Every alternative health practitioner is pushing for the absolution of saturated fat nowadays. "The science doesn't support saturated fat as being the causative agent of Cardiovascular disease." Even the Wall Street Journal had an article on it today - see here. The article is full of bias, and written by a woman who has a new book that is supported by the idea that saturated fat is null. Even worse, it starts to demonize carbohydrates - as if beans and sugar are the same. Are we really trying to move from one reductionist viewpoint to another?
I'm in full agreement that there isn't evidence to scientifically claim Saturated Fat causes heart disease. But the way that this issue is being presented is far from scientific, and often concludes things that are not valid. A few points to consider:
1. The Science of Fatty Acids - we' re seeing interesting paradigm shifts in the field, as we move beyond just "high LDL, high risk". This was the original line of thinking. We know now that CVD's not just about LDL - it's about particle size (see here), fatty acid composition of the particle and oxidative end-products (see here), antioxidant capacity (see here), monocytes adhesion (see here), and inflammation (see here). Then there's the issue of ketogenic diets and saturated fat (see here), which is an entirely different metabolic paradigm in and of itself. Is it shocking that just decreasing saturated fat intake, affecting one factor in this multifaceted pathogenesis, doesn't explain all of the picture? With all of these factors to consider, conflicting results, and more factors being looked at, many of the areas being used to argue saturated fat isn't of concern are still in their scientific infancy, and are far from being immediately translatable to clinical recommendations - see here.
1. The Science of Fatty Acids - we' re seeing interesting paradigm shifts in the field, as we move beyond just "high LDL, high risk". This was the original line of thinking. We know now that CVD's not just about LDL - it's about particle size (see here), fatty acid composition of the particle and oxidative end-products (see here), antioxidant capacity (see here), monocytes adhesion (see here), and inflammation (see here). Then there's the issue of ketogenic diets and saturated fat (see here), which is an entirely different metabolic paradigm in and of itself. Is it shocking that just decreasing saturated fat intake, affecting one factor in this multifaceted pathogenesis, doesn't explain all of the picture? With all of these factors to consider, conflicting results, and more factors being looked at, many of the areas being used to argue saturated fat isn't of concern are still in their scientific infancy, and are far from being immediately translatable to clinical recommendations - see here.
2. Dosage - All foods are mixtures of fatty acids- you'll always consume some saturated fatty acids. The meta-analysis that the WSJ article references showing that Saturated Fat isn't linked to CVD tells us nothing about how much to consume - should 50% of your kcals come from SFAs? 20%? 35%? It also does not tell us that saturated fat has major benefits - where are the studies showing that replacing beans with hard cheeses leads to a benefit?. It does not tell us that the current recommendations to consume less than 7-10 percent of our kcals from saturated fat is wrong (this still leaves room for using butter, eating steak, drinking whole milk). Meta-analyses provide future questions for researchers, but the evidence-based clinician can't really draw much of anything from this.
3. So what is evidence based? - every heart trial we have to reference (many of which can be found here), that shows marked reductions in CVD mortality, employed a multitude of therapies: reduced saturated fat intake, amongst decreases in body weight, decreases in trans fat intake, increases in fiber, increases in omega 3 intake, reduction in sodium. Do any one of these reductions solely account for the effect seen? Are there synergistic effects? Which are most pronounced? How relevant is reducing saturated fat here? As of now, the strongest evidence to show reductions in CVD combined multiple nutritional therapies - and this is reflected in the guidelines for reducing heart disease risk. Until we have a trial that employs many/all of these factor manipulations without saturated fat, and shows a reduction in CVD, how can you make an evidence-based claim that saturated fat is entirely benign? One current critique of the meta-analyses (see here) concerning SFA replacement with PUFAs is that they also employed multiple therapies, reducing saturated fat intake at the same time as addressing other risk factors. If you've followed the back and forth between Mozaffarian and Ramsden, here is a link to Willett and Mozaffarian's comment on Ramsden's omega 6 publication - their conclusion still remains that replacing SFA with a mix of n-6/n-3 will result in clinically relevant CHD benefit. For clinicians, the lack of a strong correlation between saturated fat intake and CVD does not equate to recommendations that liberalize consumption. I suggest following the data for what's most cardio protective - see here, here. There is plenty of data on the benefits of maintaining a healthy weight, nut/seed consumption, fiber, omega 3's, plant bioactive components/phytochemicals, and easy additions like green tea. Let's not make this out to be more complicated than it is. And let's also not forget to tailor the diet to the individual..
4. Normal vs Medical Nutrition - my biggest concern with articles like the one in the WSJ is the number of self-proclaimed nutritionists out there that will take this, and universalize it. Saturated Fat is certainly a concern for individuals with altered lipoprotein metabolism (potentially ApoE4 carriers, T2DM, hyperlipidemia). This debate is over population-level recommendations - translating this to the individual, without proper medical training, and understanding of the individual's CVD risk, anthropometry, biochemical markers, and genetics/family history is absolutely irresponsible, and dangerous.
4. Normal vs Medical Nutrition - my biggest concern with articles like the one in the WSJ is the number of self-proclaimed nutritionists out there that will take this, and universalize it. Saturated Fat is certainly a concern for individuals with altered lipoprotein metabolism (potentially ApoE4 carriers, T2DM, hyperlipidemia). This debate is over population-level recommendations - translating this to the individual, without proper medical training, and understanding of the individual's CVD risk, anthropometry, biochemical markers, and genetics/family history is absolutely irresponsible, and dangerous.
The moment there is a well conducted heart trial showing reduced CVD risk with a higher saturated fat intake, we can discuss calling the saturated fat crusade a waste of efforts. Maybe. First, we'll probably move onto saturated fat and Alzheimer's (see here). Then we'll have to look at saturated fat and aging - see here. And possibly even cancer - see here.
I'm hoping nutrition moves on from just looking at one nutrient. While this has many benefits in some areas, particularly in micronutrients and mechanisms, metabolism is an interactive system, and manipulating one factor will lead to a cascade of changes. Evidence is already so hard to develop, and all lines of it have flaws - see here - but the best evidence we have right now says to limit saturated fatty acids below 10% of total kcal intake - the newest AHA guidelines recommend a reduction of SFA intake to about 6% of kcals, but this isn't because we have a long-term trial showing just a reduction in SFAs, but because evidence from DASH/DELTA style diets that contain that amount (1). If you would like to be your own case study, feel free to consume more - that's your choice. Keep in mind the many other recommendations to deter heart disease, with the most important being to maintain a healthy BMI and waist circumference, keeping visceral fat to a minimum.
I'm hoping nutrition moves on from just looking at one nutrient. While this has many benefits in some areas, particularly in micronutrients and mechanisms, metabolism is an interactive system, and manipulating one factor will lead to a cascade of changes. Evidence is already so hard to develop, and all lines of it have flaws - see here - but the best evidence we have right now says to limit saturated fatty acids below 10% of total kcal intake - the newest AHA guidelines recommend a reduction of SFA intake to about 6% of kcals, but this isn't because we have a long-term trial showing just a reduction in SFAs, but because evidence from DASH/DELTA style diets that contain that amount (1). If you would like to be your own case study, feel free to consume more - that's your choice. Keep in mind the many other recommendations to deter heart disease, with the most important being to maintain a healthy BMI and waist circumference, keeping visceral fat to a minimum.
I think it's also worth mentioning that, as Dr. Katz has pointed out, the original push to reduce saturated fats was to increase consumption of fruits, vegetables, beans, whole grains and nuts/seeds - not to use vegetable oil. I can't help but feel this debate often occurs to justify which processed foods with minimal nutrition can put a label that says "Heart Healthy" on it - i'm looking at you sweetened soy milk and fiber one bars.
1. http://content.onlinejacc.org/article.aspx?articleid=1770218
1. http://content.onlinejacc.org/article.aspx?articleid=1770218
Kevin,
ReplyDeleteCan you provide a link to reference Katz's point about the push to reduce saturated fats to increase consumption of fruits, vegetables, etc. I'm interested in this topic from reading your blog and watching a Harvard "Teach In" on the subject where Dr. Lichtenstein says that “at some point” the concept of replacing saturated fat with polyunsaturated fat “got corrupted.” I gather that the author of that WSJ article you reference thinks it was some combination of egotistical scientists/government incompetence/industry conspiracy, but, to be frank, I don’t think I want to waste my time reading that stuff.
Also, as I mentioned the Harvard “Teach In,” many of the scientists recommend the population use polyunsaturated oils to lower LDL (I think the popular press would dub this a “super food”) . Yet, confusingly, at the very end Dr. Willett and others give a warning against actually using these oils as industrial high-heat processing might make linoleic acid unsafe for consumption. I believe you have alluded to this elsewhere on your blog as well. I wonder if could direct me to an evidence-based account of what the true concerns are about these oils. Thanks.
http://www.hsph.harvard.edu/news/features/saturated-or-not-does-type-of-fat-matter/
Katz has mentioned it several times after the IAoM meta analysis. Here's a couple:
Deletehttps://www.linkedin.com/pulse/20140618223130-23027997-study-saturated-fat-as-bad-as-sugar
https://www.linkedin.com/pulse/20140503183904-23027997-today-s-wsj-article-on-saturated-fat-and-heart-disease-is-nonsense
The high heat processing has long been a concern, since its damages polyunsaturated fatty acids. Cold pressed oils are pretty popular now. Was there a recording of the Harvard Teach In? I'd have to see what exactly He said, but i imagine he was alluding to the use of these oils in frying. Hydrogenated fats are great for deep frying because they arent as easily damaged, but as we move away from the use of trans fats, vegetable oils are commonly used in frying, and the PUFAs get very easily damaged (possibly adding to the carcinogen load of fried food). He might have been referring to that? If you have a link i'd appreciate and love to watch!
The war will continue to wage on over which types of fatty acids are optimal, but I'll stand by the claim that most americans would do some good replacing whole milk with skim milk and some almonds, and cream cheese with avocado.
Thanks, yes. He mentions conversion to trans fat, oxidation, and that monos are more stable. He says they are just starting to get some data together. If you follow the link I posted to "Watch live webcast" the part I'm referring to at 3h and 7m. And you'll need to turn the volume to max to even hear it. Also, slides are here: http://www.hsph.harvard.edu/nutritionsource/2014/05/15/saturated-or-not-does-type-of-fat-matter/ They really should have done a better job with the video.
DeleteYes, you've convinced me from your other post that one to try to get my fat from nutritious foods rather than added oils or butter. But I do like to saute veggies so cooking oils are still kind of a relevant to me. I've long heard that smoking the oil is carcinogenic, and possibly even the fumes are bad. But it was only recently that I've heard that the oil could be damaged before I even open the container.
Thanks! I"ll be interested to see the data they put out. This older Harvard interview with Dr. Sacks is a bit telling about his thoughts on heating oils :"http://www.hsph.harvard.edu/nutritionsource/omega-3/" . The oxidized compounds are thought to be deleterious but it's still theoretical when it comes to dosage - most who talk about oxidized PUFAs and cholesterol just say its good to avoid it when possible. I'l be interested to see how much linoleic acid is lost at the industrial side of things. I concur, though, that high mono oils (like canola) are best for heating (avoiding oxidized cholesterol and PUFAs)
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