Through the immunomodulatory, antioxidant, anti-inflammatory, antimicrobial, and metabolic regulatory effects of medicinal plants, herbalism offers valuable tools for promoting health and preventing illness.

Herbal medicine has been a fundamental component of healthcare systems across cultures for centuries. From ancient China and India to indigenous and traditional cultures in Africa and the Americas, herbal remedies have been integral to promoting health and preventing illness (1). In recent years, there has been a notable interest in holistic and natural approaches to healthcare, with herbalism emerging as a prominent contender in the realm of preventative medicine (1,2). Herbal medicine can offer a wealth of benefits for maintaining health and preventing illness. Plants have been used for their medicinal properties since ancient times, and their role in disease prevention is arguably more significant than ever. 

In recent decades, there has been a resurgence of interest in herbal medicine, driven by factors such as dissatisfaction with pharmaceuticals, concerns about adverse effects, and a growing appreciation for holistic and individualised approaches to health (2). Moreover, advances in scientific research have shed light on the biochemical mechanisms underlying the therapeutic effects of many medicinal plants, validating their traditional uses, and providing insights into their potential applications in disease prevention (3).

Herbalism is a holistic practice that acknowledges the interconnectedness of the body and mind. Rather than simply targeting isolated symptoms, herbal remedies work to restore balance and harmony within the body, addressing underlying imbalances that may contribute to disease (4). This holistic approach not only treats existing health problems, but it can also strengthen the body’s natural defences, helping to prevent future illness and promote overall well-being. 

Another strength of herbalism lies in its ability to offer personalised treatment plans tailored to individual needs (5). Herbalists consider a person’s unique constitution, lifestyle, and health goals when selecting appropriate herbs and formulations. By considering the whole person, and by being able to choose herbs that take into account individual needs, herbalism can offer a comprehensive and effective approach to preventative medicine (6).

When compared to many pharmaceutical medications, herbal remedies typically have fewer adverse effects and are generally well-tolerated. This is because plants contain a complex combination of compounds that work synergistically to produce therapeutic effects, often in lower concentrations than synthetic drugs (2). As a result, herbalism offers a gentler alternative for preventative care, reducing the risk of unwanted side effects commonly associated with conventional medications. For example, one of the well-known side effects of the anti-inflammatory drug acetylsalicylic acid (aspirin) is stomach ulcers. Aspirin was synthesised from salicylic acid containing herbs like meadowsweet (Filipendula ulmaria) (7). Meadowsweet not only has anti-inflammatory properties partly due to this phytochemical, but it does not cause stomach ulcers. In fact, it is used to treat digestive complaints (8). This is likely due to the synergistic action of all the constituents found in meadowsweet.

Plants contain bioactive phytochemicals including flavonoids, alkaloids, and terpenes, which have been found to exhibit antioxidant, anti-inflammatory, antimicrobial, and immune-modulating effects. Medicinal plants containing these phytochemicals and many others, can help to improve immune function, reduce oxidative stress, and protect against chronic diseases (8).

Herbal medicine can play a role in disease prevention through different mechanisms.

Immunomodulation

Many medicinal plants have immunomodulatory properties, enhancing the body’s immune response and thereby reducing the risk of infections and chronic diseases. For example, Echinacea spp. has been shown to stimulate immune cell activity, by enhancing the activity of macrophages, natural killer (NK) cells, and neutrophils (9). Echinacea can also encourage the activation and proliferation of T cells, which are central players in the adaptive immune response. T cells help coordinate the immune response by identifying and eliminating infected or abnormal cells (10).

Another example is how astragalus (Astragalus membranaceus) enhances immune function through its effects on cytokine production such as interferons and interleukins (11). Studies have shown that astragalus can enhance the production of interferons, particularly interferon-gamma (IFN-γ), which promotes antiviral activity and immune modulation. Astragalus can also regulate interleukin production, particularly interleukin-2 (IL-2), which is a critical interleukin for the proliferation and activation of T cells (11).

Medicinal mushrooms have significant immunomodulatory properties. They contain beta-glucans, which are bioactive polysaccharides that can trigger immune activation and cytokine production. Examples of mushrooms with potent immune modulating activity include reishi (Ganoderma lucidum), shiitake (Lentinula edodes), and maitake (Grifola frondosa) (12, 13).

There are also many studies showing how cordyceps mushroom (Cordyceps sinensis) has a particular role in disease prevention. There are studies showing how it does this by modulating immune responses, decreasing cholesterol levels, improving liver function, regulating insulin sensitivity, and promoting vasorelaxant and hypotensive activity (14).

Antioxidant activity

Oxidative stress is implicated in the pathogenesis of many diseases including cancer, cardiovascular disorders, and neurodegenerative conditions. Herbal remedies rich in antioxidants, such as green tea (Camellia sinensis) and turmeric (Curcuma longa), help neutralise free radicals and protect against cellular damage, lowering the risk for developing some chronic conditions such as coronary heart disease, neurodegenerative conditions or cancer (15, 16). 

Elderberry (Sambucus nigra) can increase the activity of antioxidant enzymes such as glutathione. A diet rich in elderberry fruits seems to have a protective action against oxidative stress. Elderberries have potent antioxidant phytochemicals that can scavenge hydroxyl radicals and inhibit lipid peroxidation (17).

Resveratrol is also considered a phytochemical with powerful potential antioxidant properties. Resveratrol can be found in grapes and red wine, blueberries, raspberries or mulberries for example. It works by inhibiting NADPH oxidase-mediated production of reactive oxygen species (ROS), by down-regulating the expression and activity of this oxidase enzyme (18). Resveratrol as a supplement has been shown to have multiple cardiovascular benefits, such as decreasing LDL cholesterol, improving blood pressure and endothelial function, and decreasing platelet aggregation (19).

Anti-inflammatory effects

Chronic inflammation is a key factor in the pathophysiology of many conditions, contributing to their progression and complications. Many medicinal plants, such as ginger (Zingiber officinale), boswellia (Boswellia serrata) and turmeric, exhibit potent anti-inflammatory effects that can help prevent and manage inflammatory conditions and associated comorbidities (8).

A randomized controlled trial investigating the anti-inflammatory effects of ginger extract in patients with osteoarthritis found that ginger supplementation significantly reduced markers of inflammation, such as C-reactive protein (CRP) and prostaglandin E2 (PGE2), when compared to placebo (20).

The anti-inflammatory action of boswellia has been demonstrated in several studies. One study showed a significant decrease in inflammatory markers in knee osteoarthritis, including CRP and matrix metalloproteinase-3 (MMP-3) highlighting its anti-inflammatory and disease-modifying effects (21). Boswellia is classified as ‘near threatened’ by the IUCN Red list of Threatened Species, therefore it is important to only source boswellia from cultivated sources and not wildcrafted.

Turmeric is a potent anti-inflammatory and can decrease generalised chronic inflammation, therefore minimising the negative effects of inflammatory conditions. In patients with rheumatoid arthritis, Turmeric led to a significant reduction in disease activity scores and inflammatory markers, including interleukin-1β (IL-1β) and tumour necrosis factor-alpha (TNF-α) (22).