The number one dietary evil in America today is saturated fat (sat fat). Ask most doctors and nutrition experts the one thing you should remove from your diet over everything else, and you are likely to be told that red meat, butter and other sources of sat fat must go. The diet dictocrats have suggested that you should substitute PUFAs (polyunsaturated fatty acids) for sat fats. The point of the exercise is to lower blood cholesterol, which has long been thought the main culprit behind heart disease.
PUFAs are found in vegetable oils, so tens of millions of Americans have followed decades of dietary recommendations and stopped cooking with butter. Instead, they have switched to “light” oils such as safflower oil. So, how did that work out? Fortunately, we have a lovely experiment that actually provides us an answer. Between 1966 and 1973 a randomized controlled trial called The Sydney Diet Heart Study (SDHS) was carried out in Australia. This is gold-standard research that trumps the usual epidemiological studies that simply look to see what people are eating on their own and how they fare.
In this study, 458 men who had recently had a “coronary event” (a heart attack or something like it) were randomly assigned to two separate dietary groups. One group was told to carry on its usual way of eating, with the expectation that it would be using the butter and ordinary margarine that was common in Australia at that time. The other group got safflower oil and margarine made from safflower oil rich in omega 6 linoleic acid. This is the most common of the PUFAs that Americans as well as Australians consume. Back in 1978 when the study results were first published, there was no analysis of which men had more heart attacks and heart attack deaths.
Scientists recently recovered the original data, dusted them off and analyzed them (BMJ, online, Feb. 5, 2013). The results were alarming. The men who had been provided with “heart-healthy” safflower oil were 60% more likely to die during the study (17.6% of them died compared to 11.8% of the men on their usual unsupervised diets). In addition, they were 75% more likely to die of coronary heart disease (16.3% of the men on the PUFA-rich diet compared to 10.1% of the men eating butter).
Even though the men consuming omega-6 PUFAs did lower their cholesterol as the investigators had hoped, this did not save their lives. Switching to a diet rich in linoleic acid was counterproductive for preventing heart disease and cardiac mortality. Here, in their own words, are the conclusions of the Australian researchers:
“In this evaluation of data from the SDHS [The Sydney Diet Heart Study], selectively increasing the n-6 PUFA LA [omega-6 polyunsaturated fatty acid linoleic acid] from safflower oil and safflower polyunsaturated margarine increased rates of death from cardiovascular disease, coronary heart disease, and all cause mortality compared with a control diet rich in SFA [saturated fatty acids] from animal fats and common margarines. This is the first published report to show an increase in mortality from cardiovascular disease and coronary heart disease, comparing this LA [linoleic acid] intervention to the control group, and demonstrating that the magnitude of increased n-6 LA intake was associated with higher risk of death.”
These results throw the traditional diet-heart hypothesis into question and suggest that overdoing on omega-6 fatty acids in the diet might not be a good idea. In fact, it might be a bad idea! And this is not the first time vegetable oils high in omega-6 fatty acids have been called into question. The Australian investigators point out that:
“These unfavorable effects of n-6 LA shown in the SDHS are consistent with two other randomized controlled trials, in which experimental dietary conditions selectively increased n-6 LA in the place of SFAs by replacing animal fats and common margarines with corn oil. Together, these three trials provide a rare opportunity to evaluate the specific effects of increasing n-6 LA without confounding from concurrent increases in n-3 PUFAs. In a pooled analysis, the increased risks of death from coronary heart disease (hazard ratio 1.33 and cardiovascular disease (1.27) approached significance. Secondary prevention trials showed significant adverse effects of n-6 LA on coronary heart disease mortality (1.84). By contrast, pooled analysis of the four randomized controlled trials that increased n-3 PUFAs alongside n-6 LA showed reduced cardiovascular mortality (0.79).”
What that means in plain English is that using vegetable oils high in omega-6 fatty acids increased the risk of death from heart disease whereas using omega-3 fatty acids actually reduced cardiovascular mortality. Our ancestors ate meat that was raised on grass rather than corn. That food was high in omega-3 fatty acids. And people who ate a Mediterranean diet also consumed foods high in omega-3 fatty acids. Olive oil is a prime example of a heart-healthy oil.
So there you have it. The diet dictocrats have been telling people to use PUFAs like safflower and corn oil because they are supposed to be “heart healthy.” Turns out they were wrong. And according to the Australian researchers, this is especially true for people who smoke or drink, exposing their bodies to excessive oxidative stress. When breakdown products of linoleic acid are oxidized, they form nasty compounds that are likely to cause clogging of coronary arteries. They now urge caution in simply substituting omega-6 PUFAs for sat fat around the world.
Once again we have learned a painful lesson. The “experts” don’t always know what is best for us. It can take decades to unscramble dietary dogma and learn that grandma’s wisdom was right after all.
To learn more about heart-healthy food and the specifics of the Mediterranean diet we suggest our book, The People’s Pharmacy Quick & Handy Home Remedies. It is loaded with common sense solutions to common problems and details about heart healthy food.
If you are having a hard time swallowing this new information we encourage you to check out the research in the BMJ for yourself. Because it does not fit with the prevailing paradigm, it is likely to sink without a trace. But when you read the original research you will see that evidence trumps long-held dietary dogma.
[BMJ, Feb. 5, 2013]
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