Nature’s Healing Arsenal in Foods

 

Nature’s Healing Arsenal: Functional Foods and Phytochemicals in Disease Prevention and Therapy

by: 

Nutritionist Lim Ju Boo and Professor Dr M Sage MD PhD  

Abstract

Functional foods are increasingly recognized for their capacity to promote health and reduce the risk of chronic diseases. Beyond providing essential nutrients, these foods contain hundreds, if not thousands, of phytochemicals and bioactive compounds. These compounds, including ergothioneine in mushrooms, sulforaphane in broccoli sprouts, curcumin in turmeric, and catechins in green tea, play vital roles in modulating oxidative stress, inflammation, metabolism, and immunity. This article provides a comprehensive overview of selected functional foods and their phytochemicals, with emphasis on mechanisms of action, disease-preventive roles, and evidence from clinical studies.

Introduction

The concept of functional foods extends beyond basic nutrition. These are everyday foods that confer specific physiological benefits or reduce disease risk, thanks to their natural bioactive components. Phytochemicals, a diverse class of plant- and microbe-derived compounds, exert health-promoting effects by interacting with cellular pathways. Unlike vitamins and minerals, phytochemicals are not considered essential nutrients, yet their presence in the human diet is associated with reduced risk of non-communicable diseases such as cardiovascular disease, cancer, diabetes, and neurodegeneration.

Among the wide array of bioactives, certain compounds stand out due to their robust mechanistic evidence and clinical evaluation. These include ergothioneine and β‑glucans from mushrooms, sulforaphane from cruciferous vegetables, curcumin from turmeric, epigallocatechin gallate (EGCG) from green tea, organosulfur compounds from garlic, lycopene from tomatoes, and isoflavones from soy. Their health effects are mediated by key molecular pathways including activation of antioxidant defenses, suppression of pro-inflammatory signals, modulation of lipid and glucose metabolism, and regulation of immune responses.

Ergothioneine: The Longevity Molecule from Mushrooms

Ergothioneine is a sulphur-containing antioxidant produced by fungi and some bacteria, but not by plants or animals. Humans acquire it exclusively through diet, with mushrooms being the richest source. Ergothioneine is transported into cells by the specific transporter OCTN1 (SLC22A4) and preferentially accumulates in tissues exposed to high oxidative stress such as the liver, kidneys, brain, and eyes. It functions as a cytoprotectant, scavenging reactive oxygen species, preserving mitochondrial function, and reducing inflammation.

Recent studies suggest that lower plasma ergothioneine levels are associated with faster cognitive decline in older adults, raising the possibility that it may be a conditionally essential nutrient. Regular consumption of a variety of mushrooms, such as shiitake, oyster, or king trumpet mushrooms, can help increase ergothioneine intake and simultaneously deliver β‑glucans with immune-modulating effects (Tian et al., 2023; Fu et al., 2022).

β‑Glucans: Immune and Metabolic Regulators

β‑Glucans are polysaccharides found in both cereals (such as oats and barley) and fungi (mushrooms and yeast). Their health benefits differ depending on the source. Cereal-derived β‑glucans form viscous gels in the gut, lowering LDL cholesterol by reducing intestinal absorption of cholesterol and increasing bile acid excretion. Large meta-analyses consistently show that consumption of 3 g/day of oat β‑glucan significantly reduces LDL cholesterol and improves lipid profiles (Yu et al., 2022; Noronha et al., 2023).

Fungal β‑glucans, on the other hand, interact with innate immune receptors such as Dectin‑1 and Toll-like receptors, priming immune cells and enhancing their pathogen-fighting ability. This “trained immunity” effect has implications for infection control and oncology, with β‑glucan supplements from mushrooms like shiitake and reishi under active clinical investigation (Cerletti et al., 2021).

Sulforaphane: A Cruciferous Defender

Broccoli sprouts are an exceptional source of sulforaphane, an isothiocyanate derived from glucoraphanin through enzymatic action by myrosinase. Sulforaphane potently activates the Nrf2 pathway, which regulates the expression of antioxidant and detoxification enzymes such as heme oxygenase‑1 and glutathione S‑transferases. In doing so, it enhances the body’s defense against oxidative damage and inflammation. Sulforaphane also influences mitochondrial function and has shown neuroprotective and anticancer properties in experimental models. Human trials indicate promising biomarker improvements, although outcome data remain mixed, often due to variability in preparation and bioavailability (Yan et al., 2024; Bessetti et al., 2025).

Curcumin: Golden Spice with Broad Potential

Curcumin, the active pigment of turmeric, is a pleiotropic molecule that targets multiple signaling pathways. It downregulates NF‑κB, a master regulator of inflammation, and influences epigenetic enzymes involved in gene regulation. Clinical studies and meta-analyses have demonstrated its efficacy in reducing C-reactive protein (CRP), tumor necrosis factor‑α, and markers of oxidative stress. Curcumin has shown benefits in conditions such as arthritis, metabolic syndrome, and certain cancers. However, its low bioavailability has limited its clinical translation, and modern formulations using piperine, phospholipids, or nanoparticles are helping to overcome this challenge (Dehzad et al., 2023; Lee et al., 2024).

Epigallocatechin Gallate (EGCG): Green Tea’s Polyphenolic Star

Green tea is rich in catechins, with EGCG being the most studied. EGCG influences multiple signaling cascades including AMPK activation, PI3K/Akt/mTOR inhibition, and suppression of NF‑κB. It exhibits anti-inflammatory, cardioprotective, and anticancer properties. Clinical evidence supports its role in improving cardiovascular risk markers and as a potential adjunct in oncology. However, caution is warranted with high-dose extracts due to rare cases of hepatotoxicity, whereas brewed green tea remains a safe and effective option (Capasso et al., 2025).

Garlic Organosulfur Compounds: Traditional Medicine with Modern Proof

Garlic has been used for centuries as both food and medicine. Its organosulfur compounds, such as allicin, diallyl disulfide, and S‑allyl‑cysteine, exhibit antimicrobial, antioxidant, and cardiovascular benefits. Mechanistically, these compounds act as hydrogen sulfide donors, reduce platelet aggregation, and modulate lipid metabolism. Clinical studies support modest reductions in blood pressure and cholesterol with garlic consumption, with effects varying by preparation type (Seki et al., 2025; El‑Saadony et al., 2024).

Lycopene: The Tomato’s Red Shield

Lycopene, a carotenoid found abundantly in tomatoes, is a powerful singlet oxygen quencher. It accumulates in tissues such as the prostate and adrenal glands, influencing signaling pathways including insulin-like growth factor‑1. Observational studies and meta-analyses have linked higher lycopene intake to reduced cancer risk, particularly prostate cancer, and lower overall cancer mortality. Lycopene absorption is enhanced by cooking and co-consumption with oils, making tomato-based dishes with olive oil particularly beneficial (Balali et al., 2025).

Isoflavones: Soy’s Phytoestrogenic Benefits

Soy isoflavones, particularly genistein and daidzein, act as selective estrogen receptor β agonists. They modulate tyrosine kinase activity and influence epigenetic regulation. Clinical evidence supports their role in reducing menopausal symptoms, improving bone health, and supporting cardiovascular function. Their impact on hormone-sensitive cancers is complex and context-dependent, requiring individualized dietary advice (Sharifi‑Rad et al., 2021; Zhang et al., 2025).

Summary Conclusion: 

Functional foods and their phytochemicals form a natural arsenal against chronic disease. They modulate oxidative stress, inflammation, immune defense, and metabolic regulation, offering preventive and adjunctive benefits. A food-first approach, emphasizing mushrooms, crucifers, turmeric, green tea, garlic, tomatoes, soy, oats, and barley, provides a practical and safe way to harness these benefits. While supplements may be useful in targeted cases, dietary integration remains the most sustainable strategy. More research is needed to define optimal intake levels, bioavailability strategies, and long-term clinical outcomes, but the existing evidence strongly supports their role in human health.

References

1. Tian X, et al. Ergothioneine: an underrecognised dietary micronutrient. Biochem J. 2023.

2. Fu TT, et al. Ergothioneine as a Natural Antioxidant Against Oxidative Damage. Front Pharmacol. 2022.

3. Cerletti C, et al. Edible Mushrooms and Beta‑Glucans: Impact on Human Health. Nutrients. 2021.

4. Yu J, et al. Effects of Oat Beta‑Glucan Intake on Lipid Profiles: Meta‑analysis. Nutrients. 2022.

5. Noronha JC, et al. Effect of Oat Beta‑Glucan on LDL‑C, non‑HDL‑C and apoB: SRMA. Eur J Clin Nutr. 2023.

6. Yan Z, et al. Sulforaphane’s NRF2 and Antiviral Activities. iScience/Cell Rep Med. 2024.

7. Bessetti RN, et al. Sulforaphane neuroprotection review. Front Neurosci. 2025.

8. Dehzad MJ, et al. Antioxidant and anti‑inflammatory effects of curcumin/turmeric: Meta‑analysis of RCTs. Phytother Res. 2023.

9. Lee YM, et al. Is Curcumin Intake Really Effective for Chronic Inflammation? Nutrients. 2024.

10. Capasso L, et al. EGCG: Pharmacological Update. Pharmaceutics. 2025.

11. Seki T, et al. Functionality of garlic sulfur compounds (Review). Exp Ther Med. 2025.

12. El‑Saadony MT, et al. Garlic bioactive substances and therapeutic applications. Front Immunol. 2024.

13. Balali A, et al. Dietary and blood lycopene with cancer risk/mortality: Meta‑analysis. Nutrients. 2025.

14. Sharifi‑Rad J, et al. Genistein: Mode of Action & Health Outcomes. Nutrients. 2021.

15. Zhang K, et al. Genistein mechanisms in oxidative stress & inflammation. Antioxidants. 2025.

Disclaimer: This article is for educational purposes only and is not a substitute for individualized medical advice. Always consult healthcare professionals such as a qualified nutritionist or a dietician before making major dietary or supplement changes.