And the Good Herb Taketh Away

This section is compiled by Frank M. Painter, D.C.
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From The October 1999 Issue of Nutrition Science News

By Ernest B. Hawkins, R.Ph.

Botanical medicines may be safer than pharmaceuticals, but the potential to cause ill effects still exists

Gentle, natural herbs have gained a reputation as being able to do no wrong. Most consumers consider them safe healing agents without the side effects of prescription drugs. And overall, herbs generally are safe when used appropriately in recommended doses. But, as with any medicine, there are points to keep in mind when taking them therapeutically.

Some commercially available herbs have potentially problematic constituents. For example, comfrey (Symphytum officinale) and coltsfoot (Tussilago farfara) contain pyrrolizidine alkaloids that, when taken in high doses, can be toxic to the liver. [1] Commonly used herbs such as ginkgo (Ginkgo biloba) and horse chestnut (Aesculus hippocastanum) may increase chances of bleeding, especially if taken with anticoagulant medications. [2,3] Sedative herbs such as valerian (Valeriana officinalis) and kava (Piper methysticum) can interact with sedative prescription drugs by increasing their effects. [4,5] Taking these and other herbs that have potential interactions with drugs can cause unwanted side effects and may necessitate medical treatment.

Certain herbs such as black cohosh (Cimicifuga racemosa) and St. John's wort (Hypericum perforatum) may be contraindicated during pregnancy and lactation because of their potential for uterine stimulation and abortifacient effects. [6,7] Likewise, diabetics on insulin should use caution when taking bitter melon (Momordica charantia) because it has the potential to lower blood sugar levels. [8] Licorice (Glycyrrhiza glabra) should be avoided by those with high blood pressure because the herb is a potential mineralocorticoid--it may increase the excretion of potassium while decreasing the elimination of sodium and water, leading to hypertension. [9]

Beyond potential effects like these, some herbs may deplete the body of important vitamins and minerals.

A health care professional can determine the appropriate use of herbs for people taking prescription medications or for those with pre-existing conditions. Retailers should concentrate on educating consumers about potential depletions or interactions. Most herb/nutrient depletion information is based on research, medical observation and theoretical interactions deduced from pharmacological properties of herbs. Following are some possible depletions.

Black cohosh, grape seed (Vitis vinifera), green and black teas (Camellia sinensis), hawthorn (Crataegus spp.), horse chestnut, saw palmetto (Serenoa repens), St. John's wort and valerian are tannin-containing herbs. They have an acid substance that can theoretically alter the absorption of calcium, copper, iron, magnesium and zinc. This possibility is based on potential chemical reactions between the tannin compound and these bivalent, or double-charged, minerals. The minerals can form an insoluble complex with the herb tannins and render themselves unusable by the body to some degree, depending on factors such as total tannin content and individual biochemical susceptibility. More research is needed to establish if this is a significant problem.

Recommend to your customers who regularly take tannic herbs that they do so either one hour before or two hours after taking vitamin and mineral supplements that include calcium, copper, iron, magnesium or zinc.

Horsetail (Equisetum arvense), celery seed (Apium graveolens), dandelion leaf (Taraxacum officinale) and elder flower (Sambucus nigra, S. canadensis) are generally used as diuretics to rid the body of excess fluid. Diuretic herbs are commonly used during detoxification and for conditions such as high blood pressure, kidney infections, obesity, and swelling associated with premenstrual syndrome. [10 ]

Diuretic supplements may cause fluid electrolyte imbalances due to the loss of water, sodium and chloride, especially if used for longer than two weeks. The danger is heightened when diuretics are used chronically in amounts that exceed the recommended dosages. Only doctors should recommend diuretic herbs to individuals with pre-existing medical conditions, especially those already on diuretics. Customers taking diuretics should replace fluid and electrolytes with liquids that have a low sugar content.

Horsetail is used to treat bone fractures, connective tissue damage, osteoporosis and tooth and nail injuries because it contains silicic acid, a constituent that provides elemental silicon. [11] Reports suggest horsetail supplements deplete the body of thiamine (vitamin B1) because they contain the enzyme thiaminase, which may destroy thiamine. [12] Thiamine helps the body produce energy and nourishes the nervous system by helping synthesize the neurochemical ester acetylcholine. [13] Thiamine deficiency symptoms include appetite loss, fatigue, nausea, and mental disturbances such as depression and memory loss.

Advise customers to take a multivitamin containing 10 to 50 mg of thiamine either one hour before or two hours after taking horsetail. Brown rice, navy beans, salmon, soybeans and whole grains are dietary sources of thiamine.

Kava is a popular dietary supplement traditionally used to manage anxiety and restlessness and to relax skeletal muscles. It also may be useful for treating epilepsy. [14] Chronic and heavy use of kava has occasionally been reported to cause a scaly, yellow skin rash that disappears after discontinuation of the herb. [15] The rash resembles one brought on by a niacin deficiency; however, a double-blind, placebo-controlled study showed no change in the rash after niacin supplementation. [16] The 29 Tonga islanders who presented with the rash after heavy kava consumption--more than 900 g/week--were given either 100 mg of oral niacinamide or placebo. No statistically significant improvement was seen in the supplementing group, suggesting niacin deficiency may not cause the rash. Until more is known, however, people taking kava regularly may also wish to take a multivitamin with at least 50 to 100 mg of niacin daily.

Licorice root is commonly used as an adrenal tonic, expectorant and demulcent because of its mucous membrane-soothing action. [17] Glycyrrhizin, the component attributed to both expectorant and adrenal activity, gives licorice mineralocorticoid effects that increase the output of the adrenal hormone aldosterone. This increase in hormones released from the adrenal glands can cause sodium retention leading to fluid retention, as well as potassium loss that can lead to hypertension and other cardiac problems. [18 ]

When glycyrrhizin is removed, the result is called deglycyrrhizinated (DGL) licorice, which is used to treat peptic ulcers. [17] DGL licorice has less than 2 percent of the glycyrrhizin content of the whole plant, so minerolocorticoid effects should not be seen when it is taken in the recommended doses.

Customers taking heart medications or who have pre-existing medical conditions such as heart, kidney or liver disease should take licorice products only under a doctor's supervision. Those taking licorice supplements may benefit from a multivitamin with adequate potassium. Dietary sources of potassium include avocados, bananas, lentils and spinach.

Senna (Cassia senna) and other laxative herbs including aloe (Aloe spp.), cascara sagrado bark (Rhamnus purshianus) and yellowdock root (Rumex crispus) can negatively affect the absorption, metabolism and excretion of nutrients, drugs and other dietary supplements. [19]

For customers inquiring about laxatives, recommend they use them for no more than 48 hours. If constipation is not alleviated within that time, they should consult their doctor. Long-term laxative use can cause electrolyte imbalances as a result of lost water, sodium, potassium and other minerals.

Also caution consumers against using laxatives when abdominal pain is present, especially if it has any of the following characteristics: localizes to a specific area of the abdomen or radiates from a particular part of the abdomen; is accompanied by sudden onset of nausea/vomiting, constipation, fever, appetite loss, or bloating; is unlike previously experienced abdominal pain; or is painful with movement. These types of pain should be addressed by a physician.

Education is Key

Herbal supplement use is undergoing a revitalization that is changing medicine. For reasons that range from an increased sense of personal responsibility to exorbitant healthcare costs, people are taking a more active role in their health and the health of their loved ones. As people turn to herbal supplements, professional, factual information on their proper use needs to be disseminated.

What this presents is an opportunity for you to communicate with your customers and educate them on appropriate uses of herbs. If a customer inquires about a specific herbal remedy, use qualified, respected references to determine potential interactions. If potential herb-induced nutrient depletion exists, discuss it and suggest appropriate supplements. Consumers with pre-existing medical conditions should use herbs only after consulting a doctor.

Ernest B. Hawkins, M.S., R.Ph., has worked for more than 10 years in hospital and retail pharmacy as well as pharmaceutical research. He is principal author, lecturer and technology specialist for Natural Health Resources in Cincinnati.


Get Smarter about Drug/Herb Interactions

Up in Smoke


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2. Pittler MH, et al. Horse-chestnut seed extract for chronic venous insufficiency. A criteria-based systematic review. Arch Dermatol 1998;134(11):1356-60

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10. Weisse RF. Herbal medicine. Beaconfield (England): Beaconfield Publishers Ltd.; 1988

11. Leung A, et al. Encyclopedia of common natural ingredients used in foods, drugs, and cosmetics. New York: Wiley-Interscience Publications; 1996. p 306-8

12. Meyer P. Thiaminase activities and thiamin content of Pteridium aquilinum, Equisetum ramo sissimum, Malva parviflora, Pennisetum clandestinum and Medicago sativa. J Vet Res 1989;56(2):145-6

13. Meador KJ, et al. Evidence for a central cholinergic effect of high-dose thiamine. Ann Neurol 1993;34(5):724-6

14. Singh YN. Kava: an overview. J Ethnopharmacol 1992;37(1):13-45

15. Norton SA, et al. Kava dermopathy. J Am Acad Dermatol 1994;31(1):89-97

16. Ruze P. Kava-induced dermopathy: a niacin deficiency? Lancet 1990;335(8703):1442-5

17. Newall CA, et al. Herbal medicines: a guide for health care professionals. London: The Pharmaceutical Press; 1996. p 183-6

18. Farese RV Jr, et al. Licorice-induced hypermineralocorticoidism. N Engl J Med 1991;325(17):1223-7

19. Baker EH, et al. Complications of laxative abuse. Annu Rev Med 1996;47:127-34

Up in Smoke

1. Piyathilake CJ, et al. Cigarette smoking, intracellular vitamin deficiency, and occurrence of micronuclei in epithelial cells of the buccal mucosa. Cancer Epidemiol Biomarkers Prev 1995;4(7):751-8

2. Piyathilake CJ, et al. Local and systemic effects of cigarette smoking on folate and vitamin B-12. Am J Clin Nutr 1994;60(4):559-66

3. Preston AM. Cigarette smoking: nutritional implications. Prog Food Nutr Sci 1991;15(4):183-217.


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