Pistachios at night transfer gut bacteria from diabetic patients

Adults who swap traditional carbohydrate-based bedtime snacks for pistachios may reshape the gut microbiome in prediabetes, according to research published in current nutrition development.

The study reveals how pistachios provide alternatives to standard dietary recommendations for managing blood sugar levels.

Researchers at Penn State found that consuming about two ounces of pistachios each night consumes two ounces of gut bacteria community each night compared to eating the recommended 15-30 grams of carbohydrates (equivalent to one or two slices of whole grain bread).

“Pistachios seem to be able to meaningfully alter the gut microbial landscape in prediabetes, especially when nighttime snacks are consumed,” explains Kristina Petersen, associate professor of nutritional sciences and senior author of the study.

Good bacteria flourish with pistachio consumption

The team analyzed fecal samples from 51 adults who participated in a randomized cross-border trial. Each participant completed a 12-week pistachio intervention and also completed a 12-week night snack recommendation.

Research shows that pistachio consumption increases the abundance of several beneficial bacterial groups while reducing potentially harmful groups. Most notably, the researchers observed higher levels:

• Rosberry bacteria, an important butyrate producer – a short-chain fatty acid that provides energy to colon cells
• lachnospipileaceae UCG-004 and UCG-008, Bacterial Family Related to Gut Health
• Other microorganisms related to improving metabolic function

Meanwhile, pistachios lower the more unfavorable bacterial levels, including hydrogen plant nutrition (producing compounds associated with kidney and heart problems) and yellow bacteria yellow bacteria (destroying beneficial antioxidants in food).

Microbiome changes without immediate metabolic effects

While the study clearly demonstrated changes in gut bacteria, these changes did not immediately translate into improvements in glycemic control or other metabolic measurements. Previous analysis from the same trial found that pistachio and carbohydrate snacks had similar effects on blood sugar levels.

“These changes in these microbiomes may bring other long-term health benefits that help slow the development of type 2 diabetes or reduce systemic inflammation – which we hope to explore in future research.”

The study used 16S rRNA gene sequencing to analyze bacterial communities, allowing researchers to identify specific changes in the gut microbiome. This approach not only reveals a simple increase or decrease in bacteria, but also changes throughout the microbial ecosystem.

Another way to snack at night

These findings provide a potential alternative to standard dietary advice for one-third of Americans with diabetes. Traditional advice usually recommends eating carbohydrates before going to bed to help regulate blood sugar levels throughout the night and in the morning.

Lead author Terrence Riley, who conducted the study while earning her PhD at Penn State University, pointed out the actual meaning: “For people with prediabetes, a common dietary advice is to consume nighttime snacks, which consists of 15 to 30 grams of carbohydrates to help regulate blood sugar levels overnight and morning.”

The advantage of this study is its design – a randomized cross-border trial in which all participants received two treatments in a random order. This approach allows researchers to isolate the effects of pistachios while controlling individual differences in the composition of the gut microbiome, which can vary widely among people.

While more research is needed to understand the long-term health effects of these microbiome changes, the study provides promising evidence that simple diet swaps may meaningfully affect gut bacteria, thus supporting metabolic health.

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