Sayur Manis: Delicious, But Also Deadly, Greens From Borneo

By Konstantin Kakaes

Published August 14, 2014 at 5:13 PM EDT

Sayur manis at a restaurant in Kota Kinabalu in Malaysian Borneo. The greens were sautéed with onions, red pepper, dry-fried shallots and egg white.

Traveling across Borneo, I came across a most delicious vegetable.

Stir-fried with red peppers, shallots and egg in a thin, juicy gravy, sayur manis tasted both rich and nutritious, like very good spinach. But it had more complexity than spinach, as though it had been fortified with broccoli and infused with asparagus. The flavor itself wasn't so much novel as it was a recombination of familiar tastes in a new and exciting way.

Sayur manis has all the traits of a "superfood." It's packed with protein, antioxidants and other nutrients like vitamin C, vitamin E and a compound called lutein, a key pigment in human retinas. It's easy to grow, at least in the tropics. It's the kind of thing health-food nuts would put in smoothies.

But sayur manis smoothies are a bad idea; though it can be eaten raw, doing so in even moderately large quantities has proven deadly. Sayur manis is hardly alone in this; in many plants, the same chemicals with health benefits might also do damage. Despite years of research, scientists still don't understand the toxicity mechanism.

Mohammed Rizman, the proprietor of the restaurant where I first tried sayur manis, explained to me that it also goes by "Sabah veggie" because it's so popular in the Malaysian Borneo province of Sabah. Though it grows wild, he buys his from a wholesaler in Kundasang, a town on the slopes of Mount Kinabalu, the highest peak in Southeast Asia at about 13,500 feet. When he served it to me, at the night market in Kota Kinabalu, Sabah's capital, it tasted like the perfect food in the perfect place.

When I returned to the U.S., I discovered that sayur manis has many more names. To rule out any confusion, your best bet may be the scientific sauropus androgynus. Sayur manis, the Malaysian name, simply means "sweet vegetable." According to Wendy Hutton's A Cook's Guide to Asian Vegetables though wild varieties are eaten across the region, commercial cultivation began in Sabah, and only the cultivated varieties have edible stems, which supply the asparagus taste.

Bee Yinn Low, a Malaysian living in California who has developed recipes for companies like Betty Crocker and Red Boat fish sauce, says that she's nostalgic for mani cai—another name for the vegetable—from her childhood in Malaysia. Even in Penang, where she grew up, she says it was the kind of delicacy prepared at home, not usually in restaurants.

Low prizes it for its texture — "more of a bite" than spinach, she says. She occasionally gets some from a friend who grows it in California but there's never been enough demand for it to be commercially grown in the U.S.

But there might be another reason for its relative scarcity: Sauropus can be deadly. It can cause lung failure, which is odd for something that you eat, rather than smoke.

Uncooked sayur manis leaves can cause lung failure. Scientists say they don't yet know which compounds in the plant do damage to the lungs.

For reasons that remain somewhat murky, in the late spring and early summer of 1995, a sauropus craze swept across southern Taiwan. As a team of Taiwanese doctors later reported in The Lancet,they were at first mystified by an epidemic of patients with respiratory problems who started showing up in their hospital that April.

Eventually they realized that their patients, young and middle-aged women, were suffering from a rare syndrome in which the bronchioles — the smallest branches of the airway in the lungs — were compressed. All the women had been drinking juice made from sauropus leaves, which they thought would help control their weight. In that first Lancet paper, the doctors were unable to explain why the vegetable was causing lung problems.

Nearly 20 years later, Bradley Bolling, a professor of food science at the University of Wisconsin-Madison, says it remains a mystery. "Despite several efforts to isolate the compounds, it seems we still don't have a good idea what compounds did cause that outbreak," he says. Of 278 patients accounted for in the Taiwanese diet fad, eight had to receive lung transplants, and nine died.

The good news is that whatever causes the toxicity is "inactivated by heat or cooking," says Bolling. So you can probably eat as much stir-fry as you like and still be okay.

But the Taiwanese outbreak was not the end of it. Another slew of would-be dieters got sick in Japan around 2005.

The obvious solution would be to abstain from the vegetable entirely. But despite the documentation of sauropus dangers — and the lack of understanding of exactly why it is dangerous — there are a variety of well-meaning efforts to increase consumption.

A Taiwanese-Indonesian group is feeding it to fish, hoping to improve growth and disease resistance in fish farms. Other researchers in Indonesia are introducing raw leaves to both broiler chickens and egg-laying chickens, and even quail. Sauropus, Bolling told me, is rich in papaverine, a drug used in the West to treat both high blood pressure and impotence in men.

No research group has yet, he says, succeeded in understanding how the chemicals in the plant are metabolized and reach the lungs. This is part of the reason that there still isn't a good therapy for treating people suffering from sauropus poisoning.

I tried to describe to Bolling, as best I could, what sayur manis tasted like. "Hearing you describe the taste," he said, "it sounds to me like there might be unidentified compounds in the plant." Whatever they are, they taste great.

If you come across it, eat it. But do cook it first.

Konstantin Kakaes is a freelance writer in Washington, D.C., and the author of the e-book The Pioneer Detectives.