Are Saturated Fats Really All That Bad?
Increasingly, scientists are thinking that the link between dietary saturated fats and heart disease is not strong, and may be nonexistent. I recently reviewed the evidence and found that:
- Some studies show no association between dietary saturated fats and heart disease.
- Some studies associate lower rates of heart disease with higher saturated fat intake.
- Higher saturated fat intake was associated with less progression of heart atherosclerosis in women.
- In a number of clinical studies, lowering saturated fat intake did not reduce deaths from heart disease or any cause.
For the last 40 years, U.S. public health agencies have told us that saturated fats - mostly derived from animal products such as red meat - are a major cause of heart disease and strokes. Saturated fats are a component of the Diet-Heart Hypothesis or the "lipid hypothesis," which can be summarized thusly:
Dietary saturated fat, total fat, and cholesterol are directly related to coronary heart disease and other forms of atherosclerosis.
Current public health recommendations are, essentially, to keep saturated fatty acids as low as possible.
Why would saturated fats be harmful? Apparently because they raise blood levels of cholesterol (including LDL cholesterol - "bad cholesterol"), which is thought to be a cause of atherosclerosis, which increases the risk of coronary heart disease and stroke.
Many of the journal articles listed below support the idea that the link between dietary saturated fats and heart disease is not strong. Read them, if you have the time, and I think you'll begin to question the reigning dogma.
For example, here's a conclusion from the Hooper article:
In this review [2001] we have tried to separate out whether changes in individual fatty acid fractions are responsible for any benefits to health (using the technique of meta-regression). The answers are not definitive, the data being too sparse to be convincing. We are left with a suggestion that less total fat or less of any individual fatty acid fraction in the diet is beneficial.
And a conclusion of the J.B. German article:
At this time[2004], research on how specific saturated fatty acids contribute to coronary artery disease and on the role each specific saturated fatty acid play in other health outcomes is not sufficient to make global recommendations for all persons to remove saturated fats from their diet.
Zarraga and Schwartz (2006) conclude:
Numerous studies have been conducted to help provide dietary recommendations for optimal cardiovascular health. The most compelling data appear to come from trials that tested diets rich in fruits, vegetables, MUFAs [monounsaturated fatty acids], and PUFAs [polyunsaturated fatty acids], particularly the n-3 PUFAs. In addition, some degree of balance among various food groups appears to be a more sustainable behavioral practice than extreme restriction of a particular food group.
Here's another of my favorite quotes on this topic, from the J.B. German article:
If saturated fatty acids were of no value or were harmful to humans, evolution would probably not have established within the mammary gland the means to produce saturated fatty acids . . . that provide a source of nourishment to ensure the growth , development, and survival of mammalian offspring.
What do you think?
-Steve Parker, M.D.
Disclaimer: All matters regarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status. Always consult your personal physician before making any dietary or exercise changes.
References (updated September 25, 2009):
Skeaff, C. Murray and Miller, Jody. Dietary fat and coronary heart disease: Summary of evidence from prospective cohort and randomised controlled trials. Annals of Nutrition and Metabolism, 55 (2009): 173-201.
German, J. Bruce, and Dillard, Cora J. Saturated fats: what dietary intake? American Journal of Clinical Nutrition, 80 (2004): 550-559.
Ravnskov, U. The questionable role of saturated and polyunsaturated fatty acids in cardiovascular disease. Journal of Clinical Epidemiology, 51 (1998): 443-460.
Ravsnskov, U. Hypothesis out-of-date. The diet-heart idea. Journal of Clinical Epidemiology, 55 (2002): 1,057-1,063.
Ravnskov, U, et al. Studies of dietary fat and heart disease. Science, 295 (2002): 1,464-1,465.
Taubes, G. The soft science of dietary fat. Science, 291 (2001): 2535-2541.
Zarraga, Ignatius, and Schwartz, Ernst. Impact of dietary patterns and interventions on cardiovascular health. Circulation, 114 (2006): 961-973.
Mente, Andrew, et al. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Archives of Internal Medicine, 169 (2009): 659-669.
Parikh, Parin, et al. Diets and cardiovascular disease: an evidence-based assessment. Journal of the American College of Cardiology, 45 (2005): 1,379-1,387.
Hooper, L., et al. Dietary fat intake and prevention of cardiovascular disease: systematic review. British Medical Journal, 322 (2001): 757-763.
Weinberg, W.C. The Diet-Heart Hypothesis: a critique. Journal of the American College of Cardiology, 43 (2004): 731-733.
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Posted by: Eleanor | Jul 6, 2009 4:18:39 PM
I take Coumadin, what are the best foods for me to eat? I am 80 years old and just started with the coumodin.My Doctor said to take the same Vitiman K each day in food. WHAT foods would be best??
Posted by: Steve Parker, M.D. | Jul 7, 2009 11:40:05 AM
Hi, Eleanor. Monica Reinagel covered your coumadin/vit K question very well here:
http://blog.nutritiondata.com/ndblog/2007/01/broccoli_wars_v.html
Your pharmacist would also love to help you with this issue.
-Steve
Posted by: Peter | Jul 7, 2009 1:09:53 PM
Apart from a few extreme cases (nicotine being one), it strikes me beyond doubt that the key is moderation across all permutations. The difficulty is, because the bar seems to change so regularly, knowing what moderation is becomes difficult from one week to the next. I speak from experience as a high cholesterol sufferer - the eternal quandary is whether animal products are to blame. And if they are, to what degree do I limit them.
Posted by: Abalone | Jul 7, 2009 3:44:44 PM
Thanks. The world needs all the sunshine it can get on the iffy nutritional dogma that pervades the discussion.
Posted by: sss | Jul 8, 2009 11:53:32 AM
nice post steve. moderation among the macronutrients - fat, protein and carbohydrates - at least as conventionally understood - is not the key. not at all. "moderation" would suggest a 1/3, 1/3, 1/3 split. but since we evolved on meat and could not possible have encountered carbs in such high amount before agriculture - which itself is only 10-12 thousand years old - then the right solution is the avoidance or at least radical reduction of starches and sugars from the diet. meat and eggs and butter and cheese are the answer while avoiding starch and sugar. read gary taubes, wolfgang lutz, the drs. eades, mary vernon, volek, phinney, su, malcolm kendrick.
Posted by: Kurt | Jul 16, 2009 5:11:22 PM
The J.B. German quote assumes that the optimum infant diet is the optimum adult diet. Infants have different dietary requirements, and they stop being breast fed at a certain age.
Not sure if these articles mean to question the diet-heart connection or the cholesterol-heart connection. Because I lowered my LDL cholesterol from 155 to 95 in two months on a diet that restricted saturated fat. Of course it's possible that some other aspect of the diet had the effect.
Posted by: Jack | Jul 16, 2009 10:13:24 PM
The next question, is that although some people think saturated fat increases cholesterol, is high cholesterol the cause of heart disease or one of the many symptoms? I would say inflammation and damage is the cause of heart disease and cholesterol mearly acts to repair the damage.
Posted by: Steve Parker, M.D. | Jul 22, 2009 2:57:20 PM
Kurt, I have to think your drop in LDL cholesterol is probably good for you. Good job.
I purposely avoided the cholesterol-heart connection in my post above. I bet Monica Reinagel has covered that at her NutritionData blog. And she's usually right. In fact, I can't think of a time when she's been wrong.
At this point, I think high blood LDL levels are causally related to heart attacks. But we sure see a lot of heart attacks in people with "normal" total and LDL cholesterol levels. That's why we need a multi-pronged approach to prevention and treatment of heart disease.
-Steve
Posted by: Bob Rogers | Jul 27, 2009 4:00:22 PM
I exercise daily, vigorously, am very fit for 65. I regularly beat 30 somethings in cycling.
I have tried two diets:
1. Almost no fat of any kind. Result: LDL went UP.
2. Dr Andrew Weil's anti inflammatory diet. Result: Total cholesterol count dropped 60 points, and I experienced a jump in athletic performance and well being. HOWEVER: 14 months later, no change in diet, my total cholesterol went up 50 (to 229) points to nearly the original level. My HDL also went from 50 to 65. However, my athletic performance continues to improve!
My doctor says it's genetics and wants me to go on cholesterol lowering drugs. I fear the muscle weakening and pain side effects will cause me to stop exercising, and that could be worse other areas of my physical and mental health, not to mention weight (I now have 5% body fat).
This is all very confusing. I do everything right, and reap the benefits, but the numbers are bad. I don't know what to do?
Posted by: Steve Parker, M.D. | Jul 30, 2009 6:51:57 PM
Bob Rogers, I understand your dilemma. I'd like to say you and your doctor are worrying too much about a lab test, but I can't do that since I don't know all the details of your case, and haven't examined you. Your specific LDL level, results of cardiac imaging or stress tests, and family history may be key to the decision in your case.
It sounds like you're considering the statin class of drugs to lower cholesterol levels. Remember that the side effects are nearly always totally reversible upon drug discontinuation.
Also note that there are non-statin drugs to lower cholesterol, such as ezetimibe, bile acid sequestrants, and niacin.
If your doctor seems to insist on a statin, you might want a second opinion from a cardiologist.
Best wishes,
-Steve
Posted by: SnowDog | Aug 5, 2009 12:13:51 PM
I don't have the link to the studies, but from what I've seen in the past year, saturated fat does raise cholesterol. It raises HDL significantly. I also raises LDL, but when closely analyzed, the LDL particle count actually drops, while the LDL measurement will go up. This occurs when average LDL particle size increases, and leads to an overall better lipid profile. Apparently, some of the smaller HDL are being counted as LDL.
Posted by: Beatle | Aug 5, 2009 3:58:59 PM
SNowdog,
It raises LDL mainly because of the way LDL is calculated. Since your Tryglycerides drop, it affects the mathematical equation, pretty much guarantying an elevation in LDL (regardles if there is actually one. Most cholesterol tests don't measure LDL directly)
Posted by: Gripe | Aug 5, 2009 8:07:52 PM
We store SFA (among other fats) in adipose tissue for lipolysis - How on Earth could it possibly be bad for us? If you actually read the medical research, apart from the standard hat tip to current dogma in the discussion, the "fat is bad" argument is virtually non-existent.
Reducing fat from the diet often reduces LDL-C, however the concentration of LDL is not as relevant as the particle size, since only small particles can penetrate the endothelium and are prone to oxidation. A low fat diet actually shifts the LDL profile to predominately pattern B. So although your LDL concentration may have gone down, the actual number of susceptible particles may well have gone up. Reducing carbohydrate intake, on the other hand, shifts LDL profile towards pattern A, and the increased fat intake also increases HDL-C while reducing TG-C. As for whether SFA in particular is "bad"; provided you don't flood the body with Omega-6 PUFA (pro-inflammatory) and transfats (cause rigidity in the cell membrane), it doesn't matter what type of fat you eat (although fats from non-organic meat are unfortunately likely to contain pesticides and other chemicals that may be harmful to us). Check the lipid profiles of various oils, and you will see that those highest in Omega-6 are the unnatural PUFA vegetable oils, while strangely the more natural animal fats that we have eaten for 4 million years are low in Omega-6 yet high in SFA. Coincidence?
Posted by: Trinkwasser | Aug 10, 2009 3:29:09 PM
Great to see yet another source of dietary sense! Great points from all contributors. My experience is also that total cholesterol went UP on a low fat diet, and LDL went up even further on further reduction of fat, to the extent my dietician accused my of not complying with her diet.
So I did the exact opposite and everything fell into line, not surprising when you consider the liver spends a lot of time making stuff into other stuff, and one of its tricks is to convert excess carbs into, yes, saturated fat.
I'm prepared to believe that some people are able to make a high carb low fat diet work for this reason, but they are probably a significant minority of the population, looking at the results of Ancel Keys' 40 year long RCT.
Most papers finding sat fats to be harmful actually find that sat fats *in the presence of excess carbs* are harmful. Do away with the carbs and things work quite differently.
Posted by: Steve Parker, M.D. | Aug 11, 2009 12:53:53 PM
Hey, Trinkwasser -
I assume "RCT" means randomized controlled trial. A huge problem with Ancel Key's diet-heart hypothesis is that there never was a randomized controlled trial of it before it became U.S. national food policy 30 years ago.
Read all about the details in Gary Taubes' "Good Calories, Bad Calories" book from 2007. I only started reading it a few days ago. Something tells me you've already seen it, TW.
-Steve
Posted by: John Myers | Aug 18, 2009 5:40:15 PM
Good Calories, Bad Calories is an amazing book. It's very dense and I had to read some of the chapters four times or more before I took hold of the concepts.
If anyone finds it too dense, wikipedia's Gary Taubes entry has links to videos of him giving one hour or so lectures that pull concepts from his book.
Once you watch the videos though you'll want to try the book again.
Here's a link to one of the lectures he gave at UC Berkeley - I hope you don't mind.
http://webcast.berkeley.edu/event_details.php?webcastid=21216
great article, Steve.
Posted by: Steve Parker, M.D. | Aug 18, 2009 6:24:28 PM
Thanks, John. I hear Taubes may be working on a version of the book for general consumption. I'm reading with a dictionary nearby - had to look up "tautology" and "solecism."
-Steve
Posted by: Trinkwasser | Sep 1, 2009 8:46:19 AM
Shush, don't interrupt! I'm still reading it and probably will be for years. There's a Cliff's Notes version here
http://www.nytimes.com/2002/07/07/magazine/what-if-it-s-all-been-a-big-fat-lie.html
and here
http://www.second-opinions.co.uk/taubes.html
"I assume "RCT" means randomized controlled trial. A huge problem with Ancel Key's diet-heart hypothesis is that there never was a randomized controlled trial of it before it became U.S. national food policy 30 years ago."
Er, that was sarcasm! The RCT is still continuing and the UK arm
http://www.fsascience.net/2009/02/10/the_appliance_of_science
is still live despite that the results long ago achieved statistical significance :(
Posted by: Robert Wilson | Nov 13, 2009 6:31:07 PM
Dear Dr. Parker,
Well, I can tell you one thing. Remember the "French Paradox?" Well, dietary scientists should also be looking at the Malaysian paradox. I spent 5 weeks in Malaysia in 2001, and I fell in love with the food. I thought, however, that Malaysians must we walking heart attacks waiting to happen. The food is smothered in coconut milk, palm oil, fatty cuts of meat and, among the Indian population, yogurt. They even snack on tasted coconut shreds. Recently, however, I ran across a newspaper article that claimed that rates of heart disease were on the rise in Malaysia because of the increase in western foods. The article even claimed that heart disease rates had always been low in Malaysia! It was that article that got me interested in the saturated fat/heart disease link, or lack thereof.
BTW, Malaysia would be an interesting place to study heart disease because the Chinese population probably consumes much less saturated fat than the Malays or Indians (except for those who live in mixed areas who have assimilated with the other groups.) It would be interesting to study heart disease rates between the Chinese and Malay.
