The Skinny on Fat

In the 1970s and 80s, fat was the bad boy of nutrition.  Since then, research has reminded us of so many of the “forgotten” good things about fat -- from the benefits of omega-3 fatty acids, to absorbing our fat-soluble vitamins and beyond.  As research goes on, more facts come to light to dispel our fears of this nutrient.

A few months ago, I reported that a Mediterranean diet rich in olive oil and nuts decreases the risk of cardiovascular disease by 30% compared to a low-fat diet.  Further analysis (1) of the data from this study (the PREDIMED study from Spain) found that the monounsaturated fat-rich Mediterranean diet also decreased diabetes risk by a third.  This is huge:  cardiovascular disease and diabetes are two of the biggest causes of death and morbidity in this country.  Focusing on low glycemic index foods like whole grains, legumes, fruits, and vegetables, as well as losing our fear of healthy fats like extra-virgin olive oil, can spell out huge health benefits.

Furthermore, a meta-analysis (a study of studies) published in the American Journal of Clinical Nutrition in 2010 (2) tore down one of the most sacred cows of nutrition and health research:  the "evil" of saturated fat.  The authors found no association of saturated fat intake with cardiovascular disease or stroke in the best-designed nutritional studies available to date.  This is mind-boggling, since everyone "knows" that chomping on a cheeseburger will instantly make your arteries clog up.  The jury is still out. but it appears that the ratio of unsaturated fat (from sources like olive oil, fish oil, or nuts) to saturated fat is more important than the absolute amount of saturated fat.  Translated into English, this means that at least half of your dietary fat should come from these healthier sources.  One word of caution, though, is that omega-6-rich fats such as vegetable oil might actually be bad for the heart.

As we sort through all of this evidence. it looks like the best recommendations we have to date are:

• Overall, a low-fat diet is not healthier for most people.
• Balance saturated fat intake (meat, dairy, coconut oil) with healthier fats (olive oil, nuts, avocados).
• Use vegetable oils sparingly (canola, corn, peanut oil).
• Do all of this in the context of a varied, fiber-rich, low glycemic index eating pattern, such as the Mediterranean Diet.

1.  Ann Intern Med. 2014;160(1):1-10-10. doi:10.7326/M13-1725
2.  Am J Clin Nutr 2010;91:535–46.

Will Fat Kill You, or Make You Live Forever?

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).