The latest on fats: Facts vs. fiction

Some confused readers have been asking me how we could have gotten it so wrong on saturated fat.  Why didn’t we see that the villain in the heart disease story isn’t saturated fat, but sugar? And how could the American Heart Association and the US National Heart, Lung, and Blood Institute have missed that, too?

These readers are talking about a recent turnaround on the attitude of some “experts” regarding dietary fat — especially saturated fat.  Given permission to indulge by the Atkins fad and a recent meta-analysis questioning the link between saturated fat intake and cardiovascular disease, many people have loaded up their plates with saturated fat.  As a result, since last year, at least in the US, wholesale prices of butter and bacon both hit record high in response to surging consumer demand. 

Take note of the following articles from some respected publications:

• New York Times food columnist Mark Bittman (“Butter is back,” ran his headline).

•  Journalist Nina Teicholz, author of The Big Fat Surprise: Why Butter, Meat & Cheese Belong in a Healthy Diet.

• Bryan Walsh, author of Time magazine’s June 23, 2014 cover story entitled, “Eat Butter.  Scientists labeled fat the enemy.  Why they were wrong.” (see photo).

But this recent “canonization of saturated fat,” as Yale preventive medicine expert David L. Katz, MD, calls the trend, is as misguided as the anti-fat extreme that led people to load up on low-fat cookies, ice cream, and salad dressings.  Saturated fat may not be the only cause of unhealthy cholesterol levels and heart disease, but that doesn’t mean it’s good for you.

Big fat confusion

Let me highlight a few points that have contributed to the confusion:

The debate over which is worse, sugar and white flour or saturated fat, has been percolating for years.  But the pot boiled over in March last year, when an “exhaustive new analysis” (as The New York Times put it) was published in the prestigious medical journal Annals of Internal Medicine.

The meta-analysis reported that people had the same risk of heart disease, whether they ate a diet high in saturated fat (in meat and dairy) or one high in polyunsaturated fat (in foods like soybean oil, mayo, salad dressing, and fish).  Newspapers, magazines, and talk shows just couldn’t resist a man-bites-dog story line like that.

Since then, however, and you haven’t read about it in Time or New York Times, that study has been blasted by leading heart disease researchers.

In a letter published in the Annals of Internal Medicine, CSPI’s (The Center for Science in the Public Interest) director of nutrition Bonnie Liebman and co-authors pointed out a crucial flaw in the meta-analysis, which combined the results of clinical trials that replaced saturated fat with polyunsaturated fat:  It included a trial in which some of the saturated fat was replaced with a high trans-margarine.  Trans fat increases the risk of heart disease.  (The authors buried the trans detail in an online supplement.)

Removing that one trial from the meta-analysis reversed the results and showed that, in fact, people who replaced saturated fat with polyunsaturated fats had a lower risk of heart disease.  (Those trials and other controlled studies, not the 1950s Seven Countries Study that Teicholtz quoted, are the evidence that experts rely on.)

That’s the problem with meta-analyses.  They are valuable tools because they pull together and analyze data from many studies so that patterns can become clearer.  However, they can produce conflicting results because of differences in what questions were examined, how the studies were designed and selected, and how the data were used in those various pooled studies.

In the case of the new meta-analysis in question, scientists were quick to point out statistical errors and the omission of key studies.  For example, the researchers misinterpreted one crucial study on omega-3 fats from seafood as showing no effect when it actually found a strong benefit.  All it took was one correction (made in the online version of the study) to change what seemed like no association between dietary omega-3s and coronary events to a protective effect.

Dog bites man.  No story.

Fat facts

What is important for you to remember is this: The best evidence still suggests that replacing saturated fats with polyunsaturated fats (including omega-3s) improves cholesterol levels and reduces the risk of cardiovascular disease.  This was shown in a 2009 analysis published in the American Journal of Clinical Nutrition, which included 11 observational studies, and a 2010 Harvard analysis of eight trials in the online journal PLOS Medicine.

But in the real world, it depends on where the polyunsaturated fats come from. Getting them from greasy fried foods or packaged cookies or chips won’t improve your coronary odds.

According to the World Health Organization, “The most effective replacements for saturated fatty acids in terms of coronary heart disease outcome are polyunsaturated fatty acids, especially linoleic acid.  This finding is supported by the results of several large randomized clinical trials, in which replacement of saturated and trans fatty acids by polyunsaturated vegetable oils lowered coronary heart disease risk.”

In late 2013, after an extensive review, the American Heart Association and American College of Cardiology released guidelines on lifestyle management to reduce cardiovascular risk that recommended sharply cutting saturated fat for people concerned about unhealthy LDL cholesterol levels, within the context of an overall healthy dietary pattern.

Bottom line

Healthy fats could have an important place in your diet, and you should give at least as much attention to reducing refined carbohydrates and sugars as to cutting back on saturated fat.  Common sense and a diet rich in vegetables, fruits, whole grains, vegetable oils, nuts and seeds, legumes, fish and low-fat dairy products should serve as a basis for a healthy dietary pattern.

Scientists, nutritionists, and physicians still advise limiting foods high in saturated fats, notably meats, and focusing more on foods rich in unsaturated fats, such as fish and nuts.  Virtually all diets known to be heart-healthy tend to be low in saturated fat — that includes vegetarian and Mediterranean diets, along with DASH (Dietary Approaches to Stop Hypertension).  Healthful diets focusing primarily on vegetables, fruits, beans, nuts, and whole grains have little room for saturated fats.

But remember, that as far as weight control goes, fats are a double-edge sword — they can make foods satiating, but they’re calorie-dense.  So moderation is the word.

And, looking for a culprit for the obesity epidemic?  Blame it on billions spent on ads for sodas and fast food, on the 1,000+-calorie restaurant meals, and on the 24/7 availability of cheeseburgers, fries, shakes, pizzas, burritos, fried chicken, movie theater popcorn, muffins, nachos, soda pop, and other fast-food meals.

It doesn’t need an exhaustive meta-analysis to see that!