In the past decade or so, the nutrition-research community has effectively driven home the message that trans fats are bad. As bad as — if not worse than — saturated fats, at least in terms of health. Communities around the nation have begun responding with proposals for local bans on the use in restaurant fare of shortening and margarines made from this type of synthetic fat.

But synthetic is the operant word, because there are natural trans fats. And the types that form naturally can have quite beneficial pharmacological properties. Known as conjugated linoleic acids — CLAs for short — these fats come in several “flavors” (what chemists refer to as isomers). Depending on which type it is, a CLA can help fight cancer, fight weight gain, fight diabetes — even fight arthritis.

In fact, the two companies that petitioned FDA for a generally regarded as safe — or GRAS — status for their products bundle the two isomers together. That way, people can get the benefits of both. Americans have been able to buy capsules containing a mix of the two isomers for years. But these products — derived by some processing of vegetable oils rich in linoleic acid — could only be served up alone and sold as dietary supplements.

To be legally added to foods, CLAs had to have FDA’s explicit approval. Which arrived in a letter to the petitioning companies late last week, notes Michael Pariza of the University of Wisconsin–Madison.

Ironically, while the message has finally reached the public consciousness that trans fats can be bad, the idea that some aren’t has remained largely below the radar screen.

Clearly, plenty of people have not been paying close attention to Science News. I first started covering CLAs’ anticancer attributes in 1984. “We had been looking for mutagens in hamburger,” recalls Pariza, and “started research on that in 1977.” Within a year, “we discovered there was actually something in our hamburger extracts that inhibited mutagenesis,” he says, “and published on it in January 1979.”

The paper concluded with a couple sentences arguing that whatever the mystery substance or substances that these researchers had stumbled upon in the ground meat, there was some chance at least one might prove anticarcinogenic. “And that turned out to be the case,” Pariza notes. In the interim, his team’s studies gave rise to all kinds of humorous reporting on Big Macs as health foods. (Hint: They weren’t and still aren’t.)

Pariza’s team finally isolated the natural anti-mutagens around 1986. By 1989, a particularly rich source of CLAs emerged: Cheez Whiz. Kraft Foods must have had a field day pointing out that this pasteurized spread was no junk food, but a more concentrated source of a potential cancer-fighting compound than any of the regular cheeses analyzed.

As one might expect, it wasn’t long before companies started synthesizing CLAs — using Mother Nature’s recipe — so that they could begin testing the fats’ potential benefits in animals, and eventually people. They hoped to one day distinguish their products from the trans fats that were by now increasingly in the news as nutritional pariahs.

And they succeeded.

At some point tomorrow I hope to hear from at least one of the companies that petitioned FDA for CLAs’ new GRAS status. Maybe then I’ll get some idea of what type of products they might show up in, and when.

But keep in mind, as with any fats, CLAs are high in calories. So here’s one instance where more is definitely not better. The goal, Pariza has always emphasized, should be simply to substitute these good fats for not-so-good ones.

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