What to Know About Rubisco, the Most Abundant Protein on Earth

The last one may not be something you know much about, but the protein found in leaves, called rubisco, is the most abundant protein on the planet. As demand for protein surges, entrepreneurs are pushing to get rubisco into people’s mouths. 

“Today, no one knows about it. But over the next 10 years, we’re going to see rubisco be one of the main proteins,” says Ross Milne, CEO of the New Zealand-based company Leaft, which makes the Leaft Blade, a liquid performance fuel shot made from rubisco that recently entered the U.S. market.

Rubisco, which stands for ribulose-1,5-bisphosphate carboxylase/oxygenase, is found in every green leaf. It’s the heavy hitter responsible for photosynthesis. Scientists talk up its qualities: it has a complete amino acid profile and can be made into a white, neutral-tasting powder. It can be gelled, emulsified, and made into just about anything. It doesn’t seem to cause allergies in people, which can’t be said for dairy or soy. Rubisco is easy to digest, compared to most plant proteins. And it’s incredibly abundant. 

“From a food-ingredient point of view, it’s one of the best natural proteins out there,” says Slavko Komarnytsky, a biologist at the Plants for Human Health Institute at NC State University. Milne, of Leaft, calls it the “utopia” protein because it has so many good attributes.  

Pat Brown, founder of the alternative-meat company Impossible Foods, told the New Yorker in 2019 that rubisco worked better than any other protein the company tried when making a prototype burger, but they didn’t end up using rubisco in burgers because they could not find enough of it.

“Every single food company that checks out this protein says, ‘We are in love with it, we want to use it, and we want a lot of it,’" Komarnytsky says, "and this is where the problems come in.”  

Why Rubisco is hard to find, even though it’s so abundant

Rubisco is the main protein in leaves, but it only makes up about 3% of the leaf’s content. By comparison, beans and soy are about 80% protein, says Grant Pearce, a senior lecturer at the University of Canterbury in New Zealand who studies protein chemistry. You have to harvest a lot of leaves to get enough rubisco to make a protein product. 

Growing and farming a lot of plants may not be a problem in itself, but it also means dealing with a lot of liquid and pulp waste once you harvest the rubisco. What’s more, getting the rubisco out of the leaves can be a challenge. The protein is hidden inside the plant cell “very well,” says Komarnytsky, so extraction is difficult. You have to break the cell wall and the chloroplast membrane, and each step brings additional costs. Eventually, it becomes more expensive to process rubisco than other proteins, and companies lose interest, he says.

Since leaves turn brown quickly once they’re harvested, companies have to harvest the rubisco within a few hours or else they won’t be able to use it. 

“Of the companies I’ve talked to, one of their biggest challenges is that they don't get a nice white powder; they get a brown sticky mess, because everything's gone brown once you start processing it,” Pearce says. 

Companies have tried to juice the leaves as soon as they’re harvested, but it can be difficult chemically to isolate the rubisco and get rid of the green color to make it into the white powder, says Pearce. “The technology is similar to what it was back in the 60s and 70s,” he says. 

Tony Martens, CEO of Plantible, which makes rubisco to sell to food companies, says he partially agrees with this assessment. Though the underlying process of pulling rubisco from leaves hasn’t changed much in half a century, he says, it has become more possible to make white rubisco protein at a commercial scale in part because of updated processing processing technologies. 

Still, Leaft CEO Milne says that five years ago, when the company was still trying to efficiently harvest rubisco, it had about one jam jar full of the protein—and that he thinks that was the largest amount of rubisco anyone had in the world at that time. Leaft has significantly improved its technology since then, but the company’s initial struggle to produce enough of the protein illustrates why there hasn’t been widespread adoption.

How companies are trying to make rubisco viable

Rubisco may be difficult to produce, but its backers argue that the harvesting process is more efficient than that of many of the other proteins. Currently, for instance, we feed greens to cows and then get milk and beef from those cows and consume that protein. But that process comes with methane emissions and waste runoff. Simply extracting protein from the leaves would lead to fewer emissions and lower water usage than beef production.

“What we’re doing is skipping the middleman and going directly to the source,” says Milne. He says that by harvesting alfalfa, one of the most common sources of rubisco, and turning it into protein, Leaft is harvesting about five times more protein per hectare of land than they would if they were raising cows for dairy. 

That efficiency could come in handy in the case of a global catastrophe or during projected global food shortages. Research published in May by ALLFED, the Alliance to Feed the Earth in Disasters, found that leaf protein concentrate, which includes rubisco, could meet global protein requirements, even in an extreme nuclear winter scenario, because green leaves are relatively easy to grow quickly all over the world.

Rubisco has been a darling of food scientists ever since it was discovered in the ‘60s and ‘70s because it’s so abundant. It was given the nickname "rubisco" because it sounded a bit like the cookie maker Nabisco, and scientists hoped it could eventually be eaten, says Pearce. But few companies have been able to figure out how to process it efficiently in the past half-century.

How to get rubisco at home

Not long ago, Leaft sent me a refrigerated package containing seven Leaft Blades, which are ready-to-drink performance fuel shots made of rubisco. The 3.4 ounce shots come in a pouch shaped like a leaf, and each pouch of greenish sludge contains 18g of protein—a little less than one third of what the average adult needs in a day. 

Leaft is one of the few companies making rubisco that people can buy and consume at home. The company operates a 30,000 square foot facility in Canterbury, New Zealand, working directly with local alfalfa farmers. It launched in the U.S. in early 2026. 

The Leaft Blade isn’t the only way to get rubisco—the company also sent me a chocolate chip cookie that contained rubisco.  It’s also working with Palmetto Superfoods, a West Coast smoothie and acai chain, to make smoothies out of rubisco. The company also makes a product called rubisco protein isolate that it sells to Japanese food manufacturer Lacto and a New Zealand grocery chain, which are planning to use the protein in their products.

Fudi Protein, a Wisconsin-based company, is marketing its rubisco product as an alternative to egg whites, though that company is still fundraising to build a commercial-scale facility.  

And Plantible, which may currently be the most successful rubisco company, only sells its product to food companies, not to consumers directly. Plantible, which has a research facility in San Diego, grows duckweed (also known as water lentils, or Lemna) in Texas and processes them to extract rubisco, which it markets as its Rubi protein. Martens, the CEO, says there’s a lot of demand from food companies for raw rubisco, especially as the cost of protein is shooting up across the world. 

In February, Plantible received a “no questions” letter from the FDA, meaning that the agency found its Rubi protein generally recognized as safe to use in food. Martens says it’s a step toward changing the food system for the better. “If you look at most of the protein sources we use, it’s been the same for thousands of years,” he says. “It’s quite ancient and outdated.”