Exploring the science of phytonutrients, immunometabolism, cellular signaling, and the gut microbiome—and why the benefits of plant-rich diets extend beyond conventional vitamins and minerals.
When we think about healthy eating, we often focus on familiar nutritional components: protein, carbohydrates, fats, fiber, vitamins, and minerals.
These nutrients are essential for sustaining life, maintaining physiological function, and supporting long-term health.
However, food contains thousands of additional naturally occurring compounds that are not classified as essential nutrients.
Many of these molecules interact with biological systems in ways that remain only partially understood.
Among the most extensively investigated are polyphenols, a diverse family of plant-derived compounds found in fruits, vegetables, herbs, spices, tea, coffee, and numerous other foods.
Historically, polyphenols attracted scientific attention primarily because of their antioxidant properties.
More recent research suggests that their biological activities may extend far beyond directly neutralizing reactive molecules.
Polyphenols can interact with cellular signaling pathways, influence microbial metabolism, and modify the activity of proteins involved in immune and metabolic regulation.
In 2021, nutrition scientist Dariush Mozaffarian published Nutrition's Dark Matter of Polyphenols and Health in Nature Food, highlighting the importance of studying these compounds through the emerging discipline of network medicine.
A related study, Network Medicine Framework Shows That Proximity of Polyphenol Targets and Disease Proteins Predicts Therapeutic Effects of Polyphenols, demonstrated how computational methods could identify previously unrecognized molecular interactions involving dietary polyphenols.
Then, in 2024, researchers published Polyphenols: Immunonutrients Tipping the Balance of Immunometabolism in Chronic Diseases in Frontiers in Immunology.
This review explored how polyphenols may influence immune-cell metabolism, mitochondrial signaling, inflammatory pathways, and epigenetic regulation.
Together, these publications illustrate an important evolution in nutrition science:
Food does more than supply the raw materials necessary for human metabolism. Some dietary compounds may also participate in regulating the biological networks through which cells respond to nutrients, environmental conditions, and physiological demands.
Understanding these relationships provides a more comprehensive perspective on nutrition, inflammation, and long-term health.
1. What Are Polyphenols?
Polyphenols are a large and chemically diverse group of compounds produced by plants.
Many are classified as secondary metabolites, meaning they are not directly required for a plant's basic growth and reproduction but contribute to functions such as environmental adaptation, pigmentation, and defense.
Different plants produce different combinations of these compounds.
Their concentrations can vary with species, growing conditions, food preparation, and processing.
Polyphenols are commonly grouped into several major categories.
Flavonoids
Flavonoids are found in numerous fruits, vegetables, teas, and other plant foods. Examples include quercetin, catechins, anthocyanins, and flavanones.
Phenolic Acids
Phenolic acids include compounds such as caffeic acid and ferulic acid, which occur in foods including coffee, whole grains, fruits, and vegetables.
Stilbenes
Resveratrol is a well-known stilbene investigated for its potential effects on cellular signaling and metabolic regulation.
Lignans
Lignans occur in foods such as flaxseed, sesame seeds, and certain whole grains. Intestinal microorganisms can transform some dietary lignans into other biologically active metabolites.
Other Phenolic Compounds
Curcumin, found in turmeric, and rosmarinic acid, present in herbs such as rosemary, are additional examples of plant-derived phenolic compounds investigated for their biological activities.
Although these compounds share certain chemical features, they should not be treated as physiologically interchangeable. Their absorption, metabolism, tissue distribution, and biological effects can differ substantially.
2. Why Polyphenols Are Part of Nutrition's “Dark Matter”
Conventional nutritional databases provide information about calories, macronutrients, vitamins, minerals, and selected additional components.
However, they do not comprehensively characterize the thousands of chemical compounds present in food.
This incomplete characterization is central to the concept of nutritional dark matter.
The term does not imply that all unmeasured compounds are beneficial or clinically important.
Rather, it describes a gap between the chemical complexity of our diet and the relatively small proportion of that complexity routinely measured or studied.
In his 2019 article, The Dark Matter of Nutrition: Dietary Signals Beyond Traditional Nutrients, Jeffrey Bland explored several examples of food-associated molecules capable of interacting with biological systems in unexpected ways.
These included unusual amino acids, infectious prion proteins transmitted through contaminated food, and emerging research involving plant-derived microRNAs.
The examples illustrate the breadth of possible food–biology interactions.
However, they also represent very different levels of scientific evidence.
Foodborne prion transmission is an established cause of particular neurological diseases, whereas several proposed mechanisms involving unusual dietary amino acids or plant-derived microRNAs remain experimental or controversial.
The central lesson is not that ordinary plant foods contain hidden dangers or that every emerging molecular hypothesis should influence dietary recommendations.
It is that nutrition science has historically characterized only part of the biochemical exposure associated with eating.
Polyphenols represent one important area in which researchers are beginning to close this knowledge gap.
3. Beyond Antioxidants: Polyphenols as Biological Signaling Molecules
Polyphenols are frequently marketed as antioxidants.
This description is based partly on their chemical ability to participate in oxidation–reduction reactions.
However, antioxidant activity measured in a laboratory does not necessarily predict what happens after a compound is consumed.
Many dietary polyphenols undergo substantial metabolism during digestion and absorption.
Their circulating concentrations may be relatively low, and the compounds reaching tissues may differ chemically from those originally present in food.
This creates an important distinction between laboratory chemistry and human physiology.
Some polyphenols may influence health through interactions with receptors, enzymes, transcription factors, or other cellular signaling proteins rather than through direct antioxidant effects alone.
For example, experimental research has investigated the ability of selected polyphenols to influence pathways involving nuclear factor kappa B (NF-κB), AMP-activated protein kinase (AMPK), and nuclear factor erythroid 2-related factor 2 (NRF2).
These pathways participate in cellular responses to metabolic and environmental conditions.
The findings suggest that polyphenols may act as biological signaling molecules.
However, the direction and magnitude of these effects depend on the specific compound, concentration, cellular environment, and experimental model.
A molecular effect observed in cultured cells cannot automatically be assumed to occur after consuming a normal serving of food.
4. Network Medicine: Understanding How Polyphenols Interact With Multiple Biological Pathways
One of the most interesting developments discussed in Nature Food is the application of network medicine to dietary compounds.
Traditional biomedical research often examines individual molecular relationships.
A substance interacts with a receptor, alters an enzyme, or influences a specific signaling pathway.
Network medicine takes a broader approach.
It investigates how proteins and other biological components interact within complex networks.
The human protein interaction network is often called the interactome.
Rather than asking whether a polyphenol acts on a single disease-related protein, researchers can investigate whether its molecular targets are located near groups of proteins associated with particular diseases.
In 2021, do Valle and colleagues developed a computational framework for examining these relationships.
Their research investigated the molecular targets of polyphenols and compared them with proteins associated with different diseases.
The researchers found that the network proximity between these groups could help predict known biological relationships and identify hypotheses worthy of further investigation.
One particularly interesting finding involved rosmarinic acid.
The computational model predicted an interaction with pathways related to platelet function.
Subsequent laboratory experiments demonstrated that rosmarinic acid could inhibit platelet aggregation and platelet granule secretion under the tested conditions.
This provided experimental support for the proposed molecular mechanism.
However, it did not establish that consuming rosemary prevents heart attacks or that rosmarinic acid should be used as an antiplatelet treatment.
That distinction matters. Network medicine can identify plausible biological mechanisms, but clinical effectiveness must still be demonstrated through appropriately designed human research.
5. Polyphenols and the Immune System: An Introduction to Immunonutrition
The immune system is often described primarily in terms of protection against infections.
In reality, immune function involves a wide range of processes, including tissue surveillance, inflammatory signaling, cellular repair, and maintenance of tolerance.
These functions require energy and must adapt to changing conditions.
The field of immunometabolism examines how immune-cell activity is influenced by metabolic pathways and how immune signaling, in turn, influences metabolism.
The 2024 Frontiers in Immunology review explores polyphenols as potential immunonutrients.
In this context, immunonutrition refers to the study or targeted use of nutritional substances that can influence immune function.
The researchers describe how polyphenols may interact with metabolic signaling networks involved in immune-cell activation, differentiation, and inflammatory responses.
Their review emphasizes several interconnected mechanisms, including nutrient sensing, AMPK and mTOR regulation, mitochondrial signaling, and epigenetic modification.
These processes are relevant because immune cells must adjust their metabolism according to their immediate functional requirements.
An immune cell responding to a pathogen may require a different metabolic program from a cell involved in immune regulation or long-term memory.
Such metabolic changes are normal components of immune function.
The objective of immunonutrition is therefore not simply to suppress inflammation or stimulate immunity.
It is to understand whether appropriate dietary interventions can support healthy immune regulation.
6. AMPK and mTOR: How Nutrient Availability Influences Immune-Cell Metabolism
Two major regulatory systems discussed in the 2024 review are AMPK and mTOR.
AMPK helps cells detect changes in energy availability and coordinate responses that restore energy balance.
mTOR integrates signals related to nutrients, growth factors, and cellular conditions, helping regulate processes such as protein synthesis and cellular growth.
These pathways interact extensively.
Their activity helps coordinate whether cells prioritize particular anabolic, catabolic, maintenance, or adaptive processes.
The review examines experimental evidence suggesting that certain polyphenols may influence these pathways.
Examples include quercetin, curcumin, epigallocatechin gallate (EGCG), and other phenolic compounds.
In selected cellular and animal models, these compounds have been associated with changes in AMPK activity, mTOR signaling, and inflammatory mediator production.
However, activating AMPK or inhibiting mTOR is not universally beneficial.
These pathways are essential for healthy physiological function, and their appropriate activity depends on cellular context.
Immune cells require different metabolic programs at different stages of activation and differentiation.
Consequently, the goal is not to maximize or suppress an individual pathway.
It is to understand how dietary exposures may influence appropriate metabolic regulation.
7. Polyphenols, Mitochondria, and Inflammatory Signaling
Mitochondria are important not only for cellular energy production but also for metabolic signaling.
Their activity can influence inflammatory responses, cellular stress signaling, and other immune processes.
The 2024 review highlights interactions involving mitochondria, the endoplasmic reticulum, and lysosomes.
These structures participate in coordinated cellular activities.
One area of interest involves the NLRP3 inflammasome.
The NLRP3 inflammasome is a molecular complex involved in certain innate immune responses.
Its activation can contribute to the processing and release of inflammatory cytokines, including interleukin-1 beta and interleukin-18.
Experimental studies suggest that some polyphenols may influence pathways associated with NLRP3 activation.
For example, the review discusses evidence involving quercetin and resveratrol in models of mitochondrial stress and inflammatory signaling.
These findings raise the possibility that certain dietary compounds could influence inflammation through mechanisms involving mitochondrial function and cellular quality-control processes.
However, the evidence is predominantly mechanistic.
We cannot conclude that consuming particular foods reliably suppresses NLRP3 activity or treats inflammatory diseases in humans.
The research instead provides potential targets for future dietary and pharmacological investigation.
8. Polyphenols, the Gut Microbiome, and Individual Variation
Many dietary polyphenols are not completely absorbed in the upper gastrointestinal tract.
A portion reaches the colon, where intestinal microorganisms can transform them into smaller metabolites.
These metabolites may differ from the original compounds in their absorption, biological activity, and distribution.
Consequently, the health-related effects of a polyphenol-rich food may depend partly on the metabolic capabilities of the intestinal microbiome.
This creates a bidirectional relationship.
Dietary compounds can influence microbial communities, while microbial metabolism can alter the compounds available to human tissues.
The composition and activity of the gut microbiome vary among individuals.
These differences may contribute to variation in responses to dietary interventions.
For example, two individuals consuming the same polyphenol-containing food may produce different patterns of microbial metabolites.
However, the clinical implications of these differences are still being investigated.
A 2026 study in Nature, Gut Micro-organisms Associated With Health, Nutrition and Dietary Interventions, examined diet, microbial profiles, and health-related measurements in more than 34,000 participants.
The researchers identified relationships among dietary patterns, microbial species, and cardiometabolic characteristics.
These findings illustrate the growing potential of microbiome-informed nutritional research.
Nevertheless, current evidence does not justify assuming that every individual requires microbiome testing to determine which polyphenol-rich foods to eat.
9. What About Dietary Polyphenols and Gene Expression?
Another fascinating area of research involves the relationship between diet and gene regulation.
Gene expression refers to the processes through which cells use genetic information to produce functional molecules.
These processes are influenced by numerous internal and external signals.
The 2019 article by Bland discusses the possibility that dietary compounds, including certain plant-derived microRNAs, could influence gene regulation.
It also describes research involving plant-derived extracellular vesicle-like particles and their interactions with intestinal microorganisms.
These findings are intriguing, particularly because they suggest possible mechanisms through which dietary substances may participate in interspecies molecular communication.
However, the presence of plant-derived RNA in food does not establish that it survives human digestion in sufficient quantities to regulate human genes.
Research on the absorption and functional significance of dietary microRNAs has produced conflicting findings, and many proposed mechanisms remain incompletely validated.
Likewise, evidence that a polyphenol affects gene expression in a laboratory model does not establish that eating the corresponding food will produce the same effect in humans.
These discoveries should be viewed as emerging research rather than established applications of personalized nutrition.
The practical implication is that dietary exposures may interact with gene-regulatory systems through multiple mechanisms.
Determining which interactions matter for clinical health remains an important scientific challenge.
10. Polyphenols and Chronic Disease: What Does Human Research Show?
Mechanistic studies provide valuable information about how dietary compounds might influence physiology.
However, human studies are necessary to determine whether these mechanisms translate into meaningful health outcomes.
A particularly relevant 2025 study in Nature Food, High Diversity of Dietary Flavonoid Intake Is Associated With a Lower Risk of All-Cause Mortality and Major Chronic Diseases, examined 124,805 participants from the UK Biobank.
Researchers investigated relationships between flavonoid intake, diversity of flavonoid sources, and long-term health outcomes.
Participants with greater diversity of flavonoid intake demonstrated approximately 6–20% lower relative risks across several measured outcomes, including mortality and selected chronic diseases.
These findings were observational.
They do not establish that increasing flavonoid diversity directly caused the observed reductions in disease risk.
Participants with diverse plant-food intake may also differ in other important health behaviors and circumstances.
Nevertheless, the research supports further investigation of dietary diversity as one potentially important dimension of nutritional quality.
What About Clinical Trials?
Clinical trials have investigated particular polyphenols and polyphenol-rich extracts for outcomes such as blood pressure, glucose regulation, and lipid metabolism.
For example, a randomized controlled trial published in the European Journal of Clinical Nutrition in 2026 investigated a specific polyphenol-rich plant extract in 120 adults with elevated LDL cholesterol.
The intervention improved several lipid measurements compared with placebo over six months.
However, the findings concern a particular standardized extract, dose, population, and study duration.
They cannot automatically be generalized to all polyphenols or ordinary food consumption.
Industry involvement also warrants careful consideration when interpreting the results.
Similarly, clinical benefits involving selected metabolic biomarkers do not necessarily establish reductions in long-term cardiovascular events.
The overall evidence suggests promise for particular compounds and dietary interventions, while highlighting the need for larger and longer-term trials.
11. Does More Polyphenol Intake Always Mean Better Health?
Not necessarily.
The relationship between dietary compounds and physiological outcomes is not always linear.
More of a biologically active substance does not automatically produce greater benefits.
Dose, bioavailability, metabolism, medications, existing health conditions, and potential adverse effects all matter.
For example, certain concentrated botanical extracts can produce exposures substantially higher than those achieved through ordinary food consumption.
Some supplement formulations can also interact with medications or introduce safety concerns.
This is particularly important for individuals using anticoagulant or antiplatelet medications, those with liver disease, and people undergoing specialized medical treatment.
A whole-food dietary pattern should therefore not be treated as equivalent to consuming large doses of isolated phytochemicals.
The clinical evidence supporting plant-rich dietary patterns is generally more established than the evidence for many individual polyphenol supplements.
The most defensible recommendation is not to pursue the highest possible polyphenol intake.
It is to emphasize dietary quality, adequate nutrition, and a variety of nutritious foods within an individualized eating pattern.
12. Where Can You Find Polyphenols in Everyday Foods?
Polyphenols occur naturally in a wide variety of plant-based foods, including fruits, vegetables, whole grains, legumes, nuts, seeds, herbs, spices, and beverages such as coffee and tea. However, different foods contain distinct combinations and concentrations of these compounds, each with potentially different biological properties. This diversity highlights the importance of consuming a varied, nutrient-dense diet rather than relying on a small selection of foods or isolated supplements.
Berries, including blueberries, blackberries, raspberries, and strawberries, are rich sources of anthocyanins and other flavonoids that contribute to their characteristic colors and have been investigated for their potential roles in cardiovascular and metabolic health. Apples and onions provide quercetin and related flavonoids, while citrus fruits contain flavanones such as hesperidin and naringenin. Green and black tea provide catechins and other polyphenols, whereas coffee contains chlorogenic acids and related phenolic compounds. Cocoa provides flavanols, which have attracted research interest for their potential effects on vascular function.
Herbs and spices also contribute substantial chemical diversity despite generally being consumed in smaller quantities. Rosemary, oregano, and other culinary herbs contain compounds such as rosmarinic acid, while turmeric provides curcuminoids that have been investigated for their interactions with inflammatory and metabolic signaling pathways. Flaxseeds and sesame seeds supply lignans, some of which are transformed by intestinal microorganisms into metabolites with potential biological activity. Extra-virgin olive oil contains phenolic compounds such as hydroxytyrosol and its derivatives, contributing to the complex chemical composition of Mediterranean-style dietary patterns.
Importantly, the concentrations and bioavailability of these compounds vary according to food variety, growing conditions, ripeness, preparation, processing, storage, and individual digestive physiology. Furthermore, the presence of a particular polyphenol does not automatically establish that consuming the food will produce a specific therapeutic effect. Many proposed benefits remain under investigation, particularly regarding the concentrations achievable through ordinary dietary intake.
Rather than emphasizing individual compounds or attempting to maximize polyphenol consumption, a practical, research-informed approach prioritizes dietary diversity, nutritional adequacy, and the regular inclusion of a broad variety of minimally processed plant foods. This approach helps individuals obtain a diverse mixture of essential nutrients, dietary fiber, and naturally occurring phytochemicals while supporting established principles of healthy eating. It also recognizes that optimal dietary choices should be adapted to individual nutritional requirements, food tolerances, cultural preferences, and health conditions.
13. Why Polyphenol Research Matters for Precision Nutrition
One of the major goals of precision nutrition is to understand why individuals respond differently to dietary interventions.
Polyphenol research is particularly relevant because biological responses may depend on several interacting factors.
These include the specific compound consumed, its chemical form, the food matrix, gastrointestinal absorption, microbial metabolism, individual physiology, medication use, and existing health conditions.
Network medicine offers another dimension by investigating the potential molecular targets of particular compounds.
Together, these approaches may eventually help researchers identify which dietary interventions are most appropriate for particular individuals or conditions.
However, many challenges remain.
Researchers must determine whether predicted molecular interactions occur at physiologically relevant concentrations.
They must distinguish the activity of isolated compounds from the effects of whole foods.
They must establish whether observed biomarker changes lead to meaningful health improvements.
And they must develop approaches that are practical, accessible, and clinically validated.
Precision nutrition is therefore an evolving research and clinical discipline rather than a justification for extensive testing or supplementation in every individual.
14. Our Approach to Phytonutrients and Nutrition
Our Eat Well philosophy recognizes that nutritional health encompasses far more than meeting calorie and macronutrient targets.
We consider the importance of nutritional adequacy, dietary quality, food diversity, lifestyle, and individual physiological needs.
The emerging science of polyphenols reinforces the value of understanding food as a complex mixture of nutrients and other biologically relevant compounds.
Within our nutritional coaching programs, we emphasize education about food quality, meal planning, practical nutrition skills, and sustainable dietary habits.
For individuals managing metabolic or other medical concerns, assessment may also involve nutritional history, established clinical risk factors, and appropriately selected laboratory investigations.
We recognize that dietary patterns can influence inflammatory and metabolic health, but we do not assume that every patient requires specialized phytochemical testing or high-dose supplementation.
Our approach aims to translate research into practical recommendations while distinguishing established clinical benefits from emerging hypotheses.
We also acknowledge that nutrition is only one component of overall health.
Physical activity, sleep, stress, medications, medical conditions, and environmental factors may influence an individual's response to dietary changes.
By considering these relationships, we seek to help patients develop informed, individualized nutrition strategies that support long-term well-being.
Conclusion: Food Is More Than Fuel
The science of polyphenols illustrates how our understanding of nutrition continues to evolve.
Food provides the essential nutrients necessary for cellular structure, energy production, and physiological maintenance.
But it also exposes the body to a complex mixture of compounds that may interact with molecular networks, microbial communities, and regulatory systems.
Research involving network medicine, immunometabolism, mitochondrial biology, and gene regulation is beginning to clarify some of these interactions.
At the same time, important uncertainties remain.
A computational prediction does not establish clinical effectiveness. A change in cellular signaling does not necessarily produce a health benefit. And a beneficial compound in food does not automatically become a safe or effective treatment when concentrated into a supplement.
These distinctions are essential for maintaining a research-informed approach to nutrition. Nevertheless, the broader implications are significant.
The future of nutrition science may depend as much on understanding how food-derived compounds influence biological regulation as on identifying the nutrients required for survival.
We believe this expanding understanding supports a comprehensive and personalized approach to nutrition—one that respects the complexity of food, the adaptability of human physiology, and the importance of translating scientific discoveries into practical, evidence-based care.
Research References
Bland JS. The Dark Matter of Nutrition: Dietary Signals Beyond Traditional Nutrients. Integrative Medicine. 2019;18(2):12–15. Full text
Mozaffarian D. Nutrition's dark matter of polyphenols and health. Nature Food. 2021;2:139–140. https://doi.org/10.1038/s43016-021-00248-2
Ferreira C, Vieira P, Sá H, et al. Polyphenols: immunonutrients tipping the balance of immunometabolism in chronic diseases. Frontiers in Immunology. 2024;15:1360065. https://doi.org/10.3389/fimmu.2024.1360065
do Valle IF, Roweth HG, Malloy MW, et al. Network medicine framework shows that proximity of polyphenol targets and disease proteins predicts therapeutic effects of polyphenols. Nature Food. 2021;2:143–155. https://doi.org/10.1038/s43016-021-00243-7
Parmenter BH, Thompson AS, Bondonno NP, et al. High diversity of dietary flavonoid intake is associated with a lower risk of all-cause mortality and major chronic diseases. Nature Food. 2025;6:668–680. https://doi.org/10.1038/s43016-025-01176-1
Gut micro-organisms associated with health, nutrition and dietary interventions. Nature. 2026;650:450–458. https://doi.org/10.1038/s41586-025-09854-7
Sirvent P, Langhi C, Vallier M, et al. Effect of a polyphenol-rich extract on LDL cholesterol in mild to moderate hypercholesterolemia: a randomized, double-blind, placebo-controlled trial. European Journal of Clinical Nutrition. 2026;80:285–292. https://doi.org/10.1038/s41430-025-01691-1
Barabási AL, Menichetti G, Loscalzo J. The unmapped chemical complexity of our diet. Nature Food. 2020;1:33–37. https://doi.org/10.1038/s43016-019-0005-1