Fructose Malabsorption is Associated with Decreased Plasma Tryptophan

Abstract

Background: Fructose malabsorption is characterize d by the inability to absorb fructose ef ciently. As a consequenc e fructose reaches the colon where it is broken down by bacteria to short fatty acids, CO 2 , H 2 , CH4 and lactic acid. Bloating, cramps, osmotic diarrhea and other symptoms of irritable bowel syndrome are the consequenc e and can be seen in about 50% of fructose malabsorbers. Recently it was found that fructose malabsorptio n was associated with early signs of depressiv e disorders. Therefore, it was investigate d whether fructose malabsorptio n is associated with abnormal tryptopha n metabolism . Methods: Fifty adults (16 men, 34 women) with gastrointestina l discomfort were analyzed by measuring breath hydrogen concentration s after an oral dose of 50 g fructose after an overnight fast. They were classi ed as normals or fructose malabsorber s according to their breath H2 concentrations . All patients lled out a Beck depressio n inventory questionnaire . Blood samples were taken for plasma tryptophan and kynurenin e measurements . Results: Fructose malabsorption (breath DH 2 production > 20 ppm) was detected in 35 of 50 individuals (70%). Subjects with fructose malabsorptio n showed signi cantly lower plasma tryptopha n concentration s and signi cantly higher scores in the Beck depressio n inventory compared to those with normal fructose absorption . Conclusions: Fructose malabsorption is associated with lower tryptophan levels that may play a role in the developmen t of depressiv e disorders. High intestinal fructose concentratio n seems to interfere with L-tryptopha n metabolism , and it may reduce availabilit y of tryptopha n for the biosynthesi s of serotonin (5-hydroxytryptamine) . Fructose malabsorption should be considered in patients with symptoms of depression and disturbance s of tryptophan metabolism.

Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome

“…Fatigue is frequently described by patients with IBS. A fructose‐reduced diet in young women with fructose malabsorption and mild depressive symptoms improved mood, 33,34 putatively by changing serum tryptophan levels (the precursor to serotonin) 35 . The effect of a high FODMAP diet on fatigue has not, however, been formally studied.…”

The role of psychological and biological factors in postinfective gut dysfunction Reply

“…Our data suggest that non-absorbed carbohydrates interfere with tryptophan metabolism, which may explain the development of anxiety, mental depression, and other signs of serotonin deficiency 4. Furthermore, most of our patients were diagnosed as having IBS before a diagnosis of carbohydrate malabsorption syndrome was made.…”

Fructose Malabsorption May Be Gender Dependent and Fails to Show Compensation by Colonic Adaptation

“…For example, depression is linked with fructose malabsorption mainly in women [12]. The mechanism is postulated to depend on decreased serotonin synthesis resulting from binding in the gut of tryptophan by fructose [38]. Another study also noted that significantly more women exhibited fructose malabsorption [6], but in that study the ratio was closer to 1.5:1.…”