Plant-based diets (PBDs), characterized by the exclusion or minimal inclusion of processed foods and the primary consumption of plant sources, are increasingly recognized for their potential health benefits. While concerns exist regarding potential micronutrient deficiencies compared to traditional diets, substantial scientific evidence supports their role in preventing chronic non-communicable diseases such as type 2 diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. These benefits are largely attributed to the rich array of plant bioactive compounds like catechins, anthocyanins, polyphenols, and phytosterols. Metabolic syndrome (MetS), a cluster of conditions including visceral obesity, insulin resistance, hypertension, and dyslipidemia, significantly increases cardiovascular risk and mortality. Studies indicate that PBDs can positively influence metabolic health, though the quality of the PBD is crucial; a healthy PBD, emphasizing whole, unprocessed foods, is vastly different from an unhealthy one dominated by refined carbohydrates and processed foods. This review aims to comprehensively analyze the evidence linking PBDs to atherosclerosis, chronic diseases, and MetS, emphasizing the role of plant bioactive compounds and the importance of a high-quality dietary approach.

The review extensively cites previous research on the effects of plant-based diets on various health outcomes. Studies examining the impact of PBDs on type 2 diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer are referenced. Furthermore, the literature regarding the role of specific bioactive compounds found in plants (e.g., catechins, anthocyanins, polyphenols, phytosterols) and their potential mechanisms of action are reviewed. Existing studies on metabolic syndrome and its relationship to PBDs, including considerations of diet quality, are also thoroughly discussed, acknowledging the diversity of plant-based dietary patterns and their varying effects on health. The differences between vegan and plant-based diets, and the need for a standardized definition of PBD for research purposes, are also highlighted.

This review employed a systematic approach to examine the existing literature on plant-based nutrition and its impact on atherosclerosis, chronic non-communicable diseases, and metabolic syndrome. The authors searched multiple databases for relevant studies, applying specific inclusion and exclusion criteria. Studies were assessed for quality and methodological rigor. Data extracted from the included studies were synthesized to provide a comprehensive overview of the current state of knowledge. The review is structured to examine the evidence concerning each health condition (atherosclerosis, specific chronic non-communicable diseases such as diabetes, hypertension, and dyslipidemia, and metabolic syndrome) separately, while simultaneously highlighting their interrelationships. The role of plant bioactive compounds in mediating the health benefits of plant-based diets is emphasized. Figures and tables are included to summarize and visually represent the key findings. The authors discuss the diversity in defining plant-based eating patterns, acknowledging that the inclusion of fish, poultry, or dairy products may vary across studies. This is considered when synthesizing the research, separating the effects of vegan, vegetarian, and other plant-based diets.

The review highlights considerable evidence suggesting that plant-based diets offer significant health benefits regarding atherosclerosis, chronic diseases, and metabolic syndrome. Regarding atherosclerosis, PBDs appear to reduce LDL cholesterol, improve the LDL/HDL ratio, lower TMAO levels (though this relationship is debated), and enhance endothelial function. These effects are partially mediated by increased consumption of unsaturated fats, fiber, and bioactive compounds with antioxidant and anti-inflammatory properties. Regarding chronic non-communicable diseases, PBDs show promise in diabetes management through improved insulin sensitivity and blood sugar control (mediated by compounds like flavonoids, polyphenols, and isoflavones), as well as in hypertension reduction by decreasing sodium intake and increasing potassium and compounds such as anthocyanins. Dyslipidemia is also positively impacted by PBDs, reducing triglycerides and LDL cholesterol while improving HDL cholesterol (though HDL's role is complex and not always straightforward) with soluble fiber and phytosterols playing a key role. In the context of MetS, PBDs show benefits in reducing visceral obesity, insulin resistance, high blood pressure, and dyslipidemia, especially when focusing on high-quality plant-based diets. The review also explores the role of gut microbiota and short-chain fatty acids in mediating many of the observed positive health outcomes. While some studies show conflicting findings (e.g., the role of TMAO and HDL in relation to PBDs), this is often contextualized to the quality of the diet followed. Importantly, the authors distinguish between high-quality (healthy) and low-quality (unhealthy) plant-based diets, recognizing that the latter might not offer consistent benefits.

The findings of this comprehensive review reinforce the growing body of evidence supporting the numerous health benefits associated with plant-based diets. The positive effects on atherosclerosis, chronic diseases, and metabolic syndrome, mediated by various mechanisms (including reduced inflammation, improved lipid profiles, and enhanced endothelial function), highlight the significant potential of this dietary approach. The review emphasizes the importance of dietary quality, noting that a healthy PBD rich in whole, unprocessed plant foods offers distinct benefits compared to unhealthy PBDs. The role of gut microbiota and its interaction with dietary components is also highlighted as crucial for understanding the mechanisms underlying the observed health improvements. The review's findings have significant implications for public health and the prevention and management of these prevalent and interconnected chronic diseases. The authors point out some inconsistencies in current research, underscoring the need for future studies to further clarify the complex interplay between dietary patterns, specific bioactive compounds, gut microbiota, and health outcomes.

This review strongly supports the adoption of a healthy plant-based diet for improving health outcomes related to atherosclerosis, chronic diseases, and metabolic syndrome. Future research should focus on standardizing the definition and implementation of PBD interventions, further investigating the role of specific bioactive compounds and gut microbiota, and clarifying the complex relationship between HDL cholesterol and cardiovascular risk in the context of plant-based diets. The authors highlight the importance of individualized dietary approaches under the guidance of qualified professionals to ensure optimal nutrition and to address individual needs and preferences.

While this review provides a comprehensive overview, several limitations should be considered. The included studies were diverse in terms of methodologies, participant characteristics, and definitions of plant-based diets, making direct comparisons challenging. Many studies were observational, limiting causal inferences. More rigorous, large-scale randomized controlled trials with standardized definitions of plant-based diets are needed to strengthen the evidence base. Further research is also necessary to fully elucidate the complex mechanisms underlying the observed associations between PBDs and the health outcomes discussed. The authors acknowledge the need for more research to fully understand the optimal balance and ratio of different macro and micronutrients for specific populations in different contexts.