The facts about fats: do saturated fats really cause heart disease?

Not all scientists are in agreement with the Association’s assessment of studies testing the link between saturated fats and heart disease. The Association’s paper seems to be grounded not so much in science as in a long-held belief that is hard to let go of.

After all, the Association has its reasons for not wanting to change its stance on saturated fats, from commercial interests to simply wanting to save face.

It was way back in 1961 that the organisation launched the world’s first official recommendations to avoid saturated fats, along with dietary cholesterol, in order to prevent a heart attack. This ‘diet-heart hypothesis’ caught on among leading experts, even though it has never been tested in clinical trials. Without these kind of trials, there is no way to actually prove a direct cause-and-effect. So the science was shaky from the beginning.

The ‘diet-heart hypothesis’ did have some basic data to back it up, and the notion itself just seemed to make sense – fat clogs your arteries like hot grease down a cold drain pipe, right? What’s more, heart disease was on the rise, and the AHA really needed to assign blame to something.

Of course, more concrete evidence was still needed, and so governments around the world spent billions of dollars trying to prove the hypothesis was true. Somewhere between 10,000 and 53,000 people were tested on diets where saturated fats were replaced by unsaturated vegetable oils.

However, the results did not turn out as expected – saturated fats weren’t the culprit.

And yet, researchers, either unable or unwilling to believe the study outcomes, did not talk about this data for decades. The results of one of the forgotten trials, carried out in America and funded by the National Institutes of Health, were not published for 16 years.

From 2010, however, researchers worldwide began to dig up these old studies and take a closer look at them. Out of nine separate reviews, none could find any evidence in the data that saturated fats affected heart health or caused death. A number of these reviewers stated in their conclusions that the results do not support the US government’s Dietary Guidelines for Americans, which suggest saturated fats should make up only 10 per cent of daily calories, or the Association advice to cap them at five per cent to six per cent.

So why do these findings differ so much from those of the Association? Well, it mainly comes down to what outcomes are being taken into consideration.

Instead of looking at undeniable “hard” outcomes, such as heart attacks, stroke, deaths from heart attacks or deaths overall, the Association examined less definitive ‘cardiovascular events’, which include not only heart attacks but other conditions which can only be observed by patients, not doctors, such as chest or heart pain.

By using this criteria, and ignoring deaths, the data can be seen to point the finger more at saturated fats. But that’s a little like reporting on midway times in a marathon while remaining silent about who won the race.

The ‘Presidential Advisory’ ignores other data, too. While the nine other papers reviewed an average of 10 trials each, the Association examined only four. And it may have also been careful about the ones it chose to review. It left out, for example, the Minnesota Coronary Experiment, in which 9,750 men and women spent a year-plus on the Association’s intervention diet, because it said all studies must be at least two years long.

Yet in the past, the Association has recommended other diets based on studies of fewer than 1,200 people altogether, and trials lasting no longer than five months. This seems to amount to what Andrew Mente, an expert on nutrition–related diseases at McMaster University, described as “cherry picking”.

So why is the Association so reluctant to listen to science and update its view of saturated fats? It could simply be that the association is too attached to the belief that is has promoted for decades.

Or it could be due to its reliance on funding from industries who profit from the saturated fats boycott, such as the vegetable-oil manufacturer Procter & Gamble, which gave the Association its first big boost back in 1948 by donating to it all the funds from a radio contest it sponsored(about US$17 million).

More recently, Bayer, the owner of LibertyLink soybeans, pledged up to US$500,000 to the Association, perhaps due to the fact that the group is an advocate of soybean oil, the main ingredient in the ‘vegetable oil’ consumed in America today.

It’s still possible that a very large, long-term clinical trial could ultimately show that saturated fats cause cardiovascular death, or even premature heart attacks. And it may be a good idea not to eat too much meat or coconut oil for reasons that have nothing to do with saturated fats. But over the last half a century, the diet-heart hypothesis has been tested more than any other in the history of nutrition, and so far, the results don’t amount to much. And if there isn’t enough evidence to convict saturated fats, perhaps it’s time they were finally acquitted.

About the writer

Investigative journalist Nina Teicholz is the author of “The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.” This op-ed, published by the Los Angeles Times, is based on a longer analysis of the recent AHA advisory that was co-written with cardiologist Eric Thorn and published this month on the medical website Medscape.