Two weeks of pistachio ingestion are found to hamper performance on a 75-km cycling time trial, possibly due to elevated levels of a raffinose-associated leukotoxin.
Apparently pistachios are not all they are cracked up to be. A study on pistachios and cycling performance found that the nuts hampered performance on a 75 km cycling time trial. The study was ironically sponsored by American Pistachio Growers; they probably were not too happy with the results. The study was published in the November 2014 issue of PLoS One (Influence of Pistachios on Performance and Exercise-induced Inflammation, Oxidative Stress, Immune Dysfunction, and Metabolite Shifts in Cyclists: A Randomized, Crossover Trial; 2014. David C. Nieman, et al.).
The subjects were 19 trained cyclists. Those who ingested 3 ounces of shelled pistachios a day for two weeks saw a 4.8% decline in performance on a 75-km cycling timetrial. The results of the time trial can be seen in the figure below.
The authors reported higher levels of plasma raffinose, sucrose and myo-inositol in the pistachio ingesting group. Raffinose is a trisaccharide found in onions and many legumes. The soluble carbohydrate is a probiotic for beneficial bacteria in the colon that may reduce inflammatory bowel disease and cancer risk. However, raffinose may increase a leukotoxin, 9,10-DiHOME, that negatively impacts mitochondria. Exercise is known to increase gut permeability and may aid in allowing raffinose, sucrose and myo-inositol to leak across the gut.
The leukotoxin 9,10-DiHOME in the plasma was correlated to increases in plasma raffinose although the mechanism is unknown. 9,10-DiHOME impairs mitochondria function by disrupting the inner membrane of mitochondria and inhibiting cytochrome C release. The raffinose-associated increase in 9,10-DiHOME may be responsible for all, some or none of the decline in cycling performance.
It should be noted that the cyclists ingested a total 3 ounces of pistachios immediately before and during the time trial. The authors caution that the metabolites measured likely resulted from chronic ingestion of pistachios because of the time required to digest and catabolize the metabolites. It might be interesting to measure performance with the exclusion of pistachio consumption on the day of the time trial. The message here is to stay away from pistachios on race day.