1 Introduction

Functional foods and medicinal substances have been in the spotlight of late due to their ability to promote health and prevent disease in addition to their normal nutritional value. Functional foods are foods that contain bioactive substances whose effectiveness reaches to chronic disease prevention and promotion of health. They are rich in bioactive constituents like polyphenols, terpenoids, carotenoids, omega-3 fatty acids, and numerous other phytochemicals and nutraceuticals (Shahidi, 2006; Adefegha, 2018; Essa et al., 2021). "Food as medicine" dates back to ancient times and was espoused by Hippocrates famously, when he wrote, "Let food be thy medicine and medicine be thy food" (Chen and Su, 2023). This traditional wisdom has in recent times been supported by current scientific research that focuses on the functional foods' role in modulating physiological processes as well as augmenting health benefits (Abuajah et al., 2015; Langhans, 2017).

Chronic disease, such as cardiovascular disease, type 2 diabetes, cancer, and neurodegenerative disease, is a leading cause of morbidity and mortality worldwide. Chronic disease is also usually linked to lifestyle disorders such as poor dietary habits, physical inactivity, and obesity (Langhans, 2017; Chen and Su, 2023). Chronic disease puts a huge burden all over the world with long-term economic and social implications. For instance, cardiovascular diseases and cancer are some of the primary causes of death globally, and their prevalence continues to rise (Ferrari and Torres, 2003; Battino et al., 2018). Food components have a central role in the pathogenesis and development of such diseases, which is why treatments using functional foods and drug-like compounds are necessary (Shahidi, 2006; Essa et al., 2021).

This study will discuss the role of food drugs in preventing and managing chronic diseases by detailing bioactive compounds, mechanism of action, and potential beneficial effects on health. By examining various functional foods, i.e., fruits and vegetables, whole cereals, and sea foods, and their effects on diseases including cardiovascular disease, type 2 diabetes, cancer, and neurodegenerative disease, this study emphasizes the utilization of these foods in dietetic intervention. This research will also elaborate more on the promise of customized nutrition interventions and the practice of functional foods as part of public health programs in the quest to counteract the rising disease burden of non-communicable diseases.

2 Definition and Types of Functional Foods and Medicinal Substances

2.1 Historical and cultural background of functional foods and medicinal substances

Functional foods have, for centuries, been known to be beneficial for health. Various societies through history have consumed some foods not only for their nutrient value but also for their therapeutic potential. For instance, the Mediterranean diet of olive oil, berries, and honey has been associated with longevity and low prevalence of chronic diseases such as cancer and cardiovascular diseases (Battino et al., 2018). Similarly, common diets in most cultures have been made up of foods that are well known for their health-giving properties, i.e., fermented food with probiotics, which has been used to sustain gut health and immunity (Yahfoufi et al., 2018).

In the last decades, science has also continued to decipher the mechanisms by which such foods exert their beneficial effects. Epidemiological studies have translated into a better knowledge of the chemistry and mode of action of bioactives and phytochemicals in the diet. This has culminated in the growing acceptance and consumption of functional foods in today's dietary patterns for the promotion of health and disease prevention (Shahidi, 2006). The concept of functional foods has thus shifted from traditional knowledge to a science-based approach to nutrition and health.

2.2 Main categories and representative functional foods

Functional foods can be broadly grouped based on their bioactive constituents and their health benefits to humans. One of the top categories is food rich in polyphenols and phenolic compounds, which includes fruits, vegetables, and grains. Such food is an antioxidant and possesses the ability to prevent cardiovascular diseases and cancers of certain types by interacting with free radicals and inhibiting the oxidation of LDL cholesterol (Shahidi, 2006; Abuajah et al., 2015).

Another notable category is marine foods, which are high in omega-3 fatty acids. Oily fish and such foods are renowned for reducing blood triglycerides as well as cholesterol, thereby reducing the risk of heart disease (Shahidi, 2006). Additionally, fermented probiotic foods such as kefir and yogurt make huge contributions to improved gut health and immune system regulation (Yahfoufi et al., 2018; Baker et al., 2021). They inhibit the development of gut diseases and improve immune function in general.

2.3 Overview of active ingredients in functional foods

Functional foods contain a number of bioactive compounds that are accountable for their positive impact on health. Polyphenols, flavonoids, phenolic acids, and lignans are some of the most well-researched compounds. They occur in high concentrations in fruits, vegetables, tea, and wine and exert antioxidant, anti-inflammatory, and anti-cancer activities (Shahidi, 2006; Adefegha, 2018). Carotenoids, another bioactive category, exist in colored fruits and vegetables and are important for their contributions to eye health and the immune system (Abuajah et al., 2015).

Omega-3 and polyunsaturated fatty acids, predominantly found in fish and some plant oils, are essential for cardiovascular health. They lower inflammation, blood pressure, and lipids (Shahidi, 2006; Alkhatib et al., 2017). Probiotics and bioactive peptides present in fermented milk foods also improve gut health and immunity (Yahfoufi et al., 2018; Baker et al., 2021). The active components function synergistically with one another and provide general health benefits and are involved in chronic disease prevention and management.

3 Mechanisms of Action of Functional Foods and Medicinal Substances

3.1 Antioxidant and anti-inflammatory effects

Functional foods and therapeutic ingredients are widely known to have potent antioxidant and anti-inflammatory activities that play a substantial role in the prevention and cure of chronic diseases. Polyphenolic honey and strawberry ingredients, obtained as an example, have been reported to suppress oxidative stress by preventing ROS production and oxidative markers. The ingredients also normalize antioxidant enzyme activities and improve mitochondrial antioxidant status and function. They also control acute and chronic inflammatory mediators, which are vital in the onset of some human diseases (Battino et al., 2020). Total antioxidant capacity of bioactive food compounds, such as food bioactives in plant food, enhances the body's intrinsic antioxidant defense by inhibiting reactive oxygen and nitrogen species, preventing DNA damage and repair, and modulation of signal transduction pathways and gene expression (Nosrati et al., 2017).

Moreover, the anti-inflammatory properties of functional foods are attested to by their ability to modulate different physiological processes. For example, bioactive compounds in functional foods can regulate pro-inflammatory processes involving nuclear factor kappa B (NF-κB) and cytokine and chemokine-related processes. Modulating them ensures prevention and development of chronic diseases, including cancer and inflammatory bowel diseases (IBD) (Nosrati et al., 2017). The consumption of functional foods with antioxidants and anti-inflammatory compounds, i.e., cranberries, grapes, pomegranate, and green tea, was linked with reduced inflammation and improved metabolic health in a number of clinical trials (Figure 1) (Luvián-Morales et al., 2021).

3.2 Immune regulation

Functional foods also play a role in immune regulation, which is critical for general health and in chronic disease prevention. Some functional foods, including probiotics, prebiotics, and synbiotics, have been established to enhance immunocompetence by modulating gut microbiota and modulating the functional activities of epithelial cells, dendritic cells, and other immune cell types. These foods modulate cytokine production and the activity of immune cells such as lymphocytes, natural killer cells, and regulatory T cells, thereby improving the immune system (Yahfoufi et al., 2018). Addition of single micronutrients like selenium and dietary antioxidants (Vitamins A, E, and C) to functional foods has also been found to enhance immune function, but the levels of intake and the amounts to be recommended are still under investigation (López-Varela et al., 2002; Mason, 2024).

Immunomodulatory activities of functional foods are not limited to the stimulation of immune cell function. They also encompass immune pathway modulation and immune homeostasis maintenance. For example, the bioactive compounds in functional foods can modulate the expression of immune response genes and thus influence the infection-fighting capability of the body and inflammation reduction. Such control is particularly crucial in chronic disease, where a balanced immune response plays an important role in disease control and prevention (López-Varela et al., 2002). The immunoregulatory function of functional foods emphasizes the importance of a diet rich in bioactive compounds in maintaining a healthy immune system and chronic disease prevention.

3.3 Metabolic regulation and chronic disease prevention

Functional foods also have a crucial role in the metabolic regulation that is central in the prevention of chronic diseases such as type 2 diabetes mellitus (T2DM), cardiovascular disease, and metabolic syndrome. The bioactive components of the foods, such as polyphenols, terpenoids, flavonoids, and unsaturated fatty acids, have been shown to improve insulin sensitivity, lower cholesterol levels, and improve metabolic and microvascular functions. For instance, the Mediterranean diet, which is made up of fruits, vegetables, oily fish, olive oil, and tree nuts, is a model of functional foods that have these metabolic advantages (Alkhatib et al., 2017). Incorporating habitual exercise into the diet of functional foods can add protection advantages, yet this approach is not well studied in certain populations (Alkhatib et al., 2017).

Other than their metabolic significance, functional foods also control autophagy, a cell process for the removal of damaged or harmful protein clumps and faulty organelles. Autophagy is a key process that aids in ensuring cellular homeostasis and prevention against chronic diseases. Resveratrol, epigallocatechin-3-gallate, curcumin, and trehalose are some of the bioactive molecules identified to regulate autophagy, thereby possessing health-improving effects and adjunct therapy for chronic disease (Xie et al., 2019). The ability of functional foods to modulate metabolic pathways and cellular processes highlights their promise in chronic disease prevention and health promotion.

4 Role of Functional Foods in Cardiovascular Diseases

4.1 Reduction of blood pressure and cholesterol

Functional foods have been shown to make a major contribution towards the reduction in blood pressure and serum cholesterol, which are the central risk determinants of cardiovascular diseases (CVD). Polyphenol-containing foods such as cocoa have been shown to decrease blood pressure and improve the lipid profile. The mechanisms through which these effects are brought about include the activation of nitric oxide synthase, increased bioavailability of nitric oxide, and antioxidant action (Ludovici et al., 2017). Moreover, oat and psyllium soluble fiber has been proven to reduce significantly levels of cholesterol, and in particular low-density lipoprotein cholesterol (LDL-C), the main cause of atherosclerosis (Sirtoriet al., 2009).

Moreover, increased intakes of fruits and vegetables have also been associated with significant decreases in blood pressure as well as cholesterol level. Toh et al. (2019), using a systematic review and meta-analysis, discovered evidence that consumption of more than three portions of fruits and vegetables per day might be associated with significant decreases in triglycerides and diastolic blood pressure. The findings advocate for the use of food modification in prevention as well as CVD management by decreasing significant risk factors.

4.2 Improvement of vascular health

Functional foods also contribute to the improvement of vascular health by enhancing endothelial function and lowering arterial stiffness. For instance, dark chocolate intake, which contains flavonoids, has been linked with better endothelial function and reduced arterial stiffness, hence improved vascular health (Ludovici et al., 2017). Similarly, omega-3 fatty foods such as fish have been discovered to enhance the compliance of arteries as well as reduce inflammation, which are highly beneficial to the healthy condition of the blood vessels (Hasler et al., 2000).

In addition, certain bioactive fruit constituents such as polyphenols and anthocyanins have also been found to maintain vascular endothelial function and reduce oxidative stress. These bioactive constituents keep blood vessels intact and prevent endothelial dysfunction, a precursor to atherosclerosis and other cardiovascular diseases (Zhao et al., 2017). Synergism of these bioactive compounds comes forth as functional foods being capable of improving vascular health and preventing CVD.

4.3 Clinical evidence in cardiovascular diseases

Clinical trials have also provided the overwhelming evidence of the cardiovascular benefits of functional foods. Clinical trials, for example, have proven the value of food with antioxidants such as green tea, garlic, and almonds in terms of cardiovascular benefit. The foods have been shown to lower blood pressure, enhance lipid profiles, and prevent inflammation, thus lowering the risk of CVD (Zhou et al., 2017). In addition, consumption of berries like grapes, blueberries, and pomegranates has also been correlated with improved cardiovascular health, including reduced oxidative stress and increased endothelial function (Zhao et al., 2017).

Besides this, inclusion of functional foods in the diet has been shown to be effective on CVD risk factors in healthy individuals as well as those with diagnosed CVD. For instance, daily intake of phytosterols and stanol esters has been shown to decrease LDL-C efficiently, while milk peptides have shown to be effective in blood pressure control (Moore, 2011). These clinical findings highlight the potential of functional foods as an adjunct to standard medical therapy in prevention and treatment of cardiovascular disease.

5 Role of Functional Foods in Metabolic Diseases

5.1 Regulation of blood glucose and insulin sensitivity

Functional foods are also of key significance in the control of blood glucose and insulin sensitivity, which is vital in metabolic disease control, such as type 2 diabetes mellitus (T2DM). Functional foods carry bioactive food constituents in the form of polyphenols, dietary fiber, and unsaturated fatty acids that enhance insulin sensitivity and glucose homeostasis. For instance, constituents of the Mediterranean diet such as fruits, vegetables, olive oil, tree nuts, and oily fish are high in polyphenols and other nutraceuticals whose mechanism has been shown to decrease fasting glucose and increase insulin sensitivity in T2DM and at-risk individuals (Alkhatib et al., 2017). Macronutrients like dietary fiber and unsaturated fatty acids also clearly regulate insulin sensitivity and thus have a crucial role to play in the prevention of insulin resistance and T2DM (Figure 2) (Yang et al., 2023).

Moreover, functional foods can control the gut microbiota, a key determinant of metabolic health. Intake of high-fiber, polyphenol-rich, and vegetable-protein functional foods during a dietary intervention influenced profoundly faecal microbiota in T2DM patients, leading to improved glycemic management and reduced inflammation (Medina-Vera et al., 2012). This implies that long-term compliance with a functional food-rich diet can significantly contribute to blood glucose control and increased insulin sensitivity, thus rendering a possible therapeutic intervention for the management of metabolic disease.

5.2 Prevention of diabetes and its complications

Intake of functional foods also contributes to diabetes prevention and complications. Functional foods have bioactive compounds that can reduce postprandial hyperglycemia, manage carbohydrate and lipid metabolism, and reduce oxidative stress and inflammation. For example, functional foods like polyphenol-rich herbs (green tea, coffee) and fruits and vegetables have clinically relevant benefits in lowering cholesterol and fasting blood sugar levels and inflammation in T2DM patients (Mirmiran et al., 2014; Alkhatib et al., 2017). These facts indicate that functional foods could be included in medical nutrition therapy in the management of diabetes.

Furthermore, functional foods can avert diabetic long-term complications such as cardiovascular disease, neuropathy, nephropathy, and retinopathy. It has been established through research that functional foods can enhance dyslipidemia and insulin resistance, which play a primary role in the pathogenesis of diabetes complications (Mirmiran et al., 2014). For instance, a functional food-based diet has been shown to reduce metabolic endotoxemia and improve biochemical abnormalities in T2DM patients, thereby constituting a general dietary approach to diabetes treatment and complication prevention (Medina-Vera et al., 2019).

5.3 Intervention in metabolic syndrome

Metabolic syndrome, characterized by obesity, insulin resistance, dyslipidemia, and hypertension, is a worldwide health problem. Functional foods have been found to play an important role in preventing and reducing metabolic syndrome. Functional foods contain components that can increase insulin sensitivity, serum lipid profiles, antioxidant status, and inflammation levels. For example, traditional food products like fruits, vegetables, flaxseed, oat, barley, whole grain, soy, and milk were found to be composed of ingredients with potential health benefits in the treatment of metabolic syndrome (Made et al., 2012; Khan et al., 2013).

Additionally, consumption of certain functional foods has been linked to improved parameters of metabolic syndrome. For instance, "superfoods" such as blueberries, cranberries, garlic, and ginger have shown evidence for human benefit in intervention trials conducted under controlled conditions, although the evidence is weak and inconclusive (Driessche et al., 2018). These foods, however, would be likely to prevent metabolic syndrome through reduced waist circumference, blood pressure, and HDL cholesterol, triacylglycerol, or glucose levels.

6 Potential of Functional Foods in Cancer Prevention

6.1 Antioxidants and anticancer mechanisms

Functional foods with antioxidant properties form a significant pathway to inhibit cancer by clearing away the reactive oxygen species (ROS) and reducing oxidative stress, a proven determinant of cancer. The polyphenols, carotenoids, and vitamins found in fruits, vegetables, and spices have been observed to control multiple cellular processes that result in cancer development. For instance, bioactive molecules present in functional foods can influence gene expression, cell cycle regulation, and apoptosis and hence inhibit the proliferation and metastasis of cancer cells (Nosrati et al., 2017; Fagbohun et al., 2023; Marino et al., 2023).

Also, such antioxidants will enhance the body's internal defense system by scavenging free radicals and repairing damaged DNA. They also modulate signaling cascades such as NF-κB, MAPK, and PI3K, which are essential in the mediation of inflammation and carcinogenesis. Synergistic interactions of such compounds, just like in whole foods, are more effective than individual phytochemicals and hence the importance of consuming a variety diet with a lot of functional foods to enhance cancer prevention (Liu, 2003; Nosrati et al., 2017; Teibo et al., 2021).

6.2 Clinical studies on preventive effects

There have been a number of clinical trials that have supported the efficacy of functional foods against cancer. For example, nutrition interventions involving high dietary intake of fruits, vegetables, and spices have been correlated with reduced risk for various cancers including colorectal, breast, and liver cancers. Clinical trials are the best example that bioactive compounds of these foods can inhibit cancer occurrence through apoptosis, cell cycle arrest, and immune system modulation (Kammath et al., 2020; Teibo et al., 2021; Marino et al., 2023).

In particular, specific spices such as turmeric, garlic, and ginger have been studied extremely well for anticancer effects. Clinical trials have provided evidence of tumor growth inhibition by these spices and also enhancement of the effectiveness of standard chemotherapy for cancer, thereby reducing side effects and quality of life in cancer patients. But while the findings above are promising, there are more studies needed to better understand the mechanisms and to optimize the utilization of functional foods in cancer prevention (Kammath et al., 2020; Fagbohun et al., 2023).

6.3 Applications in different types of cancer

Functional foods have also been shown to prevent various cancers with varied mechanisms of action. For instance, in cervical cancer, the bioactive food constituents may induce apoptosis and block the microtubular network, hence stopping cancer cell proliferation. Similarly, in breast cancer, the constituents may control signaling cascades and block specific genes that are involved in tumor growth and metastasis (Teibo et al., 2021; Zhou, 2024).

Functional foods have been found to cause autophagy and generate reactive oxygen species (ROS), which lead to the death of cancer cells in liver cancer. The multifaceted mechanism through which functional foods exert anticancer effects indicates their role in the future as complementary therapy in treating cancer. With the inclusion of a combination of functional foods in the diet, individuals can utilize the bioactive compounds to reduce the risk of cancer and improve general health (Liu, 2003; Golovinskaia and Wang, 2021; Teibo et al., 2021).

7 Health-Promoting Effects of Functional Foods

7.1 Gut health and microbiome regulation

Functional foods are also critical in the maintenance of gut health and regulation of the microbiome. Some of the most critical ingredients include prebiotics, probiotics, and dietary fibers that aid in maintaining the balance and diversity of gut microbiota. These bioactive compounds induce proliferation of beneficial microbes and production of beneficial metabolites, which then have direct actions on the host, such as enhanced immunity and resistance to pathogens (Peng et al., 2020; Banerjee et al., 2023). Prebiotic modulation of the intestinal microbiota by functional foods has been shown to lower chronic disease-facilitating states, e.g., inflammation and oxidative stress (Peng et al., 2020).

Moreover, coarse cereals, being the nutrient-rich foods, have been identified as an important source of gut microbiota. They are converted into functional compounds by gut microbiota that allow host and such constituents to interact. This interaction is central to the action of chemoprevention against life-long diseases such as obesity, diabetes, and cardiovascular disease (Ren et al., 2021). Such modulation of gut microbiota by functional foods is thus an effective method of preventing chronic disease and advancing health.

7.2 Improvement in cognitive and mental health

Functional foods also have a considerable influence on cognitive and mental health. Certain bioactive molecules in functional foods such as polyphenols, flavonoids, and omega-3 fatty acids were shown to cross the blood-brain barrier and exhibit neuroprotective effects. The molecules can enhance cognitive impairment and mitigate neuropathological markers specific to neurodegenerative diseases such as Alzheimer's and Parkinson's (Delzenne and Mullin, 2018; Guo et al., 2022). For instance, Medicine-Food Homology (MFH) formulae in traditional Chinese medicine have exhibited potent neuroprotection by inhibiting Aβ-induced toxicity and inhibiting oxidative stress and inflammation (Guo et al., 2022).

In addition, the use of functional foods in mental health includes the modulation of neurologic diseases such as schizophrenia and autism. Phytochemicals contained in the cruciferous vegetables, for example, have exhibited antimicrobial, antioxidant, and cytoprotective activities that have the potential to control these diseases (Delzenne and Mullin, 2018). The addition of functional foods to the diet can thus improve cognitive function and mental health and provide a synergistic method of disease prevention and well-being promotion.

7.3 Anti-aging and longevity

The anti-aging and longevity properties of functional foods arise from their ability to modulate major physiological functions. Bioactive compounds such as polyphenols, carotenoids, and omega-3 fatty acids bind with enzymes related to degenerative diseases, hence providing protection against diseases like type-2 diabetes, cardiovascular disease, and neurodegenerative disorders (Adefegha, 2018). The bioactive compounds also provide antioxidant activity, reduce inflammation, and improve metabolic processes, which are very important in healthy aging (Langhans, 2017).

Moreover, functional foods have been found to influence the genetic and epigenetic aspects of aging. MicroRNAs and epigenetic changes are new biomarkers for studying the influence of functional foods on aging processes (Granado-Lorencio and Hernández-Álvarez, 2016). Through the ingestion of a variety of functional foods in the diet, it is likely that one may enhance longevity as well as quality of life, making them a noble component of a healthy lifestyle.

8 Safety and Challenges of Functional Foods

8.1 Long-term safety evaluation

Long-term safety of various functional foods is a very critical factor that must be filtered thoroughly. While it has been established that most functional foods, such as those with high levels of polyphenols, carotenoids, and omega-3 fatty acids, have been found to be beneficial to human health, their long-term consumption must be monitored meticulously. For instance, curcumin and turmeric have been extensively investigated for their therapeutic properties, but the reproducibility of benefits in human clinical trials remains questionable, evidencing the requirement for long-term safety studies (Kunnumakkara et al., 2023). Besides, the interaction between functional food bioactive compounds with respect to main enzymes involved in degenerative diseases suggests that functional foods can produce sophisticated activities over prolonged durations (Adefegha, 2018).

Moreover, the variation of the functional ingredient concentration caused by variable processing practices could affect their long-term safety. Certain processing practices might reduce the concentration of the beneficial constituents, while others might enhance them, thereby causing variable effects on health (Abuajah et al., 2015). Therefore, standardized processing and consistent quality control are necessary to give confidence in the long-term safety of functional foods.

8.2 Potential side effects and drug interactions

Functional foods, while being safe, also pose the risk of side effects and drug interaction. For example, excessive intake of some functional ingredients can lead to adverse consequences. The use of functional foods or food supplements with prescription drugs can lead to increased risk for food-drug interaction, hence reducing the efficacy or increasing the drug toxicity (Eussen et al., 2011). This is particularly challenging for patients with chronic conditions who are on long-term medication therapy.

Besides, the immunomodulatory effects of probiotics, prebiotics, and synbiotics, even though natural, may also lead to unintended side effects. These foods have the ability to modulate the immune system in a way that might not be entirely predictable, and this can lead to unwanted immune responses in a subset of patients (Yahfoufi et al., 2018). For this reason, it is necessary that intensive research be carried out to ascertain the potential side effects and interaction of functional foods with other medications.

8.3 Regulation and standardization in clinical applications

Regulation and standardization of functional foods are highly important for their safety and functionality in clinical practice. Functional foods, food supplements, and nutraceuticals are already at the interface of pharma and nutrition and require an open regulatory system to be able to successfully manage their use (Díaz et al., 2020). Various different regulations being used across different geographies can lead to confusion and abuse of the products. For instance, European, American, and Japanese regulatory approaches are all distinct, as per the demands for harmonized regulation.

Moreover, health technology assessments must be used in order to compare the cost-effectiveness and benefit-risk profiles of functional foods, dietary supplements, and drugs. In this way, it can help in evaluating the added value of functional foods as a supplement to drug therapy, so that they can be effectively and safely applied in clinical practice (Eussen et al., 2011). Standardized rules and regulations will help the proper integration of functional foods into healthcare systems, their safe usage in preventing chronic diseases, and promoting health results.

9 Conclusion and Future Directions

Moreover, health technology assessments must be used in order to compare the cost-effectiveness and benefit-risk profiles of functional foods, dietary supplements, and drugs. In this way, it can help in evaluating the added value of functional foods as a supplement to drug therapy, so that they can be effectively and safely applied in clinical practice (Eussen et al., 2011). Standardized rules and regulations will help the proper integration of functional foods into healthcare systems, their safe usage in preventing chronic diseases, and promoting health results.

Although there is encouraging evidence supporting the functional role of foods in the prevention of chronic disease, there are still some limitations and loopholes in current studies. Among these, one limitation is the differential availability and efficacy of bioactive compounds due to differential food processing and preparation practices. Secondly, the majority of the studies have been conducted in animal models or in vitro and more large-scale long-term human trials are required to confirm these data. One other gap is in the absence of consensus guidelines on the suggested intake of individual bioactive compounds, and it is therefore difficult to translate research findings into practical dietary advice. Besides, synergistic activity of different bioactive compounds and their interaction with food constituents is not fully understood and needs to be thoroughly investigated.

Subsequent research needs to work towards conducting well-planned human clinical trials to establish the safety and efficacy of functional foods and bioactive compounds in chronic disease prevention. Mechanisms of action for the compounds at the molecular level also need to be elucidated to understand how they modify disease pathways. In addition, studies should establish optimal processing and preparation technologies that have the ability to preserve or enhance bioavailability of bioactive compounds in functional foods.

Development of universal guidelines for the ingestion of functional foods and their bioactive ingredients will be vital as evidence-based translation of research results to public health recommendations proceeds. Additionally, investigation of the presumed synergic action of the consumption of a mixture of various bioactive compounds and their interactions with other food molecules can result in more efficient dietetic interventions aimed at preventing chronic diseases. The incorporation of functional foods in customized nutrition programs on the basis of genetic, metabolic, and lifestyle characteristics of the individual can further augment their potential in disease prevention and health promotion.

Acknowledgments

The authors thank the anonymous reviewers for their insightful and constructive comments on the manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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