David Winston, Herbalist, AHG
Certain herbs have become popular over the last twenty years, but herbal medicine is still poorly understood by the public, medical practitioners and the media. After a brief honeymoon whereherbs have been portrayed as "wonder drugs", we are now seeing article after article on the dangersof herbs. As in most situations, the truth lies hidden under the media hype, bad or poorly understoodscience, exaggerated claims, and our natural resistance to new ideas.
Seeing herbal medicines as either panaceas or as poisons blinds us to the reality that in most cases they are neither. Lack of experience, lack of education, and lack of good information aboutherbs makes consumers easy victims of marketing exploitation and herbal myths. The same lack ofexperience, education, and information makes many physicians and other orthodox health careproviders suspicious and uncomfortable, especially with the exaggerated claims, miracle cures, andunproven remedies their patients are taking.
We as a culture are coming out of what I call the "Herbal Dark Ages", a period of time when the use of herbs virtually ceased to exist within the United States. A few ethnic communitiescontinued to utilize herbs, but from the 1920's into the 1970's the only herbs that mainstreamAmericans used were spices in cooking. Out of this almost total lack of exposure we have seen anamazing resurgence of interest in "natural" remedies.
Along with this new interest is a profound ignorance, with many people equating natural withharmlessness. Anyone who utilizes herbal products needs to understand a few basic safety rules.
The fact that something is natural does not necessarily make it safe or effective. In Cherokeemedicine we distinguish between three categories of herbs (Winston D, 1992). The "food herbs" aregentle in action, have very low toxicity, and are unlikely to cause an adverse response. Examples of"food herbs" include Lemon Balm, Peppermint, Marshmallow, Ginger, Garlic, Chamomile, Hawthorn,Rose hips, Nettles, Dandelion Root and Leaf, and fresh Oat extract. These herbs can be utilized insubstantial quantities over long periods of time without any acute or chronic toxicity (it is important tonote that allergic responses like with foods are possible, as are unique idiosyncratic reactions, andeven common foods such as grapefruit juice, broccoli, and okra can interact with medications).
The second category is the "medicine herbs". These herbs are stronger acting - they need to be used with greater knowledge (dosage and rationale for use) for specific conditions (with a medicaldiagnosis) and usually for a limited period of time. These herbs are not daily tonics and they shouldnot be taken just because "they are good for you". These herbs have a greater potential for adversereaction and in some cases, drug interactions. The "medicine herbs" include Andrographis, BlueCohosh, Cascara Sagrada, Celandine, Ephedra, Goldenseal, Jamaica Dogwood, Oregon GrapeRoot, Senna, and Uva-Ursi.
The last category is the "poison herbs". These herbs have strong potential for either acute or chronic toxicity and should only be utilized by clinicians who are trained to use them and clearlyunderstand their toxicology and appropriate use.
Even though the herb industry is often portrayed as unregulated* and irresponsible, the vast majority of the herbs in this category are not available to the public and are not sold in health food orherb stores. Examples of "poison herbs" include Aconite, Arnica, Belladonna, Bryonia, Datura,Gelsemium, Henbane, Male Fern, Phytolacca, Podophyllum, and Veratrum.
Another example of a traditional system of medicine that categorizes herbs according to safety or potential toxicity is Traditional Chinese Medicine (TCM).
* The herb industry is regulated by the FDA and laws such as DSHEA (Dietary Supplement, Health and Education act passed byCongress in 1994 The Chinese materia medica is also divided into three categories: the upper class (superior) drugsare non-toxic and are tonic remedies. The middle class (ministerial) drugs may have some mildtoxicity and they support the superior medicines. The last category is the lower class (inferior)remedies that are toxic and only used for specific ailments for limited periods of time.
A clear understanding of a herb's benefits and possible risks as well as a clearly defined patient diagnosis are essential for the practitioner to safely and effectively counsel patients as to safeand effective choices in herb use.
A second problem commonly experienced with the public is the belief that if a little of an herb (or medicine) is good, then more must be better.
A well-publicized example is the herb Ma Huang (Ephedra) which is being used for weight loss or asa stimulant. Serious adverse reactions including death have occurred and, in most cases, the peopleinvolved were foolishly taking 2-4 times the recommended dosage.
Many herbs are useful and safe in small, appropriate doses but as with any medication overdoses can cause unwanted side effects, possible injury, and, if the statistics are correct, rarefatalities.
This book is divided into two sections, one on herbal products, the other on nutritional supplements. They are not the same. A recent hysterical report claimed that herbal products couldcause Bovine Spongiforum Encephalitis (BSE) also known as mad cow disease. The author failed tonotice that herbs are from the vegetable kingdom and do not contain animal tissue. The author of thisreport is correct in noting that some supplements do contain animal glandular tissue such as liver,thymus, bone marrow, thyroid, and that the possibility of contamination by infectious proteins fromthese products may exist. If we are going to critique herbs and supplement products, let us do it withclear knowledge and understanding of the topic.
It is not uncommon for studies to be done on animals and the results extrapolated to humans even though we may metabolize or digest various phytochemicals quite differently. Researchershave done studies on a herb without authenticating it's identity making results meaningless (Leung A,2000).
It is not uncommon for information on isolated constituents to be confused with the whole herb or studies on I.V. forms of herbs to be confused with oral administration. This type ofmisinterpretation and misunderstanding gives rise to incorrect data which often continues to berepeated even decades after the original research has been disproven. Other studies have takenhamster oocytes and human sperm, put them into extracts of herbs (St. John's wort, Saw Palmetto,Ginkgo, and Echinacea) and found that in high concentrations some of the herbs denatured thesperm or inhibited the sperm from penetrating the hamster oocyte (Ondrizek PR, et al, 1999). Thisstudy was widely reported in medical journals and the popular press (NY Times). One medical editorsaid it was an important study showing a possible correlation between infertility and the use of herbs.
The author of the study, Dr. Richard Ondrizek, was "flabbergasted" that his in-vitro laboratoryresearch is being reported as evidence that these herbs can cause infertility in humans. Dr. Ondrizekstated, "there is absolutely no parallel between this study and humans".
Another recent error is due to lack of knowledge about phytochemistry. Several reports have surfaced suggesting Echinacea may be hepatotoxic. There is no evidence of this whatsoever. Theerror comes from the fact that Echinacea contains very small amounts of pyrrolizidine alkaloids, someforms of which are known hepatotoxins. Unfortunately, the authors of this misinformation failed todifferentiate between unsaturated (hepatotoxic) PA's and the non-toxic saturated PA's found inEchinacea. An easy error for the uninformed to make, but one that creates unnecessary fear andconfusion.
According to the information gathered by acclaimed researcher and scientist, Dr. James Duke, PhD, the statistics on deaths caused by herbs compared to other causes is quite revealing: If put into perspective, herbs ("food herbs" and "medicine herbs") can cause problems but they are substantially safer than over-the-counter and prescription medications. Will we find some herbscan have side effects? Definitely. Will we find some herbs interact with medications? Absolutely.
We only have to look at a recent report of St. John's wort reducing the blood levels of cyclosporin inheart transplant patients to be aware of possible risks. At the same time, reports that followed statingthat St. John's wort can interfere with birth control and would cause an epidemic of unwantedpregnancies were unfounded. Not only is there no proof of this, but millions of German women whotake contraceptive pills and St. John's wort have failed over the past 20 years to provide anysubstantiation to the concerned researchers.
Recently the FDA removed two medications from the marketplace (Rezulin and Propulsid) even though they had been through extensive testing and FDA drug approval. Ask any drugresearcher and they will tell you that for many pharmaceuticals the real test is when they are beingused by the general population. Both of these medications were deemed "safe", but caused seriousadverse effects and ultimately 60-70 deaths each. One benefit of the long history of human use ofmost herbs is that they have hundreds or thousands of years of use within the general population anda substantial record of safety or danger, effectiveness or lack thereof.
Frequently we hear complaints that herbs are poorly studied and, as such, are dangerous. It's true the research on most herbs cannot compare to the ten years of FDA clinical trials required fornew drugs. Since herbs are rarely patentable it is highly unlikely that any company is going to investthe time (approximately 10 years) and money* to have a herbal product approved as a new drug.
Herbs and supplements are sold in the U.S. as dietary supplements with no research necessarybefore being sold. There are significant numbers of studies being performed on herbal medicines butthe vast majority are done in Germany, France, Japan, China, India, and many are hard to access ornever translated in English. It would be of tremendous benefit to consumers and clinicians ifAmerican companies would increase funding for well-designed and relevant herbal research. Thequality of this research would also benefit by having clinical herbalists who understand appropriateforms of the medication, dosage, traditional, and clinical uses be a part of the research team. In1997, a study was done on the effects of the Chinese herb Dong Quai on menopausal symptoms(Hirata JD, et al, 1997). This herb is frequently utilized in TCM formulas for female reproductiveproblems. While the study clearly showed Dong Quai had no estrogenic effects and did not affectmenopausal symptoms, it failed to understand why and how this herb is used in Chinese medicine.
First, Dong Quai is never used as a simple.
* approximately $350 million to $500 million dollars It is not used for its estrogenic effects, but for its ability to improve cardiac function, increase uterinecirculation, reduce anxiety, and mildly stimulate bowel function. Someone who understood this couldhave helped to design a much more useful and beneficial study.
The gold standard for proof of efficacy for a medication is the controlled double-blind trial.
Many herbs, probably the majority, have not been subjected to this type of study. While these studiesare very valuable and may offer proof of activity and effectiveness, we need to also understand theusefulness of other types of herbal data.
In addition to controlled double-blind trials and meta-analysis, less definitive but still valuable are well-designed unblinded trials, small uncontrolled clinical trials, population (epidemiological)studies, as well as some animal and phytochemical studies.
The herbalist should use all of these resources but also incorporates additional information often ignored by academians. Traditional herb use, ethnobotanical use, and practical clinicalexperience are extremely valuable tools that stand as the basic foundation of good herbal practice.
When you find three disparate groups of people using the same herb or closely related species forthe exact same use you can be fairly certain that it does indeed have the stated effect. A goodexample would be Coptis, used as an effective antibacterial and antifungal agent by NativeAmericans, Northern Europeans, and the Chinese.
During the 1940's and 50s drug companies spent millions of dollars doing random drug screenings on plants, fungi, and soil microorganisms in search of the starting materials for new drugs.
There were a few notable successes such as the Madagascar Periwinkle (Vinca rosea), the source ofVinblastine and Vincristine. All in all, the programs were failures. Rarely did any new drug developfrom random screenings. In the last ten years, pharmaceutical companies have once again begun tosearch the plant kingdom for new bioactive phytochemicals but now they use ethnobotanists andeven old herbals to do the preliminary searching (Holland BK, 1996). Why? Because they haverealized that over hundreds or thousands of years indigenous people depended on these herbs totreat illness. Keen observers of their world native people used what worked. In addition to theknowledge of pre-literate peoples, the accumulated folk wisdom of Europe has been printed in bookssince the 1500's. While some of the information is exaggerated, some fantastical, and some totallywrong, much of this herbal wisdom is the basis for modern European phytotherapy and we are usingmany of the same herbs for the same conditions as did our distant ancestors.
Traditional systems of medicine such as Ayurveda (India), Traditional Chinese Medicine (TCM), Tibetan Medicine, Unani-tibb (Greco-arabic) and Kampo (Japan) have a long and impressivehistory of effectiveness. Modern research has now confirmed the usefulness and safety of what hasbeen used as primary medical care by much of the world's population.
In the United States, Eclectic Medicine was practiced widely from the 1830's until 1940. This sectarian medical system was founded by a physician, Wooster Beach, MD, who rejected themainstream medical practice of bleeding, leeching, purging, and using toxic medicines such asarsenic and mercury (Winston D, Dattner A, 1999). As an alternative, Beach and his followersembraced and studied the "American vegetable materia medica". Eclectic physicians during the1890's constituted 10% of the total number of doctors in the U.S.
Their clinical experience of treating millions of patients over one hundred years was carefullychronicled in their voluminous literature. Today this is an extremely valuable body of experientialknowledge, the successful clinical use of herbal medicines, in a time without antibiotics or theadvances of technological medicine.
Modern clinical herbalists in the U.S. and even more so in Great Britain and Australia (where herbalists are recognized practitioners) have also begun to carefully chronicle their clinical experienceand even to conduct small scale clinical studies of herbal treatments.
All of this data is valuable and, along with personal clinical experience, gives the individual clinician a strong understanding of the appropriate, safe, and effective use of a herb or herbalprotocol. In my own clinical experience working from this accumulated knowledge is a highlyaccurate way of matching effective protocols to each patient.
Where this type of proof doesn't work well is when physicians I consult with call wanting to knowabout which herbs may be useful for liver transplant patients, patients undergoing dialysis orsomeone who has just had a bone marrow transplant. In these instances, where there is no tradition,our only guide then must be careful observation and research studies.
As I mentioned earlier in this introduction, over the past ten years certain herbs (Black Cohosh, Echinacea, Garlic, Kava, Milk Thistle, Saw Palmetto, and St. John's wort) have become very popularbut herbal medicine has not.
There is a very real difference between the Allopathic use of a herb and the practice of good herbal medicine. Different systems of herbal medicine have their own views and distinctive practices,but they all have 3 things in common. First they have an underlying philosophy that creates afoundation and structure for the practice of medicine. Frequently, the underlying belief focuses onwhat naturopathic medicine calls Vis Medicatrix Naturae or the healing power of nature (Kirchfield,Boyle, 1994). This idea was a central tenet of medicine as taught by Hipprocrates, Maimonides, theGerman physician C.W. Hufeland, MD, and the early American physician Jacob Bigalow, MD. Inmany systems of medicine, not only is the body inherently self-healing, but there is an importantrelationship and connection between the physical, emotional, and spiritual aspects of each patient. InChinese, Tibetan, and Cherokee medicine (Nvwoti), attention may also be given to what we perceiveas external relationships and the effects of the family, community and the environment on eachpatient.
The second and third aspects of traditional systems of medicine are interrelated, A system of Energetics and Differential Diagnosis. Energetics is a way of describing the activity and qualities of agiven herb. Does it increase (stimulate) or decrease (sedate) function, does it increase nutrition,tonify an organ or moisten or dry tissue. Energetics is an effective way of understanding a herb notby its constituents, which can be very problematic*, but by its activity and effects on the human body.
This traditional form of pharmacology is utilized along with various types of differential diagnosis, sothere is an understanding of the underlying imbalances or disease and the treatment is specific to thepatient. Good Herbal Medicine treats people, not diseases.
In consulting and educating physicians and nurses, they are always surprised that the protocols are so patient specific. Two different patients, both with Rheumatoid arthritis (RA), canhave almost entirely different treatments. Why? Well most clinical herbalists do not see two cases ofRA. They might see John Smith, age 68, with achlorhydria, chronic constipation, impaired circulation,and RA very differently then Alice Jones, age 38, who experiences severe PMS, depression, biliarydyskinesia, and has RA. The focus in good Herbal, Naturopathic, Chinese, or Ayurvedic medicine isaffecting the terrain. Strengthen the organism, improve overall function (circulation, digestion,elimination, endocrine and immune function), reduce stress, and improve sleep and nutrition. Manydiseases, especially chronic degenerative diseases, respond very well to this type of treatment.
Benign Prostatic Hyperplasia (BPH) is a good example. The orthodox treatment is Hytrin® orFinasteride. Saw Palmetto as an allopathic herbal substitute works about as well as thepharmaceuticals, costs less, and has fewer adverse effects. As a herbalist I will probably use SawPalmetto as a part of my protocol, but in addition I might add Nettle Root, White Sage, Bidens, orCollinsonia to improve activity, effectiveness, and specificity of the formula. This combination ofherbs in my clinical experience is far superior to the pharmaceutical agents or Saw Palmetto as anindividual remedy. Herbal Medicine, like orthodox medical practice, is an art as well as a science.
Knowing how to combined herbs together to create a synergistic effect is more than randompolypharmacy.
* individual constituents can have widely divergent effects as isolates. Chinese Ginseng (Panax ginseng) is a good example;Ginenoside Rb1 is sedating while Ginsenoside Rg1 is a CNS stimulant. Despite these opposing effects, the whole herb has an overallstimulating effect Another example of a herbal formula having superior benefits over individual herbs would be my protocol for seasonal affective disorder (SAD). St. John's wort is touted as an effective herbalantidepressant and in some cases it is. For SAD St. John's wort alone is inadequate. In this situationcombining Lemon Balm and Lavender with St. John's wort increases its benefits while also improvingdigestion and sleep quality. Other dietary and lifestyle changes would be considered as well asadditional herbs specific to the patient.
It is also important to recognize that serious acute illnesses such as MI's, bacterial meningitis, stroke, acute asthma attacks, head trauma, liver and kidney failure are not treatable in this manner.
For many years both patients and practitioners have tended to view this difference in treatmentparadigms as a choice - one or the other. Nothing could be further from the truth. Where Westernmedicine is most effective, herbal medicine is often ineffective, but where herbal medicine is mosteffective, orthodox medicine often has little to offer patients. Not only can the use of botanicals bevery useful in many chronic degenerative or mild to moderate functional ailments, they also can havean important role to play in recovery from serious illness. Once head trauma victims have beenstabilized, the use of Ginkgo, Rosemary, St. John's wort and Bacopa have dramatically reducedrecovery time, and improved memory as well as cognitive and motor functions.
Western medicine and herbal medicine working in concert offers the best of both worlds and the patient is the beneficiary in this new relationship.
Herbs as medicines can be administered in many forms. Some can be taken as foods, consumed regularly in the diet, like Basil, Blueberries, Garlic, or Ginger.
Teas (infusions or decoctions) are a reliable way of administering some herbs. Drinking a hot cup of a pleasant tasting tea can be a wonderfully relaxing and healing experience in itself. Liquidsare also absorbed more quickly, especially in patients with impaired digestion. For certain herbs(Green Tea, Slippery Elm) tea is the most effective way to take them. The drawbacks to teas are thatmany herbs have constituents that are poorly water-soluble (Boswellia, Ginkgo, Gum Guggal, MilkThistle) and are not effective as teas. Other herbs have an unpleasant taste (Saw Palmetto,Feverfew, Valerian) and getting patients to drink cupfuls of a noxious tasting brew will limit patientcompliance. Some patients will also find having to make teas too much of a bother.
Tinctures are hydro-alcoholic extracts of herbs. While not very concentrated (1:5 w/v), tinctures have the benefits of being a liquid, the menstruum (alcohol and water) extracts a wide rangeof constituents, alcohol increases absorption of the herb by approximately 30% (Mediherb, 1998), thedoses are much smaller than with teas, so the taste factor is less of a problem, and they areconvenient. A patient can carry a small 1-oz. dropper bottle and the tincture can be placed in water,tea, or juice when needed. An additional benefit to tinctures is that fresh herbs that lose potencywhen dried (Echinacea, Eyebright, Scullcap) can be made into fresh tinctures (1:2 w/v) whichpreserves their activity very effectively. The biggest limitation for tinctures is that they contain alcoholand people with alcohol abuse issues or serious liver disease should avoid its consumption.
Fluid extracts are more concentrated alcohol and water extracts (1:1 w/v) and they offer many of the same benefits as tinctures, with greater potency and a smaller dosage. True fluid extracts arenot common in the American marketplace and there is great confusion as different manufacturers usedifferent terminology, technology, and menstruums (extracting liquids) to produce their products. ThePharmaceutical definition of a fluid extract includes the use of heat in the manufacturing process,which can be useful for heat soluble constituents or damaging the heat sensitive constituents.
Spray-dried extracts are liquid extracts that are spray-dried onto a powdered carrier (cellulose, powdered herbs). These extracts are fairly concentrated (4:1, 5:1, w/v), maintain the activity of thewhole herb, and are easily encapsulated, so taste is not an issue. The drawbacks of capsules ingeneral, whether they contain ground herbs or a spray-dried extract, is they are more difficult todigest than liquids and patients, especially young children, who can't swallow capsules cannot usethis type of product.
Capsules containing ground, dried herbs tend to have very limited activity and digestibility. Herbs thatshould be taken in this form are ones containing minerals as primary constituents (Alfalfa, Horsetaill,Nettles, Oat Straw). As long as the patient has reasonable digestive function, capsules are a superiorway to ingest mineral rich herbs.
Gelcaps are a useful method of ingesting oily nutrients like Vitamin E or oil based supplements such as Borage Seed Oil, Flax Seed Oil, or Evening Primrose Seed Oil. Gelcaps are easier toswallow than capsules or tablets, but the ingredients are subjected to considerable heat duringprocessing and rancidity of the oils is a substantial problem.
Tablets are often difficult to digest, but greater amounts of herbs and herb extracts can be squeezed into this format. Uncoated tablets are harder to swallow, but are more absorbable.
Most tablets contain proprietary herb/supplement formulas and their effectiveness is dependent onthe quality of ingredients and the validity of the formula as a therapeutic regimen.
Standardized herbal products are frequently recommended in the literature, especially by authors who are not herbalists. The idea that each dose of a herb has the exact same levels of activeconstituents is an attractive concept and a comfortable one for practitioners used to dealing withpharmaceutical products. You need to know that 0.25 mg of Lanoxin is exactly that. Too much cancause arrhythmias and death, too little and the patient may die of congestive heart failure. Themajority of herbs are not used for life threatening conditions, nor do they have the toxicity of Lanoxin,so dosages do not need to be as precise. The belief that each herb has an active constituent is false- most herbs have dozens or even hundreds of constituents that may contribute to its activity. Someof the constituents may have direct activity, while other "inert" ingredients may increasebioavailability, reduce toxicity, or stimulate function via a synergistic activity. To most herbalists, theactive constituent is the herb itself. Many manufacturers and academic "herbal authorities" wouldhave you believe that only standardized herbal products work and that all herbs should bestandardized, this is disingenuous and more about marketing and belief system than fact. The realityis that less than 10% of the standardized products in the marketplace are standardized to knownactive constituents. There are actually two types of "standardization". The first is truestandardization, where a definite phytochemical or group of constituents is known to have activity.
Ginkgo with its 26% Ginkgo flavones and 6% terpenes is a good example of real standardization.
Other products that meet these parameters are Milk Thistle, curcumin from Turmeric, Coleusforskollii, and Saw Palmetto (85-95% fatty sterols). These products are highly concentrated; they nolonger represent the whole herb, and are now phytopharmaceuticals. In many cases they are vastlymore effective than the whole herb (Coleus forskollii, Ginkgo, Milk Thistle), but some effects of theherb may be lost and the potential for adverse effects and herb/drug interactions may increase.
Curcumin* may have stronger antiinflammatory activity than whole Turmeric, but in large doses it actsas a gastric mucosa irritant, where the whole root extract has a gastroprotective effect.
The standardized Saw Palmetto (Serenoa) is believed to be much more effective than crude extracts of the berry, but again no comparative studies have ever been done. The dried berries andtincture, in addition to reducing BPH symptoms, have beneficial effects on the immune system, lungs,and GI tract, which are lost in the standardized Saw Palmetto.
The other type of "standardization" is based on manufacturers guaranteeing the presence of a certain percentage of a marker compound. Rarely are these known active constituents and whilethey may help to identify the herb, they are not indicators of therapeutic activity. An Echinaceaproduct standardized to caffeic acid or a St. John's wort product standardized to 0.3% hypericin isvirtually meaningless. Neither of these compounds represents the therapeutic activity or quality of theherb. This is not to say that no quality standards are needed - they most certainly are. First, everyherb product needs to be botanically identified to make sure the correct herb is in the product.
Adulteration of Scullcap with Germander has resulted in liver damage in several people.
* There are no studies comparing the activity of one to the other and many additional antiinflammatory constituents of Turmericrhizome have been discovered since the curcuminoids were deemed "the active ingredients" Recent substitution of Aristolochia species for the Chinese herb Stephania has caused kidney failureand renal cancers.
In addition to accurate botanical identification it is very important that the right part of the plant is used, that it is harvested at the right time, prepared properly, and the appropriate pharmaceuticaltechniques are utilized to make the best medicines.
Herbalists have always standardized their herbal products. St. John's wort was gathered in bud or flower and only the tops of the plants picked. The tincture or oil of hypercum should turn adeep burgundy red and have a strong and distinctive aroma. How much hypericin is present perdose, I don't know; how much hyperforin per dose, I don't know. What I do know is this preparationwill be active and will work because the markers herbalists have always looked for are present.
Herbalists have standardized their medicines to quality, not numbers.
As the herbal marketplace continues to grow, simply using the old quality standards probably isn't practical. I would suggest that simply applying random levels of an easy to test forphytochemical isn't the answer either. A synthesis of traditional herbal knowledge and modernresearch will benefit the herbal manufacturer, the consumer, and the practitioner.
The bridge between traditional herbalism and modern phytotherapy and the interface between academia and industry needs to be a person who has spent their lifetime gaining a hands-on practicalknowledge of botanic medicine - the herbalist.
Anonymous, Alcohol Improves Bioavailability, Mediherb Monitor, 1998.
Eldin S, Dunford A, Herbal Medicine in Primary Care, Butterworth-Heinemann, Oxford, UK, 1999.
Kirchfield F, Boyle, W, Nature Doctors, Medicina Biologica, Portland, OR, 1994.
Hirata JD, Swiersz LM, et al, Does Dong Quai Have Estrogenic Effects in Postmenopausal Women? A Double-Blind Placebo-Controlled Trial, Fertility and Sterility, 68(6): 981-986, 1997.
Holland BK [Ed.], Prospecting for Drugs in Ancient and Medieval European Texts, Harwood Academic Pub, Amsterdam, The Netherlands, 1996.
Lueng A, Scientific Studies and Reports in the Herbal Literature: What are we studying and Reporting?, HerbalGram, 48:63-64,2000.
Ondrizek PR, et al, An Alternative Medicine Study of Herbal Effects on the Penetration of Zona-free Hamster Oocytes and the Integrity of Sperm Deoxyribonucleic Acid, Fertility, and Sterility,71(3): 517-522, 1999.
McCaleb R, Research Reviews: Possible Shortcomings of Fertility Study on Herbs, Winston D, Nvwoti, Cherokee Medicine and Ethnobotany, in Tierra M, [Ed.], American Herbalism, The Crossing Press, Freedom, CA, 1992.
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