WASHINGTON -- New York has banned trans fats from its restaurants. Philadelphia and Los Angeles are considering following its example. Starbucks has just announced it is the latest chain going trans fat-free. So what will replace trans fats in our foods? Meet the dreadful new word: "interesterified fats."
Food manufacturers loved trans fats. They were essential to baked goods and fried food. They prolonged a processed food's shelf life. They stabilized its flavor. What was not to like?
Well, many things really. What happened when vegetable oil was solidified by means of adding hydrogen to it - the process behind the making of trans fats - was that they raised our so-called bad cholesterol, while diminishing the cholesterol that was good for our hearts.
But if trans fats are withdrawn, something has to take their place if we are to continue eating processed and fried foods.
Enter interesterified fats. These are fats modified by procedures that include hydrogenation, followed by the rearrangement of fat molecules through a process called interesterification. Already they are being introduced into a number of processed foods as the most popular substitute for hydrogenated oils.
Watch out, though! Interesterified fats may be better for our cholesterol, but they could be bad for our blood glucose.
Trans fats were not too good for it either. But in a study just published in Nutrition and Metabolism, Dr. K.C. Hayes of Brandeis University in Massachusetts, and T. Karupaiah and Kalyana Sundram from the Malaysian Palm Oil Board discovered that while trans fat "has a weak negative influence on blood glucose," interesterified fat "appears even worse in that regard, raising glucose 20 percent in a month."
Their findings should be weighed with a certain caution, since the three authors are employed by, or connected to, the Malaysian Palm Oil Board, which funded it. Palm oil, which may have overtaken global soybean oil production, is an almost solid vegetable oil, relatively high in saturated fats, and used widely in Asia and Latin America.
Still, it is alarming that the healthy volunteers spent only four weeks on interesterified fats before their blood glucose levels rocketed. There were 30 volunteers, following three different diets for four weeks each time.
What distinguished the diets was the type of fat providing roughly 30 percent of the calories from fat in each. One diet was based on palm oil, one on partially hydrogenated soybean oil, and the third on an interesterified soybean oil.
In the latter, the volunteers' "good" cholesterol levels were lowered while their blood sugar levels increased by 20 percent compared to the palm oil diet.
Before we rush to judgment, another study, by the National Institute of Food Hygiene and Nutrition in Budapest, Hungary, fed rats with one diet containing sunflower oil and lard, and another with sunflower oil and interesterified lard. When they checked the distribution of fatty acids and good and bad cholesterol in the heart muscle and liver, they concluded that there was little difference between the two diets. In fact, in certain cases they found the diet with the interesterification of the lard "slightly more favorable."
The Unilever Research Laboratory in the Netherlands compared the impact of commonly-used edible vegetable fats against interesterified fats on 60 humans. Those researchers found no particular adverse effect with the latter. Unilever, of course, is a major producer of processed foods, and keen to find an acceptable replacement for trans fats.
We may be in for a possible replay of the time we were advised to discard butter in favor of margarine, until it was realized that margarine, being a trans fat, was less healthy than natural butter. Who knows, trans fats may be back in our diets some time in the future.
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