Herbal medicine (also calledherbalism,phytomedicine orphytotherapy) is the study ofpharmacognosy and the use ofmedicinal plants, which are a basis oftraditional medicine.[1] With worldwide research intopharmacology, some herbal medicines have been translated into modern remedies,[2] such as the anti-malarial group of drugs calledartemisinin isolated fromArtemisia annua, a herb that was known inChinese medicine to treat fever.[3][4] There is limitedscientific evidence for the safety and efficacy of many plants used in 21st-century herbalism, which generally does not provide standards for purity or dosage.[1][5] The scope of herbal medicine sometimes includesfungal andbee products, as well asminerals,shells and certain animal parts.[6]
Paraherbalism describesalternative andpseudoscientific practices of using unrefined plant or animalextracts as unproven medicines or health-promoting agents.[1][5][7][8] Paraherbalism relies on the belief that preserving various substances from a given source with less processing is safer or more effective than manufactured products, a concept for which there is no evidence.[7]
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Archaeological evidence indicates that the use ofmedicinal plants dates back to thePaleolithic age, approximately 60,000 years ago. Written evidence of herbal remedies dates back over 5,000 years to theSumerians, who compiled lists of plants. Some ancient cultures wrote about plants and their medical uses in books calledherbals. In ancient Egypt, herbs were mentioned inEgyptian medical papyri, depicted in tomb illustrations, or on rare occasions found in medical jars containing trace amounts of herbs.[9] In ancient Egypt, theEbers papyrus dates from about 1550 BCE, and covers more than 700 compounds, mainly of plant origin.[10] The earliest knownGreek herbals came fromTheophrastus of Eresos who, in the 4th century BCE, wrote inGreekHistoria Plantarum, fromDiocles of Carystus who wrote during the 3rd century BCE, and from Krateuas who wrote in the 1st century BCE. Only a few fragments of these works have survived intact, but from what remains, scholars have noted overlap with the Egyptian herbals.[11]
Seeds likely used for herbalism were found in archaeological sites ofBronze Age China dating from theShang dynasty[12] (c. 1600 – c. 1046 BCE). Over a hundred of the 224 compounds mentioned in theHuangdi Neijing, an early Chinese medical text, are herbs.[13] Herbs were also commonly used in thetraditional medicine of ancient India, where the principal treatment for diseases was diet.[14]De Materia Medica, originally written in Greek byPedanius Dioscorides (c. 40 – c. 90 CE) ofAnazarbus,Cilicia, a physician and botanist, is one example of herbal writing used over centuries until the 1600s.[15]
TheWorld Health Organization (WHO) estimates that 80 percent of the population of some Asian and African countries presently uses herbal medicine for some aspect of primary health care.[16]
Someprescription drugs have a basis as herbal remedies,[2] includingartemisinin,[17]digitalis,quinine andtaxanes.
In 2015, theAustralian Government's Department of Health published the results of a review of alternative therapies that sought to determine if any were suitable for being covered byhealth insurance; herbalism was one of 17 topics evaluated for which no clear evidence of effectiveness was found.[18] Establishing guidelines to assess the safety and efficacy of herbal products, theEuropean Medicines Agency provided criteria in 2017 for evaluating and grading the quality of clinical research in preparing monographs about herbal products.[19] In the United States, theNational Center for Complementary and Integrative Health of theNational Institutes of Health funds clinical trials on herbal compounds, provides fact sheets evaluating the safety, potential effectiveness and side effects of many plant sources,[20] and maintains a registry of clinical research conducted on herbal products.[21]
According toCancer Research UK as of 2015, "there is currently no strong evidence from studies in people that herbal remedies can treat, prevent or cure cancer".[6]
The use of herbal remedies is more prevalent in people withchronic diseases, such as cancer,diabetes,asthma, andend-stage kidney disease.[22][23][24] Multiple factors such as gender, age, ethnicity, education and social class are also shown to have associations with the prevalence of herbal remedy use.[25]
There are many forms in which herbs can be administered, the most common of which is a liquid consumed as a herbal tea or a (possibly diluted) plant extract.[26]
Herbal teas, or tisanes, are the resultant liquid of extracting herbs into water, though they are made in a few different ways.Infusions are hot water extracts of herbs, such aschamomile ormint, throughsteeping.Decoctions are the long-term boiled extracts, usually of harder substances like roots or bark.Maceration is the cold infusion of plants with highmucilage-content, such assage orthyme. To make macerates, plants are chopped and added to cold water. They are then left to stand for 7 to 12 hours (depending on the herb used). For most macerates, 10 hours is used.[27]
Tinctures are alcoholic extracts of herbs, which are generally stronger than herbal teas.[28] Tinctures are usually obtained by combining pure ethanol (or a mixture of pure ethanol with water) with the herb. A completed tincture has an ethanol percentage of at least 25% (sometimes up to 90%).[27] Non-alcoholic tinctures can be made with glycerin but it is believed to be less absorbed by the body than alcohol based tinctures and has a shorter shelf life.[29] Herbal wine andelixirs are alcoholic extracts of herbs, usually with an ethanol percentage of 12–38%.[27]Extracts include liquid extracts, dry extracts, and nebulisates. Liquid extracts are liquids with a lower ethanol percentage than tinctures. They are usually made by vacuumdistilling tinctures. Dry extracts are extracts of plant material that areevaporated into a dry mass. They can then be further refined to a capsule or tablet.[27]
The exact composition of a herbal product is influenced by the method of extraction. A tea will be rich inpolar components because water is apolar solvent. Oil on the other hand is anon-polar solvent and it will absorb non-polar compounds. Alcohol lies somewhere in between.[26]
Many herbs are applied topically to the skin in a variety of forms.Essential oil extracts can be applied to the skin, usually diluted in a carrier oil. Many essential oils can burn the skin or are simply too high dose used straight; diluting them in olive oil or another food grade oil such as almond oil can allow these to be used safely as a topical.Salves, oils,balms, creams, and lotions are other forms of topical delivery mechanisms. Most topical applications are oil extractions of herbs. Taking a food grade oil and soaking herbs in it for anywhere from weeks to months allows certainphytochemicals to be extracted into the oil. This oil can then be made into salves, creams, lotions, or simply used as an oil for topical application. Many massage oils, antibacterial salves, and wound healing compounds are made this way.[30]
Inhalation, as inaromatherapy, can be used as a treatment.[31][32][33]
It is a popular misconception that herbal medicines are safe and side-effect free.[35] Consumption of herbs may causeadverse effects.[36] Furthermore, "adulteration, inappropriate formulation, or lack of understanding of plant and drug interactions have led to adverse reactions that are sometimes life threatening or lethal."[37] Proper double-blind clinical trials are needed to determine the safety and efficacy of each plant before medical use.[38]
Although many consumers believe that herbal medicines are safe because they are natural, herbal medicines and synthetic drugs may interact, causing toxicity to the consumer. Herbal remedies can also be dangerously contaminated, and herbal medicines without established efficacy, may unknowingly be used to replace prescription medicines.[39]
Standardization of purity and dosage is not mandated in the United States, but even products made to the same specification may differ as a result of biochemical variations within a species of plant.[40] Plants have chemical defense mechanisms against predators that can have adverse or lethal effects on humans. Examples of highly toxic herbs include poison hemlock and nightshade.[41] They are not marketed to the public as herbs, because the risks are well known, partly due to a long and colorful history in Europe, associated with "sorcery", "magic" and intrigue.[42]
Although not frequent, adverse reactions have been reported for herbs in widespread use.[43] On occasion serious untoward outcomes have been linked to herb consumption. A case of major potassium depletion has been attributed to chronic licorice ingestion,[44] and consequently professional herbalists avoid the use of licorice where they recognize that this may be a risk. Black cohosh has been implicated in a case of liver failure.[45]Few studies are available on the safety of herbs for pregnant women,[46] and one study found that use of complementary and alternative medicines is associated with a 30% lower ongoing pregnancy and live birth rate during fertility treatment.[47]
Examples of herbal treatments with likely cause-effect relationships with adverse events includeaconite (which is often a legally restricted herb),Ayurvedic remedies,broom,chaparral, Chinese herb mixtures,comfrey, herbs containing certain flavonoids,germander,guar gum,liquorice root, andpennyroyal.[48] Examples of herbs that may have long-term adverse effects includeginseng, the endangered herbgoldenseal,milk thistle,senna,aloe vera juice,buckthorn bark and berry,cascara sagrada bark,saw palmetto,valerian,kava (which is banned in the European Union),St. John's wort,khat,betel nut, the restricted herbephedra, andguarana.[37]
There is also concern with respect to the numerous well-established interactions of herbs and drugs.[37][49] In consultation with a physician, usage of herbal remedies should be clarified, as some herbal remedies have the potential to cause adverse drug interactions when used in combination with various prescription andover-the-counter pharmaceuticals, just as a customer should inform a herbalist of their consumption of actual prescription and other medication.[50][51]
For example, dangerously low blood pressure may result from the combination of a herbal remedy that lowers blood pressure together with prescription medicine that has the same effect. Some herbs may amplify the effects of anticoagulants.[52]Certain herbs as well as common fruit interfere with cytochrome P450, an enzyme critical to much drug metabolism.[53]
In a 2018 study, the FDA identified activepharmaceutical additives in over 700 analyzed dietary supplements sold as "herbal", "natural" or "traditional".[54] The undisclosed additives included "unapproved antidepressants and designer steroids", as well asprescription drugs, such assildenafil orsibutramine.
Researchers at theUniversity of Adelaide found in 2014 that almost 20 percent of herbal remedies surveyed were not registered with theTherapeutic Goods Administration, despite this being a condition for their sale.[55] They also found that nearly 60 percent of products surveyed had ingredients that did not match what was on the label. Out of 121 products, only 15 had ingredients that matched their TGA listing and packaging.[55]
In 2015, theNew York Attorney General issuedcease and desist letters to four major U.S. retailers (GNC,Target,Walgreens, andWalmart) who were accused of selling herbal supplements that were mislabeled and potentially dangerous.[56][57] Twenty-four products were tested byDNA barcoding as part of the investigation, with all but five containing DNA that did not match the product labels.
In some countries, formalized training and minimum education standards exist for herbalists, although these are not necessarily uniform within or between countries. In Australia, for example, the self-regulated status of the profession (as of 2009) resulted in variable standards of training, and numerous loosely formed associations setting different educational standards.[58] One 2009 review concluded that regulation of herbalists in Australia was needed to reduce the risk of interaction of herbal medicines withprescription drugs, to implement clinical guidelines and prescription of herbal products, and to assure self-regulation for protection of public health and safety.[58] In the United Kingdom, the training of herbalists is done by state-funded universities offering Bachelor of Science degrees in herbal medicine.[59] In the United States, according to the American Herbalist Guild, "there is currently no licensing or certification for herbalists in any state that precludes the rights of anyone to use, dispense, or recommend herbs."[60] However, there are U.S. federal restrictions for marketing herbs as cures for medical conditions, or essentially practicing as an unlicensed physician.
Over the years 2017–2021, theU.S. Food and Drug Administration (FDA) issuedwarning letters to numerous herbalism companies for illegally marketing products under "conditions that cause them to be drugs under section 201(g)(1) of the Act [21 U.S.C. § 321(g)(1)], because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease and/or intended to affect the structure or any function of the body" when no such evidence existed.[61][62][63] During theCOVID-19 pandemic, the FDA and U.S.Federal Trade Commission issuedwarnings to several hundred American companies for promoting false claims that herbal products could prevent or treatCOVID-19 disease.[63][64]
TheWorld Health Organization (WHO), the specialized agency of the United Nations (UN) that is concerned with international public health, publishedQuality control methods for medicinal plant materials in 1998 to support WHO Member States in establishing quality standards and specifications for herbal materials, within the overall context of quality assurance and control of herbal medicines.[65]
In the European Union (EU), herbal medicines are regulated under theCommittee on Herbal Medicinal Products.[66]
In the United States, herbal remedies are regulateddietary supplements by theFood and Drug Administration (FDA) undercurrent good manufacturing practice (cGMP) policy for dietary supplements.[67] Manufacturers of products falling into this category are not required to prove the safety or efficacy of their product so long as they do not make 'medical' claims or imply uses other than as a 'dietary supplement', though the FDA may withdraw a product from sale should it prove harmful.[68][69]
Canadian regulations are described by the Natural and Non-prescription Health Products Directorate which requires an eight-digit Natural Product Number or Homeopathic Medicine Number on the label of licensed herbal medicines or dietary supplements.[70]
Some herbs, such ascannabis andcoca, are outright banned in most countries though coca is legal in most of the South American countries where it is grown. TheCannabis plant is used as a herbalmedicine, and as such islegal in some parts of the world. Since 2004, the sales ofephedra as a dietary supplement is prohibited in the United States by the FDA,[71] and subject to Schedule III restrictions in the United Kingdom.
Herbalism has been criticized as a potential "minefield" of unreliable product quality, safety hazards, and the potential for misleading health advice.[1][8] Globally, there are no standards across various herbal products to authenticate their contents, safety or efficacy,[40] and there is generally an absence of high-quality scientific research on product composition or effectiveness for anti-disease activity.[8][72] Presumed claims of therapeutic benefit from herbal products, without rigorous evidence of efficacy and safety, receive skeptical views by scientists.[1]
Unethical practices by some herbalists and manufacturers, which may include false advertising about health benefits on product labels or literature,[8] and contamination or use of fillers during product preparation,[40][73] may erodeconsumer confidence about services and products.[74][75]
Paraherbalism is thepseudoscientific use ofextracts of plant or animal origin as supposed medicines or health-promoting agents.[1][7][8] Phytotherapy differs from plant-derived medicines in standardpharmacology because it does not isolate andstandardize the compounds from a given plant believed to be biologically active. It relies on the false belief that preserving the complexity of substances from a given plant with less processing is safer and potentially more effective, for which there is no evidence either condition applies.[7]
Phytochemical researcherVarro Eugene Tyler described paraherbalism as "faulty or inferior herbalism based on pseudoscience", using scientific terminology but lacking scientific evidence for safety and efficacy. Tyler listed tenfallacies that distinguished herbalism from paraherbalism, including claims that there is aconspiracy to suppress safe and effective herbs, herbs cannot cause harm, whole herbs are more effective than molecules isolated from the plants, herbs are superior to drugs, thedoctrine of signatures (the belief that the shape of the plant indicates its function) is valid, dilution of substances increases their potency (a doctrine of the pseudoscience ofhomeopathy), astrological alignments are significant, animal testing is not appropriate to indicate human effects,anecdotal evidence is an effective means of proving a substance works and herbs were created by God to cure disease. Tyler suggests that none of these beliefs have any basis in fact.[7][76]
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Up to 80% of the population in Africa uses traditional medicine as primary health care.[77]
Native Americans used about 2,500 of the approximately 20,000 plant species that are native to North America.[78]
InAndean healing practices, the use ofentheogens, in particular the San Pedro cactus (Echinopsis pachanoi) is still a vital component, and has been around for millennia.[79]
Some researchers trained in both Western andtraditional Chinese medicine have attempted to deconstruct ancient medical texts in the light of modern science. In 1972,Tu Youyou, a pharmaceutical chemist andNobel Prize winner, extracted the anti-malarial drugartemisinin fromsweet wormwood, a traditional Chinese treatment for intermittent fevers.[80]
In India,Ayurvedic medicine has quite complex formulas with 30 or more ingredients, including a sizable number of ingredients that have undergone "alchemical processing", chosen to balancedosha.[81] In Ladakh, Lahul-Spiti, and Tibet, theTibetan Medical System is prevalent, also called the "Amichi Medical System". Over 337 species ofmedicinal plants have been documented byC.P. Kala. Those are used by Amchis, the practitioners of this medical system.[82][83] The Indian book, Vedas, mentions treatment of diseases with plants.[84]
InIndonesia, especially among theJavanese, thejamu traditional herbal medicine may have originated in theMataram Kingdom era, some 1300 years ago.[85] Thebas-reliefs onBorobudur depict the image of people grinding herbs with stonemortar and pestle, a drink seller, a herbalist, andmasseuse treating people.[86] The Madhawapura inscription fromMajapahit period mentioned a specific profession of herb mixer and combiner (herbalist), calledAcaraki.[86] The book fromMataram dated from circa 1700 contains 3,000 entries of jamu herbal recipes, while Javanese classical literatureSerat Centhini (1814) describes some jamu herbal concoction recipes.[86]
Though possibly influenced by IndianAyurveda systems, theIndonesia archipelago holds numerous indigenous plants not found in India, including plants similar to those in Australia beyond theWallace Line.[87] Jamu practices may vary from region to region, and are often not recorded, especially in remote areas of the country.[88] Although primarily herbal, some Jamu materials are acquired from animals, such ashoney,royal jelly, milk, andAyam Kampungeggs.
Herbalists tend to use extracts from parts of plants, such as the roots or leaves,[89] believing that plants are subject to environmental pressures and therefore develop resistance to threats such as radiation,reactive oxygen species and microbial attack to survive, providing defensivephytochemicals of use in herbalism.[89][90]
Indigenous healers often claim to have learned by observing that sick animals change their food preferences to nibble at bitter herbs they would normally reject.[91] Field biologists have provided corroborating evidence based on observation of diverse species, such as chickens, sheep,butterflies, andchimpanzees. The habit of changing diet has been shown to be a physical means of purging intestinal parasites. Sick animals tend to forage plants rich insecondary metabolites, such astannins andalkaloids.[92]
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