What is Interesterified Fat?

Michael Pollick
Michael Pollick

When scientific studies exposed the inherent dangers to public health in trans fats, many processed food manufacturers scrambled to find a suitable replacement. They needed to find a form of fat which would still provide the extended shelf life of partially-hydrogenated oils, but did not contain trans fatty acids. One solution arrived in the form of interesterified fat, a fully hydrogenated product with many of the same characteristics as trans fat, but closer to saturated fat chemically. Interesterified fat is produced through a process called interesterification, which rearranges the molecular structure of fatty plant oils.

Interesterified fat is believed to lower levels of the good HDL cholesterol while raising the levels of bad LDL cholesterol.
Interesterified fat is believed to lower levels of the good HDL cholesterol while raising the levels of bad LDL cholesterol.

It might be helpful to look at the term as "inter-ester-ified fat," since the interesterification process generally affects compounds known as esters in the oils used. The chemistry which produces interesterified fat is a bit complicated, but essentially, a natural vegetable oil such as rapeseed is combined with stearic acid and various alkylinic catalysts. The fat components of the oil are chemically altered to become more saturated, much like artificially turning margarine (a partially hydrogenated fat product) into beef lard, a saturated fat. Interesterified fat provides the best of both worlds for manufacturers of processed foods-- an increased shelf life and a better mouth feel.

Raised glucose levels as a result of interesterified fat could lead to the development of diabetes.
Raised glucose levels as a result of interesterified fat could lead to the development of diabetes.

The problem with interesterified fat for consumers is that in many ways the cure is worse than the disease. The reduction or elimination of harmful trans fat should have led to a safer fat product for general consumption. Instead, interesterified fat may be even worse than the partially-hydrogenated products it replaced. Recent studies on the effects of interesterified fat on humans revealed that interesterified fat has roughly the same negative effects on HDL/LDL cholesterol as trans fat. Interesterified fat is believed to lower levels of the good HDL cholesterol while raising the levels of bad LDL cholesterol.

In addition, interesterified fat also showed signs of raising glucose levels as much as 20%, which could lead to the development of pre-diabetic conditions or diabetes itself. The scientists who conducted these studies on interesterified fat suggest that a diet containing the previously maligned saturated fat in moderation would be safer than a diet high in interesterified fat. Although interesterified fat is not the same as partially-hydrogenated oils, the unnatural rearrangement of the lipid molecules does create many of the same health concerns for consumers. Chemically speaking, interesterified fat is the saturated fat alternative the developers of trans fat were hoping to create but couldn't. Time will tell if interesterified fat will face the same fate as the trans fat it replaces.

Michael Pollick
Michael Pollick

A regular wiseGEEK contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments


Coconut oil all the way for deep frying or high heat cooking in general. It's much healthier than peanut oil, as well as having a high smoke point.


@earlyforest -- Anything is better than those fakey modified oils, seriously, anything. People may talk about the horrors of coconut oil fat and how horrible palm oil fat is, but they are nothing compared to those chemically modified oils.

I would say that as far as the best cooking oils go, healthy olive oil is always a good choice, although it might not be the best for deep-frying, since as I recall that it has a fairly low smoking point.

So you may want to go with peanut oil. Although the taste can take some getting used to in the beginning, it actually makes a pretty dry deep fry, and is not nearly as unhealthy as those modified oils.

If you're really concerned, then you can actually ask a nutritionist -- they know all the ins and outs of oil.


So what would you consider to be the best deep frying oil? Because I've heard that you really have to use modified oils like this rather than using grapeseed oil for cooking like that, or whatever those other ones are, coconut oil fat or palm oil fat, those things.

I don't do a whole lot of deep frying, but about twice a year my whole family gets together and I'm always in charge of the fried chicken, so you can see why I would need a good oil for deep frying.

I would hate to think that I was putting all those nasty chemicals into my family's body, so what should I use instead? Can anybody help me out with this?


Wow, talk about the cure being worse than the disease, just like you said. I can't believe that they actually managed to find a modification that increased glucose by 20 percent! If I wanted that I'd just go eat a few candy bars.

See, this is why I'm so big on olive oil use. Olive fat is natural, and so, so much healthier than other kinds of fat whether they're "good" or "bad" fats.

People have known for years that olive oil is one of the best healthy cooking oils, but somehow it's gotten relegated to the top shelves for use in fancy kitchens and most people don't even think about using it.

I think that's just so sad, because olive oil is not only healthier for cooking, it simply tastes better, almost richer, I think. After I had started using olive oil for a few weeks, even the smell of modified oils just made my stomach turn.

Seriously, try it out -- you'll be amazed by how much better you feel, and how much better it tastes!


So, industry gets to say "No Trans Fat" while giving us a food-like substance that has all the heart attack and stroke causing factors as trans-fats, increased bad cholesterol, decreased good cholesterol and as an added bonus, we get increased levels of blood glucose (which will result in increased triglycerides).

I would love to see a warning labels on foods rather than big fancy long names that attempt to fool people.

Shame on the food industry and their scientists for trying to pull another one over on the public. Remember guys, when you do this stuff, people get sick, suffer and die. And they unknowingly pay you to do it.

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