Updated: August 27th, 2020
Medicinal herbs have been used medicinally for centuries in Traditional Chinese Medicine (TCM), Ayurvedic medicine, and other indigenous systems of medicine worldwide. But did you know that the medicinal use of herbs is prevalent in conventional and integrative medicine too? Many modern pharmaceutical medications are derived from or inspired by herbal ingredients. (9) For example, aspirin from willow bark, digoxin from foxglove, quinine from cinchona bark, and morphine from the opium poppy. (52)
Beyond their use in indigenous medicine and pharmaceuticals, medicinal herbs are also commonly used as dietary supplements. In a 2015 National Consumer Survey including over 26,000 respondents across the United States, 35% of participants reported using herbal supplements. The use of herbal supplements was found to be greater in individuals over the age of 70, with a disease or health condition, an education above high school level, and those taking prescription or over-the-counter medications. (41)
There is a body of scientific literature supporting the use of herbal supplements for general health, disease prevention, and in the treatment of a number of health conditions. Read on to learn more about medicinal herbs and their delivery forms, medicinal effects, and safety.
What are medicinal herbs?
Medicinal herbs are plants that are used in herbal medicine, also known as herbalism, for their therapeutic properties. Several parts of a plant may be used, such as the root, rhizome, bark, stem, leaves, seeds, flowers, and fruit, each of which can vary in their therapeutic action. (11) These therapeutic actions can be attributed to a wide variety of constituents found in herbs including alkaloids, anthocyanins, anthraquinones, cardiac glycosides, coumarins, cyanogenic glycosides, flavonoids, glucosinolates, phenols, saponins, and tannins. (34) For example, curcumin is a type of phenol that is one constituent of turmeric herb root. Research shows that the therapeutic effects of curcumin include antioxidant and anti-inflammatory actions. (49)
Medicinal versus culinary herbs
Although there is some overlap between culinary and medicinal herbs, a culinary herb or spice is used in food preparation and seasoning, while a medicinal herb is a plant used for its therapeutic effects. (2) In the United States and Canada, medicinal herbs are sold as dietary supplements.
Regulation of herbal dietary supplements
In the U. S., herbal dietary supplements are regulated by the FDA. The Dietary Supplement Health and Education Act of 1994 classified medicinal herbs as food supplements that don’t require a prescription. Making health claims on the supplement label isn’t permitted. (52) The Current Good Manufacturing Practices (CGMPs) are applied to all dietary supplement manufacturers, which includes herbal remedies and supplements. The FDA developed CGMPs to ensure supplements are produced in a consistent manner, and meet quality and safety standards. (14)
In Canada, herbal dietary supplements are regulated by Health Canada under the Natural and Non-prescription Health Products Directorate (NNHPD). Herbal supplements must be assigned a natural product number (NPN). This means they are assessed by Health Canada before being sold on the market, while foods (including culinary herbs) do not require pre-market review. (16) All natural health products, including herbal supplements, are subject to Good Manufacturing Practices (GMPs), which ensure that standards for testing, manufacturing, storage, handling, and distribution are met. (15)
Medicinal herbs are processed to extract the medicinal properties of the herb using various manufacturing and preparation methods. Delivery forms will vary based on the extraction method used, the intended use of the supplement (e.g., topical or internal), and the desired form of the supplement (e.g., tea, liquid, capsule, tablet, etc.). Some common delivery forms are listed below.
The extraction process involves using a solvent to separate the active medicinal component of the plant from inert or inactive components. (32) The process can differ based on the extraction technique (e.g., maceration, infusion, distillation, microwave-assisted extraction, etc.) and the type of solvent used (e.g., water, ethanol, methanol, acetone, etc.).
Essential oils are the volatile oils extracted from certain herbs, which contain compounds, such as terpenes, aromatic compounds (e.g., aldehyde, alcohol, phenol, etc.), and terpenoids. Essential oils may be manufactured using several methods, including steam distillation, solvent extraction, and supercritical extraction. (48) They can be ingested, applied topically, and used for aromatherapy.
An herbal extract made by soaking herbs in alcohol or vinegar base for several weeks. The liquid is then strained to remove the plant. (2) Tinctures may be adjusted to reach a specific ratio of herbal material to liquid solvent. (59) Those who have trouble swallowing capsules or tablets may prefer taking herbal medicine as liquid tinctures.
An herbal extract made by soaking the plant in a glycerine base over two to six weeks. The plant matter is strained and removed from the glycerite before use. (2) A glycerite is similar to a liquid tincture but doesn’t contain ethanol, making it suitable for children and individuals who can’t consume alcohol.
Herbal oils are made using an extraction process in which the herb is soaked in a carrier oil for about two weeks. The volatile compounds in the plant are extracted into the oil and the plant matter is strained before the infused herbal oil can be applied topically. (2)
Solid extracts are made by evaporating the liquid from a liquid herbal extract, such as a tincture or glycerite. The end result is a solid powder used in capsules or tablets. (29)
Standardized extracts contain a specific amount of a desired component of the herb, providing a consistent dose of that therapeutic component. On a dietary supplement label, the guaranteed amount is usually shown as a percentage of the total herb content. (57) For example, the label for a standardized extract of turmeric (Curcuma longa) may read like this: Theracurmin®: 300mg (Standardized to contain 30% curcumin: 90mg).
A tea in loose-leaf or bagged form can be made from various parts of the medicinal plant, including the dried roots, leaves, or flowers. The dried herb is covered in hot or boiling water and left to infuse for 5-20 minutes. (59)
Also known as inhalations, vapors are meant to be administered via respiration. These come as dry powder inhalers or liquid preparations for inhalation and require an evaporating device, such as a vapor pen. (59)
Proprietary herbal blend
A proprietary blend is a combination of ingredients unique to the manufacturer. The weight of the blend is listed on the label, however, it is not mandatory to disclose the ratio or amount of each individual ingredient. (30)
How are medicinal herbs named?
The naming of plants is referred to as medicinal nomenclature. Herbs can be named by their:
- Latin scientific name: e.g., Bupleurum chinense
- Common name: e.g., bupleurum
- Pharmaceutical name or pharmacopoeial name: e.g., Radix Bupleuri, or
- Specific herbal drug names (as used in TCM or Indian herbal medicine): e.g., Chaihu (from TCM) (9)
Most commonly, medicinal names are listed by their common or vernacular name, followed by the Latin name italicized in brackets (e.g., bupleurum (Bupleurum chinense)).
The actions of medicinal herbs
The terminology below is used in herbal medicine to describe the therapeutic or medicinal actions of herbs. (47) Individual herbs have many components and can exert multiple therapeutic actions. (1)(10)
Adaptogen – helps the body adapt to stress by supporting the adrenal glands of the endocrine system
Analgesic – reduces or eliminates pain
Anti-catarrhal – reduces inflamed mucous membranes, specifically of the head and throat
Anti-inflammatory – helps to control or reduce inflammation
Anti-microbial – destructive to microbes
Anti-spasmodic – calms involuntary muscle spasms or cramps
Bitter – stimulates the digestive function and appetite; helps reduce toxins in the blood
Cardiotonic – increases heart strength and tone
Carminative – helps promote peristalsis (movement through the digestive tract); helps prevent and release gas from the intestines
Cholagogue – stimulates the gallbladder to release bile
Diaphoretic – increases perspiration, promotes circulation
Diuretic – promotes urine production and secretion
Emmenagogue – helps to regulate and induce menstruation
Emollient – softens and soothes skin; used topically
Expectorant – helps to clear mucus from the respiratory system
Hepatic – promotes liver health and increases bile secretion
Hypotensive – lowers blood pressure
Nervine – a nerve tonic; calms and soothes nerves
Tonic – increases the strength and tone of an entire system (2)(47)
Medicinal herb safety
Medicinal herb supplements should be approached with the same care as other dietary supplements or medications. Some populations may have special considerations, including pregnant or breastfeeding women, individuals with a medical condition, or individuals currently taking pharmaceutical medications.
An overview study of systematic reviews found that herbal medicines were generally safe. However, adverse effects that were reported ranged from mild (e.g. allergic reactions, constipation, dizziness, dermatitis, etc.) to severe (e.g. acute psychosis, respiratory arrest, hemorrhage, liver damage, etc.) (36) Taking an herb in the correct dose and form can help prevent potential adverse effects. (29)
The following are some specific examples of medicinal herbs that should be used with caution.
Kava (Piper methysticum)
Cases of hepatotoxicity (liver damage) have been reported with the herb kava. The researcher suggested that prescription adherence, product quality control, and avoidance of co‐medications may help prevent kava hepatotoxicity. (7)
Comfrey (Symphytum officinale)
Pyrrolizidine alkaloids (PA) are compounds found particularly with species of comfrey. The key pattern of liver injury from PAs is Veno-Occlusive disease (VOD). (7)
Ma huang (Ephedra sinica)
Ephedrine alkaloids in the Chinese herb ma huang were found to have a risk of cardiovascular complications and death. Adverse cardiovascular effects include stroke and myocardial infarction. (3) This herb was banned by the FDA in 2004. (28)
Certain herbs may interact with over-the-counter or prescription medications. Ask your doctor or pharmacist about any contraindications. Some of the common herb-drug interactions include:
St. John’s-wort (Hypericum perforatum)
St. John’s-wort induces the cytochrome P450 3A4 (CYP3A4) system. This can impact drug metabolism, including protease inhibitors, cyclosporin (an immunosuppressant), oral contraceptives (birth control), midazolam (an anesthesia medication), and warfarin (an anticoagulant). (8)
Ginkgo (Ginkgo biloba)
There may be an increased risk of bleeding when ginkgo is combined with nonsteroidal anti-inflammatory drugs (NSAIDs) and anticoagulants. However, in a review from Drug Metabolism Reviews, no clinically relevant interaction potential was found for standardized ginkgo biloba leaf extract (GLE) at the recommended dose of 240mg/day. (50)
Grapefruit (Citrus paradisi)
Over 85 pharmaceuticals are known to interact with grapefruit. These include statin medication (e.g. lovastatin, simvastatin, etc.), anticancer drugs (e.g. crizotinib, dasatinib, etc.), and immunosuppressants (e.g. cyclosporin, everolimus, etc.). The interactions occur because grapefruit inhibits the enzyme CYP3A4 in the gastrointestinal tract. CYP3A4 is an enzyme that oxidizes drugs so that they can be removed from the body. (5)
For more information, visit Nutrient Depletions/Interactions in the Fullscript Integrative clinical education hub.
The bottom line
Medicinal herb supplements have many therapeutic benefits in integrative medicine. Navigating which herbs are appropriate, as well as which delivery form to use can be complicated. Further, safety concerns include adverse effects and herb-drug interactions. Be sure to work with your integrative healthcare practitioner to develop a treatment protocol that takes into account your current medications, supplements, and health history.
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