Clinically proven benefits of 6 popular 'plant medicines'

By John Murphy, MDLinx
Published October 11, 2019

Key Takeaways

It's highly likely that plants were early man's first medicines. Nowadays, modern medicine sometimes looks askance at "plant medicines"—but consumers certainly don't. Herbal supplements had record US sales growth from 2017 to 2018, increasing by an estimated 9.4%, for a total of $8.842 billion, according to the American Botanical Council.

There must be something more than mysticism to all these herbs and botanicals. And, as a matter of fact, there is. Here are a handful of popular botanicals whose folk-medicine traditions are supported by recent scientific research.


Elderberry (usually in the form of elderberry syrup) has been used for centuries as a homespun cold remedy. But now, investigators are scientifically testing this old folk medicine to see if it actually does treat colds and flu. In fact, researchers have shown in a recent meta-analysis that elderberry syrup substantially reduces the severity of cold and flu upper respiratory symptoms as well as the duration of these symptoms.


Lavender has been used for thousands of years to improve anxiety and mood. Indeed, it's currently selling well as an "essential oil" used for inducing relaxation and enhancing sleep. Along those lines, researchers have found that lavender (as well as rosemary) may have anxiolytic and neuroprotective effects because its compounds can modulate T-type calcium channels, which are associated with neuronal excitability, neuroprotection, sensory processes, and sleep.

In a newly published study, other investigators showed that lavender (as well as fennel seed extract and chamomile) activates a specific potassium channel (KCNQ5) in blood vessels that can lower blood pressure. This discovery may lead to new medicines for hypertension and KCNQ5 loss-of-function encephalopathy, the investigators said.


Originally a Native American remedy, echinacea has become popular in Europe and the United States as a treatment for colds. But the evidence for its efficacy has been mixed, in no small part because preparations made from echinacea may come from different plant species, different parts of the plant, and different extraction methods. Notably, authors of a Cochrane Review concluded that echinacea products taken preventively may slightly reduce the risk of getting a cold in healthy individuals, but there's only weak evidence to show that echinacea might reduce the duration of a cold.


It doesn't sound like a household item, but horehound (Marrubium vulgare) was the top-selling herbal supplement in mainstream US retail outlets in 2018. A member of the mint family, horehound has been used as a flavoring in old-fashioned candy, with plenty of sugar added to sweeten its bitter taste. As a traditional medicine, horehound has been used for respiratory conditions such as coughs, colds, asthma, and bronchitis, and is now a common ingredient in cough drops and lozenges. It's also been used to as a remedy for digestive conditions such as stomachache, loss of appetite, and flatulence.

More recently, researchers used a horehound extract to demonstrate its cardioprotective effect against myocardial ischemia-reperfusion injury.

Milk thistle

Milk thistle extract is commonly used to protect the liver and help support liver function. It's taken as a supplement by people with liver damage due to non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis, or liver cancer.

The major active compound from the milk thistle plant (Silybum marianum) is silybin. Despite mixed results from previous clinical trials over the years, silybin has been shown to have anti-inflammatory and antioxidant properties in more recent studies—and not only for the liver. Silybin is currently being investigated as a potent cancer fighter.


Ashwagandha? Gesundheit!

Ashwagandha, also called Indian ginseng, is an herb used in Ayurvedic medicine that is known for relieving stress, anxiety, fatigue, and pain. Researchers are now turning this traditional medicine into clinical treatment. In a recent randomized, double-blind, placebo-controlled trial that included 60 participants, investigators showed that ashwagandha extract significantly reduced measures of stress and anxiety in adults with self-reported high stress.

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