SAN DIEGO, April 24, 2012—A preliminary 16-person study suggests that eating pistachios may help alter levels of potentially beneficial bacteria in the gut, a finding that holds promise for supporting digestive health(1). The research, presented as an abstract this week at the Experimental Biology conference, is the first study of pistachios and almonds and their modulating role on the gut microbiota composition.
"Gut microbiota, or the microbial environment in the gastrointestinal tract, provides important functions to the human host," said Volker Mai, PhD, lead study author and assistant professor at the University of Florida's Institute of Food and Agricultural Sciences. "Modifying microbiota towards a 'beneficial' composition is a promising approach for supporting intestinal health, with potential effects on overall health, and it appears that pistachios may play a role in this modification."
Pistachios Deliver Essential Compounds to the Gut
Pistachios appear to have prebiotic characteristics; they contain non-digestible food components such as dietary fiber, which remain in the gut and serve as food for naturally occurring bacteria. They also contain phytochemicals that have the potential to modify microbiota composition. Foods with prebiotic properties may enhance the growth of beneficial bacteria in the digestive tract.
To examine this relationship between prebiotics found in pistachios and the gut, researchers conducted a feeding study at the Beltsville Human Nutrition Research Center in Maryland. Sixteen healthy individuals were randomly assigned to eat an American-style, pre-planned diet that included either 0 ounces, 1.5 ounces or 3 ounces of pistachios or almonds per day. Each participant's diet was calorie-controlled to ensure they neither gained nor lost weight during the intervention. Multiple stool samples were collected throughout the study and analyzed for bacterial community composition. The researchers also quantified the amounts of Lactic Acid Bacteria and Bifidobacteria in the stool, two groups of live microorganisms that reside in the digestive tract and help break down food substances.
After controlling for age, dietary factors and other relevant variables, the researchers observed that after 19 days, people who ate up to 3 ounces of pistachios (about 147 nuts or 2 servings) per day had increased changes in levels of various gut bacteria. According to the abstract, people who ate pistachios showed an increase in potentially beneficial butyrate-producing bacteria. Butyrate has been shown to be a preferred energy source for colonic epithelial cells and is thought to play an important role in maintaining colonic health in humans(2). The difference in gut microbes was stronger in people who ate pistachios rather than almonds. The researchers used "modern high throughput sequencing" to quantify specific gut bacterial DNA signatures before and after nut consumption. According to the researchers, this is the first study using this method to observe that pistachios and almonds may have the ability to help change the amounts of bacteria thriving in the gut.
"Fibers and incompletely digested foods, including nuts, that reach the proximal colon provide compounds required for maintaining a diverse microbiota," said Mai. "While still in the early stages of research, this study is a promising sign that increasing consumption of nuts, specifically pistachios, provides a novel means to modify the number of the gut's 'healthy' microbiota, with potential health benefits."
The research was funded by the Paramount Farms International and the Almond Board of California.
In-Shell Pistachios Offer a Package of Nutrients
A one-ounce serving of pistachios, with 49 kernels and 160 calories, provides 3 grams of dietary fiber, which is 12 percent of the recommended daily value, more than is found in a serving of wheat bread. Pistachios are also an excellent source of vitamin B6, copper and manganese and a good source of phosphorus and thiamin.
(1)Ukhanova M, Fredborg M, Daniels S, Netter F, Novotny JA, Gebauer SK, Xiaoyu W, Baer D, Mai V. Human gut microbiota changes after consumption of almonds or pistachios. Presented at 2012 Experimental Biology meeting in San Diego, CA on 4/23/2012.
(2)Appl Environ Microbiol. 2000 Apr;66(4):1654-61.
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