I’ve been shocked, and somewhat bewildered at what I’ve found in looking at the current medical literature on the subject. It’s actually a little embarrassing that I have a terminal public health degree and have been so wrong for so many years, but nonetheless. As with most people, I operated from the same paradigm governing our current dietary recommendations of eating less fat and replacing those calories with carbohydrates. Surely these recommendations reflect years of scientific evidence and the various federal and non-profit agencies making these recommendations are on top of it. I trusted prevailing wisdom and never really looked into it further with any type of rigor. We all know this by now but the current recommendations call for reducing fat consumption to less than 30% of total calories (<10% if you are at risk of heart disease) and replacing these calories with carbohydrates, which should comprise 50%-60% of your calories. Eating more vegetables/fruits is also recommended, which is pretty much universally accepted and no one takes exception with. This sounds reasonable enough, so what’s the problem?
The problem is since the current recommendations gained widespread acceptance in the 1970’s, the waistlines of Americans have continued to grow accordingly. Between 1980 and 2008 the rate of obesity in the US has more than doubled increasing from 15% in 1980 to 35% in 2008. I examined published data from the National Health and Nutrition Examination Survey (NHANES) to look at macronutrient intake (fat, carbohydrate, protein) during this same time period. I was surprised to find the percent of total calories from fat and saturated fat in the average American diet has actually decreased by 9% and 17%, respectively. Perhaps you will find it more interesting to know that carbohydrate consumption as a percent of total calories increased by 12% in the average American diet. Based on this data it would appear we have indeed followed these recommendations by reducing fat consumption and replacing it with carbohydrates. Now, these are precisely the type of ecological data you should be very weary of and these numbers should not be taken to imply causal inference. These data do not distinguish between the types of carbohydrate consumed and likely reflects increases in sugar sweetened beverages and other cheap, readily available forms of empty calories. However, it is interesting to note aggregate changes in consumption of macronutrients seem to reflect historical nutritional recommendations; yet, rates of obesity are moving in the opposite direction. The obvious question is what’s up with that?
Choose your Paradigm Carefully
A good friend of mine suggested I read a book published by Thomas Khun titled “The Structure of Scientific Revolutions.” This is an older book I would not recommend to anyone unless you have insomnia and need a non-medicinal alternative to get some sleep; or, unless you are a researcher/nerd who gets into this stuff. Either way the take home point of this book is a poignant one and provides a nice illustration for discussing how these things came to be. The book focuses on paradigms or sets of assumptions, concepts, values, and practices that constitutes a way of viewing reality. It examines how paradigms become a reality and more importantly how they change. The interesting thing about science is once a specific paradigm takes root and gains widespread acceptance, it spawns a flurry of scientific activity continually building from the original paradigm. This in and of itself is not a bad thing and can yield tremendous advances in knowledge and science rapidly. Periodically, new paradigms come along challenging the conventional wisdom of the prevailing paradigm. New paradigms are often met with skepticism and bear the burden of proof. However, if they stand up to the rigorous backlash they can become a paradigm shifter. As a paradigm shifts the body of work built on the original paradigm comes into question and must be seriously examined in the context of the new paradigm.
Perhaps it might be easier to visualize scientific progress as a Jenga puzzle. Once a paradigm (base) has been established researchers add pieces creating a very large, complex puzzle. What happens when the pieces building the tower get pulled out in the context of an emerging paradigm? Better yet, what happens to the mountain of pieces if the corner piece of the base is removed? If the original paradigm turns out to be wrong then the mountain of research built on the paradigm is severely compromised and is called into question. This is not an affront on the quality of research completed that built the original puzzle; rather, the problem is with the original paradigm itself. Perhaps the more important question is what happens when a shaky paradigm finds its way into public policy? Unfortunately a faulty paradigm translating to public policy is the case with our current nutritional recommendations.
The Science
Let’s quickly visit the fat consumption, high cholesterol, heart disease paradigm most of us have been working from. The science driving this paradigm dates back to research completed from the 1960’s through the 1980’s, before the sub-typing cholesterol by HDL (good) and LDL (bad). Early research did find that saturated fat intake increased cholesterol; therefore, must increase the risk of heart disease. Although fat consumption does generally increase total cholesterol there is a differential effect of fat on good/bad cholesterol. Most scientists would agree the Total/HDL (good) cholesterol ratio is the more important predictor of heart disease than total cholesterol. More recent data has indicated the HDL /Triglyceride (circulating fat in the blood) ratio is an even more important predictor than LDL (bad) cholesterol levels. It turns out saturated fat consumption (depending on the specific type of saturated fat) can increase LDL (bad) levels; however, it also raises HDL (good) levels proportionally higher than LDL (bad) levels and decreases triglyceride levels. So, the net risk/benefit of saturated fat consumption tilts in your favor. This is the basis for much of the more current research that continues to exonerate saturated fat from sweeping indictments in the current recommendations (pulling pieces from the original paradigm Jenga puzzle).
Don’t just take my word for it. Let me give you an excerpt from a section in an Exercise Physiology Sports Nutrition and Energy Metabolism textbook published in 2008 (Wolinsky and Driskell).
“There has been much controversy about both the health and effectiveness of lower carbohydrate diets. New studies from leading institutions including Duke and Harvard Universities have shown low carbohydrate diets are safe, healthy, and lead to more permanent fat and weight loss, and have shown improvements in the dieters blood lipid and cholesterol levels.The effect of high fat/protein and low carbohydrate diets on weight loss and blood lipid is one thing, but what about the longer term effect of saturated fat consumption and adverse cardiovascular events? Loren Cordain outlines some of this in his most recent book “The Paleo Answers.” I pulled the reference articles he discusses in the book and took a look for myself. It’s not that I don’t trust what I’m reading, but we all should make it a habit of not blindly following what someone tells us without looking into it further (so feel free to check up after me).
Several studies have shown that low carbohydrate diets are more effective for weight and fat loss than high carbohydrate diets. The results of a study published in 2002 showed that long-term use of a low carbohydrate diet resulted in increased weight and fat loss, and dramatic improvement in blood lipid profiles (decreased cholesterol, triglycerides, and LDL, and increased HDL levels). Two studies published in 2003 in the New England Journal of Medicine found that people on high protein, high fat, and low carbohydrate diets lost twice as much weight over 6 months as those on a standard low fat diet recommended by most major health organizations. In both studies, the low carbohydrate dieters generally had better levels of “good” cholesterol and triglycerides, or fats in the blood. There was no difference in “bad” cholesterol or blood pressure………….
In the latest study, researchers from the Harvard School of Public Health, after analyzing data collected over 20 years from more than 82,000 women participating in the Nurses Health Study, concluded that low carbohydrate diets do not seem to be linked to higher risk of heart disease in women.”
So, the most recent evidence is outlined in a paper published in 2010 in Lipids, by Micha and Mozaffarian. This study reviewed the most recent studies to date specifically examining the association between saturated fat consumption and various cardiovascular events. I was surprised to find the mountain of evidence on saturated fat consumption and cardiovascular events only included 11 prospective studies (studies that follow people over time) and 8 randomized controlled trials (the gold standard for research). This in and of itself should raise some red flags about the supposed mountain of evidence. The limited number of studies in this area raises serious concerns of publication bias; rather, there are many more studies that showed no significant findings that were not published. Nonetheless, this review of published studies showed no effect of saturated fat consumption on cardiovascular events. What’s interesting is this particular study also examined these relationships in the context of other macronutrient substitution. So, if you replaced saturated fat consumption with other types of fats (monounsaturated, polyunsaturated) or carbohydrates what happens? The review found replacing saturated fat with carbohydrates actually increased the risk of cardiovascular events. Review of the 8 randomized controlled trials showed similar results, no significant affect of saturated fat consumption and cardiovascular events.
Let me pause and make a public confession. I used to be a low carbohydrate hater. Yes it’s true and boy do I feel stupid. I was wrong and feel I should issue a public apology. I remember spouting off relentlessly when someone even breathed the word “Atkins Diet” in my presence. Now I don’t advocate for the Atkins Diet for various reasons, but I am a believer in a low/smart carbohydrate approach to eating.
Now that my public apology is over, let’s get back to the point. If the most current review of the medical literature available indicates no association between saturated fat intake, blood lipid levels, and cardiovascular events, why do the current dietary recommendations say we should reduce fat intake and eat more carbohydrates? Excellent question that directs us back to the issue of paradigms.
Public Policy
The original paradigm guiding the current recommendations can be traced back to a gentleman named Ancel Keys and the Seven Countries Heart Study published in the late 1960’s. In many regards this study was ahead of it’s time and was probably the best that could be done with the resources available. This was before things like SAS, STATA, SPSS and various other statistical software packages were available making it way too easy for anyone (including myself) to do statistical analysis. Anyway, this study found a perfect linear correlation between fat consumption and coronary heart disease using seven countries as data points. Although an ecological study, the results seemed pretty darn convincing. The results of this study became the guiding paradigm reflected in our current nutritional recommendations. There’s only one problem, there were actually 22 countries included in the original study (not 7). I do not want to beat up on Dr. Keys or question the gentleman’s scientific integrity, but it does seem like a classic case of data cherry picking. When examining these same relationships including all 22 countries available, it turns out there was no detectable correlation between fat consumption and coronary heart disease. In fact, you can easily show the exact opposite correlation if you select seven different countries. This issue has been documented in several places so I don’t want to belabor the point. You can look this stuff up for yourself. If you want more information on the data with 22 countries you can find it here http://high-fat-nutrition.blogspot.com/2009/02/cholesterol-presentation-between.html or look up Gary Taubes. This has been well documented.
Shortly after Keys released his study, the McGovern Committee on Nutrition and Human Needs released their dietary recommendations for the country (1977). Acutely aware of Dr. Key’s work, to no surprise the committee recommended avoiding saturated fat and increasing carbohydrate consumption. Again, I don’t want to beat up on the McGovern Committee; this group did a tremendous amount of excellent work on poverty, food insecurity, and malnutrition. However, the fact remains this committee promulgated the same faulty paradigm institutionalizing the low fat/high carbohydrate message into the medical community and general populous. After the recommendations were met with significant opposition from various industries and others in the scientific community, the responsibility for providing nutritional recommendations were handed over to the United States Department of Agriculture (USDA) and the Department of Health and Human Services (DHHS) in 1980. The results were no different, the continued promulgation of a faulty paradigm. What’s interesting to me is the fact these recommendations have been met with opposition from other scientists from day one. The science behind the paradigm was never overwhelming or indisputable.
To make a bad situation worse mix in the Nixon administration, farm subsidies, and the proliferation of cheap grains into the food supply and you have yourself a nice little perfect storm of poor nutrition policy. For various reasons that are beyond the scope of this post, the Nixon administration was met with rising inflation and food prices heading into an election year. In an effort to stabilize food prices, in 1973 the administration altered the structure of farm subsidies to grain farmers, flooded the market with inventory driving down prices for grains (wheat, corn, soy). This made the production of things like high fructose corn syrup (sugar sweetened beverages) and various other low fat, high carbohydrate rich foods very cheap, easy to produce, and readily available for consumers. The affect of these polices spilled over into other areas as grains for cattle feed became much cheaper artificially lowering the price and quality of meat from cattle farms. Ironically, the subsidies available making grain prices artificially low are not readily available for fruit, vegetable, and range cattle farmers.
What’s the point?
The point is this, much of the historical basis for our current nutritional recommendations stemmed from a study that turns out to be very misleading. This is compounded by the fact governmental food policies have made calorically dense/nutrient deficient carbohydrates readily available for consumption (see paragraph 3). The science supporting a high carbohydrate/low fat diet is shaky at best and I would argue there’s more evidence to the contrary. Referring to our previous analogy, current evidence continues to pull the corner piece from the Jenga puzzle; the prevailing paradigm guiding nutritional policy for the past 30 years is crumbling. So why doesn’t the puzzle fall? At least from my perspective it’s because the paradigm found its way into public policy rather quickly and once something becomes public policy it’s darn near impossible to weed it out. It requires politicians to admit they were wrong and those financially benefiting from these recommendations to let it go. When’s the last time that happened? The final point is you are really on your own when it comes to figuring out what type of approach to eating you should take. We have all received bad advice for the past 30 years. Thankfully, solid science is emerging and we can now educate ourselves and adjust accordingly.
What does this mean to you…
High fat/protein, low carbohydrate diets are not some fringe, gimmicky diet. They are legitimate and the most current research available indicates they actually perform better than high carbohydrate/low fat diets for weight loss and blood lipid control. From my perspective a Paleo approach to eating is by far the most well balanced, practical approach to eating I’ve come across that has the science to back it up. Eating lean meats, vegetables, fruits, nuts, seeds, roots, and tubers by default keeps carbohydrate consumption smart/low, controlling blood sugar swings and insulin responses. Moreover, this approach to eating makes your body an efficient fat burner which is great for increased energy and performance.
Should you consume copious amounts of saturated fat eating Paleo? Not necessarily, but you shouldn’t be scared of it. If you recall from above, substitution of saturated fat with carbohydrates was associated with an increase in adverse cardiovascular events; however, substitution with monounsaturated fats and to some degree polyunsaturated fats of the fish variety is associated with a decrease in cardiovascular events. Eating a well-balanced Paleo diet should provide a good mix of quality saturated, monounsaturated, and polyunsaturated fat. Regular consumption of Paleo staples such as coconut oil, avocados, olive oil, nuts, and omega-3 rich meats/fish, vegetables and fruits while limiting intake of grain based carbohydrates should put you in pretty good shape.
Let me be explicitly clear. The absolute worse thing you can do is consume a diet rich in saturated fat and high in carbohydrates, I would call this the biscuits and gravy approach to eating. You get the short end of both sticks and a ticket to early departure. You are left with two options. You can choose to continue following the current recommendations of the past 30 years, starve to death, and continue to be frustrated with the results. Or, you can join me in eating Paleo , not be hungry, have plenty of energy, and look better naked.
To get started on Paleo, check out my July post Paleo-Jitsu: Black Belt Nutrition
