While I was in Brussels last month for the EU Homeopathy Day, I caught wind of preparations for a Europe-wide media campaign against herbal medicine
to instil fear in those who use over-the-counter medicinal herbs. The campaign will aim to suggest that herbal preparations may induce changes in DNA and increase the rate of mutations, especially during the early stages of pregnancy, which could trigger cancer. This prompted me to review the available literature myself.
- Arctostaphylos uva-ursi (bear-berry). Tests using bacteria to determine DNA damage have mostly found no evidence of mutagenicity (Yakugaku Zasshi, 1982; 102: 596-601; Mutat Res, 1982; 97: 81-102). The single exception was
a water extract preparation (Mutat Res, 1982; 97: 81-102).
- Astragalus membranaceus (milk vetch). A mouse study (which may not apply to humans) found modest evidence of mutagenicity, but only when a large dose (1 g/kg of body weight) of extract was injected directly into the stomach lining-unlike ordinary human use, in which herbs are taken orally (Mutat Res, 1991; 260: 73-82).
- Capsicum annuum (chilli or cayenne pepper). Mutagentic effects have only been seen with isolated extracts of capsaicin, a major constituent of this plant, and only on animal cell lines in
the lab (Cancer Lett, 1989; 48: 109-13), which again may not be relevant.
- Matricaria recutita (German chamomile). Chamomile flower extract, prepared as an infusion with boiling water, caused a rela-tively high degree of mutagenicity in animals (Yakugaku Zasshi, 1982; 102: 596-601), although this was only because coumarins-toxic chemi-cals that are commonly found in many plants-present in the extract were activated by exposure to light (Fitoterapia, 1992; 63: 387-94).
- Schisandra sphenanthera (mag-nolia vine). Although an increase in mutagenicity was observed in the test-tube with cell lines, again, these results probably represent much greater exposure to toxins than would occur in real life (Food Chem Toxicol, 1986; 24: 903-12).
- Uncaria guianensis (cat's claw). A freeze-dried preparation of the root bark showed no mutagenicity in five different tests using four different concentrations. Other tests examining the effects of certain alcohol extracts on bacteria and animal-cell particles (microsomes) were also negative (J Ethnopharmacol, 1993; 38: 63-77). However, when components called 'alkaloids' were isolated and used in an alcoholic extract of the bark, they showed weak activity in yeast tests (Planta Med, 1999; 65: 759-60).
- Valeriana officinalis (valerian or all-heal). In valerian plants that had decomposed, two of its con-stituents caused mutations in bacteria (DeSmet et al., eds. Adverse Effects of Herbal Drugs, vol 3. NY: Springer-Verlag, 1997: 165-80). However, although these decomposition products are rapidly metabolized in the human body and the metabolites display no mutagenic-ity, until there is total clarity, the best precautionary measure is to avoid valerian products, such as tinctures, that have been stored for two months or longer (Phyto-medicine, 1998; 5: 219-25). If they were to affect humans, the main sites of possible injury would be the liver and gastrointestinal tract.
- Zingiber officinale (ginger). A review of mutagenic studies of this plant and its constituents found mixed results. One study of an alcoholic root extract showed mutagenicity; another using an extract of whole ginger found no such activity; while a third study, also of ginger extracts, ironically found that the toxicity to DNA of a number of carcinogens was suppressed (J Environ Pathol Toxicol Oncol, 1999; 18: 131-9).
Although there is some preliminary evidence that specific herbal extracts could damage DNA, these have only been demonstrated in animals or in bacteria or cell lines grown in the laboratory, which may not apply to humans or to 'real life'. In many cases, the damage only results when individual constituents are isolated and adulterated (such as by exposure to light) and then taken-which is tantamount to using herbs as a drug. In other instances, problems have only arisen when the herbs were degraded. In yet other instances, the culprit was the medium itself (either alcohol or water). In all cases, these problems don't reflect how herbs are normally taken. Anyone wishing to use herbal medicine should consult a knowledgeable practitioner who can advise on what are the safe doses and formulations to take.
Harald Gaier, a registered naturopath, osteopath, homeopath and herbalist, practises at The Allergy and Nutrition Clinic, 22 Harley Street, London, and the Irish Centre of Integrated Medicine, Co. Kildare (www.drgaier.com).
The safe, non-mutagenic herbs
- Actaea racemosa (black cohosh) (Adv Ther, 1998; 15: 45-53)
- Allium sativum (garlic) (Mutat Res, 1984; 136: 85-8; Herbal Medicines: A Guide for Healthcare Professionals. London: The Pharmaceutical Press, 1996: 129-33)
- Angelica polymorpha (dong quai) (Yakugaku Zasshi, 1982; 102: 596-601)
- Carduus marianus or Silybum marianum (milk thistle) (Mutat Res, 1994; 307: 395-410)
- Cordyceps sinensis (caterpillar fungus) (J Altern Complement Med, 1998; 4: 429-57).