One man’s trash is sometimes another man’s treasure, and when it comes to the murky brown liquid left after pressing olives into olive oil, that, my friend, is a treasure. So much so that the bitter byproduct, officially known as olive mill wastewater (OMW), is touted as a superfood.  

Historically, OMW was discarded due to its strong taste and unpleasant smell, but a recent scientific analysis out of Sapienza University in Rome identified the liquid’s exceptionally high levels of beneficial compounds as a hero for fighting harmful pathogens (microorganisms that cause disease) and boosting overall health. The analysis also showed that the wastewater contains oligogalacturonides, which can protect plants from infections. 

So, should you stock up on OMW? And what are the health benefits, exactly? Here’s what experts really think.

What is olive mill wastewater?

OMW is the leftover liquid from pressing olives to make olive oil. “For years, it was seen as a waste product, but it’s now getting attention for potential health benefits since it’s packed with antioxidants and bioactive compounds that don’t make it into olive oil,” says Pamela Tambini, MD, an internal physician and medical director at Engage Wellness. 

Mediterranean cultures have long used OMW as a natural remedy, but it wasn’t until researchers dug deeper into the substance’s bioactive compounds — such as flavonoids, hydroxytyrosol, and oleuropein — that they realized we should all take advantage of its perks.

“Studies found that OMW is loaded with polyphenols, antioxidants, and anti-inflammatory compounds, and though these compounds are also present in olive oil, they’re in much smaller amounts,” Tambini says. “Scientists essentially realized that what was once considered waste could actually be a super-concentrated health booster.”

Is olive mill wastewater healthy?

You bet. At its core, OMW is rich in polyphenols, plant compounds known for their antioxidant and anti-inflammatory effects, which help the body fight oxidative stress (an imbalance in free radicals and antioxidants that can lead to cell damage) linked to aging, heart disease, and other chronic illness, Tambini says. The acidic liquid is also deemed a nutraceutical since it provides health benefits beyond basic nutrition, helping to prevent or manage disease, says functional medicine physician Shivani Amin, MD.

“It can have a very selective process toward cancer cells,” says Adriana Albini, PhD, a cancer researcher who has also studied olive mill wastewater and a scientific collaborator at the European Institute of Oncology.

Albini conducted a study examining the effects of an extract from olive oil wastewater, referred to as A009, on cancer cells and endothelial cells that line blood vessels, lymphatic vessels, and the heart. Her findings revealed that A009 prevented the growth of cancer cells and demonstrated possible beneficial effects on cardiovascular health. Olive mill wastewater may even help with cholesterol, weight management, and blood sugar control, she says. 

But wait, there’s more. Here’s a closer look at the health benefits of OMW.

• Fights inflammation. Thanks to its polyphenols, such as oleocanthal, which has powerful anti-inflammatory properties, studies suggest OMW may help fight inflammation. Some inflammation is necessary for the body to properly heal and fight invaders like bacteria and viruses, but adding more OMW to your diet could ward off excess inflammation linked to arthritis and muscle soreness, Tambini says.
• Supports heart health. Olives are generally associated with a decreased risk of cardiovascular disease since they reduce bad cholesterol and maintain good cholesterol, and Tambini says OMW carries the same weight. Research also suggests that OMW lowers arterial pressure (the force exerted by blood on the walls of the arteries) and prevents cardiac infections. 
• Boosts cognitive function. The antioxidants and polyphenols in OMW may protect against oxidative stress, which contributes to neurodegenerative diseases like Alzheimer’s, so the liquid is often considered a champion for cognitive function, Amin says. Research supports this, finding that OMW protects and preserves the health and function of neurons (nerve cells) in the brain and spinal cord. 
• Promotes digestion. Amin says OMW contains organic acids that support gut health and help balance the gut microbiome (the collection of organisms that live in the intestines). Research also suggests that OMW is associated with improved intestinal barrier function, which protects the body from dangerous substances while allowing nutrients to pass through efficiently.  

How is olive mill wastewater different from olives and olive oil?

It’s no secret that olives and olive oil pack their own nutritional punch, but OMW contains a much higher concentration of polyphenols for fighting infection and disease, Tambini says. Some reports even found that OMW can have up to 10 times more polyphenols than extra virgin olive oil. 

OMW also contains higher levels of hydroxytyrosol (one of the most potent antioxidants) than olives and olive oil, which has been linked to improved heart health, reduced inflammation, and enhanced brain function, Amin says.

“This is because many of the beneficial compounds are water-soluble,” she explains. “They get left behind in the water phase during olive oil extraction rather than making it into the final oil,” she explains.

That said, OMW does not contain the caliber of healthy monounsaturated fats that olive oil is famous for, so while it may offer certain antioxidant advantages, Amin says it doesn’t completely replace the benefits of consuming olive oil itself.

How to consume olive mill wastewater

OMW isn’t widely available (yet), but small producers like Olive Mill Water Company and Fattoria La Vialla bottle the superfood as a functional beverage you can buy online. 

If you can get your hands on a bottle, Tambini recommends drinking OMW as a straight shot. Can’t stomach the strong, bitter taste? No problem. Mix it into a juice, smoothie, or salad dressing.

Just be mindful that OMW is highly concentrated with bioactive compounds, so less is more. Consuming in excess can lead to digestive discomfort, including bloating or diarrhea, so Tambini recommends starting with a tiny daily shot, around 25 ml, and seeing how your body reacts.