Lately one of my patients asked me about fructose intolerance and depression. I couldn’t answer the question, so I looked up PubMed and found a study, which had been published in October 2000. Alimentary fructose intolerance is better called fructose malabsorption.
M. Ledochowski and colleagues published a study on: „Fructose- and sorbitol-reduced diet improves mood and gastrointestinal disturbances in fructose malabsorbers.” They concluded: “Fructose- and sorbitol-reduced diet in subjects with fructose malabsorption does not only reduce gastrointestinal symptoms but also improves mood and early signs of depression.” (1)
M. Ledochowski and (other) colleagues published a study on: „Fructose malabsorption is associated with decreased plasma tryptophan.” They concluded: “Fructose malabsorption is associated with lower tryptophan levels that may play a role in the development of depressive disorders. High intestinal fructose concentration seems to interfere with L-tryptophan metabolism, and it may reduce availability of tryptophan for the biosynthesis of serotonin (5-hydroxytryptamine).” (2)
Fructose malabsorption is diagnosed by a hydrogen breath test as a high load of unabsorbed fructose will be fermented by intestinal bacteria producing hydrogen, carbon dioxide, methane and more, which leads to bloating or flatulence. People with fructose malabsorption should keep a diet (3).
There are hints that fructose malabsorption might influence mood, but there hasn’t been any research since the year 2001, which makes it hard to believe that the association is relevant. Therefore gastrointestinal symptoms should be guiding dietary measures.