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.

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