Saturday, July 14, 2007

Saturated Fat

Autumn asks:
"What do you think of Dr. Mary Enig's research on fats and her suggestion that saturated fat is not the devil we've been lead to believe?"

That's a hot potato, Autumn.

First, I'll admit I don't know much about Enig's research. I haven't read her book, Know Your Fats.

But, superficially at least, I agree. I don't think saturated fat should be as maligned as it is.

I don't feel comfortable promoting that fact because:
  1. If you remove the red flag from saturated fat, some people will take that as a license to consume more whole milk, cream, high butterfat cheese, fatty steaks ... which aren't inherently bad foods, but they're more caloric than their low-fat alternatives and can promote weight gain. (Studies provide isocaloric diets. That is, they adjust amounts of macronutrients: fats/carbohydrates/proteins, but keep the same number of calories. In reality, people will eat a serving of, say, yogurt and not adjust the amount depending on the fat, thus calorie, content. That's my experience.)

  2. Consumption of foods that contain saturated fat supports the livestock factory farming industry. These foods may also come packaged with undesirable substances (antibiotics, growth hormone, prions, E. coli, etc.).

  3. Regarding our evolutionary past, the selection of genes in meat-eating hunter-gatherers millions of years ago was influenced by environmental pressures distinct from pressures of modern man. For example, infection (which serum fats aid in protection against) may have been a greater health risk then than cardiovascular disease is today. Hunting and gathering are also heart-pumping, calorie-expending activities.
There's a lot to know about saturated fatty acids (SFAs), and I can't say I know a ton. As you know, there isn't one type of SFA; they differ by their chain length. And different SFAs translate into different functions ... more than just providing calories or stuffing lipoproteins. Different SFAs also have different affects on serum lipids, an area of ongoing research.

There do appear to be benefits associated with saturated fat consumption:
  1. SFAs increase HDL (Delta Study). MUFAs1 and PUFAs2 do this too, when substituted for carbs, but SFAs do it best.

  2. Although SFAs are associated with increases in LDL, they may decrease Lp(a), a type of lipoprotein derived from LDL thought to be an independent risk factor for heart disease. (The saturated fat used in this 2003 study came from coconut oil.)

  3. One oft-cited study suggested SFAs are the preferred fuel for the heart, at least the rat heart.

  4. Reduction of saturated fat in the diet is often accompanied by increases in carbohydrate, a macronutrient adjustment that has been shown (example) to increase triglycerides and lower HDL.
That said, people differ in their response to fat in the diet. That's a really important piece of the puzzle, individual response. Some people respond better (weight loss, better serum lipids) with a low-fat diet, others with a low-carb/higher fat diet. (For example, the latter may be beneficial for a person with insulin resistance, low HDL and low LDL.) Broad recommendations are risky.

So, I'm back to where I started. Some amount of saturated fat in the diet appears to be beneficial. But I don't want to take responsibility for someone construing that to mean I endorse a diet of double bacon cheeseburgers and Ben & Jerry's.
1 Monounsaturated Fatty Acids (olive oil, canola oil)
2 Polyunsaturated Fatty Acids (corn oil, safflower oil)
Photo of New York Strip Steak by Nicole Weston via Link includes recipe.

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