As you might expect, it depends on the kind of fat. As I wrote about a few weeks ago, the standard advice from the 1970s and 80s about following a low-fat diet turned out to be less healthy than including “good” fats from foods like nuts and olive oil. Another recent scientific paper from Australia, published in the British Medical Journal, further blows to top off the old dietary fats advice, showing that saturated fat may not be as bad as we thought it was.
A few decades ago, researchers started noticing a correlation between intake of saturated fats (from foods like meat, dairy products, and shortening) and cardiovascular disease. The recommendation, therefore, was to replace these fats with healthier polyunsaturated fats from vegetable sources. In this study, researchers examined data about 458 men, half of whom received advice to replace saturated fats with omega-6 oils from vegetable sources. The other half (the control group) received no specific dietary advice. After about seven years, it turned out that the death rate in the omega-6 group was 17.6%, versus 11.8% in the control group. Heart disease rates were also 60% higher in the vegetable oil group.
Wait. Take a look at those numbers. Don’t we all know that a saturated fat laden cheeseburger will just clog up our arteries as we’re sitting there? Isn’t this why all the lard and shortening have been replaced with “healthy” vegetable oil for frying?
It turns out that not all polyunsaturated fats are created equal. There are two major categories of PUFAs: omega-6 and omega-3. Ideally, the ratio of our intake of omega-6 to omega-3 should be about 2 to 1. A higher intake of omega-3 fatty acids has been shown over and over again to decrease cardiovascular disease risk, and lower mortality rates. However, the current ratio in America is about 20 to 1, omega-6 to omega-3. This is a major reason why chronic degenerative diseases continue to escalate in this country. Maybe it’s those french fries that are killing us, not the burgers.
So what are we to do with this information? No, this is not carte blanche to go and scarf down as much meat as you want; we still know that a plant-based eating pattern such as the Mediterranean diet is highly protective overall. For cooking, use smaller amounts of healthy saturated fat, such as extra-virgin coconut oil. Extra-virgin olive oil is also a good choice, as a source of monounsaturated fats (and yes, contrary to popular belief, you absolutely can cook with it). A fish oil supplement is a must for most people, to ensure adequate omega-3 intake. Skip deep-fried foods altogether, since the omega-6 fats in the vegetable oils may actually increase our mortality risk (either by themselves, or by transformation into trans fats).
The more we learn, the more we’ll untangle which fats are good for us!
Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.e8707 (Published 5 February 2013).