Dietary Flavonoid Intake and Chronic Sensory Conditions: A Scoping Review

Association of 15 common dietary factors with tinnitus: a systematic review and meta-analysis of observational studies

OBJECTIVE

A systematic analysis was conducted to investigate the association between tinnitus incidence and daily dietary patterns.

DESIGN

We conducted a systematic review and meta-analysis of observational studies.

DATA SOURCES

The PubMed, Embase, Web of Science and Cochrane Library databases were searched from their inception to 25 May 2024.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included observational studies from peer-reviewed English-language journals that examined tinnitus presence or severity in adults aged 18 years or older, including associated prevalence estimates.

DATA EXTRACTION AND SYNTHESIS

Data extraction was independently conducted by two evaluators, who assessed research bias using the Agency for Newcastle-Ottawa Scale and applied evidence classification criteria for aggregate grade strength assessment. This study adhered to the guidelines of the Preferred Reporting Project (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and Meta-Analysis of Epidemiological Observational Studies, as well as the PROSPERO Registry protocols. A mixed-effect model combined maximum adjusted estimates, with heterogeneity measured using the I2 statistic. Sensitivity analysis validated the robustness of the analysis, and publication bias was assessed qualitatively and quantitatively.

RESULTS

A total of 10 retrospective studies were identified and included in this analysis, with the last eight studies incorporated into the meta-analysis. Fifteen dietary factors were examined. Fruit intake, dietary fibre, caffeine and dairy product consumption were negatively correlated with tinnitus incidence (OR=0.649 (95% CI 0.532, 0.793), p<0.0001), (OR=0.918 (95% CI 0.851, 0.990), p=0.03), (OR=0.898 (95% CI 0.862, 0.935), p<0.00001), (OR=0.827 (95% CI 0.766, 0.892), p<0.00001), respectively. A sensitivity analysis confirmed the robustness of the findings.

CONCLUSIONS

This systematic review and meta-analysis suggest a link between particular dietary elements and a lower incidence of tinnitus.

PROSPERO REGISTRATION NUMBER

CRD42023493856.

Sensory Characteristics and Impact of Flavanol-Rich Grape and Blueberry Extract on Blood Flow Velocity and Oxidative Stress

BACKGROUND

Several epidemiological studies and intervention trials have demonstrated that grapes and blueberries, which are rich in flavanols, can lower the risk of cardiovascular disease. However, the mechanisms of action of these compounds remain unclear due to their low bioavailability.

OBJECTIVE

This study aimed to characterize the sensory properties, blood flow velocity, and oxidative stress of a polyphenol rich grape and blueberry extract (PEGB) containing approximately 16% flavanols (11% monomers and 4% dimers).

METHOD

A sensory property of PEGB was compared with quercetin at uniform concentration using healthy young subjects. In addition, the reactivity of PEGB with O2•- was also compared with quercetin utilizing a luminescence method. Furthermore, the effect of a single administration of PEGB on the blood flow velocity of skeletal muscle arterioles was investigated using a laser Doppler method in rats.

RESULTS

At a concentration where quercetin was barely tasteful, flavanol in PEGB exhibited a robust astringent taste. Furthermore, under pH conditions mimicking the oral cavity and intestinal tract, PEGB promoted O2•- production at low concentrations and scavenging O2•- at high concentrations. In contrast, quercetin demonstrated antioxidant activity. A single oral administration of PEGB significantly increased the blood flow velocity of skeletal muscle arterioles.

CONCLUSION

The results demonstrate that PEGB exhibited a pronounced astringent taste, O2•- production at low concentrations in neutral pH environments, and significantly enhanced blood flow to skeletal muscle following a single administration to rats. These findings highlight the necessity for further investigation into the causal relationships between oral perception, redox properties, and bioactivity of polyphenols.

Sensory Nutrition and Bitterness and Astringency of Polyphenols

Recent studies have demonstrated that the interaction of dietary constituents with taste and olfactory receptors and nociceptors expressed in the oral cavity, nasal cavity and gastrointestinal tract regulate homeostasis through activation of the neuroendocrine system. Polyphenols, of which 8000 have been identified to date, represent the greatest diversity of secondary metabolites in plants, most of which are bitter and some of them astringent. Epidemiological studies have shown that polyphenol intake contributes to maintaining and improving cardiovascular, cognitive and sensory health. However, because polyphenols have very low bioavailability, the mechanisms of their beneficial effects are unknown. In this review, we focused on the taste of polyphenols from the perspective of sensory nutrition, summarized the results of previous studies on their relationship with bioregulation and discussed their future potential.

A systematic review exploring the mechanisms by which citrus bioflavonoid supplementation benefits blood glucose levels and metabolic complications in type 2 diabetes mellitus

BACKGROUND

Citrus bioflavonoids are polyphenolic compounds that are derived from citrus fruits and vegetables. Although they are well known for their powerful antioxidant properties, their effects on glycemic control are not well understood. This review aims to highlight the potential benefits of using citrus bioflavonoids in patients with type 2 diabetes mellitus and its metabolic complications, as well as the medicinal effects of known subclasses of naturally occurring citrus bioflavonoids.

METHODS

In this systematic review, a survey of studies was conducted from January 2012 to February 2023 using various databases (PubMed, Medline, Google Scholar, and Scopus) to determine the effects of citrus bioflavonoid supplementation on reducing oxidative stress, improving lipid profiles, and glycemic index in patients with diabetes mellitus, as well as the proposed mechanisms of action.

RESULTS

The results of the survey indicate that citrus bioflavonoids may have a positive impact on reducing oxidative stress levels in patients with type 2 diabetes mellitus. In addition to reducing oxidative stress, citrus bioflavonoids may also have a positive impact on other markers of diabetes. For example, studies have shown that they can reduce non-enzymatic protein glycation, which is a process that occurs when glucose molecules bind to proteins in the body.

CONCLUSION

The reduction in oxidative stress that can be achieved using citrus bioflavonoids may help to maintain antioxidant levels in the body, thereby reducing the severity of diabetes and its complications. These findings suggest that citrus bioflavonoids may be a useful complementary therapy for patients with diabetes.

Metabolomics Reveals Nutritional Diversity among Six Coarse Cereals and Antioxidant Activity Analysis of Grain Sorghum and Sweet Sorghum

Coarse cereals are rich in dietary fiber, B vitamins, minerals, secondary metabolites, and other bioactive components, which exert numerous health benefits. To better understand the diversity of metabolites in different coarse cereals, we performed widely targeted metabolic profiling analyses of six popular coarse cereals, millet, coix, buckwheat, quinoa, oat, and grain sorghum, of which 768 metabolites are identified. Moreover, quinoa and buckwheat showed significantly different metabolomic profiles compared with other coarse cereals. Analysis of the accumulation patterns of common nutritional metabolites among six coarse cereals, we found that the accumulation of carbohydrates follows a conserved pattern in the six coarse cereals, while those of amino acids, vitamins, flavonoids, and lipids were complementary. Furthermore, the species-specific metabolites in each coarse cereal were identified, and the neighbor-joining tree for the six coarse cereals was constructed based on the metabolome data. Since sorghum contains more species-specific metabolites and occupies a unique position on the neighbor-joining tree, the metabolite differences between grain sorghum 654 and sweet sorghum LTR108 were finally compared specifically, revealing that LTR108 contained more flavonoids and had higher antioxidant activity than 654. Our work supports an overview understanding of nutrient value in different coarse cereals, which provides the metabolomic evidence for the healthy diet. Additionally, the superior antioxidant activity of sweet sorghum provides clues for its targeted uses.