The Dirt On Herbs
By Ernest B. Hawkins, M.S., R.Ph.
Gentle, natural herbs have gained a reputation for being able to do no wrong. Most people consider them safe healing agents without the side effects of prescription drugs. And overall, herbs generally are safe when used appropriately in recommended doses—the way they have been safe for thousands of years. However, the recent advent of standardized herbal preparations—those herbs that are guaranteed to have a certain concentration of chemical constituents—has increased the chances of adverse side effects. As with any medicinal agent, there are points to keep in mind when taking herbs therapeutically.
For all their good, some commercially available herbs have potentially problematic constituents. For example, comfrey (Symphytum officinale) and coltsfoot (Tussilago farfara) contain alkaloids that, when taken internally in high doses, can be toxic to the liver. Likewise, commonly used herbs such as ginkgo (Ginkgo biloba), garlic (Allium sativum), feverfew (Tanacetum parthenium), reishi mushroom (Ganoderma lucidum), bilberry (Vaccinium myrtillus) and horse chestnut (Aesculus hippocastanum) may increase chances of bleeding, especially if taken with anticoagulant medications and even aspirin-containing products. Sedative herbs such as valerian (Valeriana officinalis), hops (Humulus lupulus), passionflower (Passiflora spp.) and kava (Piper methysticum) can interact with sedative prescription drugs by increasing their effects. These herbs also may potentiate the effects of alcohol. Taking these and other herbs that have potential interactions with drugs can cause harmful side effects and may necessitate medical treatment.
Commonly used herbs such as black cohosh (Cimicifuga racemosa) and St. John's wort (Hypericum perforatum) may be harmful during pregnancy and lactation because of their potential to stimulate the uterus and cause a miscarriage. St. John's wort may also alter the levels of many prescribed medications, including digoxin, theophylline and drugs used to treat HIV infections, due to its effects on liver-metabolizing enzymes.
Similarly, diabetics should use caution when taking herbs such as bitter melon (Momordica charantia) and gymnema (Gymnema sylvestre) because they have the potential to lower blood sugar levels, altering the need for medication. Licorice root (Glycyrrhiza glabra) should be avoided by those with high blood pressure because the herb can itself lead to hypertension.
Herbs May Deplete
In addition to potentially dangerous interactions, some herbs may deplete the body of important vitamins and minerals. A pharmacist, naturopath or other health care professional can determine the appropriate use of herbs for people taking prescription medications or for those with preexisting conditions. But for your own health safety, you should educate yourself 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 of vitamins and minerals. Black cohosh, grape seed, green and black teas, bilberry, hawthorn, horse chestnut, saw palmetto, St. John's wort and valerian contain an acid called tannin. In theory, tannins can alter the absorption of calcium, copper, iron, magnesium and zinc. However, more research is needed to determine if this is a significant problem.
If you regularly take tannic herbs, 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.
Diuretic supplements may cause fluid electrolyte imbalances due to water, sodium and chloride loss, 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 preexisting medical conditions, especially those already on diuretics or those taking antihypertensive medicines. People taking diuretics may replace lost fluid and electrolytes with liquids that have a low sugar content.
Horsetail is also 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. Reports suggest that because horsetail contains an enzyme that may destroy thiamine, it may deplete the body of this B vitamin, which is crucial for energy production and nourishing the nervous system. Thiamine deficiency symptoms include appetite loss, fatigue, nausea and mental disturbances such as depression and memory loss.
To remedy this problem, take a multivitamin containing 10-50 mg of thiamine either one hour before or two hours after taking horsetail. Brown rice, navy beans, salmon, soybeans and whole grains are also sources of thiamine.
Kava is a popular dietary supplement traditionally used to manage anxiety and restlessness and to relax skeletal muscles. Chronic and heavy use of kava has occasionally been reported to cause a scaly, yellow skin rash that disappears after discontinuation of the herb. 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. Until more is known, people taking kava regularly may also wish to take a daily multivitamin with at least 50-100 mg of niacin.
Licorice root is commonly used as an adrenal tonic, expectorant and demulcent because of its mucous membrane-soothing action. Glycyrrhizin, the active component in licorice, can cause sodium retention, which leads to hypertension and other cardiac problems. When the glycyrrhizin is removed, the result is called deglycyrrhizinated (DGL) licorice. This form is commonly used to treat peptic ulcers and does not have the unwanted side effects associated with regular licorice root supplements.
If you take heart medications or have preexisting medical conditions such as heart, kidney or liver disease, 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 sagrada bark (Rhamnus purshianas) and yellowdock root (Rumex crispus) can negatively affect the absorption, metabolism and excretion of nutrients, drugs and other dietary supplements.
When taking laxatives, use them for no more than 48 hours. If constipation is not alleviated within that time, consult your health care practitioner. Long-term laxative use can cause electrolyte imbalances as a result of lost water, sodium, potassium and other minerals.
Refrain from 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 your health care practitioner.
For reasons that range from an increased sense of personal responsibility to exorbitant health care costs, people are taking a more active role in their health and the health of their loved ones. But when you turn to supplements, make sure you know what it is you are taking, how it works, and if it's OK to take with other medications. Your pharmacist or other health care provider should be an excellent source of education.
Ernest B. Hawkins, M.S., R.Ph., is a consultant and author of several books including Natural
Therapeutics Pocket Guide (LexiComp, 2000).