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PART
4: Pyrrolizidine Measurements and Limits of Detection
A
BO supplier assures us that pyrrolizidine alkaloids "have
NEVER been found in borage seed oil"27. The statement
implies absence of PAs, non-toxicity, and (therefore) safety
for human consumption.
However,
several reputable sources express concerns regarding the safety
of BO:
- The
Canadian Pharmacy Journal reads:
"Borage
seeds do contain small amounts of the liver toxins called pyrrolizidine
alkaloids (PA). However, despite the fact that testing has
demonstrated the presence of less than 5 micrograms (ug) per
gram of the alkaloid in the seed oil, the consumption of two
to four 500mg capsules of borage seed oil could result in an
intake of such alkaloids approaching 5 - 10ug per day. In the
interests of public safety, borage oil should be PA-free and
follow the example set by the German Health Agency, which suggests
that no more than 1ug of PA be consumed daily when the herb
(sic) is taken as directed."28
- Herbal
Medicines: a Guide for Health-Care Professionals reads:
"In
view of the known toxic pyrrolizidine alkaloid constituents,
excessive or prolonged ingestion of borage should be avoided."29
"In
view of the documented pyrrolizidine constituents and lack
of toxicity data, borage should not be used during pregnancy
or lactation."29
"It
is unclear whether borage oil, currently available in food
supplements, contains any pyrrolizidine alkaloids."29
- Regarding
borage seed oil, Tyler's Herbs of Choice: the Therapeutic
Use of Phytomedicinals states:
"Borage
seeds have been shown to contain small amounts of pyrrolizidine
alkaloids, including the known hepatotoxic amibilene. That
alkaloid was not detected in samples of seed oil down to levels
of 5ug/g. Consumption of 1 to 2g of borage seed oil daily could,
nevertheless, result in an intake of toxic unsaturated pyrrolizidines
(UPAs) approaching 10ug. As De Smet has pointed out, the German
Federal Health Agency now limits internal consumption of such
products to not more than 1ug of UPA daily. This means that
in the interest of consumer safety, borage seed oil should
be certified free of UPAs down to the level of 0,5 to 1ug/g.
The
fact that GLA-rich oils are now available commercially from
three different plant sources does not alter the conclusion
that the product's efficacy for any condition remains unproven.
Likewise, its safety on long-term usage requires additional
verification. This is especially important for borage seed
oil, which may contain small amounts of UPAs."20
- In
the same book, regarding pyrrolizidines in comfrey and borage,
we can read:
"In
1992, the German Federal Health Agency, in an attempt to balance
the popularity of certain herbs containing toxic PAs with a
recognized need for their restricted use, established standards
for such preparations. These limitations restricted the amount
of total PAs with 1,2-unsaturated necine moieties that might
be obtained from certain registered preparations to not more
than 100ug per day when used externally and 1mcg when taken
internally. An exception was made for comfrey tea, which was
permitted to provide a maximum internal daily dose of 10ug.
In the case of non-registered preparations, the limitations
were reduced to 10ug externally and 0.1ug internally daily.
"It
is necessary to point out that these limitations, which
apply not only to comfrey but to such other herbs as borage,
coltsfoot, life root, and heliptrope, are meaningless in the
United States because none of the preparations sold here has
been assayed to determine its content of PAs. Further,
no adjustment has been made in any of the available dosage
forms to assure that safe levels of toxic alkaloids are not
exceeded. For this reason, safety requires adherence to the
five rules* stated above when dealing with comfrey. Similar
precautions should be taken with all herbs containing toxic
PAs."20 (emphasis added)
{*
The five rules referred to are: "1. The internal use
of any species of [comfrey] should be avoided. 2. [Comfrey]
root should never be used medicinally. 3. Only the mature
leaves of [S. officinale] should be applied externally, and
then only to intact skin for limited periods of time. 4.
[Comfrey] should never be used by pregnant or lactating women
or by young children. 5. Because there are so many other
nontoxic yet effective treatments for minor skin ailments
that do not present the hazards associated with this herb,
[comfrey] has little, if any, place in our modern materia
medica."20}
- The
same sentiment is expressed in a 1998 comment faxed by Varro
E Tyler, PhD, ScD, Dean and Distinguished Professor Emeritus
of Purdue University in West Lafayette, IN and a strong ally
for the (safe) use of herbs in health care, to the American
Botanical Council:
"The
July 1, 1998 HerbClip (060985) errata on Borage Oil requires
comment. 1. True, one study on one sample of oil (Parvais, et
al 1994)30 did not detect UPAs (unsaturated pyrrolizidine
alkaloids) at a level of 0.1ppm. What about the other samples
of the oil? Do the producers monitor them on a continuing basis?
2. The figure of 0.5ppm in the Botanical Safety Handbook is
a typographical or a calculation error. The references cited
give it as 5ppm (5ug/g); 3. The methodologies of other studies
citing low UPA levels have not been published. This includes
the Agr. studies in Canada, so no evaluation is possible; 4.
No long-term human toxicity studies have ever been conducted
with borage oil. Summary: In my opinion, all batches of product should
be certified as UPA-free down to levels of 0.5 to 1 ppm
in order to assure consumer safety."21
A
method for identifying pyrrolizidines in borage oil is described
by Mierendorff, but he fails to say whether or not the pyrrolizidines
he found in his study were from BO or borage plant material31.
So, we still don't know.
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