Vegetable Oil and Heart Disease: New news from the way-back machine

Since the 1970’s, we’ve reduced our sugar, salt, and saturated fat intake, and we’ve dramatically reduced our rates of smoking, high serum cholesterol and high blood pressure. At the same time, rates of chronic disease, including coronary heart disease, have increased—in some cases, dramatically.

The best that we can say is that since the 1970s, rates of myocardial infarction have decreased slightly—but only in white folks.

If the current health prescription is valid, then we should see dramatic differences in rates of disease and mortality between those who follow the prescription and those who don’t, and we should see clear and strong associations between “healthy” food choices and good health (because the same people eating a “healthy” diet are also taking care of their health in other ways). Yet this is not what we see.

Is it possible that our low-fat diet has removed some protective factors from our nutritional profile and exposed us to increased levels of nutrients that have negative impacts on health? I think it is, and a recent study in BMJ supports this notion.

I am a long-time admirer of one of the researchers, Daisy Zamora, and she is a good friend of mine. She’d been dropping hints about this great study she was working on for a while now—but was sworn to secrecy and now I know why. What she and her co-investigators have uncovered is data from a long-ago diet study, conducted from 1966-1973. It’s a decently large, well-run, randomized controlled trial that replaces saturated fat with safflower oil, a vegetable oil particularly high in one kind of PUFA—omega-6 (n-6) linoleic acid—and low in another kind of PUFA—omega-3 (n-3) alpha linolenic acid. The idea was that replacing “bad” saturated fat with “healthy” vegetable oil in men with premature coronary heart disease would improve survival. This did not turn out to be the case. For some reason, though, the original study only reported all-cause mortality and not deaths from cardiovascular disease and coronary heart disease.

Daisy and her co-investigators climbed into their way-back machine and this is what they found: Not only did the participants in the intervention group have an increased risk of all-cause mortality, but they had an increased risk of death from cardiovascular disease and coronary heart disease.

The blue line is the safflower oil group; the red line is the control group. To put it rather simplistically, the widening gap between the two groups means the intervention group died a lot faster than the controls.

Although the switch to safflower oil did lower total cholesterol, these reductions didn’t help those participants live any longer than those who kept eating saturated fat. In fact, as the authors note, “the increased risk of death in the intervention group presented fairly rapidly and persisted throughout the trial.”  (Hmm. Maybe this whole “cholesterol lowering” thing isn’t as important as we thought.)

Furthermore, the authors go on to point out that the relationship between linoleic acid consumption and increased mortality was particularly robust in smokers and drinkers, “suggesting that diets high in n-6 [linoleic acid] may be particularly detrimental in the context of oxidative stress induced by smoking and alcohol.”

Everyone knows that if you are a smoker you should quit and that alcohol should be used in moderation. But, with this evidence in mind, if you decided to keep on smoking and/or you want to drink immoderately, you may want to consider a breakfast of eggs and bacon rather than whole wheat toast and “heart healthy” margarine before you do.

The entire article is available online. Read it for yourself and see what you think.  Anybody besides me wondering how the American Heart Association will respond to this study?

Advertisements

Guest Post: James Woodward on Why Science May Not Be Enough

I’d like to introduce readers to a friend and fellow grad student, James Woodward. His undergraduate work was in economics at Ohio University, and he has a Master’s in public policy from the University of Kentucky. He is continuing at UK as a PhD student in public policy and administration. He and I have had some of the most thought-provoking email threads in any of my correspondence & I give him a lot of credit for helping me think through the economics and policy parts of food-health system reform puzzle. His post will serve as a bridge to my next series on “Eatanomics” which will explore how food, health, and the economy are intertwined. James would like everyone to know that all the disclaimers that appear on this page apply equally to what appears in this post. His views are his own, and as with the best of minds, he anticipates that most are subject to change. But he raises some very interesting questions—he’s nearly as long-winded as I am, but it is worth a read.

Why New Science May Not Be Enough – James Woodward

Before going into my social science background, I thought I would mention my professional background as it relates to food. It’s nearly as extensive as my academic background. I worked in fast food for about two years, a pizza place for about two years, a dining hall for a quarter, and, finally, a pseudo-Mexican restaurant for about two years. As a result, my feelings toward actual food and, especially, its preparation are fairly ambivalent at this point. The fact that I spent large amounts of time working with flour (I made tens of thousands of tortillas over the course of my tenure at the Mexican place) is rather ironic given my recent decision to avoid the stuff as much as possible.

Nutrition Science Initiative founders Gary Taubes and Peter Attia are hoping to give the public some solid science on food-health relationships.

My schooling in economics was concurrent with much of this work and my reasons for working these jobs had much more to do with my own economic situation than with any particular desire to work with food. But my background in economics and, now, public policy, leads to me to view the issue of food and nutrition policy a bit differently than many others writing on this topic. Many approach problems relating to nutrition and health in terms of their public health consequences. Others stress the fact that nutrition policy is the product of bad and/or misinterpreted science. Gary Taubes and Peter Attia just launched their organization, NuSI, to address, and hopefully settle, that particular aspect of this issue. Both lines of research clearly have their merits. Ultimately, though, I think what everyone is most interested in is influencing the behavior of individuals.

Contrary, perhaps, to Peter Attia’s quote from Richard Feynman in a recent blog post, I think there is a role for social scientists to play in understanding the many issues and controversies surrounding diet, health and public policy. Some of us in the social sciences are, in fact, sensitive to the difficulty of establishing real truths from the data available to us. Further, I do not think that social phenomena like behaviors and decision-making are reducible to physical and chemical relationships quite yet. How fitting that nutrition, and especially nutritional epidemiology, often bears more resemblance to bad social science than it does to any sort of ‘hard’ science.

Ignoring the controversy surrounding what it is that makes people fat and what constitutes an ideal diet, it would be hard to argue that people are making “good” decisions about what they are eating, given the high prevalence of (ostensibly) diet-related health problems in the United States, the most visible of which is obesity. Since most people buy their own food rather than growing or raising it themselves, food buying decisions tend to be highly correlated with food eating decisions. So, to me, the ultimate question is: “What influences food buying decisions?” Again, Gary and Peter have, with good reason, chosen to stress the importance of food consumption decisions being driven by good science. But there are clearly more factors that influence food purchasing decisions than a careful weighing of the scientific evidence. I would argue that such an approach to most decisions is, in fact, fairly rare. To the extent that Gary and Peter are ultimately trying to influence public policy, I think it is self-evident based on a reading of the history that policymakers are not that likely to employ such an approach either.

One of the many things besides science that may influence food purchasing and consumption.

This is why I tend to conceptualize the problem in the area of food and nutrition policy as one of bad information rather than attributing it purely to bad science. If one takes the time to dig, there is plenty of science which refutes the conventional wisdom regarding the relationship between diet and health. So, while no rigorous, carefully controlled studies have been performed to refute the conventional wisdom and/or confirm the “insulin hypothesis”, to use Gary’s term, there is already a lot of evidence to suggest that it is valid and plenty of evidence which refutes the conventional wisdom. Performing such a rigorous test of these competing theories is obviously warranted, given the importance of the implications for settling this debate, but there is no guarantee that the results will be convincing to skeptics, policymakers, stakeholders or the public at large.

Thirty-odd years ago policymakers perceived an obvious threat to public health (saturated fat) and saw a clear remedy (tell people not to eat so much saturated fat) which made it more or less a no-brainer to act on that information and tell people to avoid eating saturated fat containing foods. Since then, those original beliefs about diet and health have had time to percolate and become more or less embedded in how most people think about what they eat. Adele and I have talked a little bit about overcoming our own biases when we decided to eat differently, biases that we were not necessarily aware we had in the first place.

How you spend your food dollar may depend on how many food dollars you have to spend.

There are more factors that influence food purchasing decisions than just beliefs about how that food will affect one’s health. Taste, culture, geography, morality, ethics, politics, and socioeconomic status are just a few observable characteristics of an individual that might affect what he or she decides to eat. In many people’s minds, there is very little conflict between these concerns and health-related ones. For example, there is a perception that following a vegetarian lifestyle is good for one’s body, one’s soul, and the environment compared to a diet based around animal products. Upon closer inspection, however, there is a great deal of ambiguity to this belief in all three spheres. Similarly, many athletes seem to be operating under the impression that carbohydrates are required to perform at a high level. Peter’s well-documented experience calls that belief into question. Breakfast is often lauded as the most important meal of the day in the United States yet I frequently snub it to no ill-effect. And so on.

I think it is important to keep these biases in mind when thinking about we’d like to go about changing behavior. It is tempting to think “if only the science were better” people’s behavior would change. This is clearly not enough, in my mind anyway. It is just as important to be convincing as it is to be right. If/when NuSi successfully settles this debate and has the biggest names in the field to back up its research; there is still the matter of convincing everyone else. NuSi does acknowledge this aspect of the issue, though I am interested to see how it is addressed in practice. There are the cognitive biases of all the other scientists to contend with. There are also the material and non-material incentives that seem to be ingrained in many of the stakeholders involved in this particular area of policy. For example, it has been noted elsewhere that stressing the importance of calories is convenient for those involved in the production of food since doing so means no particular foods (e.g., wheat and sugar) are likely to be admonished against because of their unique effects on the body per se but, rather, because of their caloric content. I have to imagine that such firms will do their very best to refute any evidence that says otherwise and may hire their own experts to do so.

In a “calories in, calories out” world, there’s room for all foods in a “healthy” diet.

Beyond the obvious material costs to stakeholders of changing the current nutritional paradigm are the much more difficult to quantify costs of changing people’s beliefs about such things. Despite taking a nutrition course years ago (for an easy science credit, I will admit), I did not have particularly strong thoughts about nutrition prior to about a year and a half ago. I knew I made less than optimal choices about what I ate (according to conventional wisdom that is) but I mostly ignored those concerns since my health seemed fine (more or less). It was therefore fairly costless for me to change my mind about how I approach my diet after the conventional wisdom failed for me. Physicians and dietitians are not like me, however. Many of them have devoted years of their lives to dispensing information and advice that they believe to be correct and helpful. Faced with an opposing and incongruent view, it is perfectly understandable that they would be very resistant to the implication that they have been misleading their patients. In a less extreme form, I am sometimes asked by friends and acquaintances for my thoughts relating to diet and health and then, after giving them, met with resistance and facts or beliefs that supposedly refute my position(s). Most of these people are not experts on this topic but, like most people, they need some justification for what they believe.

So what is my point in all this? It is probably not breaking news that people’s eating decisions are not purely based on a careful reading of the scientific evidence. Better science is probably a necessary part of making the case but I do not think it will be sufficient to affect the type of change that many people in the ‘Paleo’ or ‘Ancestral Health’ communities (or whatever other term you prefer) would like to see. As mentioned, most people are averse to the notion that their beliefs are wrong and, in my experience, will try to come up with some reason for why that is not the case, sometimes resorting to questionable sources for support. This is human nature, I think– cognitive dissonance perhaps, to borrow a term from the psychologists. Based on what I can see, most people are not even willing to entertain the idea that there is a controversy or room for debate about these competing paradigms. Especially skinny people.

I think this state of affairs needs to change if further research is to bear any fruit in the form of affecting individual behavior and/or public policy. Fortunately, there are many bloggers writing on this topic, all bringing their own perspectives to the table. The challenge will be finding enough common ground to get this message to a larger audience so that we get an actual public debate going. I read the New York Times ‘Health’ section fairly regularly (as a barometer for this type of thing, not necessarily for good information) and I am not seeing it so far. It would be a real shame if all that came of this renewed interest in an old paradigm was a relatively minor reduction in the prevalence of obesity.