impairment in spatial memory in rats, the rats were consuming a high-fructose diet consisting of 60% fructose.
- Fructose is not distinguished from sucrose or high-fructose corn syrup. It is not typical for people to consume solely fructose, but rather fructose along with glucose in sucrose or high-fructose corn syrup. In the review, it does not always appear that this distinguishment is made and therefore it appears that fructose by itself is responsible for the increase in rates of obesity.
- Fructose does not cause obesity. The authors argued that an increase of fructose in the American diet over the past few decades and the booming obesity epidemic over the same time period are related. However, obesity is a multifactorial disease, which unlikely to be caused by any one ingredient in our diets. Studies that have shown a link between fructose and obesity, tested diets with levels of fructose much greater than what most people eat. Studies that have looked at fructose as how people normally consume it have not shown a link with obesity. Thus, obesity is probably coming from the extra calories, not fructose itself.
Many factors contribute to optimal health, such as eating habits (including balance and moderation), exercise and long-term commitment. Health problems are unlikely to be caused by one particular food ingredient such as fructose.
- Lakhan, S. E. & Kirchgessner, A. (2013). The emerging role of dietary fructose in obesity and cognitive decline.Nutrition Journal, 12(1): 114.