In this Part IV of the series (Part I; Part II; Part III), I have decided to do go about this in a different way than I’d indicated before. I covered the Paleo Principle in Part II, but more in terms of our having evolved to eat meat and not with a lot of specifics about saturated fat in particular. Accordingly, this is perhaps what Part III would have been had I not got sidetracked on cognitive dissonance.
One of the pioneers of the Paleo Diet is Dr. Loren Cordain, PhD. Back in the early 2000s he wrote and published The Paleo Diet. It’s a frustrating read because, whereas he got so much right, he just wasn’t correct on the issue of saturated fats in the view of so many, including myself. I’ve blogged about this before. While he was certainly correct about the fat composition of wild animals vs. today’s manufactured ones, many believed he went way overboard in recommending lean meats, avoiding chicken skin, using processed canola oil for god’s sake, etc. And many rightly pointed out that everything we know about hunter-gatherers suggests that they prized fat above all.
What’s now important, however, is that Dr. Cordain recently got wind of something that has caused him to backtrack on saturated fat. His latest paper:
Dietary Fat Quality and Coronary Heart Disease Prevention: A Unified Theory Based on Evolutionary, Historical, Global, and Modern Perspectives
Christopher E. Ramsden, MD; Keturah R. Faurot, PA, MPH; Pedro Carrera-Bastos, BA; Loren Cordain, PhD;
Michel De Lorgeril, MD, PhD; Laurence S. Sperling, MD
The money quote:
The Seven Country Study, a cross-cultural analysis, reported strong positive associations among a population’s average SFA intake, serum total cholesterol concentrations, and 25-year death rates from CHD. However, it is important to note that several groups with very high SFA intakes from coconut fat (up to 40% of energy) and apparently low CHD rates have since been identified. In the Nurses’ Health Study, a large prospective cohort study, a weak but significant positive association between SFA intake and CHD risk was initially seen. With long-term follow-up, this association was no longer significant. Any association between SFAs and CHD appears to be a small fraction of that observed for TFAs [trans-fatty acids]. Other observational studies and dietary trials have been unconvincing or even contradictory. In general, experimental evidence does not support a robust link between SFA intake and CHD risk.
Coconut fat is almost 90% saturated fat. I’ll save the details on those populations for a subsequent post in the series.
In summary, high total cholesterol or LDL levels do not increase CVD risk–rather oxidized LDL increases risk of CVD. To produce oxidized LDL requires the factors mentioned above. Hence, consumption of saturated fatty acids is not an issue if we control several other factors such as those mentioned.
Now that’s an enormous step from using the arterycloggingsaturatedfat mantra over and over in his book. So then, Dr. Cordain seems to have realized that fear of saturated fat just didn’t pass the smell test. While he chose to focus in on epidemiology that I’ll address later, here’s four good reasons to believe that saturated fat is not only not harmful but on the contrary, quite healthful.
1. Guess what happens to 100% of excess dietary carbohydrate, i.e., once liver and muscle glycogen (stored carbs) is full up (about 2,000 kcals)? It gets converted to fat. What kind, you ask? I’m glad you asked: palmitic acid. And what’s that, you ask? I’m glad you asked again: saturated fat. The evildoer.
I wanted to confirm this once again so I asked Dr. Stephen Guyenet, PhD (biology):
If it isn’t burned or stored as glycogen, it’s turned into palmitic acid in the liver and exported in VLDLs. It’s called de novo lipogenesis. There’s a caveat though: under average fat:carb ratios not much de novo lipogenesis (DNL) happens. Fructose and alcohol gets turned into palmitic acid pronto, and very high-carb diets promote DNL too. The Kitavans have a bunch of palmitic acid in their lipoproteins even though their dietary intake of palmitic acid is low.
Yes, so even if you aren’t eating carbs to super excess, still, all fructose and alcohol go straight to the liver and converted into saturated fat immediately.
2. What’s the composition of your own body fat which, actually, is in a constant state of turnover?
Lard: 38 percent saturated, 11 percent polyunsaturated, and 45 percent monounsaturated with the rest being trace fats.
Human: 35 percent saturated, 51 percent monounsaturated, and the rest polyunsaturated and trace.
Pretty similar. So if saturated fat intake above 10% of total calories is such a killer, then how come your own body uses it to the tune of 35% of all fat storage?
3. And how about all that fiber you are admonished to eat? All those fruits (oops: fructose; palmitic acid), vegetables, legumes & grains? Ever heard of Butyrate? You can also call it butyric acid and it’s a saturated fat. Guess how you get it in your diet? Well, the chief source is butter (get it: BUTyrate). But there’s another source too. Turns out the bacteria in your gut produce it when they go to work on fiber, both soluble and insoluble.
Dr. Guyenet recently posted all about it for those who want the depth.
…In industrialized countries, fiber may contribute 5 to 10 percent of total calorie intake, due to its conversion to short-chain fatty acids like butyrate in the large intestine (free full text). This figure is probably at least twice as high in cultures consuming high-fiber diets. It’s interesting to think that "high-carbohydrate" cultures may be getting easily 15 percent of their calories from short-chain fats. Since that isn’t recorded in dietary surveys, they may appear more dependent on carbohydrate than they actually are. The Kitavans may be getting more than 30 percent of their total calories from fat, despite the fact that their food is only 21 percent fat when it passes their lips. Their calorie intake may be underestimated as well.
4. And last but not least, human breast milk is a whopping 41% saturated fat.
Saturated fatty acids, polyunsaturated fatty acids and monounsaturated fatty acids of human milk constituted 40.7 ± 4.7%, 26.9 ± 4.2% and 30.8 ± 0.6% of the total fatty acids, respectively.
So, given the above and pretending you know nothing of the bad reputation of saturated fat over the last four decades & more, would you not be quite surprised to be told it was unhealthful, a killer? Since it exists in such high concentrations in our own biology, would you not rather assume it to be rather healthful?