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“[The new study] may possibly be used by some as a license to ignore these decades of good advice, common sense and Grandma’s advice, and go right for the cheese breads.” Duffy MacKay, Senior Vice President, Council for Responsible Nutrition (Reuters.com, March 17, 2014)
Saturated Fat Not Heart Risk, Massive Study Finds; New Focus on Entire Diet
Headlines around the world are trumpeting the international study finding no link between heart disease and saturated fat, the kind found most abundantly in meat, butter, and cheese. Some are rejoicing, while others are puzzled; they don't know what to believe. Some see it as an embarrassment to the experts. One high profile researcher is demanding that the study be withdrawn with similar press promotion. I’m with those who see it as a major step forward in our understanding of healthy eating.
Let’s look at the study, published March 17, 2014—and corrected the next day—in the Annals of Internal Medicine, and then how various experts are responding. I’ll also give you my take.
First, it should be understood that the new study is not the first to question whether saturated fat in and of itself is linked to cardiovascular disease; for example, a 2007 meta-analysis led by Siri-Tarino found no connection between saturated fat and heart disease. First author Rajiv Chowdhury, MD, PhD, Cambridge University (UK), and an international team of researchers followed up in a big way, analyzing 76 studies with a total of 600,000 participants: 32 observational studies of fatty acids from dietary intake, 17 observational studies of blood biomarkers, and 27 randomized, controlled trials of fatty acid supplements. The studies included were based in North America, Europe, Asia-Pacific, and two were multinational. Seventy-two unique studies were identified. All of them looked at the correlation, if any, between fatty acids and cardiovascular disease over one year to 30 or more.
Observational studies based on food questionnaires are, of course, least reliable. Studies actually measuring blood lipids are objective and more reliable. Randomized, controlled trials are the gold standard and most reliable.
“In conclusion,” Chowdhury et al wrote, “the pattern of findings from this analysis did not yield clearly supportive evidence for current cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of saturated fats.” As we’ll see, that’s a matter of interpretation. Certain fats do appear to strongly influence cardiovascular risk, for good and bad.
Keep in mind that there are many forms of dietary fat; saturated fat and polyunsaturated fat are broad categories. There are five main categories of fatty acids—saturated, monounsaturated, omega 3 and omega 6 (which are polyunsaturated), and trans—each made up of two or more individual fatty acids.
Polyunsaturated fatty acids are found in fish and plant-based foods such as vegetables, vegetable oils, seeds, and nuts, and are divided into two families: omega-3 and omega-6. Omega-3 is especially high in fish and flaxseed, while omega-6 is plentiful in corn and other vegetable oils. Monounsaturated fatty acids and trans fatty acids were also analyzed. Monounsaturated fatty acids are found most abundantly in canola and olive oil. Trans fatty acids are found in hydrogenated oils added to processed foods.
Chowdhury and his team analyzed the relative coronary disease risk in the five main categories, and then the risk in 23 individual fatty acids, along with three fatty acid supplements.
The observational studies of dietary fatty acid intake assessed the cardiovascular risk in the five main categories by comparing the top and bottom thirds in each category. The researchers found no association between total saturated, monounsaturated, or omega-6 fatty acids and coronary risk. These three types of fat, consider as a whole, showed no significant association with coronary risk.
They did, however, find that the long-chain omega-3 fatty acids found in fish were significantly associated with lower risk of coronary disease; omega-3 fatty acids in flaxseed and other plant oils showed no association. Interestingly, the beneficial correlation for fish was one of the corrections made the day after the study was published. (More about that below.)
As expected, total trans fatty acids were found to be significantly associated with coronary disease.
The studies measuring circulating blood fats likewise showed no meaningful association between total saturated fatty acids and coronary risk. The one exception was margaric acid, a saturated fat found in milk and dairy products, which was founds to be associated with significantly lower coronary risk.
Monounsaturated fatty acids (total and individual) were again neutral. The trans fatty acid analysis was again strongly negative.
The real action was in the omega 3 and 6 categories.
Alpha-linolenic acid (ALA)—found in flaxseed and to a lesser extent in canola oil, olive oil, walnuts, and other nuts, as well as trace amounts in green leafy vegetables—was associated with slightly lowered risk, while the long-chain omega-3 fatty acids EPA, DHA, and DPA (found in fish) were strongly associated with less coronary risk, with DPA (distinctive to fish) showing the lowest coronary risk on the chart.
The omega-6 sub-groups (high in sunflower, soybean, corn, and safflower oils) were neutral to somewhat negative. Interestingly, arachidonic acid (AA), found in meat, had the lowest risk ratio in the omega-6 group.
Finally, the controlled trial studies found the relative risk in fatty acid supplements mixed, neutral to somewhat protective. ALA supplements showed little effect, while long-chain omega-3 fatty acid and omega-6 fatty acid supplements demonstrated less coronary event risk than controls. Surprisingly, the omega-6 supplements registered the lowest risk ratio.
In spite of the consistently positive readings for the fatty acids found in fish, the researchers stuck to their conclusion that recommendations to increase polyunsaturated fats are not clearly supported. They called for more study.
So, where does that leave us?
What the Experts Say
The experts agree on one thing: The new study is not a license to pig out on burgers, fries, onion rings, and chocolate chip cookies.
The new focus is away from individual dietary components and toward the whole diet. Away from saturated fat and toward what comes along with it.
“We are not saying the guidelines are wrong and people can eat as much saturated fat as they want,” senior author Emanuele Di Angelantonio, MD, PhD, (also from Cambridge) told Science/AAAS: News. “We are saying there is no strong support for the guidelines and we need more good trials.”
“My take on this would be that it’s not saturated fat that we should worry about,” first author Chowdhury told The New York Times. “It’s the high carbohydrates or sugary diet that should be the focus of dietary guidelines.”
Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health, who was not involved in the study, told The Times that the findings should not be taken as a ”green light” to eat more steak, butter, and other foods rich in saturated fat. “I think future guidelines will put more emphasis on real food rather than giving an absolute upper limit or cutoff point for certain macronutrients.”
Another co-author, from Harvard, Dariush Mozaffarian, MD, DrPH, concurred: “Guidelines that focus on the nutrients, single nutrients, as targets for preventing chronic disease don’t make a lot of sense. I think we need to move to food-based guidelines, to really talk about food, not nutrients.”
King’s College London Professor Emeritus Jeremy Pearson, associate medical director at the British Heart Foundation, which helped fund the new study, harkened back to an earlier guideline gone wrong. “We were looking at the wrong part of people’s diet—it wasn’t the eggs but the way they were cooked—in saturated bacon fat for example—and what they were eaten with,” he wrote in The Guardian. Pearson was in the hot seat, because he also participated in formulating the current British guidelines.
Eggs are a good example, because we were once advised to strictly limit consumption, because eggs were thought to raise cholesterol, increasing our risk of cardiovascular disease. It has since been determined that cholesterol comes far more from the liver than cholesterol in the diet. Eggs are high in cholesterol, but relatively low in saturated fat.
Pearson says the new study tells us that saturated fat isn’t as damaging as thought—not that it’s good for the heart.
Dr. Alice Lichtenstein, a nutritional biochemist at Tufts University, lead author of the American Heart Association dietary guidelines, concurred with Professor Pearson. She told The New York Times: “It would be unfortunate if these results were interpreted to suggest that people can go back to eating butter and cheese with abandon,” citing evidence that replacing saturated fat with foods that are high in polyunsaturated fats—instead of simply eating more carbohydrates—reduces cardiovascular risk. (See my article “Cutting Saturated Fat Alone Not Enough” http://www.cbass.com/CuttingSatFat.htm )
The key thing to get across, says Professor Pearson, is that focusing of any single nutrient—saturated fat, sugar, salt or something else—is not very helpful. We don’t eat a single nutrient, we eat food, meals and whole diets that contain a range of nutrients that can all impact on our heart disease risk. He says the whole diet should be our focus.
Saying “the single macronutrient approach is outdated,” Dr. Hu agrees with Professor Pearson that the Mediterranean diet is a good whole-diet approach, with fats mainly from unsaturated sources as well as more fruit and vegetables, and fewer sugary and fatty treats.
“The Mediterranean diet is naturally lower in saturated fat, but the benefits seem to come not from one specific element, but from the sum of the parts,” Pearson wrote in The Guardian.
That brings us back to the corrections made in the Chowdhury study the day after the initial publication.
Perhaps more unsettling than the finding that saturated fat does not clearly increase heart disease risk was the report—especially the initial report—that omega-3 polyunsaturated fats are not clearly beneficial.
Dr. Chowdhury told Science/AAAS: News that scientists began pointing out errors even before the paper was published. For instance, the authors took one study on omega-3 fats to show a slightly negative effect when, in fact, it had shown a strongly positive effect. The correction now says that people who report eating lots of this particular fat have significantly less heart disease, when it initially said there was no significant effect.
Chowdhury says the paper’s bottom line conclusions are nevertheless valid—until randomized trials show otherwise. Co-author Dariush Mozaffarian, however, admits that he is not happy with the key conclusion that the evidence does not support a benefit from polyunsaturated fats. “Personally, I think the results suggest that fish and vegetable oils should be encouraged,” he told Science/AAAS. But the paper was written by a group of authors, he pointed out. “And science isn’t a dictatorship.”
Walter Willett, chair of the nutrition department at the Harvard School of Public Health, says correcting the paper isn’t enough. “It is good that they fixed it for the record, but it has caused massive confusion and the public hasn’t heard about the correction.” The paper should be withdrawn, he argues.
So, where are we now? I’d say in a pretty good place.
Saturated fat is not so bad, but it’s probably not so good either. Pretty clearly, the fatty acids found in fish and perhaps some plant foods are beneficial. And just about everyone agrees that whole foods should be favored over processed foods. That’s progress.
I’m happy with the new study as corrected. I believe it’s unlikely that individual diets can be reliably controlled long enough to accurately measure heart disease risk. Can you imagine overseeing everything participants put in their mouth for a year, much less the time it takes for heart disease to become clearly apparent? (There’s a reason why the only controlled trials involved fatty acid supplements, which can be easily monitored.) Almost 80 studies, most observation and some controlled, from North America, Europe, and Asia-Pacific, is about as good as we’re going to get.
As noted above, I believe the Chowdhury study is a major step forward in our understanding of healthy eating. Along with the expert commentary above, it tells me to stay the course.
I’m going to continue enjoying organic whole milk and yogurt, along with fatty fish, eggs, canola oil, olive oil, nuts, and seeds—with chicken, bison, or range-feed beef from time to time. I’ll continue to avoid sugar and processed foods—and eat plenty of beans, fruits, vegetables, and whole grains.
I’ll also continue to enjoy myself on special occasions eating every dessert that comes my way.
Put together thoughtfully—Carol’s vegetable stews and nutrient-rich salads are superb examples—this is a wonderfully satisfying way to eat. You’re rarely hungry. Combined with regular exercise, this pattern of eating is the odds-on favorite to keep us both lean and healthy.
Carol, shown here doing the Glute-Ham Raise on the eve of her
71st birthday, thrives on a balanced diet of whole foods and regular exercise.
Photo by Clarence Bass
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