April 18, 2016

Animal Fats Healthier Than Vegetable Oils

The science behind the recommended change to vegetable oils about 50 years ago appears to be very faulty and even the trail itself was not that great. The research suggests that the switch from animal to vegetable (corn) fats may be not only unnecessary, but it may misguided. Studies have arrived at similar findings before, but the new one, which looks at the heart health of people eating animal fats vs. corn oil, suggests that people who use the latter may actually be at an increased heart risk.

The team looked at data from a study that started in the late 60s, using 9,400 residents from several mental hospitals and one nursing home (the participants coming from these two communities may be a problem in itself). It wasn’t published until 1989, for reasons that aren’t very clear, and it reported that switching from animal fats to corn oil was beneficial for cholesterol; it did not report that the switch had any effect on heart disease.

A team at the NIH, the University of North Carolina and several other universities uncovered the entire data set and ran the stats again, because some had been omitted. The reconsidered results were strange: People who ate vegetable oils had lower cholesterol, but also had a significantly higher risk of heart attack.

Though the research authors would not say this, it looks like the previous researchers were cherry picking data to arrive at the conclusion desired at the time. “Altogether, this research leads us to conclude that incomplete publication of important data has contributed to the overestimation of benefits–and the underestimation of potential risks of replacing saturated fat with vegetable oils rich in linoleic acid,” said Daisy Zamora.

The omega-6 fatty acid linoleic acid (LA) is known to have some major health drawbacks. “An odd thing about this is the outdated substitution of linoleic acid for unspecified saturated fat,” says David L. Katz, founder of the Yale Prevention Research Center. “Linoleic acid is an omega-6, and it’s clear now that there are many problems associated with excessive omega-6, notably interference with the production of long-chain omega-3s.”

The two types of fats need to be consumed into the body in balance, otherwise omega-6s usurp the machinery needed to make omega-3s. But researchers have been aware of this danger for some time. Omega-6 has also been linked to increasing, rather than decreasing, inflammation.

Sunflower oil in the US was ‘upgraded’ through selective breeding to produce a high-oleic-acid variety (high monounsaturated fatty acid) that now prevails, and avoids the potential harms noted in this paper. The same thing is now being done to soybean oil, and the high monounsaturated fatty acid version of that will soon replace the old variety.”

So the new study may simply underline that swapping animals fat for corn oil may lead to more health problems than it solves. And as Katz points out, no one today would think that making the swap the study made is terribly informative.

The evidence that replacing saturated fat in general with a balanced portfolio of unsaturated fats from a variety of foods is still questionable. The Dietary Guidelines advise, oils from whole foods: nuts, seeds, avocado, fish. These do not provide the excess of omega-6 likely in this case. Different varieties of imbalance tend to represent different ways of eating badly. The body needs, and responds well to, balance.”

For possible clarification of the unnamed studies and more information, please read this blog by Dr. Malcolm Kendrick. He does name the studies and makes the discussion clearer.

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