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Herbalism

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CONTENTS

1. WHAT IS IT?

2. DOES IT WORK?

3. WHAT'S THE EVIDENCE?

4. SUMMARY OF COMMON HERBAL PRODUCTS

5. IS IT SAFE?

6. TOO LONG; DIDN'T READ! (TLDR)

7. REFERENCES

WHAT IS IT?

Herbalism is an alternative medical practice that uses plant-based remedies (‘herbal products’) to prevent and treat illness. An ‘herb’ may be a whole plant or one or more of its parts (e.g. flowers, stem, seeds, leaves, root, etc.). Herbal products may be ‘raw’ herbs (i.e. unaltered plant parts), herbal extracts (i.e. an herb treated with a solvent to extract its chemicals), or mixtures of herbs.

Unlike many alternative medical practices, herbalism is actually quite plausible [1]. Plants are known to contain chemicals that have medicinal properties. In fact, many modern pharmaceutical drugs originated from plants, as herbs were a main source of medicine in the pre-pharmacology world [1-2]. However, plants contain thousands of compounds. For some plants, they may contain a few compounds that have medicinal value. Unfortunately, these few useful molecules exist within the larger mixture of thousands of chemicals. Hence, an herbal product (be it a whole plant, extract, or otherwise) is just a crude mixture of plant compounds that might contain a small number of medicinal molecules. Essentially, they are unpurified drugs.

 
Herbs are unpurified drugs
 

It is also important to recognize that plants can contain harmful chemicals. Many herbs are known to produce toxic molecules that are meant to deter herbivores. For example, plant-produced “alkaloids” have a bitter taste and may cause harmful effects if ingested. Commonly-known alkaloids are cocaine, nicotine, and morphine. Perhaps unsurprisingly, these compounds (and many others) can be toxic to humans [3]. Thus, just because an herbal product is “natural” does not mean that it is necessarily “safe” (see below: IS IT SAFE?).

 
Natural Does Not Mean Safe
 

Herbal products are highly popular and are commonly purchased over-the-counter (e.g. in pharmacies, health food stores, etc.) or from natural health practitioners (e.g. naturopaths). An incredibly wide variety (thousands) of herbal products exists for a range of proposed uses that is similarly diverse. However, some herbs are much more common than others [1-2]. These include:

  • Echinacea: a flower that is believed by some to have immune-system-enhancing medicinal effects. It is usually marketed for the prevention and treatment of the common cold.

  • St. John’s Wort: a flower, Hypericum perforatum, that is commonly promoted for the treatment of depression.

  • Ginkgo biloba: the maidenhair tree, the leaves of which are believed to have cognitive-enhancing and other effects.

  • Garlic: a popular cooking spice, from the plant Allium sativum. In addition to its culinary uses, garlic is believed by some to have medicinal properties. Garlic-containing health products are commonly marketed for the prevention and treatment of the common cold, as well as to lower blood pressure and cholesterol.

  • Ginseng: the root of the Panax genus of plants, believed to possess many medicinal properties. Products containing ginseng are often marketed for the prevention and treatment of the common cold, cognitive enhancement, blood sugar control, lowering blood pressure, treating the symptoms of menopause, and many other uses.

  • Ginger: the root of Zingiber officinale, a flowering plant. Ginger is commonly used as a cooking spice, and is popularly promoted as a treatment for nausea and vomiting.

  • Cranberry: a common commercial crop fruit, used to make juice, jam, dried fruit, and many other food products. Cranberry is popularly believed to prevent and treat urinary tract infections.

  • Green tea: a popular beverage made by steeping the leaves of Camellia sinensis in water. Green tea is promoted for many medicinal uses, including weight loss, cancer prevention, and protection against heart disease.

  • Black cohosh: a flowering plant that is commonly used to treat the symptoms of menopause.

  • Saw Palmetto: a palm plant, Serenoa repens, the fruit of which is used to treat enlargement of the prostate.

  • Others

DOES IT WORK?

It depends on the herb.

Some herbal remedies work – but the majority do not.

WHAT'S THE EVIDENCE?

As mentioned above, herbs should be considered unpurified drugs. In the context of pharmaceutical companies, the majority of drugs that are researched and developed do not end up working in humans [4]. The drugs that make it through the rigorous scientific testing process are few and far between. The same is true of herbal remedies – some herbal products work, but the majority do not [1-2]. The difference, however, is that most herbal remedies are advertised by their manufacturers/prescribers as being effective, regardless of the evidence to support those claims.


 

Quick Definition: "Systematic Review"

A systematic review (and/or “meta-analysis”) is a scientific study that examines the agreement between many clinical trials. Instead of looking at a single study, systematic reviews attempt to analyse the totality of evidence related to a topic. By doing so, the true answer to a given question can be more accurately estimated. For example, a single study might indicate that a particular treatment is effective, leading readers to believe that this treatment works. However, what if three other studies conclude that the same treatment does not work? A systematic review might analyse the data from all four of these trials and conclude (correctly) that the totality of the evidence indicates that the treatment does not work (3 say no, only 1 says yes). The relative importance of each study is determined by things like study size (number of participants – more is better), chance for bias, consistency of measurements, and many others.

Because of their strength, systematic reviews are generally considered one of the highest standards of evidence. However, they are also not perfect, and are subject to the quality of the contributing clinical studies. Hence, if only low-quality studies are used, low-quality results will emerge (a.k.a. “garbage in, garbage out”).

 

Individualized Herbal Medicine

Some natural health practitioners (e.g. herbalists, naturopaths) promote the use of “individualized” herbalism. This practice involves prescribing unique mixtures of herbs that are specifically catered for treating a patient’s given combination of symptoms. Thus far, it has not been shown to be effective for any condition [5].

Specific Herbs

Given the vast number of herbal products that exist (and the limited evidence available for most of them), it is difficult to summarize the totality of herbalism research. Instead, this section will focus on common/popular herbs (see above: WHAT IS IT?). The information provided is therefore not exhaustive, but covers some of the most common claims of some of the most common herbal products.

 

Echinacea

Echinacea is commonly promoted as a treatment for the common cold. A systematic review assessing the agreement between 24 clinical studies found no reliable evidence that Echinacea products can effectively treat or prevent the cold [6-7]. None of the studies showed a reduction in cold occurrence with Echinacea use. Likewise, no convincing evidence was found to suggest that Echinacea products can reliably treat cold symptoms or reduce the duration of a cold [6-7]. Simply put: there is little to no reason to believe that Echinacea works for colds (or any other health condition). For more information, please see: Natural Cold Remedies.

 

St. John's Wort

St. John’s Wort is most commonly advertised as a treatment for depression. For mild to moderate depression, St. John’s Wort appears to be effective [8]. A systematic review of clinical trials of St. John’s Wort concluded that the herbal product is comparable in effectiveness to standard antidepressant drugs for treating mild to moderate depression [8]. However, a more recent clinical trial has refuted this conclusion – it found that both St. John’s Wort and a common antidepressant drug are not effective for treating a milder form of depression [9]. Thus, uncertainty still exists surrounding the true effectiveness of St. John’s Wort (and even some conventional antidepressants). Additionally, St. John’s Wort is known to have serious (i.e. potentially life-threatening) interactions with many pharmaceutical drugs [2, 10], so patients must use extreme caution when deciding to use this herbal product. It is important to consult a physician before starting any drug, including herbal remedies.

 

Ginkgo biloba

Ginkgo is a popular herb for brain-related functions. Mainly, it is promoted for its supposed memory- and cognition-enhancing effects. For this reason, it has also been suggested as a treatment for Alzheimer’s disease and dementia. Unfortunately, none of these claims appear to be supported by reliable evidence. Clinical studies have consistently demonstrated that there is no reliable evidence that ginkgo works to enhance memory [11-12], or prevent or treat dementia, cognitive impairment, or age-related cognitive decline [13-16]. There is also no convincing reason to believe that ginkgo can treat tinnitus [17], intermittent claudication (leg pain while walking) [18], stroke [19], or age-related macular degeneration [20]. Overall, there is no reliable evidence that ginkgo works for any health condition.

 

Garlic

In addition to flavoring foods, garlic is promoted for several different herbal uses. Mainly, it is recommended for the treatment and prevention of the common cold, and for lowering blood pressure and cholesterol. Unfortunately, none of these claims are supported by reliable evidence. A systematic review of the use of garlic for the cold concluded that there is no reliable evidence to recommend garlic for preventative or therapeutic purposes [21] (for more information, please see: Natural Cold Remedies). Likewise, other systematic reviews found unconvincing evidence that garlic can lower blood pressure [22], or prevent pre-eclampsia (dangerously high blood pressure during pregnancy) [23]. A clinical trial of garlic for lowering cholesterol also found no evidence of an effect of its use [24]. Additionally, garlic does not appear to have any effects on peripheral arterial disease [25]. Therefore, overall, garlic does not appear to be effective for any health condition (other than hunger).

 

Ginseng

Ginseng is a highly popular herbal remedy that is believed to have many medicinal properties. It is promoted for prevention of the common cold, cognitive enhancement, blood sugar control, lowering blood pressure, treating the symptoms of menopause, and many other uses. However, for the majority of these indications, there is little to no supporting evidence. A systematic review of clinical trials of ginseng products for the prevention and treatment of colds found no reliable evidence to suggest that ginseng works for these purposes [26] (for more information, please see: Natural Cold Remedies). Likewise, systematic reviews have found no convincing clinical evidence that ginseng can enhance cognition [27] reduce blood pressure [28], or treat menopause symptoms [29]. Another systematic review found that ginseng might be able to reduce fasting blood sugar levels, but the effect is likely very small and of questionable clinical relevance [30]. Thus, like many other herbal products, the popularity of ginseng is likely unwarranted.

 

Ginger

Ginger is widely believed to be an effective remedy for treating nausea and vomiting. This may be true – a systematic review concluded that clinical evidence demonstrates a possible effect of ginger on reducing nausea (but not vomiting) during pregnancy [31]. However, a more recent systematic review highlighted that this evidence is inconsistent and of questionable quality [32]. Thus, uncertainty remains with respect to the true effectiveness of ginger for nausea control.

 

Cranberry

Cranberry juice is commonly believed to be a helpful remedy for urinary tract infections (UTIs). Unfortunately, the evidence does not support this. A systematic review of clinical trials concluded that cranberry products are not effective for preventing UTIs [33]. An earlier review also found no evidence to support the use of cranberry for the treatment of UTIs [34]. Hence, the consumption of cranberries should only be determined by one’s dietary preferences, not their medical needs.

 

Green Tea

The purported health effects of green tea include weight loss, cancer prevention, and protection against heart disease. According to systematic reviews of clinical trials, green tea is not effective for weight loss or the maintenance of weight loss [35], and there is no reliable evidence to suggest that it can prevent cancer [36]. However, other reviews have found that green tea might help to lower blood pressure and cholesterol, but the effects are small and the overall evidence is of questionable quality (small number of trials, risk of bias, etc.) [37-38]. Thus, while green tea might help to slightly reduce heart disease risk, it is not effective for many of its advertised benefits.

 

Black Cohosh

Black cohosh is popular for treating menopausal symptoms (e.g. hot flashes). Unfortunately, clinical evidence does not support this. A systematic review concluded that there is insufficient evidence to support the use of black cohosh for menopausal symptoms [39].

 

Saw Palmetto

Saw palmetto is popular among men for treating enlargement of the prostate (benign prostatic hyperplasia, BPH). Unfortunately, as with so many other herbal remedies, the evidence does not support this: a systematic review concluded that saw palmetto, even at high doses, does not work for treating BPH or its associated symptoms [40].

SUMMARY OF COMMON HERBAL PRODUCTS

 
Summary Common Herbal Products
 

IS IT SAFE?

Once again, it depends on the herb. Just as every drug has its own toxicities, side effects, and drug-drug interactions, so does every herb. After all, herbs are simply unpurified drugs.

Many herbal remedies can cause moderately severe side effects [3], and others (such as St. John’s Wort) may negatively interact with conventional pharmaceutical drugs [10]. Thus, before using an herbal remedy, patients should ask their doctor about any known toxicities, and any potential interactions with their current prescriptions. It is important to remember: ‘natural’ does not mean ‘safe’.

Another risk of herbalism is the potential indirect harm that may result if sick patients choose to use unproven therapies over science-based treatments. If patients avoid or delay medically necessary care because they have decided to use herbs instead, serious harm or death can result. This is especially concerning in the case of serious illnesses such as cancer.

TOO LONG; DIDN'T READ!

Herbs are unpurified drugs. Some work, but most don’t. “Natural” does not mean “safe” – many herbs have known toxicities and may interact negatively with other drugs.

REFERENCES

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2)  Bent S. Herbal medicine in the United States: Review of efficacy, safety, and regulation. Journal of General Internal Medicine. 2008;23(6):854–859. doi:10.1007/s11606-008-0632-y.

3)  Posadzki P, Watson LK, Ernst E. Adverse effects of herbal medicines: An overview of systematic reviews. Clinical Medicine. 2013;13(1):7–12. doi:10.7861/clinmedicine.13-1-7.

4)  Hay M, Thomas DW, Craighead JL, Economides C, Rosenthal J. Clinical development success rates for investigational drugs. Nature Biotechnology. 2014;32(1):40–51. doi:10.1038/nbt.2786.

5)  Guo R, Canter PH, Ernst E. A systematic review of randomised clinical trials of individualised herbal medicine in any indication. Postgraduate Medical Journal. 2007;83(984):633–637. doi:10.1136/pgmj.2007.060202.

6)  Karsch-Völk M, Barrett B, Kiefer D, Bauer R, Ardjomand-Woelkart K, Linde K. Echinacea for preventing and treating the common cold. Cochrane Database of Systematic Reviews. February 2014. doi:10.1002/14651858.cd000530.pub3.

7)  Karsch-Völk M, Barrett B, Linde K. Echinacea for preventing and treating the common cold. JAMA. 2015;313(6):618. doi:10.1001/jama.2014.17145.

8)  Linde K, Berner MM, Kriston L. St John’s wort for major depression. Cochrane Database of Systematic Reviews. October 2008. doi:10.1002/14651858.cd000448.pub3.

9)  Rapaport MH, Nierenberg AA, Howland R, Dording C, Schettler PJ, Mischoulon D. The treatment of minor depression with St. John’s wort or citalopram: Failure to show benefit over placebo. Journal of Psychiatric Research. 2011;45(7):931–941. doi:10.1016/j.jpsychires.2011.05.001.

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11)  Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement. JAMA. 2002;288(7):835. doi:10.1001/jama.288.7.835.

12)  van Dongen MCJM, van Rossum E, Kessels AGH, Sielhorst HJG, Knipschild PG. The efficacy of ginkgo for elderly people with dementia and age-associated memory impairment: New results of a Randomized clinical trial. Journal of the American Geriatrics Society. 2000;48(10):1183–1194. doi:10.1111/j.1532-5415.2000.tb02589.x.

13)  Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database of Systematic Reviews. January 2009. doi:10.1002/14651858.cd003120.pub3.

14)  DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008;300(19):2253–2262. doi:10.1001/jama.2008.683. http://dx.doi.org/10.1001/jama.2008.683.

15)  Snitz BE, O’Meara ES, Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009;302(24):2663–2670. doi:10.1001/jama.2009.1913.

16)  Carlson JJ, Farquhar JW, DiNucci E, et al. Safety and efficacy of a ginkgo Biloba–Containing dietary supplement on cognitive function, quality of life, and Platelet function in healthy, Cognitively intact older adults. Journal of the American Dietetic Association. 2007;107(3):422–432. doi:10.1016/j.jada.2006.12.011.

17)  Hilton MP, Zimmermann EF, Hunt WT. Ginkgo biloba for tinnitus. Cochrane Database of Systematic Reviews. March 2013. doi:10.1002/14651858.cd003852.pub3.

18)  Nicolaï SP, Kruidenier LM, Bendermacher BL, et al. Ginkgo biloba for intermittent claudication. Cochrane Database of Systematic Reviews. June 2013. doi:10.1002/14651858.cd006888.pub3.

19)  Zeng X, Liu M, Yang Y, Li Y, Asplund K. Ginkgo biloba for acute ischaemic stroke. Cochrane Database of Systematic Reviews. October 2005. doi:10.1002/14651858.cd003691.pub2.

20)  Evans JR. Ginkgo biloba extract for age-related macular degeneration. Cochrane Database of Systematic Reviews. January 2013. doi:10.1002/14651858.cd001775.pub2.

21)  Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database of Systematic Reviews. November 2014. doi:10.1002/14651858.cd006206.pub4.

22)  Stabler SN, Tejani AM, Huynh F, Fowkes C. Garlic for the prevention of cardiovascular morbidity and mortality in hypertensive patients. Cochrane Database of Systematic Reviews. August 2012. doi:10.1002/14651858.cd007653.pub2.

23)  Meher S, Duley L. Garlic for preventing pre-eclampsia and its complications. Cochrane Database of Systematic Reviews. July 2006. doi:10.1002/14651858.cd006065.

24)  Gardner CD et al. Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate Hypercholesterolemia. Archives of Internal Medicine. 2007;167(4):346. doi:10.1001/archinte.167.4.346.

25)  Jepson RG, Kleijnen J, Leng GC. Garlic for peripheral arterial occlusive disease. Cochrane Database of Systematic Reviews. April 2013. doi:10.1002/14651858.cd000095.pub2.

26)  Seida JK, Durec T, Kuhle S. North American (Panax quinquefolius) and Asian ginseng (Panax ginseng) preparations for prevention of the common cold in healthy adults: A systematic review. Evidence-Based Complementary and Alternative Medicine. 2011;2011:1–7. doi:10.1093/ecam/nep068.

27)  Geng J, Dong J, Ni H, et al. Ginseng for cognition. Cochrane Database of Systematic Reviews. December 2010. doi:10.1002/14651858.cd007769.pub2.

28)  Komishon AM, Shishtar E, Ha V, et al. The effect of ginseng (genus Panax) on blood pressure: A systematic review and meta-analysis of randomized controlled clinical trials. Journal of Human Hypertension. April 2016. doi:10.1038/jhh.2016.18.

29)  Kim M-S, Lim H-J, Yang HJ, Lee MS, Shin B-C, Ernst E. Ginseng for managing menopause symptoms: a systematic review of randomized clinical trials. Journal of Ginseng Research. 2013;37(1):30–36. doi:10.5142/jgr.2013.37.30.

30)  Shishtar E, Sievenpiper JL, Djedovic V, et al. The effect of ginseng (the genus Panax) on Glycemic control: A systematic review and Meta-Analysis of Randomized controlled clinical trials. PLoS ONE. 2014;9(9):e107391. doi:10.1371/journal.pone.0107391.

31)  Viljoen E, Visser J, Koen N, Musekiwa A. A systematic review and meta-analysis of the effect and safety of ginger in the treatment of pregnancy-associated nausea and vomiting. Nutrition Journal. 2014;13(1):20. doi:10.1186/1475-2891-13-20.

32)  Matthews A, Haas DM, O’Mathúna DP, Dowswell T. Interventions for nausea and vomiting in early pregnancy. Cochrane Database of Systematic Reviews. September 2015. doi:10.1002/14651858.cd007575.pub4.

33)  Jepson RG, Williams G, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews. October 2012. doi:10.1002/14651858.cd001321.pub5.

34)  Jepson R, Mihaljevic L, Craig J. Cranberries for treating urinary tract infections. The Cochrane Database of systematic reviews. May 2000. http://www.ncbi.nlm.nih.gov/pubmed/?term=10.1002%2F14651858.CD001322.

35)  Jurgens TM, Whelan AM, Killian L, Doucette S, Kirk S, Foy E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database of Systematic Reviews. December 2012. doi:10.1002/14651858.cd008650.pub2.

36)  Boehm K, Borrelli F, Ernst E, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database of Systematic Reviews. July 2009. doi:10.1002/14651858.cd005004.pub2.

37)  Hartley L, Flowers N, Holmes J, et al. Green and black tea for the primary prevention of cardiovascular disease. The Cochrane Database of Systematic Reviews. June 2013. doi:10.1002/14651858.cd009934.pub2.

38)  Onakpoya I, Spencer E, Heneghan C, Thompson M. The effect of green tea on blood pressure and lipid profile: A systematic review and meta-analysis of randomized clinical trials. Nutrition, Metabolism and Cardiovascular Diseases. 2014;24(8):823–836. doi:10.1016/j.numecd.2014.01.016.

39)  Leach MJ, Moore V. Black cohosh ( Cimicifuga spp.) for menopausal symptoms. The Cochrane Database of Systematic Reviews. September 2012. doi:10.1002/14651858.cd007244.pub2.

40)  Tacklind J, MacDonald R, Rutks I, Stanke JU, Wilt TJ. Serenoa repens for benign prostatic hyperplasia. The Cochrane Database of Systematic Reviews. December 2012. doi:10.1002/14651858.cd001423.pub3.