Is it safe to use comfrey tea, pills, oils, creams etc?
Is it safe to use medicinal comfrey leaves or
roots?
INTERNALLY consuming REGULAR /EXCESSIVE amounts of
comfrey may cause liver / kidney damage
To be safe, anyone with serious
liver or kidney disease or taking hepatotoxic drugs should not use comfrey
internally
The U.S. FDA warns that REGULAR consumption of LARGE amounts
of comfrey tea, pills, root powder and/or extracts can lead to sinusoidal
obstruction syndrome (SOS)(formally called hepatic veno-occlusive
disease. Potentially, this is a fatal form of liver damage
caused by drugs /toxins, which can trigger fibrosis by altering DNA),
and/or
similar kidney cell damage. In the U.S., comfrey- pepsin capsules are a
likely source for concern;
Comfrey contains several potentially toxic UNsaturated
pyrrolizidine alkaloids (uPAs) (saturated PAs are
NON- toxic). Including symphytine,
echimidine, symglandine and lycopsamine. uPAs are present in the plant
families: Boraginaceae (E.g. Symphytum offinale (comfrey), Borago offinales
(borage)),Fabaceae and Asteraceae (e.g. summer ragwort, gravel root, boneset,
butterbur and coltsfoot), as
part of their defense mechanism. If the liver's normal detoxification pathways
are compromised or overwhelmed (e.g. by high dose uPAs), then uPA's are metabolized by the cytochrome P450 enzymes into highly toxic pyrrole
metabolites with alkylating properties that can damage hepatic endothelial cells
and can lead to SOS. Similarly, pyrrole can damage kidney
cells. Damage can accrue slowly, silently and cumulatively with low- level
comfrey consumption. Pyrrole can be broken down in the liver by
glutathione and glutathione S- transferase enzymes in the liver
Liver injury is typically seen 1- 2 months after regular,
EXCESSIVE comfrey consumption. Beginning with right upper quadrant pain, nausea and
fluid retention/weight gain, which is followed by jaundice. Infants seem to be particularly susceptible. It is noted that as of
2015, studies have only shown association, and not
causation , of comfrey PA's with liver toxicity. An inference is made
that comfrey must cause toxicity, because PA's in other herbs, such as senacio,
have shown causal liver toxicity.
What are the risk factors for uPA-associated
damage?
- Family history.
SOS, liver cirrhosis,
pulmonary hypertension and right heart failure
- Poor liver health.
History of infection,
alcohol abuse
- Children 1- 14.
Even after consideration of
lower body weight
- Babies / fetuses.
Due to higher copper
levels in their livers
- Pregnant / lactating mothers.
uPAs cross placental
barrier, show up in milk
- Regular honey consumption.
May provide chronic
low- dose of uPAs if bees visited PA- containing plants;
- Concurrent use of certain herbs.
E.g. Hypericum perforatum (St John's Wort) /
medications that induce CYP450 metabolic pathway
- Low glutathione levels.
Possibly caused by high
alcohol intake, low dietary sulfur / protein / selenium or genetic factors
Alkaloid Content of comfrey
Varies according to different studies
- but generally PAs vary by:
- Species - and even
by Individual
plant; more prickly species (E.g. Prickly, Russian) contain more PAs than
less hairy leafed species.
- Growth state - age of
plant; young leaves have higher concentration than older
leaves; Small leaves of S. x Uplandicum found to have 16- fold increase
over larger leaves. Mattocks AR (1980)
Toxic pyrrolizidine alkaloids in comfrey Lancet 2 1136 - 7
- Plant part - roots have
~10 times more PAs than stems, flowers, leaves (Roitman 1981); highest concentration in small young roots, extreme exodermis and
rhizome center.
- Time of harvesting and location
PAs convert to N- oxides, which forms are also toxic and not always counted in
studies - estimated to be 7 times PA count
PAUL M. RIDKER, SEITARO OHKUMA, WILLIAM V. McDERMOTT, CHARLES TREY, and RYAN J.
HUXTABLE, Hepatic Venocclusive Disease Associated With the Consumption of
PyrrolizidineContaining Dietary Supplements, (1985)
GASTROENTEROLOGY;88:1050- 4
A high concentration of symphytine is present in tea as its more soluble N- oxide
- these derivatives could be reduced
in vivo to their native PA and subsequently metabolised to the
hepatotoxic pyrrole.
Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale):
Reduction of N- oxides results in order of magnitude increases in the measurable
concentration of pyrrolizidine alkaloids (2004)
Public Health Nutrition 7(7):919- 24
Unsaturated PAs are both water- and alcohol- soluble - and so can be found in teas and tinctures
Echimidine (likely the most toxic
PA in comfrey) - in prickly and Russian comfrey, and ~25% of tested
samples
of Common comfrey.
Jaarsma, T.A., et al., Chemotaxonomy of the Symphytum
officinale agg. (Boraginaceae). Plant Systematics and Evolution, 1989. 167(3- 4):
p. 113- 128.Ref
Symphytum Species
Leaf PAs Conc.
Leaf PA Daily intake
Root PAs Conc.
Root PA Daily intake
Notes
S. Officinale 15- 55 ug/g
3 cups tea:
450- 8320 ug/g
Roitman 1981
S. x Uplandicum 30- 2200 ug/g
100- 2270 ug/g
S. Asperum
1400 and 4000 ug/g
Comfrey- pepsin capsules
6 capsules:0.9 mg PAs (includes N oxides)
6 capsules contain 9.6mg PAs
Comfrey- pepsin: typically taken 6/day
6 Leaf capsules contain 0.9mg PAs
270 - 2900 ug PAs/g;Huxtable et al 1986; PA count includes N oxides;
one capsule contains ~350mg comfrey
