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“Grapes are nutritional powerhouses that have been shown to have a variety of health benefits.”

Grapes are nutritional powerhouses that have been shown to have a variety of health benefits. They are a great source of fiber and contain many essential vitamins and minerals including copper, potassium, manganese, Vitamins K, C, E, B1, and B2. Each of these nutrients plays a critical role in the body, such as aiding red blood cell formation and nerve function (copper), blood clotting and bone health (Vitamin K), as well as immune system function, tissue growth and repair (Vitamin C). Grapes are also rich in polyphenols, large molecules that require the gut microbes to break them down into health promoting, absorbable compounds.

“…grape consumption may impact the gut microbiome, enzyme production, and biochemical pathways…”

Over the last few years, researchers have been investigating the neurocognitive and health benefits of grapes. A new study published May 2023 in the scientific journal Nature suggests that grape consumption may impact the gut microbiome, enzyme production, and biochemical pathways in very specific ways. This work follows two 2022 studies using mouse models. The first study found that mice fed a high fat diet supplemented with grape powder exhibited fewer anxiety-like behaviors, expedited time to complete a novel object recognition test, and increased gene expression. The addition of grape powder seemed to attenuate the negative effects of a high fat diet and these mice exhibited behavior, cognition, and genetic expression more like those fed a standard diet, rather than an exclusively high fat diet. The second study found that supplementing a high fat diet with grape powder led to upregulation of genes associated with reduction of oxidative stress and detoxification, delay in development of non-alcoholic fatty liver disease, and improvement in survival by delaying muscle wasting and frailty.

“…the relative abundance of different microbiota species was altered after two weeks of grape consumption…”

In the 2023 Nature study, researchers led by Dr. John M. Pezzuto, from the Western New England University College of Pharmacy and Health Sciences, investigated the impact that grapes have on the gut microbiome in humans. They examined the microbiome composition as well as blood, urine, and fecal metabolites of 29 healthy adult male and female subjects over the course of 8 weeks. For the first two weeks, all volunteers followed a controlled dietary regimen without grape consumption. For the second two weeks, all volunteers supplemented the controlled diet with freeze-dried grape powder, using the equivalent of three servings of grapes per day. For weeks 5-8 volunteers again followed only the controlled diet without grape consumption, during a ‘washout’ period. No difference in overall microbiome composition was found when the data of all 29 volunteers was taken together. However, the relative abundance of different microbiota species was altered after two weeks of grape consumption: Streptococcus thermophiles, a microbe which produces lactic acid in the gut, was elevated and Holdemania spp was decreased. During weeks 5-8, some altered enzyme levels and metabolic pathways persisted while other changes continued to occur, including a consistent increase in organisms that produce beneficial metabolites like anti-inflammatory short chain fatty acids .Thus, there may be delayed, beneficial effects of consuming grapes.

It is important to note that this was a small study using only 29 volunteers, which limits its generalizability and significance of findings. Nevertheless, this work provides convincing evidence that grape consumption modulates human microbiome composition in specific ways and provides insight into how this may occur through enzyme and pathway activation. Future studies may further elucidate the general applicability, biological consequences, and physiologic significance of grape consumption on the microbiome.