Anise has shown blood-pressure-lowering effects in animal studies, but no human clinical trial has confirmed this effect. The most compelling evidence comes from rat experiments in which an aqueous extract of anise seeds reduced blood pressure across multiple test groups, and the mechanism appears to involve blocking calcium channels in blood vessels. That is a real pharmacological finding, and it overlaps with how some prescription blood pressure drugs work. But the leap from “it lowered blood pressure in rats” to “it will lower your blood pressure” is one the research has not yet made.
What the Animal Research Actually Shows
The strongest direct evidence comes from a preclinical study that tested an aqueous extract of Pimpinella anisum (the botanical name for common anise) on rats. The extract reduced blood pressure in every group tested. Researchers ruled out several possible mechanisms: the blood pressure drop was not caused by a diuretic effect, was not due to suppression of the sympathetic nervous system, and did not work by blocking angiotensin receptors or by increasing nitric oxide-driven relaxation of blood vessels.1PubMed. Preclinical investigation of the cardiovascular actions induced by aqueous extract of Pimpinella anisum L. seeds in rats What it did do was inhibit calcium from entering smooth muscle cells in the portal vein, pointing strongly toward a calcium channel blocking mechanism.
Separate work using both ex-vivo (tissue samples outside the body) and in-vivo (live animal) models confirmed that aniseed extracts produce vasodilation, meaning they cause blood vessels to relax and widen, and also exhibit cardio-suppressant effects. These researchers found the same underlying mechanism: calcium channel blocking activity was the primary route through which aniseed relaxed blood vessel walls.2eCommons@AKU. Pharmacological basis for cardio-protective effects of aniseed and caraway, alone and in combination, using ex-vivo and in-vivo animal models The same study also found improvements in lipid profiles, which adds a secondary layer of potential cardiovascular benefit beyond the blood pressure effect itself.
The Calcium Channel Connection
To understand why the calcium channel finding matters, consider that an entire class of widely prescribed blood pressure medications, called calcium channel blockers (drugs like amlodipine and nifedipine), works on this same principle. When calcium flows into the smooth muscle cells lining your blood vessels, those muscles contract and the vessels narrow, which raises blood pressure. Block that calcium entry, and the muscles relax, the vessels widen, and pressure drops.
The rat studies suggest anise extract does something functionally similar. In depolarized portal vein tissue, the extract inhibited calcium influx, which is the same basic action that calcium channel blocker drugs perform.1PubMed. Preclinical investigation of the cardiovascular actions induced by aqueous extract of Pimpinella anisum L. seeds in rats This finding was echoed in research on anise extract’s ability to reduce uterine contractions in pregnant rats. In that study, the extract reduced contractions that had been induced by a calcium channel agonist (a compound that forces calcium channels open), and it also reduced the force generated in tissue that had been artificially depolarized with a high-potassium solution, a standard lab test for calcium channel blocking activity.3ScienceDirect. Pimpinella anisum extract attenuates spontaneous and agonist-induced uterine contraction in term-pregnant rats
The convergence of findings from different research groups, different tissues, and different experimental setups builds a reasonably convincing case that anise genuinely does interact with calcium channels. The question is not really whether it has this pharmacological property. The question is whether the effect is strong enough, bioavailable enough, and consistent enough in humans to matter for blood pressure in any practical way.
Why the Human Evidence Is Still Missing
A comprehensive pharmacological review of Pimpinella anisum noted that despite the plant’s broad spectrum of effects demonstrated in preclinical research, very few clinical studies have been conducted, and it recommended more clinical trials to evaluate whether those benefits translate to people.4PubMed Central. Review of Pharmacological Properties and Chemical Constituents of Pimpinella anisum That review was published over a decade ago, and the situation has not changed dramatically since. There are still no large, well-designed randomized controlled trials testing anise specifically for blood pressure reduction in humans.
This gap is not unusual for culinary herbs. Running a clinical trial is expensive, and pharmaceutical companies have little incentive to fund trials on a plant that cannot be patented. Academic researchers sometimes conduct small pilot studies, but these tend to be underpowered (too few participants to detect a real effect reliably) and often use different preparations, doses, and populations, making them hard to compare. The result is a frustrating limbo: promising animal data sits waiting for human confirmation that may be slow to arrive.
What makes this gap especially important is that many things lower blood pressure in rats without doing so meaningfully in people. Rat physiology differs from human physiology in metabolism, body composition, and cardiovascular regulation. A compound might be broken down and cleared from the human body too quickly to reach effective concentrations, or the dose required might be impractically large, or the effect might be too small to detect against the normal variation in human blood pressure readings. Without human data, there is simply no way to know.
Active Compounds That Might Explain the Effect
Anise seeds contain a range of bioactive compounds, and at least two of them have independent research linking them to cardiovascular or anti-inflammatory activity. Analysis of aniseed fractions has identified apigenin and luteolin as the most predominant polyphenolic compounds present.5American Journal of Phytomedicine and Clinical Therapeutics. Anti-Peroxidative and Anti-Diabetic Activities of Aniseeds (Pimpinella anisum l.) and Identification of Bioactive Compounds
Apigenin is a flavonoid found in many plants, including chamomile, parsley, and celery. It has been studied for a variety of biological effects, including relaxation of smooth muscle. Luteolin, found in artichokes, peppers, and several herbs, has drawn attention for its anti-inflammatory properties. Both flavonoids have shown vasodilatory potential in laboratory settings, which makes them plausible contributors to the blood pressure effects seen in the whole-extract animal studies. However, it remains unclear how much apigenin and luteolin you would actually absorb from a cup of anise tea or a teaspoon of anise seeds, and whether that amount would be enough to move the needle on blood pressure.
The other major compound in anise is trans-anethole, the essential oil component responsible for anise’s distinctive licorice-like flavor and aroma. Trans-anethole has its own pharmacological profile, but the calcium channel blocking effects observed in the animal studies were specifically attributed to the aqueous (water-based) extract, not to the essential oil fraction. This distinction matters because the compounds that dissolve in water and those that dissolve in oil are different sets. If you are steeping anise seeds in hot water to make tea, you are extracting a different chemical profile than if you were using anise essential oil.
Anise Is Not Star Anise
One important clarification that frequently gets lost in popular discussions: Pimpinella anisum (anise or aniseed) and Illicium verum (Chinese star anise) are completely different plants from different botanical families. They share a similar flavor because both contain anethole, but their chemical profiles are otherwise distinct. The blood pressure research discussed here involves Pimpinella anisum specifically.
The distinction matters for safety reasons as well. Star anise has been involved in toxicity cases, partly because it can be adulterated with or confused with Japanese star anise (Illicium anisatum), which contains toxic compounds called sesquiterpene lactones.6PubMed Central. Case series: star anise toxicity presenting to the emergency department in Eastern Regional Referral Hospital in Bhutan Common anise (Pimpinella anisum) does not carry this particular risk, but anyone exploring “anise” for health purposes should be clear about which plant they are actually using. Buying a product labeled “star anise” thinking it is interchangeable with aniseed could introduce safety issues that have nothing to do with blood pressure.
What About Anise and Blood Sugar
Blood pressure and blood sugar regulation are intertwined in the body, so it is worth noting that anise has metabolic effects beyond the cardiovascular system. One study found that aniseed oil significantly increased glucose absorption from the rat intestine by boosting the activity of a sodium-potassium pump that drives sugar transport.7PubMed. Aniseed oil increases glucose absorption and reduces urine output in the rat The same study found that aniseed oil reduced urine output in rats.
At first glance, increased glucose absorption might sound unhelpful if you are trying to manage metabolic health. But the relationship is more complex than “more absorption equals worse.” The study was looking at mechanisms of action in the gut, not at what happens to blood sugar levels over time with regular anise consumption. Other research on anise has explored antioxidant and anti-diabetic properties. The point here is that anise is pharmacologically active across several systems, which means it is not a simple, single-target substance. If you are taking medications for blood sugar, blood pressure, or both, that broad activity profile is worth being aware of.
Practical Considerations If You Are Thinking About Trying Anise
The most common ways people consume anise are as whole or ground seeds in cooking, steeped as a tea, or as an ingredient in liqueurs like ouzo, arak, or sambuca. The doses used in the rat studies were standardized aqueous extracts at specific concentrations per kilogram of body weight, which is very different from sprinkling some anise seeds on bread or drinking a cup of anise tea after dinner.
If you enjoy anise tea and are curious whether it might be contributing to your cardiovascular health, the honest answer is: it might, a little, or it might not at all. The calcium channel blocking effect is real in lab and animal settings, but nobody has measured whether the concentration of active compounds in a typical cup of anise tea is sufficient to produce a clinically meaningful drop in blood pressure in a human being. There is a wide gulf between “pharmacologically active in a controlled experiment” and “effective at real-world dietary doses.”
For someone already taking calcium channel blocker medications (amlodipine, diltiazem, verapamil, and others), there is a theoretical concern about additive effects. If anise extract genuinely does block calcium channels, combining it in large amounts with a prescription calcium channel blocker could, in theory, cause blood pressure to drop too far. This is speculative since human pharmacokinetic data on anise and blood pressure is lacking, but it is the kind of theoretical interaction that a cardiologist would want to know about if you were consuming anise in concentrated supplement form rather than just as a culinary spice.
Where the Traditional Use Fits In
Aniseed has a long history of use in traditional medicine across South Asia and the Middle East, where it has been valued for digestive relief, respiratory health, and cardiovascular benefits.2eCommons@AKU. Pharmacological basis for cardio-protective effects of aniseed and caraway, alone and in combination, using ex-vivo and in-vivo animal models Traditional use is not evidence of efficacy by modern standards, but it is not nothing, either. When a plant has been used for centuries for a particular purpose and modern pharmacology then identifies a plausible mechanism for that use, it raises the prior probability that the traditional observation was tracking something real.
The history of drug development is full of examples where traditional plant use led to the discovery of real pharmacological agents. Aspirin traces back to willow bark. Digoxin comes from foxglove. The statin class of cholesterol drugs was inspired by a fungal compound. None of this means every traditional remedy will pan out, and most do not. But the combination of traditional cardiovascular use plus a demonstrated calcium channel blocking mechanism plus consistent vasodilatory effects in animal models puts anise in a somewhat stronger position than the average herbal remedy that has only folklore going for it.
Lipid Effects and the Broader Cardiovascular Picture
Blood pressure is just one component of cardiovascular risk. The research on aniseed also found improvements in lipid profiles in animal models, meaning shifts in cholesterol and triglyceride levels in a favorable direction.2eCommons@AKU. Pharmacological basis for cardio-protective effects of aniseed and caraway, alone and in combination, using ex-vivo and in-vivo animal models Again, this is animal data, but it suggests that anise’s cardiovascular potential might extend beyond just pressure reduction.
Interestingly, that same body of research compared aniseed with caraway (Carum carvi) and found that while both herbs produced vasodilation, they did so through partially different mechanisms. Aniseed relied primarily on calcium channel blocking, while caraway used multiple pathways including calcium channel blocking, potassium channel opening, and nitric oxide involvement. When the two were combined, the cardiovascular effects were present as well, suggesting that traditional spice combinations used in South Asian and Middle Eastern cuisines might have a pharmacological logic that goes beyond flavor pairing. Whether that logic translates to measurable health benefits at dietary doses remains, as with so much of this topic, an open question that human trials would need to answer.