The Truth About Fructose

Mouse Study Comparing Fructose and Glucose Diets with Sucrose (Sugar) Diets Not Applicable to Humans

Findings presented in a study titled “Compared to Sucrose, Previous Consumption of Fructose and Glucose Monosaccharides Reduces Survival and Fitness of Female Mice” by Ruff et al.1 should be interpreted with caution. The authors overstate that “This study provides unique experimental evidence that the consumption of a 1:1 ratio of F/G can dramatically decrease female mammalian health compared with the intake of an isocaloric amount of sucrose” as it is well-established that findings in one species are often different that those in other species. The study was conducted on mice and it is well known that humans and rodents metabolize substances differently. The authors report that female, but not male, mice eating fructose and glucose live less and reproduce less than mice fed sucrose. Unfortunately, no necropsy or physical exams including blood parameters and metabolic tests throughout the study were reported so any potential reason proposed for these findings would simply be speculation. As Dr. Luc Tappy, a researcher that focuses on environmental and dietary factors involved in the development of obesity and type 2 diabetes commented on this study, “There is presently no hint regarding the possible underlying mechanisms.”2

In addition, the Calorie Control Council** cites the following as serious limitations of the study:

  • The organismal performance assay (OPA) testing environment introduces unique stressors. Mice appear to respond comparably to Fructose/Glucose or sucrose when fed diets prior to being housed in the OPA environment. However, when mice are placed in an environment that stimulates competition, mice respond differently. While these mice were previously fed different diets, once in the OPA environment, they are all competing for a single source and type of feed, which can introduce stress to the mice that could contribute to the effects observed by the study authors.
  • The authors do not account for natural rodent behavior. Mice are known to kill and cannibalize one another. It is unknown if the reduced female survival in this study was due to natural rodent behavior. Also, while the study reports differences in the total number of offspring, the authors do not describe if the number of offspring per female was affected.
  • There are differences between rat and human bodily processes and it cannot be assumed that the reported results of this study would apply in humans. .
  • Other factors may have influenced the findings. Although authors controlled for many variables that could have affected the outcome of the study, many important behavioral and dietary factors were not accounted for. For example, mice responded similarly to the two diets for 40 weeks. It was not until the mice were placed in a potentially stress-inducing environment, while consuming the same diet, that they behaved differently.

The metabolism of fructose has been studied for decades and is well documented in the scientific literature and has not been shown to cause metabolic problems. Regardless of the fructose source (e.g., fruits, vegetables, honey, high fructose corn syrup (HFCS), crystalline fructose or table sugar), fructose is metabolized using the same metabolic pathways. Many factors contribute to optimal health, such as eating habits (including balance and moderation) and exercise. Health problems are unlikely to be caused by one particular food ingredient such as fructose.


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1 Ruff, JS, SA Hugentobler, AK Suchy, MM Sosa, RE Tanner, ME Hite, LC Morrison, SH Gieng, MK Shigenaga, WK Potts. Compared to Sucrose, Previous Consumption of Fructose and Glucose Monosaccharides Reduces Survival and Fitness of Female Mice. J. Nutr. 2015 jn.114.202531. First published December 10, 2014, doi: 10.3945/jn.114.202531.


2 Tappy, L. Health Effects of Sugars: In Search of Novel, Unsuspected Pathogenic Pathways. J. Nutr. 2015 jn.114.206912. First published online December 24, 2014. doi:10.3945/jn.114.206912

** The Calorie Control Council (the “Council”) is an international association of manufacturers of low-calorie, reduced-fat and “light” foods and beverages. Companies that make and use low-calorie sweeteners are among the Council’s members.