Herbal tea, or a tisane, is an infusion made from the leaves, roots, flowers, or seeds of any plant other than Camellia sinensis. This distinction is significant because true teas—black, green, oolong, and white—all come from the Camellia sinensis plant and contain varying levels of caffeine. Herbal infusions are typically caffeine-free but contain a vast array of pharmacologically active botanical compounds. Whether a particular herbal tea can raise blood pressure depends entirely on the specific plant compounds present and their biological effects on the cardiovascular system.
Active Components That Influence Circulation
Plant compounds can influence blood pressure through several distinct mechanisms involving the circulatory and renal systems. One pathway involves stimulant action, where certain compounds mimic the body’s adrenergic hormones. This effect leads to the narrowing of blood vessels (vasoconstriction) and an increase in heart rate, which collectively elevates pressure within the arteries.
Another potent mechanism involves the body’s fluid and electrolyte balance, specifically through a mineralocorticoid effect. Some compounds interfere with kidney enzymes that regulate sodium and water retention, mimicking the action of the hormone aldosterone. When the kidneys retain more sodium and water, the total volume of fluid in the bloodstream increases, which directly raises blood pressure.
Conversely, many plant compounds affect circulation by promoting the opposite action, such as causing vasodilation or acting as diuretics. Vasodilators relax the muscles in the blood vessel walls, widening the arteries and reducing resistance to blood flow. Diuretic compounds increase the excretion of sodium and water by the kidneys, reducing blood volume and helping to lower blood pressure.
Herbal Teas Associated with Increased Blood Pressure
Certain herbal teas contain compounds documented to elevate blood pressure, particularly when consumed regularly or in high concentrations. Licorice root (Glycyrrhiza glabra) tea is the most prominent example due to its active component, glycyrrhizin. Glycyrrhizin interferes with an enzyme that normally deactivates the stress hormone cortisol in the kidneys.
The resulting buildup of active cortisol mimics the effects of aldosterone, leading to a condition called pseudo-aldosteronism. This hormonal interference causes the kidneys to retain sodium and water while promoting the loss of potassium. Research indicates that consuming as little as 100 milligrams of glycyrrhizin daily for two weeks can cause a significant increase in systolic blood pressure. Experts caution against regular, high-volume consumption, as the average cup of licorice tea can contain around 32 milligrams of glycyrrhizin.
Other herbs, such as Ginseng (Panax species), are associated with blood pressure elevation, especially at therapeutic doses. While low, occasional doses may be safe, regular consumption of high-dose Ginseng can stimulate the cardiovascular system, raising both heart rate and blood pressure. Similarly, teas or blends containing ephedra-like compounds contain stimulants that directly constrict blood vessels and increase cardiac output, posing a risk for raising blood pressure.
Herbal Teas Used to Support Healthy Blood Pressure
While some teas pose a risk, others are studied for their beneficial effects on cardiovascular health and blood pressure maintenance. Hibiscus tea, made from the calyxes of the Hibiscus sabdariffa flower, is a notable example. This tea is rich in anthocyanins and other polyphenols that function as antioxidants.
The primary mechanism of hibiscus involves promoting vasodilation, helping to relax and widen blood vessels and reducing resistance to blood flow. Clinical studies suggest that regular consumption of hibiscus tea is associated with measurable reductions in both systolic and diastolic blood pressure. This effect is likely due to its mild diuretic and angiotensin-converting enzyme (ACE) inhibitor-like properties.
Hawthorn (Crataegus species) is another herb traditionally used for heart health. Hawthorn leaf, flower, and berry contain bioflavonoids and proanthocyanidins that exert a cardiotonic effect, supporting heart function. These compounds help to dilate the coronary arteries, improving blood flow and oxygen supply to the heart muscle. This contributes to a healthier circulatory system and supports blood pressure regulation.
Factors Affecting Risk and Consumption Guidelines
The risk of an herbal tea affecting blood pressure depends on consumption factors beyond the presence of an active ingredient. Dosage and duration are variables; even glycyrrhizin typically only causes issues when consumed at high levels over a sustained period. The concentration of the active compound can vary drastically between tea bags, loose leaf, and herbal extracts, making consistent dosing difficult to monitor.
A concern is the potential for interactions with prescription medications used to manage hypertension. Certain herbal compounds can interfere with how the body metabolizes blood pressure drugs, such as ACE inhibitors or beta-blockers. For instance, green tea extract may reduce the absorption and effectiveness of the ACE inhibitor lisinopril, potentially leading to increased blood pressure.
Herbal teas can also interact with diuretics or blood thinners like warfarin, either by enhancing their effects or making them less effective. Individuals diagnosed with hypertension or any other cardiovascular condition should consult with a healthcare provider or pharmacist before incorporating any new herbal tea into their daily routine. Natural products contain powerful bioactive substances that require the same caution as pharmaceuticals.