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Herbs or Natural Products
That May Cause Cancer and Harm
Part Four of a Four-Part Series
Muriel J. Montbriand, PhD, RN
Key Points . . .
Purpose/Objectives: To provide evidence-based research information
about 27 herbs and natural products that have the potential to cause
cancer and harm.
The 27 herbs and natural products discussed in this review
Data Sources: Natural Medicines Comprehensive Database and
may be poisonous or harmful and may cause cancer.
Lawrence Review of Natural Products­Monograph System. Information
about these herbs has been found in evidence-based studies cited in
Consumers should be aware of these herbs and natural prod-
the references.
ucts and avoid their use.
Data Synthesis: Early research shows that some herbs and natural
Oncology nurses can become better resources for healthcare
products appear to have the potential to cause cancer and harm. Oncol-
professionals and patients regarding herbs and natural products.
ogy nurses who receive this information can become resources for
patients and other healthcare professionals.
Conclusions: Consumers and healthcare professionals are wise to
weigh the benefits or risks and possibly limit or avoid the use of these
This is the fourth article in a four-part series dedicated to
Implications for Nursing: The table and text in this article are
providing information about herbs and natural products for
presented as quick resources for healthcare professionals working in
healthcare professionals in clinical oncology. The herbs and
clinical oncology.
natural products discussed are those that may cause cancer and
harm. The target group for this article is individuals who do not
have cancer but are concerned about its development; however,
his review alerts consumers and healthcare professionals
all consumers may benefit from this information, taking note of
about herbs and natural products that have the potential
these products and avoiding them when possible.
to cause cancer and harm. Some herbs and natural prod-
As indicated in previous articles in this series, some overlap
ucts can be extremely poisonous or cause severe adverse reac-
in categories should be expected because early evidence, es-
tions, which has been well documented by many authors (Bisset,
pecially in vivo and in vitro evidence, often shows contrary
1994; Blumenthal et al., 1998; Brigden, 1995; Duke, 1987;
results. For example, black tea was discussed in Part Two,
Duke & Vasquez, 1994; Facts and Comparisons, 2001; Foster
where the emphasis was on its estrogenic properties and
& Duke, 1990; Foster & Tyler, 1999; Leung & Foster, 1996).
Preliminary research reviewed for this article indicates that 27
herbs and natural products have the potential to potentiate cancer
Muriel J. Montbriand, PhD, RN, is an associate professor in the
and/or cause additional harm. Anecdotal and lay advertisement
College of Nursing and a research associate in applied research/psy-
may stimulate interest in these products, attracting individuals
chiatry in the College of Medicine at the University of Saskatchewan
who wish to protect themselves against cancer. These individu-
in Saskatoon, Canada. During this work, the author was a recipient
of two Health Services Utilization and Research Commission, Socio-
als may never have experienced cancer; however, all consumers
Health Grants, in Saskatoon. (Mention of specific products and opin-
should take note of these products, weigh the possible risks or
ions related to those products do not indicate or imply endorsement
benefits, and limit or avoid their use. The evidence-based infor-
by the Oncology Nursing Forum or the Oncology Nursing Society.)
mation in this article will assist healthcare professionals to be
better resources for consumers and patients.
Digital Object Identifier: 10.1188/05.ONF.E20-E29
potential to enhance cancer growth. Black tea also contains
tion, burning, and sloughing (Facts and Comparisons). For
tannins and could be (but is not) included in this article's
treatment of photo-aged skin, alpha hydroxy acid products
discussion. Products that contain tannins are controversial
in concentrations of 8% (Stiller et al.) typically are used,
in the literature; numerous studies and evaluations have
whereas Wehr et al. used 12% preparations.
indicated that tannins have carcinogenic and anticancer
Areca has the scientific name Areca catechu and is popu-
properties (Leung & Foster, 1996; McGuffin, Hobbs, Upton,
larly known as betel nut. Areca sometimes is chewed for recre-
& Goldberg, 1997). More instances of controversy appear in
ational purposes or used in self-medication for central nervous
this article.
system stimulation (Gruenwald, Brendler, & Jaenicke, 1998).
The names of herbs and natural products have been se-
Sullivan, Allen, Otto, Tiobech, and Nero (2000) reported that
lected from listings in the Natural Medicines Comprehensive
this product has been used in Palau to treat schizophrenia;
Database (2004) and Lawrence Review of Natural Prod-
however, chewing areca nut is associated with oral cancer
ucts­Monograph System (Facts and Comparisons, 2001).
(VanWyk, 1997). In addition, excessive consumption of areca
Evidence about these herbs has been found in the studies
can cause convulsions and death (Facts and Comparisons,
cited in the references. Other products that potentiate cancer
2001). Chewing approximately 11 whole nuts per day is con-
or harm may exist; however, this review includes only herbs
sidered a typical dose when used therapeutically for treatment
and natural products recognized by the authors, professionals,
of schizophrenia (Sullivan et al.), but chewing and ingesting
or advisory boards of the resources noted.
larger quantities of areca are considered unsafe.
The majority of the studies cited are in vitro, performed in
Aristolochia has the scientific names Aristolochia ser-
glass on tissue from a living organism, or in vivo, performed
pentaria, Aristolochia reticulata, and other Aristolochia
on tissue not removed from a living organism (i.e., animal
species and commonly is called snakeroot or snakeweed.
studies). Most studies have not advanced to clinical trials in-
Aristolochia is used for self-medicating gastrointestinal and
volving humans. The few human studies cited are preliminary
gallbladder colic (Gruenwald et al., 1998). This herb contains
clinical trials; therefore, although results may seem favorable
aristolochic acid, which is nephrotoxic and carcinogenic and
or unfavorable, treat these findings with caution.
is associated with cancers of the kidney, bladder, stomach,
Neither the author nor publisher makes any medical
lung, and lymphoma in rodents. Aristolochia acid also is as-
claims for any of the herbs or natural products in this
sociated with cancers of the bladder, ureter, and renal pelvis
review or the table. This is informational literature. Note
in humans (Nortier et al., 2000). Nortier et al. reported more
that some of the herbs described are deadly poisons and
than 100 cases of nephropathy, referred to as "Chinese herb
some are extremely dangerous.
nephropathy," associated with use of this herb. Of these, 43
Table 1 provides the names of herbs and natural products
cases progressed to end-stage renal failure requiring dialysis
discussed in the text. Common names as well as brand names
or transplants. As a result, the U.S. Food and Drug Admin-
and manufacturers are included. Some products have numer-
istration reported that this herb is unsafe (Natural Medicines
ous brand names, making a complete listing prohibitive. The
Comprehensive Database, 2004). Lust (1974) warned of
number of brand names found is included in the table. When
aristolochia's toxicity and indicated that those who wish to use
a brand name contains only one ingredient, it often bears the
this herb should do so only under the guidance of a healthcare
product's common name. Single-ingredient products are identi-
fied in the table. Other brands with numerous ingredients also
Beer and alcoholic beverages: As well as being an appetite
are indicated. In the first three parts of this series, single-in-
and digestive stimulant, beer is used medicinally to prevent
gredient brands were recommended over multiple-ingredient
many ailments such as cardiovascular disease, Alzheimer dis-
brands; however, here, all brands that contain the herbs and
ease, cancer, gallstones, and kidney stones. Chronic ingestion
natural products listed in this article should be avoided because
of three or more alcoholic drinks per day can lead to physical
of their potential to potentiate cancer growth or harm.
dependence, malnutrition, amnesia, dementia, somnolence,
cardiac myopathy, hepatotoxicity, and cirrhosis, among
Products That May Potentiate
other conditions, as well as cancers of the mouth, esophagus,
pharynx, larynx, and liver (Micromedex Inc., 2004; Thun et
Cancer Growth
al., 1997). Traditionally, more than one alcoholic drink daily
Alpha hydroxy acid has the scientific names hydroxysuccinic
may increase mortality among women with breast cancer by
as much as 30% (Thun et al.). One drink is equivalent to 4
acid, monohydroxysuccinic acid (malic acid), 2-hydroxypro-
oz (120 ml) of wine, 12 oz of beer, or 1 oz of spirits (Micro-
pionic acid (lactic acid), hydroxyacetic acid (glycolic acid),
dihydroxysuccinic acid (tartaric acid), and gluconolactone.
medex Inc.).
Individuals self-medicate with alpha hydroxy acid to treat
Beta-carotene has the same scientific name, beta-carotene.
discomfort and pain associated with fibromyalgia (Russell,
Notice this is not the same product as canthaxanthin (dis-
Michalek, Flechas, & Abraham, 1995). Reactions to alpha
cussed in Part Three of this series) with the scientific names
hydroxy acid are not associated with oral use but are related
4,4-diketo-beta-carotene and Beta,beta-carotene-4,4-dione.
to topical applications to photo-damaged skin (Stiller et al.,
Beta-carotene and canthaxanthin are two different chemical
1996) and dry skin (Kempers, Katz, Wildnauer, & Green,
compositions; therefore, carefully scrutinize all scientific
1998; Wehr, Krochmal, Bagatell, & Ragsdale, 1986). Products
names. Individuals self-medicate with beta-carotene, a source
containing this acid can cause increased sensitivity to the sun
of vitamin A (McEvoy, 1998), to decrease exercise-induced
and ultraviolet light and can increase the danger of skin dam-
asthma (Cooper, Eldridge, & Peters, 1999) and prevent cancer
age and skin cancer, especially with long-term use (Facts and
(Cooper et al.; Omenn, 1998), cardiovascular disease, and
Comparisons, 2001). Use of high concentrations of products
age-related macular degeneration (Cooper et al.; Price &
containing alpha hydroxy acid can result in severe skin irrita-
Fowkes, 1997). Smokers who take more than 20 mg of beta-
Table 1. Herbs and Natural Products That May Potentiate Cancer Growth and Harm: Common and Brand Names
Herb or Natural Product
Brand Name and Manufacturer or Other
Alpha hydroxy acid
#14 Colon (Systemic Formulas)b
Other names: AHA, alpha-hydroxyethanoic acid, apple acid, citric acid, dihy-
Chitosan Plus (Progressive Labs)b
droxysuccinic acid, gluconolactone, glycolic acid, hydroxyacetic acid, hydroxy-
Lava (Universal Nutrition)b
capylic acid, hydraoxypropionic acid, hydroxysuccinic acid, lactic acid, malic
PMS Escape (Back Bay Scientific)b
acid, mixed fruit acid, monohydroxysuccinic acid, tartaric acid
Firm Lotion (Mannatech)b
Vascular Complete (Rexall-Sundown)b
123 brand names found
No brand names found
Other names: areca nut, betel nut, betel quid, pinag, pinlag
No brand names found
Other names: birthwort, long birthwort, pelican flower, red river snakeroot,
sangree root, sangrel, serpentaria, snakeroot, snakeweed, Texas snakeroot,
Virginia serpentary, Virginia snakeroot
Beer and alcoholic beverages
Available in numerous varieties
Beta Carotene (Puritan's Pride)a
Other name: provitamin A
Beta Carotene (Olympian Labs)a
Beta Carotene 5,000 IU Chewable (Jamieson)a
Beta Carotene 10,000 IU (Jamieson)a
Beta Carotene 25,000 IU (Jamieson)a
Beta Carotene 25,000 IU With Vitamin C and E (Jamieson)b
Brand names too numerous to count
Bishop's weed
No brand names found
Other names: ajava seeds, ajowan, ajowan caraway, ajowan seed, ajowanj,
bishop's flower, bullwort, carium, flowering ammi, omum, yavani
Black and white pepper
Advanced Formula (Biotech Corp.)b
Other names: blanc poivre, kosho, pepe, pepper, pepper extract, pepper plant,
OcuPower (Nutraceutical Sciences Institute)b
peppercorn, pfeffer, pimenta, pimienta, piper, poivre, poivre noir
Super Prostate Formula (Physician's Choice)b
7 Day Smoke Away­Lung Saver (The Quit Smoking Co.)b
42 brand names found
Calcium +D (Rexall-Sundown)b
Other names: bone meal, calcium acetate, calcium aspartate, calcium carbon-
Calcium 500 mg (Rexall-Sundown)b
ate, calcium chelate, calcium chloride, calcium citrate, calcium citrate malate,
Calcium 600 mg (Pro Health)b
calcium gluconate, calcium lactate, calcium lactogluconate, calcium orotate,
Calcium Oyster Shell 1,000 mg (Rexall-Sundown)b
calcium phosphate, di-calcium phosphate, heated oster shell-seaweed calcium,
Brand names too numerous to count
hydroxyapatite, oyster shell calcium, tricalcium phosphate
BLF #30 Head-X (Health Center for Better Living)b
Other names: garden marjoram, gartenmajoran, knotted marjoram, majo-
Liga-Pane (Nutri-Quest)b
ran, majorana aetheroleum oil, majorana herb, marjolaine, mejorana, sweet
PMS Fort (Futurebiotics)b
Sedivitax (Aboca USA, Inc.)b
6 brand names found
Amino Acid 1,000 mg (Nature's Life)b
Other names: DL-methionine, DL methionine, L-methionine
Beef Liver 1,500 mg (Nature's Life)b, c
Metabolol II (Champion Nutrition)b
#150 Pro Nutro Protein (Systemic Formulas)b, c
#408 CLNZ Toxin Chelator (Systemic Formulas)b, c
145 brand names found
(Continued on next page)
This herb or natural product is the only ingredient in this brand.
This brand name is an example of a product in which the herb or natural product is included along with other herbs and products. Monitor for all possible side
effects of all ingredients in these products.
Safety of this product is a concern. The product contains animal material, possibly diseased animals that may harbor bovine spongiform encephalopathy (i.e.,
mad cow disease).
Table 1. Herbs and Natural Products That May Potentiate Cancer Growth and Harm: Common and Brand Names (Continued)
Herb or Natural Product
Brand Name and Manufacturer or Other
Omega-6 fatty acids
The Missing Link: Master Nutrient Formula (Designing Health, Inc.)b
Other names: N-6, N-6 EFAs, N-6 essential fatty acids, omega 6, omega-6,
Our Daily Fish (Functional Products)b
omega-6 oils, polyunsaturated fatty acids, PUFAs
Ultimate Oil (Nature's Secret)b
#132 FLX Vegetable Omega-3 Flax Seed Oil (Systemic Formulas)b
19 brand names found
Pau d'arco
Amazon A-F (Raintree Nutrition, Inc.)b
Other names: ipe, ipe roxo, ipes, Lapacho, Lapacho colorado, Lapacho mo-
Amazon Prostate Support (Raintree Nutrition, Inc.)b
rado, pau de arco, purple lapacho, red lapacho, taheebo, taheebo tea, trumpet
Pau D'Arco (Source Naturals)b
Pau d'Arco­Black Walnut Virtue (Blessed Herbs)b
51 brand names found
BLF #47 Rest Ease Ingredients (Health Center for Better Living)b
Other names: ague tree, cinnamon wood, common sassafras, kuntze saloop,
T-CAN (Dial Herbs)b
sassafrax, saxifrax
5 brand names found
Shark liver oil
Shark Oil (Futurebiotics)b
Other names: basking shark liver oil, deep sea shark liver oil, dog fish liver
2 brand names found
oil, shark liver, shark oil
St. John's wort
St. John's Wort (Gala Herbs)a
Other names: amber, amber touch-and-heal, demon chaser, fuga daemonum,
St. John's Wort (Metabolic Response Modifiers)a
goatweed, hardhay, hypereikon, hyperici herba, hypericum, Johns wort, klam-
St. John's Wort (Swanson)a
ath weed, millepertuis, rosin rose, Saint Johns wort, tipton weed
Appleheart St. John's Wort (Appleheart)b
Bio St. John's (Pharmanex)b
St. John's Wort (Jamieson)b
St. John's Wort (Celestial Seasonings)b
168 brand names found
Tannin: American chestnut
No brand names found
No other names
Tannin: bistort
T-MSLE (Dial Herbs)b
Other names: adderwort, dragonwort, Easter giant, Easter mangiant, oderwort,
1 brand name found
osterick, patience dock, red legs, snakeweed, sweet dock
Tannin: black walnut
Fingerprinted Black Walnut Hulls, GNC Herbal Plus (GNC)b
Other names: nogal Americano, nogueira-preta, noyer noir, schwarze wal-
Fresh Green Black Walnut Wormwood Complex (Now)b
39 brand names found
Tannin: coffee
Numerous brand names
Other names: café, caffea, espresso, java, mocha
Tannin: English walnut
Clear Skin (PhytoPharmica)b (a homeopathic product)
Other names: fructus cortex, juglans, juglandis, juglandis folium, walnussblät-
4 brand names found
ter, walnussfrüchtschalen, walnut
Tannin: Mormon tea
Brigham Tea (Nature's Way)b
Other names: Brigham tea, desert tea, popotillo, teamster's tea, squaw tea
HAS Original Formula (Nature's Way)b
Yucca-AR Formula (Nature's Way)b
10 brand names found
Tannin: oak bark
C&F Formula (Dial Herbs)b
Other names: common oak, durmast oak, eichenrinde, English oak, pedun-
Psoriacin (Dr. Clayton's Naturals)b
culate oak, quercus cortex, sessile oak, stave oak, stone oak, tanner's bark,
9 brand names found
tanner's oak
(Continued on next page)
This herb or natural product is the only ingredient in this brand.
This brand name is an example of a product in which the herb or natural product is included along with other herbs and products. Monitor for all possible side
effects of all ingredients in these products.
Safety of this product is a concern. The product contains animal material, possibly diseased animals that may harbor bovine spongiform encephalopathy (i.e.,
mad cow disease).
Table 1. Herbs and Natural Products That May Potentiate Cancer Growth and Harm: Common and Brand Names (Continued)
Herb or Natural Product
Brand Name and Manufacturer or Other
Tannin: pomegranate
Midlife Care (Health Factor)b
Other names: granada, grenadler, shi liu gen pi, shi liu pi
Optein (Solgar)b
Estrolean Fat Burner Supreme (Bodyonics, Ltd.)b
8 brand names found
Tannin: quillaia
MSM Rejuvenator (Progressive Labs)b
Other names: China bark, murillo bark, Panama bark, soapbark, soap tree
1 brand name found
Tannin: sorrel
Quanterra Sinus Defense (Pfizer)b
Other names: acedera com n, azed-brava, garden sorrel, sorrel dock, sour
SinuComp (PhytoPharmica)b
dock, wiesensauerampfer
3 brand names found
Tannin: willow bark
White Willow Bark Extract (Nature's Way)a
Other names: basket willow, bay willow, brittle willow, crack willow, Daphne
Pain-Less (Herbalist)b
willow, knackweide, laurel willow, lorbeerweide, osler rouge, pupurweide,
Herbal Pain and Fever Relief (Holista)b
purple osler willow, reifweide, salicis cortex, silberweide, violet willow, wei-
129 brand names found
denrinde, white willow, white willow bark
Tannin: witch hazel
Atri-Verm (Atrium Inc.)b
Other names: hazel, hmamelis, snapping tobacco wood, spotted elder, winter
Body Guard (Jamieson)b
bloom, witchazel
Circusome (Jamieson)b
16 brand names found
This herb or natural product is the only ingredient in this brand.
This brand name is an example of a product in which the herb or natural product is included along with other herbs and products. Monitor for all possible side
effects of all ingredients in these products.
Safety of this product is a concern. The product contains animal material, possibly diseased animals that may harbor bovine spongiform encephalopathy (i.e.,
mad cow disease).
carotene have a significantly higher risk of developing lung
(orally) with pepper to treat gastric, bronchial, and cancer
or prostate cancer ("The Effect of Vitamin E and Beta Caro-
conditions (Leung & Foster, 1996). Early evidence indicates
tene," 1994; Heinonen et al., 1998; Omenn; Omenn et al.,
that black pepper may protect against colon cancer (Nalini,
1996; Pryor, Stahl, & Rock, 2000). Premenopausal women
Sabitha, Viswanathan, & Menon, 1998). Conversely, Singh
who consume five or more servings of fruit or vegetables
and Rao (1993) found that black pepper induces the enzymes
rich in beta-carotene appear to have a lower risk of breast
that cause liver tumors (el-Mofty, Khudoley, & Shwaireb,
cancer (Zhang et al., 1999). Adverse effects for high usage
1991). Aspiration of large amounts of black pepper has
of this product include a yellow or orange pigmentation of
caused deaths (Cohle et al., 1988; Sheahan, Page, Kemper,
the skin (McEvoy) and liver damage (Health and Welfare
& Suarez, 1988). Typical doses range from 300­600 mg
Canada, 1990; Montbriand, 1994). Natural Medicines
or as much as 1.5 g per day (Gruenwald et al., 1998); 0.25
Comprehensive Database (2004) indicated that the Institute
tsp is equivalent to 1.25 g dry weight. Treat this herb with
of Medicine reviewed beta-carotene but did not provide a
recommended daily intake, citing lack of sufficient evidence.
Calcium has the same scientific name, as well as Ca. People
Health and Welfare Canada has not revised its recommended
self-medicate with calcium to treat hypocalcemia, osteopo-
daily dosages since 1990 and has not provided a recom-
rosis, rickets, premenstrual syndrome, and leg cramps and to
mended dose for beta-carotene.
reduce susceptibility to colorectal cancer (Natural Medicines
Bishop's weed has the scientific names Ammi majus and
Comprehensive Database, 2004). Epidemiologic research
Ammi visnaga. Individuals self-medicate with bishop's weed
shows that high intake of dietary calcium tends to increase
for digestive disorders, asthma, angina, and kidney stones.
the risk of prostate cancer (Chan et al., 1998). Gastrointestinal
Bishop's weed also is used as a diuretic (Chevallier, 2000).
irritation, belching, and flatulence have been reported as ad-
Bishop's weed can cause skin malignancies in patients predis-
verse effects associated with high oral calcium intake (Martin-
posed to cancer (Fetrow & Avila, 1999). This herb can cause
dale, 1999). The recommended daily intake for individuals 19
photosensitivity, contact dermatitis, and allergic reactions, as
years and older is 1,200­1,300 mg (Yates, Schlicker, & Suitor,
well as nausea, vomiting, and headache when taken orally
1998). The recommended doses can be taken with confidence,
(Natural Medicines Comprehensive Database, 2004). No
but higher doses put an individual at risk.
reliable information speaks for this herb's safety. In addition,
Marjoram has the scientific name Origanum majorana,
no commercial brands containing bishop's weed have been
which is synonymous with Majorana hortensis. Individuals
found; therefore, users may be collecting this herb in the wild.
self-medicate with marjoram to treat coughs and colds as
No typical dose has been reported.
well as gall bladder and gastrointestinal conditions (Natural
Black pepper has the scientific name Piper nigrum, which
Medicines Comprehensive Database, 2004). The marjoram
refers to black and white peppers. Individuals self-medicate
flower, leaf, and oil contain arbutin and hydroxyquinone.
The latter seems to have the potential to cause cancer (Blu-
a rationale for limited use nor do they give an indication of
menthal et al., 1998). According to Gruenwald et al. (1998),
toxicity. Avoidance of this herb is prudent.
a typical dose of marjoram is 1­2 C of tea, prepared by
Sassafras has the scientific names Sassafras ablidum,
steeping 1­2 tsp of the flower or leaf in 250 ml of boiling
which is synonymous with Sassafras officinale, and Sassa-
water for five minutes.
fras varifolium. Individuals self-medicating with sassafras
Methionine has the scientific name L-2-amino-4-
believe it is a tonic or blood purifier (Tyler, 1994). Prelimi-
(methylthio)butyric acid. Individuals self-medicate with me-
nary evidence shows that sassafras root bark and oil contain
thionine to support their liver function and prevent liver dam-
safrole and related components that are carcinogenic, caus-
age in acetaminophen poisoning (Vale, Meredith, & Goulding,
ing liver cancers in experimental animals (Duke, 1987; El-
1981). Found in meat, fish, and dairy products, methionine is
lenhorn, 1997; McGuffin et al., 1997; Newall, Anderson, &
a sulfur-containing essential amino acid (Martindale, 1999).
Phillipson, 1996; Tyler, 1993). Sassafras, in large amounts
With high intake of methionine, salt, and nitrite in the diet,
or with chronic use, can cause hallucinations lasting for
the risk of gastric cancer increases (La Vecchia, Negri, Fran-
several days (Newall et al.), tremors, vomiting, dilated pu-
ceschi, & Decarli, 1997). Manufacturers' packages may give
pils, hypertension, tachycardia, stupor, collapse (Facts and
typical doses, but other than the amount in food, extra doses of
Comparisons, 2001), abortion, paralysis, liver cancer, and
methionine are considered possibly unsafe (Natural Medicines
death (Facts and Comparisons; Newall et al.). In addition, a
Comprehensive Database, 2004). Methionine should be used
few drops of sassafras oil can be fatal to children (Newall et
only for medical emergencies (e.g., acetaminophen poisoning)
al.). No typical dose has been recorded (Natural Medicines
by healthcare professionals (Vale et al.)
Comprehensive Database, 2004).
Omega-6 fatty acids, with the scientific name omega-6
Shark liver oil has the scientific names Cetorhinus maxi-
polyunsaturated fatty acids, are found in vegetable oils.
mus, Centroporus squamosus, and Sqaulus acanthias. Indi-
Do not confuse this product with the omega-3 fatty acids
viduals self-medicate with shark liver oil to treat leukemia
that are found in fish oils. Not only are the properties of the
and other cancers (Facts and Comparisons, 2001; Hasle &
two fatty acids different, they also compete metabolically:
Rose, 1991). Animal studies demonstrate that shark liver oil
Omega-6 fatty acids inhibit the incorporation of omega-3
has antiangiogenesis properties in certain cancers, including
fatty acid into tissue lipids (Hwang et al., 1997). Although
cutaneous lesions, kidney cancer, and urinary bladder cancer
omega-3 fatty acids in fish oil seem to have anticancer prop-
(Skopinska-Rozewska et al., 1999). Other research disputes
erties, preliminary in vivo and in vitro research indicates that
these findings (Hasle & Rose). Aspiration of shark liver oil has
omega-6 fatty acids may play a role in the development of
resulted in lipoid pneumonia (Asnis, Saltzman, & Melchert,
breast cancer (Godley, 1995). Other scholars speculate that
1993; Lee, Im, Song, Seo, & Lim, 1999; Lee, Lee, et al.,
omega-6 fatty acids may prevent breast and prostate cancers
1999). No typical dose has been reported (Natural Medicines
(Rose, 1996). Individuals self-medicate with omega-6 fatty
Comprehensive Database, 2004).
acids to prevent heart disease, lower cholesterol, and reduce
St. John's wort has the scientific name Hypericum per-
cancer risk (Natural Medicines Comprehensive Database,
foratum. Individuals self-medicate with St. John's wort for
2004). Omega-3 and omega-6 frequently are found in the
many mood disturbances, such as anxiety and depression. A
same products. Until the potential for metabolic competi-
component of St. John's wort, hyperforin, seems to inhibit
tion has been researched further, individuals should weigh
growth of a variety of cancer cells (Schempp et al., 2002).
the potential risks of taking these supplements. No typical
However, St. John's wort also interferes with numerous
dose has been provided.
prescription drugs such as calcium channel blockers, an-
Pau d'arco has the scientific names Lapacho colorado;
tifungals, glucocorticoids, cisapride, alfentanil, fentanyl,
Tabebuia avellanadae, which is synonymous with Tabe-
losartan, fluoxetine, midazolam, omeprazole, ondansetron,
buia impetiginosa; and Tabebuia heptaphylla. Pau d'arco
fexofenadine, and chemotherapeutic agents (e.g., etoposide,
commonly is known as taheebo. People self-medicate with
paclitaxel, vinblastine, vincristine, vindesine), making
pau d'arco to treat cancer, Candida, and viral and parasitic
therapy less effective (Henderson, Yue, Bergquist, Gerden,
infections (Natural Medicines Comprehensive Database,
& Arlett, 2002; Hennessy et al., 2002; Roby, Anderson,
2004). Anticancer activities have been noted, particularly
Kantor, Dryer, & Burstein, 2000; Schulz, 2001; Wang et al.,
in the treatment of sarcomas, but studies have been discon-
2001). St. John's wort was banned in France because of the
tinued because, in testing, no more than 30 mcg of lapachol
numerous drug-herb interactions, and Canada, Japan, and
(the active constituent) could be reached per 1 ml of plasma
the United Kingdom are implementing cautionary informa-
without causing extreme toxicity (Duke, 1987; Facts and
tion on product labels (Richter, 2000). The typical dose
Comparisons, 2001; Foster & Tyler, 1999). High doses cause
for depression is 300 mg three times a day (Kim, Streltzer,
severe nausea, vomiting, diarrhea, dizziness, anemia, and
& Goebert, 1999). St. John's wort is included in this alert
risk of hemorrhage (Duke; Facts and Comparisons; Foster
review not because it directly causes cancer (although it
& Tyler). Although no evidence suggests that pau d'arco
may precipitate cancer growth through its interactions) but
has the potential to cause cancer, it has been included in
because of its cancer connection, public popularity, and
this discussion because this product often is taken to treat
potential to cause harm.
or prevent cancer. However, pau d'arco can cause serious
Tannin-Containing Preparations
harm. Significant evidence of the toxicity of this herb has
been amassed; therefore, pau d'arco should be used with
extreme caution (Natural Medicines Comprehensive Data-
Tannins, whether gallic acid or catechin, exhibit carcino-
base). Some manufacturers warn that their products should
genic and anticarcinogenic properties (Leung & Foster, 1996;
be taken for no more than seven days, but they do not offer
McGuffin et al., 1997). More recent research still demonstrates
these ambiguities (Chen, Chang, & Lin, 2003; Fujiki et al.,
branches of this herb in 150 ml of boiling water for 5­10
2003; Krajka-Kuzniak & Baer-Dubowska, 2003; Labieniec &
minutes (Fetrow & Avila, 1999).
Gabryelak, 2003; Marienfeld, Tadlock, Yamagiwa, & Patel,
Oak bark has the scientific names Quercus robur, Quercus
2003). All of the following herbs have high tannin concentra-
petraea, and Quercus alba. Individuals self-medicate with
tions, and regular consumption increases the risk of esopha-
this herb to treat diarrhea (Blumenthal et al., 1998), colds, or
geal or nasal cancer (Leung & Foster; McGuffin et al.). This
loss of appetite (Gruenwald et al., 1998). Oak bark contains
list is not all inclusive.
8%­12% tannins. Adverse reactions include gastrointestinal
American chestnut has the scientific names Castanea
disturbances, kidney damage, and liver necrosis. A typical
dentata and Castanea americana. Individuals self-medicate
dose is one cup of a tea prepared from oak bark as much as
with American chestnut to treat respiratory ailments or for its
three times a day for a maximum of three to four days (Bis-
sedative or tonic activity (Natural Medicines Comprehensive
set, 1994).
Database, 2004). Typically, this herb is taken as tea prepared
Pomegranate has the scientific name Punica granatum.
with 1 tsp of leaves and bark (Weiner & Weiner, 1994).
The fruit rind of pomegranate contains as much as 28%
Bistort has the scientific name Polygonum bistorta and is
tannins. People generally self-medicate with this product
used to self-medicate for digestive disorders, particularly di-
to treat diarrhea, dysentery, tapeworms, or opportunistic
arrhea (Natural Medicines Comprehensive Database, 2004).
intestinal worms (Gruenwald et al., 1998). Overdoses of
This herb usually is taken orally as an infusion made of the
pomegranate cause strychnine-like effects (i.e., heightened
powdered rhizome and root. Ointments and extracts made
reflex arousal that can escalate to paralysis). Doses in excess
with the powdered root are used topically (Gruenwald et al.,
of 80 g are known to cause vomiting, bloody emesis, diz-
ziness, chills, vision disorders, collapse, and possible death
Black walnut has the scientific name Juglans nigra and is
from respiratory failure (Gruenwald et al.). No typical dos-
used to treat diphtheria, leukemia, and syphilis (Duke, 1987).
age has been reported (Natural Medicines Comprehensive
Natural Medicines Comprehensive Database (2004) did not
Database, 2004).
report any adverse reactions for black walnut and indicated
Quillaia has the scientific name Quilliaja saponaria.
that the typical oral dose of black walnut hull is 1,000 mg
People self-medicate with quillaia to treat colds (Natural
three times daily.
Medicines Comprehensive Database, 2004). Many adverse
Coffee has the scientific name Coffea arabica. Coffee in-
effects are associated with ingestion of large amounts of
take may increase the risk of breast cancer in obese women
quillaia: liver damage, diarrhea, respiratory failure, stom-
and ovarian cancer for all women; it also increases the risk
ach pain, convulsions, coma (Duke, 1987; McGuffin et al.,
of pancreatic cancer (McGuffin et al., 1997; Tyler, 1993,
1997) red blood cell hemolysis (Duke; Leung & Foster,
1994). Drinking one liter or more of strong unfiltered coffee
1996), and renal failure (McGuffin et al.). Duke indicated
per day can increase total cholesterol levels by 10%. Coffee
that the Quillaja saponin sapotoxin is very poisonous; digi-
also is known to increase low-density lipoprotein cholesterol
talis is recommended as an antidote. No typical dosage has
levels and triglycerides (Gruenwald et al., 1998; McGuffin et
been listed in Natural Medicines Comprehensive Database;
al.; Schulz, Hansel, & Tyler, 1998). Tyler (1993) suggested
however, Bisset (1994) reported that a typical single dose
that a safe intake of caffeine is no more than 250 mg per day
is 0.2 g chopped and steeped as tea. One teaspoon is ap-
(about two-and-a-half cups of boiled coffee or four cups of
proximately 2.3 g.
instant coffee).
Sorrel has the scientific name Rumex acetosa. Sorrel con-
English walnut has the scientific name Juglans regia. Black
tains 7%­15% tannins (Leung & Foster, 1996). Individuals
walnut has resulted in tongue cancer and lip leukoplakia (Blu-
often self-medicate with sorrel to treat colds (Gruenwald et
menthal et al., 1998), and mutagenic effects have been found
al., 1998). Adverse reactions include diarrhea, nausea, poly-
in animal studies (McGuffin et al., 1997). The hull of the
uria (Facts and Comparisons, 2001), and dermatitis (Newall
English walnut is thought to contain the constituent juglone,
et al., 1996). Oxalic acid is a poisonous constituent of sorrel
which has a carcinogenic effect. The hull is used topically
that has a corrosive effect on the digestive tract and can lead
for skin diseases; however, the amount of juglone in the hull
to oxalic crystals in the kidneys, blood vessels, heart, lungs,
varies. The leaf portion is probably safe if used for a short
and liver, as well as hypercalciumia (Ellenhorn, 1997). Clini-
period of time (Natural Medicines Comprehensive Database,
cal trials studying sorrel in the treatment of acute and chronic
2004). A typical dose of oral English walnut leaf is 1.5 g in a
sinusitis used Quanterra Sinus Defense Sinupret® (Bionorica,
cup of tea three times daily (Bisset, 1994). In self-medication,
Kerschensteinerstrasse, Germany) tablets, three times daily
English walnut fruit is used to lower cholesterol, the hull is
for as much as two weeks (Marz, Ismail, & Popp, 1999; Neu-
used to treat gastrointestinal inflammation, and the leaf is used
bauer & Marz, 1994; Schulz et al., 1998). Sinupret contains
to treat diarrhea (Blumenthal et al.).
29 mg of sorrel, in addition to other herbs such as gentian,
Mormon tea has the scientific name Ephedra nevadensis.
elder flower, European vervain, and primrose.
Mormon tea and a product called ephedra often are confused.
Willow bark has the scientific names Salix alba, Salix
Ephedra or Ma Huang, which has the scientific name Ephedra
purpurea, and Salix fragilis. Willow bark constituents in-
sinica, is considered an unsafe herb (McGuffin et al., 1997).
clude flavonoids, tannins, and salicylates. Attention usually
Mormon tea does not contain ephedrine (a component of
is given to salicylates that are in very low concentrations in
Ephedra sinica) and therefore is alkaloid-free and lacks the
most willow bark. Willow bark often is used as a self-medica-
potential therapeutic and toxic effects of ephedra (McGuffin
tion to treat colds, headaches, and joint pain (Bisset, 1994).
et al.). Other than tannin, no adverse reactions to Mormon
Gastrointestinal disturbances and kidney and liver damage are
tea have been recorded (Natural Medicines Comprehensive
possible adverse effects, perhaps related to the tannin content
Database, 2004). Mormon tea is prepared by steeping dried
(McGuffin et al., 1997).
Achieving medicinal quantities of salicylates greater than 1%
popularity among consumers but also have an enormous
from willow bark is difficult. Salicylates usually are extracted
potential to be dangerous.
with very hot water (Facts and Comparisons, 2001; Tyler,
No brand names were found for some of the herbs listed
1993). Tyler (1993) indicated that the volume of liquid needed
in Table 1 (e.g., aristolochia, areca, bishop's weed). In addi-
to extract a therapeutic salicylate dose from most willow bark
tion, the typical doses for American chestnut, bistort, Eng-
is an overwhelming 38 gallons. Using superior willow bark, 1.5
lish walnut, marjoram, Mormon tea, oak bark, and quillaia
gallons of willow bark tea per day would need to be ingested to
are instructions for making a tea. This instruction may lead
obtain pain relief, equivalent to 4.5 g of aspirin, approximately
some individuals to believe that concoctions can be made by
the daily dose for a person treated with rheumatoid arthritis
finding these herbs in the wild or purchasing them in their
(Robbers & Tyler, 1999). On the basis of these quantities of
natural state. Inclusion of these instructions for making teas
liquid, using willow bark may be less convenient than taking
is for information only--these are harmful herbs. Weigh the
aspirin, which does not contain tannin.
risks and benefits carefully before embarking on any health
Witch hazel has the scientific name Hamamelis virginiana.
regimens that include their use.
The astringent and hemostatic properties of witch hazel are
The list of herbs that contain tannins is not all inclusive.
attributed to tannin constituents in the plant (Newall et al.,
This section of the review serves as an alert for the possible
1996). Individuals orally self-medicate with witch hazel to
harmful and cancer growth properties of tannin. Read all
treat diarrhea, tuberculosis, colds, and fever (Natural Medi-
labels carefully on natural products and herbals. If a label
cines Comprehensive Database, 2004). Oral intake of witch
contains any of the products listed in Table 1 of this review,
hazel can cause stomach irritation and, in rare cases, liver
decrease your dose to the safe recommended amount or, in
damage (Bisset, 1994). Tannins can cause nausea, vomiting,
many cases, avoid that product or herb.
and possible bowel impactions with regular intake of 1 g of
The focus of these four review articles has been herbs
this herb (Facts and Comparisons, 2001). The typical dose of
or natural products that cause or protect against cancer.
2 g of dried leaves taken three times daily or as a tea (Newall
Healthcare professionals are encouraged to use the tables in
et al.) seems high considering the side effects following inges-
these reviews as quick references and the text for additional
tion of 1 g (Facts and Comparisons).
information. With this information, oncology nurses have
an opportunity to be better resources for their patients and
Conclusions and Implications
healthcare colleagues.
The author gratefully acknowledges the continuing support of Carl D'Arcy,
This review of 27 herbs and natural products offers an
PhD, director of applied research/psychiatry at the University of Saskatch-
alert to consumers and healthcare professionals. Although
ewan in Saskatoon, Canada.
many natural products and herbs have the potential to be
poisonous or harmful, the herbs reviewed here have the
Author Contact: Muriel J. Montbriand, PhD, RN, can be reached at
added potential to cause cancer. Two herbs, pau d'arco and
montbriand@skyway.usask.ca, with copy to editor at rose_mary@
St. John's wort, are included because they have enormous
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