Is Saturated Fat Bad for You? - Aspire Natural Health

Is Saturated Fat Bad for You?

After being told repeatedly for the past 20 years that saturated fat is the most evil of all nutrients, we finally see the truth emerging that saturated fat is, in fact not only NOT unhealthy, but it is actually healthy for us.

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UPDATE:  As always the concept of bio-chemical individuality (we are all a bit different) reigns supreme.  While saturated fat is really NOT a problem for most of us, there are people who do poorly on a diet containing more saturated fat.  Or who do poorly on a lower-carb higher fat diet.  What these studies tell us is that the fear around saturated fat is wrong, but as always, we need to find what the right diet for each of us is.

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Ask anyone about saturated fat and they will tell you that it will clog your arteries and give you a heart attack or a stroke, or that it will make you diabetic.  In fact, it does none of these things.

Two articles have recently been published that lend proof to these (perhaps) shocking words.

The first:

Am J Clin Nutr. 2010 Mar,91(3):535-46. Epub 2010 Jan 13. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.  Siri-Tarino PW, Sun Q, Hu FB, Krauss RM.

And the study concluded:  “A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD [heart attack] or CVD [stroke].”

The second:

Am J Clin Nutr. 2010 Mar,91(3):502-9. Epub 2010 Jan 20.  Saturated fat, carbohydrate, and cardiovascular disease.  Siri-Tarino PW, Sun Q, Hu FB, Krauss RM.

The study concluded: “In summary, although substitution of dietary polyunsaturated fat for saturated fat has been shown to lower CVD risk, there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate. Furthermore, particularly given the differential effects of dietary saturated fats and carbohydrates on concentrations of larger and smaller LDL particles, respectively, dietary efforts to improve the increasing burden of CVD risk associated with atherogenic dyslipidemia should primarily emphasize the limitation of refined carbohydrate intakes and a reduction in excess adiposity.”

Which is a complicated way of saying that replacing saturated fat in the diet with more carbohydrate, which is what virtually all mainstream nutrition advice suggests you do, causes MORE build-up in the arteries (and a higher risk of heart attack and stroke).  Instead, the authors of the study suggest that refined carbohydrates (such as sugar and flour) should be limited.

A new meta-analysis

But wait! You might say.  Didn’t I just hear about a new study just come out the other day saying that replacing saturated fat with seed oils (polyunsaturated fat) lowers the risk of heart disease?

The study:

Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials Dariush Mozaffarian, Renata Micha, Sarah Wallace.

Doesn’t this suggest we’d be healthier if we replaced the saturated fat in my diet with vegetable oils?  Stephan Guyenet, PhD has done a very nice analysis of this study (which I’ve posted below), suggesting it’s fundamentally flawed, and you’d be better off ignoring it.

If you have not read Stephan’s blog, and this sort of thing interests you, you owe it to yourself to get over there.  He has a wealth of posts on a variety of health and nutrition related issues

Rebuttal by Stephen Guyenet

March 23, 2010

New Review of Controlled Trials Replacing Saturated fat with Industrial Seed Oils

Readers Stanley and JBG just informed me of a new review paper by Dr. Dariush Mozaffarian and colleagues. Dr. Mozaffarian is one of the Harvard epidemiologists responsible for the Nurse`s Health study. The authors claim that overall, the controlled trials show that replacing saturated fat with polyunsaturated fat from industrial seed oils, but not carbohydrate or monounsaturated fat (as in olive oil), slightly reduces the risk of having a heart attack:

These findings provide evidence that consuming PUFA in place of SFA reduces CHD events in RCTs [how do you like the acronyms?]. This suggests that rather than trying to lower PUFA consumption, a shift toward greater population PUFA consumption in place of SFA would significantly reduce rates of CHD.

Looking at the studies they included in their analysis (and at those they excluded), it looks like they did a very nice job cherry picking. For example:

  • They included the Finnish Mental Hospital trial, which is a terrible trial for a number of reasons. It wasn`t randomized, appropriately controlled or even semi-blinded*. Thus, it doesn`t fit the authors` stated inclusion criteria, but they included it in their analysis anyway**. Besides, the magnitude of the result has never been replicated by better trials, not even close.
  • They included two trials that changed more than just the proportion of SFA to PUFA. For example, the Oslo Diet-heart trial replaced animal fat with seed oils, but also increased fruit, nut, vegetable and fish intake, while reducing trans fat margarine intake! The STARS trial increased both omega-6 and omega-3, reduced processed food intake, and increased fruit and vegetable intake! These obviously aren`t controlled trials isolating the issue of dietary fat substitution. If you subtract the four inappropriate trials from their analysis, which is half the studies they analyzed, the result disappears. Those four just happened to show the largest reduction in heart attack mortality…
  • They excluded the Rose et al. corn oil trial and the Sydney Diet-heart trial. Both found a large increase in total mortality from replacing animal fat with seed oils, and the Rose trial found a large increase in heart attack deaths (the Sydney trial didn`t report CHD deaths, but Dr. Mozaffarian et al. stated in their paper that they contacted authors to obtain unpublished results. Why didn`t they contact the authors of this study?).

The authors claim, based on their analysis, that replacing 5% of calories as saturated fat with polyunsaturated fat would reduce the risk of having a heart attack by 10%. Take a minute to think about the implications of that statement. For the average American, that means cutting saturated fat nearly in half to 6% of energy, which is a real challenge if you want to have a semblance of a normal diet. It also means nearly doubling PUFA intake, which will come mostly from seed oils if you follow the authors` advice.

So basically, even if the authors` conclusion were correct, you overhaul your whole diet and replace natural foods with bland unnatural foods, and…? You reduce your 10-year risk of having a heart attack from 10 percent to 9 percent. Without affecting your overall risk of dying! The paper states that the interventions didn`t affect overall mortality at all. That`s what they`re talking about here. Sign me up!

* Autopsies were not conducted in a blinded manner. Physicians knew which hospital the cadavers came from, because autopsies were done on-site. There is some confusion about this point because the second paper states that physicians interpreted the autopsy reports in a blinded manner. But that doesn`t make it blinded, since the autopsies weren`t blinded. The patients were also not blinded, so the study overall was highly susceptible to bias.

** They refer to it as “cluster randomized”. I don`t know if that term accurately applies to the Finnish trial or not. The investigators definitely didn`t randomize the individual patients: whichever hospital a person was being treated in, that`s the food he/she ate. There were only two hospitals, so “cluster randomization” in this case would just refer to deciding which hospital got the intervention first. Can this accurately be called randomized?

Bottom line:

If you want to care for your heart and health, forgot about saturated fat and concentrate on reducing refined carbohydrates (sugar and flour, the ‘crack’ of our food supply). Update:  But make sure you have a good health professional on your team to make sure that what you’re doing is really working for you.

Other resources

Have a hard time swallowing that saturated fat could possibly be healthy?  Don’t take my word for it, check out the following resources.

  • Good Calories, Bad Calories – THE book.  It’s thick and quite a read, but if you want to understand the past 100 years of nutrition science and how the whole idea that saturated fat is bad for you got started, you owe it to yourself to read this book.  UPDATE:  While some people vigorously debate Taubes’ conclusions, no one has debated his history of the science
  • Great Cholesterol Con by Malcolm Kendrick – Cholesterol is also NOT bad for you.  This is a very readable, user friendly book written by a British medical doctor (MD).  Highly recommended

And a trio of great blogs

  • Whole Health Source Blog – Stephen Guyenet, PhD’s blog.  Highly recommended
  • High Fat Nutrition Blog – by Petro Dobromylskyj a British vet.  Quite technical, but Peter does a fantastic job of analyzing studies and revealing what they truly show.
  • Michael Eades Blog – very readable blog by Michael Eades, MD a long time proponent of a carbohydate controlled eating style.  Some fantastic gems in the archives.

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