THE DIETARY FAT CONUNDRUM--PART 4

The Dietary Fat Conundrum—Part 4

I’m winding down here.  The previous three blog posts can be summarized as follows:

Synthetic trans fat is “bad,” saturated fats are probably “neutral”, omega-6 fatty acids in abundance are probably “bad,” omega-3 fatty acids are “good,” and the category of polyunsaturated fatty acids is probably meaningless. 

I can also add that you should ignore ANY website that purport to make recommendations concerning dietary fat (including this one!).

And here’s why.  Now, you’d think that everything published by the Mayo Clinic would be pretty reliable.  I’d have to put Mayo’s right up there with the “best available information for the general public.”  What this means is that if I were interested in learning about heart valve replacements, I’d certainly consider the Mayo Clinic to be a reputable source of information.  And if I were interested in learning about what I should put in my mouth, they should be pretty reliable on that score too—certainly when compared to websites with titles such as “fitday” or “nutristrategy” or “healthyeating” or “paleohacks” or  “dreamfieldsfoods” or “moonbeameating” . . . . I made that last one up, but it does summarize my sentiments regarding a lot of the dietary information out there.  Just moonbeams.  Wishful thinking straight out of la la land.

Here is a recommendation regarding fat intake copied directly from the Mayo Clinic’s website:

     “All fats are high in calories, so limit serving sizes.”

     “Choose monounsaturated or polyunsaturated fats.  Limit saturated fats and trans fats.”

     “Choose regular soft margarines that list liquid oil as the first ingredient, or choose reduced-calorie margarines made with liquid oil that list water as the first ingredient.”

Well, let’s take a look at this recommendation piece by piece.  Certainly fats are high in calories.  Gram for gram, when compared to protein and carbohydrates, fat has the most.  So, assuming you need to reduce calories, maybe it’s a good idea to “limit serving sizes.”  Next, you’re supposed to eat monounsaturated or polyunsaturated fats.  I presume this is because you’re not supposed to eat saturated fats, and the only kinds left are monounsaturated and polyunsaturated.   Well, this is just plain dogma.  First, the evidence for reducing saturated fats is pretty sketchy (see blog post #1 in this series).  Second, polyunsaturated fats are a grab bag of good and bad fats (see blog post #2 in the series).  So the Mayo Clinic is recommending that you eat fats that a lot of the evidence says are “bad” for you.  What’s with that?  Finally, I guess the reason they are recommending margarine with liquid oil is so that you will know for sure that you’re not consuming saturated fats, which are solid at room temperature.  See previous sentence.

And what about the monounsaturated fat recommendation?   First, monounsaturated fats are fatty acids with only one double bond—hence the “mono” prefix.  Like polyunsaturated fatty acids, they are liquid at room temperature.  There are two common monounsaturated fatty acids: palmitoleic acid and oleic acid.  They are found in meat, milk, nuts, avocados, olive oil and lots of other foods.  Olive oil, for example, is about 75% monounsaturated fat. There is a variety of sunflowers that is 85% mono.  Canola oil is 58% mono.  And even in meat, almost 50% of  the fatty acids are monounsaturated.  Actually, if you look at a food chart, you will find that almost everything we eat contains significant amounts of monounsaturated fats.

So, any recommendation that you increase your intake of monounsaturated fatty acids is almost meaningless—they are everywhere.  In fact, your own body can turn stearic acid (a saturated fat) into oleic acid (a monounsaturated fat)!  Therefore, if you eat a juicy steak, which is already about 50% monounsaturated fatty acid, some of the remaining (saturated) fat could be turned into monounsaturated fat.  So you could get some olive oil equivalents from eating a steak.  How cool is that?

Hmmm.  I wonder if anybody has figured out the percentage of stearic acid that is converted to oleic acid by our bodies?  Oh, yes, I see that they have—in a 1994 study using radioactively labeled palmitic and stearic acid.

This is actually an interesting study.  It involved 7 subjects, young men.  They were fed radioactively-labeled stearic acid and palmitic acid, both saturated fatty acids.  Then, over 24 hours, the researchers watched what happened to these tagged fatty acids.  First, two of the subjects didn’t absorb the palmitic fatty acids at all.  I thought this was strange at first, but apparently fatty acids are absorbed more readily when they are mixed with other triglycerides (the main constituent of fats and oils).  So, this tells us that absorption of fatty acids varies from person to person and depends in part on diet. 

What the researchers found was that the subjects (the ones who were able to absorb the radioactively-labeled fatty acids) converted between 6% and 14% of the stearic acid and between 2.8% and 4.2% of the palmitic acid to monounsaturated fatty acids.   (Not all saturated fatty acids behave similarly, however.)

OK, so, this little study was not earth-shaking, but it supports the statement that a percentage of saturated fatty acids are converted in the human body to oleic acid (again, oleic acid is a monounsaturated fatty acid that makes up about 75% of the fat in olive oil),  with the amount of conversion varying from person to and person and being dependent, to some degree, on diet.

As you may have noticed, we are again kind of circling around to the beginning of the fat story.  We started with saturated fatty acids in the first blog post, and I am still talking about saturated fatty acids in the last one.  Well, I really have no choice, because ALL of the saturated fatty acids can be converted to monounsaturated fatty acids (each of the saturated fatty acids has its own complementary monounsaturated fatty acid).  So it’s impossible to talk about one without the other.

Let me also point out that saturated fatty acids account for between 30% and 40% of total fatty acids in animal tissues, with palmitic acid comprising 15-25% of saturated fatty acids, stearic 10-20%, myristic acid 0.5%-1%, and lauric less than 0.5%.

And let me say something else:  as of 2010, stearic acid appears to have NO effect on cardiovascular disease.  It is neutral—although it may be involved in promoting obesity.  Wonder if olive oil makes you fat?  With all the great things we hear about olive oil, I guess not.

What about palmitic acid (the number one saturated fatty acid)?  Now this is really interesting—it can be converted into a monounsaturated fatty acid (sapienic acid) that has been implicated in the development of acne!   And the story gets even more interesting.    Myristic acid (a saturated fatty acid found in coconut oil and butter) can either be converted into one of the polyunsaturated omega-3 fatty acids, or enhance their formation!  What??  And get this:  in humans, a diet with myristic acid comprising less than 1.2% of energy requirements ENHANCED omega-3 fatty acids (DHA and EPA), while a diet with more than 1.2% DECREASED omega-3 fatty acids!

Okay, I think this is a good place to pause.  What do we know?  Well, saturated fatty acids are not a uniform class—they have different metabolic end points with different effects. Different concentrations in diets may have different, even opposite, results.  All of this supports my conclusion in blog post #1 that the relationship between saturated fatty acids and cardiovascular disease is not settled.  Heck, the right amount of myristic acid may be as good as eating fish oil!

Just for fun, let’s look at the three most common saturated fats individually:

1.             The evidence indicates that STEARIC acid does not cause cardiovascular disease.

2.   I found no evidence that PALMITIC acid has any effect on cardiovascular disease.

3.   I found no evidence that MYRISTIC acid has any effect on cardiovascular disease.

So at present, there appears to be no basis for believing that the top three saturated fatty acids cause harm to the human cardiovascular system.   So what’s left in this class of fatty acids?  Could it be lauric acid (less than 0.5% of animal tissues) that’s causing all the trouble?  No, it has been has been shown to increase HDL (the “good” cholesterol).   So why all the ranting and raving about lowering saturated fat?  I have no idea. 

I should also point out that, of course, we don’t eat saturated fats, or any other fatty acids, in a vacuum.  They come to us as complex mixtures, and who knows how they react with each other.   Maybe two “good” fatty acids make something harmful.  Or vice versa.  I don’t know, and I’d be willing to bet that nobody else does either.  But one thing we do know is that the saturated fat story is not nearly as clear-cut as the Mayo Clinic’s dietary recommendation would lead you to believe.  And besides that, it’s probably just outright WRONG.

Okay, back to monounsaturated fatty acids.  At this point, you can probably guess that we shouldn’t focus on the monos as a uniform class.  The saturated fats aren’t, and neither are the polyunsaturated fats.  So let’s look at some of the monos as individual fatty acids.  First, the most popular one:  oleic acid, named after the olive (genus Olea, get it?).  Who says scientists don’t’ have a sense of poetry!

Certainly olive oil gets a lot of favorable press.  It is central to the “Mediterranean Diet,” and it has been correlated with both fat loss and increased cardiovascular health.  I found almost no information saying that olive oil is bad for you—in fact, just the opposite.   It has been correlated with an increase in the oxidation of many fatty acids—so maybe it helps “burn” other fats.  It has been associated with decreasing LDL (the “bad” cholesterol), increasing HDL, and decreasing blood pressure.  And while there is a small amount of data indicating that olive oil may promote breast cancer, there is also evidence that it may inhibit breast cancer.   So I guess I place oleic acid in the class of one of the “good” monos.  With the breast cancer caveat.

The next most common monounsaturated fatty acid is palmitoleic acid.

Well, in searching  the web for data on palmitoleic acid and found a 2011 editorial.  Great—current literature.  The writer’s only citation was  a 1994 study showing that a diet rich in palmitoleic acid increased LDL (bad cholesterol) and decreased HDL (good cholesterol).  As usual, I went to the study myself to see what the authors actually reported, and it’s a good thing I did, since the actual data showed the exact OPPOSITE.  In comparison with a baseline “normal” diet, the high-palmitoleic diet very slightly increased HDL, decreased LDL, and decreased total cholesterol.  Beneficial results all around.  So how did the reviewer get it so wrong?  Well, the study did report  that palmitoleic acid decreased HDL and increased LDL, but only relative to oleic acid.  So in other words, palmitoleic acid didn’t increase HDL or increase LDL quite as much as oleic acid did.   And guess what—in the same study, it was found that palmitic acid (a saturated fat) increased good HDL cholesterol more than palmitoleic acid did (even though palmitoleic acid is a monounsaturated fat).  Palmitic acid also lowered LDL cholesterol as much as palmitoleic acid did, although not as much as oleic acid.  And it’s worth noting that even though the differences were apparently statistically significant, they were very very small.

All of this is just so complicated and interconnected.  Like blindly feeling something rough and thinking it is an elephant, when it is really a rhino.  Or an oak tree. 

So I throw my hands in the air.   I’ve run out of energy trying to figure it out.  Shoulders sagging, I’m about done with this fatty acid mess.  And here is where I stand after a four-week review of the literature:

1.             Most dietary recommendations regarding consumption of saturated, monounsaturated, and polyunsaturated fatty acids are misleading, overly simplistic, and probably wrong.

2.            There is conflicting data regarding saturated fats, but they are probably at least neutral and may even be good for you.  I guess it’s possible that they could be bad, but the support for that proposition is sketchy at best.

3.            Polyunsaturated fatty acids are a mixed bag, some good (omega-3 fatty acids) and some bad (omega-6 fatty acids).

4.            Synthetic trans fats are bad, and natural trans fats are good.

And where have a few decades of recommendations to “reduce our saturated fat intake”  gotten us?  McDonald’s french fries are a good example.   They used to be cooked in beef tallow, but in 1990 McDonald’s switched to partially hydrogenated vegetable oil to reduce saturated fat and thus make them “healthier”.  Then in 2002 it was announced that they would be again be changing their french fry oil, this time to a different vegetable oil that was lower in trans fats.  And finally in 2009 it was announced that McDonald’s oil would in the future be 100% trans fat free.  So what has really happened is that saturated fats (neutral or good) and monounsaturated fats (good) have gradually been replaced by trans fats (bad) and/or unspecified polyunsaturates (either bad or good).

Take a look at the fat profiles of the different cooking oils McDonald’s has used in the past 30 years.  With any luck, they may eventually go back to beef tallow.

MCDONALD’S FRENCH FRY OIL (UNITED STATES)*

	Saturated	Monounsaturated	Polyunsaturated	Trans fat
Beef tallow (before 1990)	43%	50%	4%	3% or less (naturally-occurring)
Vegetable oil (announced 1990)	23%	32%	12%	33% (synthetic)
Vegetable oil (announced 2002)	19%	32%	32%	18% (synthetic)
Canola/corn/soy blend (announced 2009)	14%	?**	?**	0% (or less than 1%)

  *All percentages rounded to closest whole number, which may result in a total other than 100%.

**I couldn’t find any numbers for monounsaturates or polyunsaturates in the oil McDonald’s is currently using.

For purposes of comparison, here are fat profiles for some of the most common oils used for cooking in the United States.

OILS COMMMONLY USED IN COOKING*

	Saturated Fat	Monounsaturated Fat	Polyunsaturated Fat
Canola oil	7%	63%	28%
Olive oil	14%	73%	11%
Corn oil	15%	30%	55%
Soybean oil	16%	23%	58%
Lard	39%	45%	11%
Coconut oil	91%	6%	3%

*All percentages rounded to closest whole number, which may result in a total other than 100%.

So what am I going to do with my own diet?  Use lard for frying, use olive oil for everything else, and increase my omega-3’s by taking fish oil capsules.  Avoid synthetic trans fats, (which will not be difficult because they have been eliminated from most foods already).  Take my Lipitor.  Reduce carbs and sugar except when I’m exercising, which is most of the time!