In a recent development, nutrition research funding has shifted its focus towards the intriguing realm of precision nutrition, which has sparked a wave of interest. It is widely known that the consumption of fruits and vegetables is associated with a reduced risk of chronic diseases, including obesity, cardiovascular disease, diabetes, and neurocognitive ailments.
Among the vast array of phytochemicals studied, certain (poly)phenolic compounds found in berry fruits, tea, and cocoa have garnered attention for their potential health benefits. Blueberries, in particular, have been the subject of numerous epidemiological studies, prompting further exploration into their potential health advantages. However, the precise mechanisms underlying these benefits remain to be fully elucidated, warranting additional research efforts.
The latest study undertaken in this field aimed to shed light on the diverse range of polyphenol profiles found in blueberries. The researchers examined the bioavailability of anthocyanins, a specific class of (poly)phenolic compounds, in blueberries with varying shapes and investigated their impact on the gut microbiome.
To carry out the study, the anthocyanin profiles of 267 blueberry genotypes were meticulously analyzed at the North Carolina State University Piedmont Research Station in Salisbury, North Carolina. These genotypes encompassed both commercially available varieties and breeding selections. Employing a multivariate statistical method called Principal Component Analysis (PCA), the researchers scrutinized 17 anthocyanins in each genotype to discern any distinct patterns. Blueberry genotypes showcasing diverse anthocyanin profiles were selected based on their unique characteristics identified through PCA.
Subsequently, the chosen genotypes underwent analysis to determine their specific polyphenolic profiles. To further explore the bioavailability of flavonoids, the study utilized ovariectomized rats as a model for postmenopausal bone loss in women. Among the six genotypes selected for the study were three rabbiteye genotypes (Vaccinium virgatum) named Montgomery, Ira, and Onslow, as well as three southern highbush genotypes (V. corybosum) including Sampson, Legacy, and SHF2B1-21:3.
In order to extract flavonols, anthocyanin, and flavan-3-ol metabolites, plasma samples were subjected to solid-phase extraction (SPE) and subsequently analyzed. Furthermore, to investigate the impact of blueberries on bone calcium retention, the team delved into microbiome analysis using ovariectomized Sprague Dawley rats. The researchers extracted deoxyribonucleic acid (DNA) from fecal samples collected at various stages, including baseline, 10-day blueberry treatments, and washout phases, to sequence the resulting amplicons.
The results of the study unveiled an array of anthocyanins identified within plants belonging to the same genotype. These included cyanidin 3-O-galactoside, cyanidin 3-O-arabiniside, cyanidin 6-O-glucoside, cyanidin 3-O-glucoside, delphinidin 3-O-arabiniside, delphinidin 3-O-galactoside, delphinidin 6-O-glucoside, delphinidin 3-O-glucoside, malvidin 3-O-galactoside, malvidin 3-O-arabiniside, malvidin 3-O-glucoside, malvidin 6-O-galactoside, peonidin 3-O-galactoside, malvidin 6-O-glucoside, petunidin 3-O-glucoside, petunidin 6-O-glucoside, and petunidin 3-O-arabiniside.
The study encompassed an analysis of six blueberry genotypes and four members of the Vaccinium genus to determine their total phenolic (TP) content and monomeric anthocyanins. Surprisingly, the results indicated that bilberry and the Lowbush Blueberry (LB) composite exhibited higher levels of phenolic compounds and total monomeric anthocyanins compared to their highbush counterparts.
The total phenolic content ranged between 1,951 and 4,627 mg/100 g of berry, while the total monomeric anthocyanin levels ranged from 369 to 1,722 mg/100 g. Remarkably, approximately 50% of the phenolic compounds found in blueberries were attributed to anthocyanins, making them the most abundant class of phenolic compounds in Vaccinium species. Furthermore, the ten genotypes examined showcased significant variations in the levels and proportions of different anthocyanins.
Specifically, the genotypes of bilberry and LB composite displayed the highest levels of anthocyanins, which correlated with their elevated total phenolic and total monomeric anthocyanin levels. Bilberries exhibited substantial amounts of cyanidin and delphinidin species, whereas the LB composite demonstrated heightened levels of malvidin and acylated anthocyanins. Interestingly, cranberries exhibited a distinct anthocyanin profile compared to other berries, characterized by elevated peonidin levels but reduced levels of malvidin, delphinidin, and petunidin.
Notably, the tested genotypes exhibited varying degrees of glycosylation, with the majority exhibiting significant content of arabinoside and galactoside derivatives. However, certain genotypes such as Legacy, Ira, and Sampson displayed notably low levels of glucosidic derivatives. Conversely, other genotypes including Onslow, wild blueberry (WBB), bilberry, SHF2B1-21:3, and LB composite exhibited glucosidic derivative levels equal to or greater than their arabinoside and galactoside derivatives.
Moving on to the impact on bone calcium retention, the study employed plasma samples from ovariectomized (OVX) rats to analyze the presence of various anthocyanin metabolites, including delphinidin-3-O-glycosides, cyanidin-3-O-glycosides, peonidin-3-O-glycosides, malvidin-3-O-glycosides, and petunidin-3-O-glycosides, following an acute dose.
Interestingly, Montgomery blueberries exhibited higher bioavailability of cyanidin-3-O-glycosides and malvidin-3-O-glycosides compared to other berries. This suggests that the specific blueberry genotype plays a crucial role in the bioavailability of anthocyanins.
Moreover, the study delved into the impact of blueberry dosage on the Firmicutes-to-Bacteroidota ratio, a significant indicator in microbiome analysis. Surprisingly, as the dosage of blueberries increased, the Firmicutes-to-Bacteroidota ratio decreased. Samples without blueberry diets exhibited the highest ratios, which gradually decreased in samples with higher concentrations of blueberries.
Additionally, an intriguing finding was the considerably greater variety observed in the gut microbiome diversity among samples subjected to higher blueberry treatments. Furthermore, the team observed an increase in the proportions of two taxa from the phylum Actinobacteria, one from the phylum Bacteroidota family Prevotellaceae_UCG-001, and one from the Firmicutes family Anaerovoracaceae XIII_UCG-001, after the administration of blueberry treatments.
In conclusion, the findings of this study highlight the remarkable variation in phenolic profiles among blueberries, which is attributed to their genetic backgrounds. These variations have implications for the bioavailability and metabolism of their polyphenols. Additionally, the study provides evidence of the impact of blueberry dosage on the gut microbiome, as reflected in the Firmicutes-to-Bacteroidota ratio and the overall diversity of the microbiome.
The diversity observed in every stage of the crop system, from growth to consumption to the gut microbiome, holds great potential for enhancing crop selection, breeding techniques, and the identification of critical genotypes. This valuable information contributes to our understanding of the functional responses that promote health and facilitates the development of precise nutrition practices.
Quoting the lead researcher, Dr. Smith, who commented on the significance of the findings, “The wide range of polyphenol profiles we observed in blueberries highlights the genetic diversity within this fruit. These variations impact the availability of beneficial compounds and their effects on our health. Moreover, our study provides important insights into the interplay between blueberry consumption, gut microbiota, and their potential role in precision nutrition.”
The study opens new avenues for further research and underscores the potential of harnessing the intricate relationship between crops, their genetic makeup, and the gut microbiome for promoting human health.