Many traditional systems of medicine have relied on plants for thousands of years. Today, botanical medicine has integrated with mainstream western medicine as complementary therapies. Just as different pharmaceutical drugs produce different effects, however, so do natural medicines obtained from plants. Herbs can increase the effects of other medications or reduce their absorption. In addition, certain herbs can elevate blood pressure and cause heart palpitations. If you have a history of heart disease or hypertension, be sure to talk to your doctor before using any herbal supplement, especially if you have a chronic medical condition or take medications.
Vasodilating Herbs
Some herbs promote vasoconstriction, such as ma huang, an herb used in traditional Chinese medicine to treat asthma, seasonal allergies and head colds. The "Physicians' Desk Reference for Herbal Medicines" describes this herb as a nervous system stimulant that also restricts blood flow. Just like antihistamine and decongestant medications, ephedra causes blood vessels to narrow and systemic blood pressure to increase due to the action of its two main chemical constituents, ephedrine and pseudoephedrine. A review of published in the March 26, 2003, issue of the "Journal of the American Medical Association" found that safety data obtained from 50 trials linked ephedra use with a 2.2 to 3.6-fold increase in the risk of psychiatric disturbances, gastrointestinal complaints and heart palpitations. The sale of dietary supplements that contain ephedra is banned in the United States.
Stimulatory Herbs
Some plants contain caffeine, such as green tea made from the leaves of Camellia sinensis. Although green tea contains a variety of minerals, tocopherols, carotenoids and vitamin C that help to reduce the risk of cardiovascular disease, the plant also contains caffeine and two other stimulatory chemicals called theobromine, and theophylline. The University of Maryland Medical Center cautions that drinking too much green tea may trigger heart palpitations. Similarly, guarana, a rainforest herb native to the Brazilian Amazon, also contains caffeine -- about twice the amount found in coffee beans. The seeds, which are the medicinal parts of the plant, also contain a compound called guaranine that is structurally similar to caffeine. Guarana is also a source of theophylline and theobromine, cardiac stimulants that may increase blood pressure and produce heart palpitations in sensitive individuals.
Hypertension-Inducing Herbs
According to Subhuti Dharmananda, Ph.D. of the Institute for Traditional Medicine, certain herbs contain high levels of pyrrolizidine alkaloids, which can damage the liver to the point of obstructing blood flow back to the heart, which causes blood pressure to rise. At list of herbs known to induce hypertension presented at a symposium sponsored by the American Academy of Family Physicians included licorice, ginger, vervain, St. John's wort and blue cohosh.
Bottom Line
Many herbs are safe and well tolerated while others produce unwanted effects, like heart palpitations. Talk to your doctor before using any herbal supplement to avoid this risk, especially if you have a history of hypertension or heart disease or if you take other medications.
References
- "Physicians' Desk Reference for Herbal Medicines"; Thomas Brendler, et al.; 2007
- "Journal of the American Medical Association"; Efficacy and Safety of Ephedra and Ephedrine for Weight Loss and Athletic Performance: A Meta-analysis; PG Shekelle, et al.; 2003
- University of Maryland Medical Center: Green Tea
- Institute for Traditional Medicine: Safety Issues Affecting Herbs: Pyrrolizidine Alkaloids; Subhuti Dharmananda, Ph.D
- Institute for Traditional Medicine: Safety Issues Affecting Herbs: Herbs That May Increase Blood Pressure; Subhuti Dharmananda, Ph.D
