The FDA ruled in June to ban trans fats, which is good. But the alternatives — palm oil and interesterified vegetable oil — may not be much better.

Share story

On Nutrition

The Food and Drug Administration (FDA) ruled in June to ban trans fats, otherwise known as partially hydrogenated oils, from our food supply. That’s a good thing, because trans fats, once hailed as a healthier alternative to saturated fats, have more recently been called “metabolic poison” by many health and nutrition experts, citing their role in heart disease and type 2 diabetes risk.

A trans fat is a liquid vegetable oil (unsaturated fat) that has been bombarded with extra hydrogen atoms (hydrogenation) to make it semisolid at room temperature, closer to a solid saturated fat like butter or animal fat.

Because saturated fats were linked to heart disease and unsaturated fats were known to be heart-healthy, trans fats were supposed to offer the best of both worlds: heart-healthy unsaturated fats with the culinary properties of saturated fats. As anyone who likes to bake knows, some recipes require a solid fat.

As it turns out, once unsaturated fats are hydrogenated, they are no longer heart-healthy. In fact, trans fats are even worse for heart health than saturated fats were ever believed to be. Clinical trials have shown that while saturated fats can raise “bad” LDL cholesterol, trans fats both raise LDL and lower “good” HDL cholesterol.

Although some experts expressed concern about trans fats early on, it took decades before mounting scientific evidence revealed trans fats’ true nature. In the meantime, trans fats had seeped into all areas of food preparation.

Restaurants were frying in partially hydrogenated oils instead of beef fat. Home cooks got the message that margarine was heart-healthy and that butter was not. It became rare to find a cracker, cookie, coffee creamer, frosting or mass-produced bakery item that didn’t contain partially hydrogenated oil.

While the new trans-fat ban is a good thing, there is some concern about what might take the place of partially hydrogenated oils in processed foods. Could the ban be a double-edged sword?

For commercial frying, partially hydrogenated oils are simply being replaced by vegetable oils that are stable at high heat. But to replace solid fats, such as those used for baking and spreads, the trend so far is to produce trans fat-free shortenings using either palm oil or interesterified vegetable oil.

Palm oil is a tropical oil that comes from the fruit portion of the palm fruit. Most health and nutrition experts agree that this saturated fat is a lesser evil than trans fats, but it’s unclear what effect palm oil may have on blood cholesterol and heart disease — good, bad or neutral.

Interesterified oils have been used since the 1930s, including as a replacement for cocoa butter in cheap chocolate, but interest in them increased as the trans fat backlash began. The concern is that these chemically altered oils may have the same negative effects on our cholesterol and blood sugar levels as trans fats.

What can you do now until we know more about these fats? First, don’t assume that the words “trans fat free” mean that a food is healthful. Second, if you eat more whole foods and fewer processed foods, you’ll naturally be eating less of whatever type of fat is used in place of trans fats. This means you will be less affected if years from now it turns out that these trans fat alternatives aren’t any better for us.