For the first time ever, global health officials have asked countries to completely banish an ingredient from the entire food supply.

The enemy is trans fats, found in cooking oils and butter alternatives like shortening and margarine. Denmark became the first country to eliminate them from its food supply in 2004, and since then, countries across Europe and North America, including the US, have followed suit. The battle was waged by public health officials in the face of decades of scientific research showing that eating trans fat is associated with an increased risk of coronary heart disease and heart attack.

But this push hasn’t been spread evenly around the world. In North Africa, the Middle East, and South Asia, partially hydrogenated cooking oils that contain trans fat are commonly used in the home and by street vendors for frying and baking. And trans fat is thought to be responsible for an estimated 500,000 premature deaths from cardiovascular disease every year worldwide, according to the World Health Organization.

Related Why it took the FDA nearly 40 years to ban trans fats

Now, the WHO, along with the Bloomberg Philanthropies and the Gates Foundation-funded health nonprofit Resolve to Save Lives (an initiative of Vital Strategies), has set out to change that. On Monday, the agency launched Replace, a guide to eliminating trans fat from the global food supply by 2023. If successful, they say it could save more than 10 million lives worldwide by reducing cardiovascular disease.

“Trans fat is an unnecessary toxic chemical that kills,” said Dr. Tom Frieden, president and CEO of Resolve to Save Lives and a former director of the US Centers for Disease Control and Prevention, “and there’s no reason people around the world should continue to be exposed.”

This is also the first time the WHO has called for the global elimination of a risk factor for a chronic disease, Frieden added. The WHO “successfully led the elimination of other infectious diseases, such as smallpox and river blindness, but never before has the world set its sights on eliminating a noncommunicable disease.”

And that’s why this announcement is such a big deal. Chronic diseases, like heart disease and diabetes, are quickly outpacing infectious diseases as the leading killers in countries around the world.

“The WHO statement is an important recognition that eliminating trans fat can substantially reduce risk of death and suffering at little or no cost,” Walter Willett, a Harvard Chan School of Public Health professor who has studied the effects of trans fat, told Vox.

Whether countries follow the advice is another question, he added, since the WHO has no enforcement power.

To understand why the WHO is seeking to phase out a single food ingredient, you need to know what trans fat is, why it’s harmful, and why people around the world keep putting it in food. Here’s a quick primer.

Trans fats are cheap, artery-clogging oils and shortenings that are still used in many countries

Trans fatty acids, or trans fats, are a type of unsaturated fat that can occur naturally at very low levels in some meat and dairy products. But it’s the man-made kind, like partially hydrogenated oil, that’s the health concern.

These artificial trans fats occur when hydrogen is added to liquid vegetable oil, like corn, soy, or cottonseed oil, to make it solid (think shortening or margarine) through a process called hydrogenation.

Trans fats were popularized in the 1950s, and their uses slowly expanded until they were ubiquitous in the food supply. They were baked into muffins, cookies, pies, and pizzas. French fries were fried in them, and they were even used in coffee creamers and microwave popcorn.

The reasons for the popularity are simple: The oils were relatively inexpensive to produce compared with solid animal fats, they increased the shelf life of food, they tasted good, and — at a time when saturated fats in butter were vilified — they were billed as a healthy alternative. (Think margarine versus butter.)

But over the past couple of decades, evidence has been mounting that even a small amount of trans fat increases bad (LDL) cholesterol in the blood and decreases the amount of good (HDL) cholesterol — raising the risk of coronary heart disease and heart attacks.

As this 2006 research in the New England Journal of Medicine shows, for every 2 percent of calorie intake that comes from trans fats, a person’s heart disease risk increases by an incredible 23 percent. While there’s still some debate about the relative health merits of saturated and unsaturated fat, health experts now pretty unequivocally reject trans fat.

That’s why the Food and Drug Administration in the US has worked to phase trans fat out of the food supply. In 2006, the FDA required manufacturers to start labeling their foods with trans fat content information. By 2013, the agency tentatively determined that trans fat could no longer be considered safe for people to eat. And by 2015, it asked food manufacturers to remove trans fat from their products by 2018.

This policy brought the US in line with other countries that have already banned trans fat, including Denmark, Austria, Iceland, and Switzerland. And it came after a number of cities across the United States, starting with New York City, banned the use of this type of fat in restaurants. After these changes went into effect, researchers doing follow-up studies found a decrease in cardiovascular disease rates (more on that below).

But trans fats are still finding their way into baked goods, solid fats like ghee and shortening, and restaurant and street food in many places — especially low- and middle-income countries, where they haven’t been banned and cardiovascular disease rates are on the rise.

In just 20 years, ischemic heart disease and cerebrovascular disease — two types of cardiovascular disease that affect the heart and brain, respectively — leaped from the fourth and fifth leading cause of premature mortality to the first and second, respectively, bumping lower respiratory infections and neonatal preterm birth complications from the top killers globally. The majority of these deaths from cardiovascular disease, more than 75 percent, occur in low- and middle-income countries.

Not all of this disease burden can be explained by trans fat. But eliminating it would have an impact, said WHO Global Ambassador for Noncommunicable Diseases Michael Bloomberg in a statement. “Banning trans fats in New York City helped reduce the number of heart attacks without changing the taste or cost of food, and eliminating their use around the world can save millions of lives.”

University of North Carolina nutrition policy researcher Barry Popkin said the WHO is likely underestimating the impact trans fat elimination would have in Asia and Africa. “The proportion of energy from fats and oils in Asia and Africa is double that from Europe and the US and in many countries that are dominated by palm oil and partially hydrogenated oils,” he said. “In India alone, the fats used have as much as 45 to 50 percent trans fats. This compares with the much smaller proportion of trans fats in higher-income countries, and the effect that eliminating even this much smaller level of trans fats significantly improved health.”

To understand the potential impact of the WHO campaign, look at Denmark and New York

The new WHO action plan has six suggestions countries can follow to eliminate trans fats from their food supply. These include passing regulations or legislation to ban industrially processed trans fats, creating public awareness campaigns about their health harms, and enforcing the compliance of trans fat regulations. In other words, they’re encouraging low- and middle-income countries to go the way of Scandinavia and the US.

The impact could eventually be very large, and Denmark and New York show why.

Researchers who studied Denmark’s policy found that three years after it went into effect, the mortality rate from cardiovascular disease declined by an average of 14.2 deaths per 100,000 people per year relative to a control scenario showing what would have happened if Denmark didn’t introduce the policy.

In New York state, researchers looked at the impact of artificial trans fat restrictions. The main finding: The regulations reduced the cardiovascular death rate by 4.5 percent. Another study found hospital admissions for heart attack and stroke also declined by 6 percent in New York counties with trans fat restrictions compared to state counties without.

“There are billions of people around the world who are eating foods with trans fat, and they don’t know, leading to half a million deaths every year,” Resolve’s Frieden added. “That’s why a public health approach, through effective policies, can save the most lives.”

But not every country has the resources of Denmark or the US to follow through on a trans fat ban. And just because the WHO sent out these guidelines doesn’t mean we’ll see the results anytime soon. The recommendations are voluntary, and governments may not take them up. It’s impossible to crack down on individual food vendors, which is why countries need to pass regulations that eliminate trans fat from the manufacturing process or implement nationwide bans.

“I expect there will be some pushback from industries that are accustomed to use of trans fat-containing ingredients,” said Eric Brandt, a cardiovascular disease fellow at Yale University School of Medicine who studied the impact of New York’s trans fat ban. “Hopefully precedents set by companies in countries with trans fat restrictions already in place will ease these transitions.”

Even so, the Replace action plan is worth watching. It’s taking lessons from successes fighting tobacco, except in this case, the enemy is a dietary risk factor.

“A comprehensive approach to tobacco control allowed us to make more progress globally over the last decade than almost anyone thought possible,” Bloomberg said. “Now, a similar approach to trans fat can help us make that kind of progress against cardiovascular disease, another of the world’s leading causes of preventable death.”