What Do You Really Know About Dietary Fat?

A commenter on my recent Lard post highlighted a post by Dr. Mary Dan Eades, and that reminded me of a section in Taubes' Good Calories Bad Calories.

Let's take a look at both. First to Eades.

Now let’s compare lard to that darling of the disciples of the Mediterranean diet: olive oil. Olive oil contains 71% oleic acid, that heart-healthy, monounsaturated fat that we’re supposed to get more of. Lard contains 44% oleic acid, which is more than sesame oil (41%) and double or nearly so the amount in corn oil (28%), walnut oil (28%), and flaxseed oil (21%), more than double the amount in cottonseed oil (19%) and sunflower oil (19%), and nearly triple that in grapeseed oil (15%) and safflower oil (13%). The oleic acid content of lard also exceeds that in beef tallow (43%), butterfat (29%), and human butterfat (ie the fat of breast milk at 35%).

Lard also contains a fair amount (14%) of the 18-carbon saturated fat, stearic acid, which has been shown in clinical testing to lower cholesterol. […]

Like olive oil, lard contains 10% of the omega-6 fatty acid linoleic acid, again, roughly the same as human butterfat (breast milk) at 9%.

Lard contains 2% myristic acid, a 14-carbon saturated fat that has been shown to have important immune enhancing properties. Human butterfat contains about 8% myristic acid, as a booster for the newly minted and incompetent infant immune system. Other animal milk fats also contain a fair amount. By comparison with the exception of cottonseed oil (1%) and the tropical oils, coconut oil (18%) and and palm kernal oil (16%) vegetable oils have zero.

The big bugaboo with lard, then, must come from the last component of its composition: palmitic acid a 16-carbon saturated fatty acid that is believed by some to be Beelzebub, Barlow, and the Bermuda Triangle all rolled into one. Lard contains 26% of the stuff and olive oil only 13%. Aha! There it is. The smoking gun! That must be what makes lard so bad and olive oil so good!

And the punchline:

There’s one fly in that explanatory ointment, however: human butterfat contains 25% palmitic acid, just a silly 1% different from lard. Are we to believe that nature would have designed a food for human infants that contained too much?

So let’s now compare lard’s basic fatty acid composition to the real gold standard, the butterfat of human breast milk and see how it stacks up.

Saturated Monounsaturated Polyunsaturated
Breast Milk 48% 35% 10%
Lard 42% 44% 10%

Here's what this reminded me of in Taubes:

The observation that monounsaturated fats both lower LDL
cholesterol and raise HDL also came with an ironic twist: the
principal fat in red meat, eggs, and bacon is not saturated fat,
but the very same monounsaturated fat as in olive oil. The
implications are almost impossible to believe after three
decades of public-health recommendations suggesting that any
red meat consumed should at least be lean, with any excess
fat removed.

Consider a porterhouse steak with a quarter-inch layer of
fat. After broiling, this steak will reduce to almost equal parts
fat and protein. Fifty-one percent of the fat is
monounsaturated, of which 90 percent is oleic acid. Saturated
fat constitutes 45 percent of the total fat, but a third of that
is stearic acid, which will increase HDL cholesterol while
having no effect on LDL (Stearic acid is metabolized in the
body to oleic acid, according to Grundy's research.) The
remaining 4 percent of the fat is polyunsaturated, which lowers
LDL cholesterol but has no meaningful effect on HDL. In
sum, perhaps as much as 70 percent of the fat content of a
porterhouse steak will improve the relative levels of LDL and HDL cholesterol, compared with what they would be if
carbohydrates such as bread, potatoes, or pasta were
consumed. The remaining 30 percent will raise LDL
cholesterol but will also raise HDL cholesterol and will have
an insignificant effect, if any, on the ratio of total cholesterol
to HDL. All of this suggests that eating a porterhouse steak
in lieu of bread or potatoes would actually reduce heart-disease risk, although virtually no nutritional will say so publicly. The same is true for lard and bacon.

Do you understand what you're up against?

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  1. Chris - Zen to Fitness on September 21, 2008 at 02:39

    This is a great post, it lays things out very clearly but sadly I bet you culd show it to the "low fat" crowd and they would all fail to believe it or doubt the truth.

    Great progress BTW and well done with your blogging the weekends posts have been a joy to read….

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