This week I went to a lunch time talk by James McCormack, PhD Pharmacy, called “Nutrition and the Evidence Conundrum: What We Know (Very Little) and What We Will Likely Never Know (A Lot) About Nutrition.” Although the title caught my interest, I attended for more sinister reasons. The poster promised free snacks and I was desperate for new blog material. Though my life is busy these days—mostly deciding whether my son’s poo is “normal,” “semi-soft” or “in need of prunes”—not much of what I do is worth discussing. I continue to work out 5-6 days a week, lifting weights, enjoying full-body training with DYT, and teaching spin classes. In fact, I have done 795 push-ups so far this month. Bored shitless yet?
Back to Dr. McCormack: He is not a nutritionist. Instead, he is adept at analyzing scientific studies, examining their methodology, use of statistics, and conclusions to decide whether or not they are valuable. This skill is especially important these days, when we are bombarded by media reports that claim dubious things: eggs are as bad as smoking, salt is the devil in disguise, vaccines cause autism, etc. Deciding what to make of such publicized studies requires critical training in quantitative assessment, qualitative methods, logical thinking, and historical knowledge, key areas taught at universities. Simply reading a lot of crap online is not the same thing as being educated [this blog excluded. Hee!]. Dr. McCormack’s response to the current information overload is to put better crap online, namely his popular medical podcasts (http://therapeuticseducation.org/bs-medicine-podcast) and such youtube music video parodies as “Bohemian Polypharmacy” (http://www.youtube.com/watch?v=Lp3pFjKoZl8), “Choosing Wisely” (http://www.youtube.com/watch?v=FqQ-JuRDkl8), and “Viva La Evidence” (http://www.youtube.com/watch?v=QUW0Q8tXVUc). He also gives popularized and entertaining lectures at universities to students lured by free coffee and cookies [Aside: here I am suppressing a rant about the increasing association of quality education with easy to digest entertainment, but that would be me going off on a tangent…]. Ahem.
Dr. McCormack advocates evidence based health care, asserting that clinical trials are the best way to assess the health impact of dietary modifications. Yet it is incredibly difficult to perform randomized control trials on food or supplement intake. Such trials require thousands of participants, tracked over a set period of time, with other factors removed. Even if a group of 10,000 people agreed to increase its intake of broccoli for a month, it would be impossible to determine whether or not broccoli was responsible for subsequent measured changes in blood pressure or BMI, for example. According to Dr. McCormack, only a few randomized control trials—maybe 10—have been undertaken to test nutrition hypotheses, and they have primarily shown differences in the extremes. So people who ate no broccoli might have “worse” scores than those who exclusively ate five pounds of broccoli per day. This result is not very subtle or useful, but would be eaten up by the media, which is always hungry for any pronouncement that is new or different (remember that “exercise won’t help you lose weight” advice from Dr. Oz?). Most nutrition research is actually done with mechanism trials which focus on a single element and are stymied by surrogate markers. These markers, including among others blood pressure, hormone balance, insulin, and glucose levels, might change but do not necessarily have a guaranteed relationship to the clinical trial itself. In other words, eating more broccoli might appear to lower insulin levels, but that would be impossible to isolate from other factors. Plus the test subject may have lied about the amount of broccoli eaten, or at least overestimated it, while forgetting to mention her new workout program or any number of other small changes that could have lowered her insulin.
After explaining these problems, Dr. McCormack proceed to “myth bust” a number of silly studies by pointing out the weaknesses in their methodologies. There is no clear evidence for health bulletins claiming that we should all cut down on salt, avoid eggs, or go on a low-fat diet. Speaking of diets, evidence based research shows that the popular or fad diets—Weight Watchers, Jenny Craig, Slimfast etc.—are more or less equally effective. Dr. McCormack had special disdain for the paleo diet, calling it the “Atkins diet with cavemen added.” But the bottom line is that cutting calories will result in weight loss. Are all calories therefore equal? Probably not, even as there is simply no solid or extensive data on which to decide which calories are better than others. After surveying the field of nutrition research, Dr. McCormack found that the Mediterranean Diet (however that is defined) has been consistently linked with long term health. In the end, however, the commonsense phrase “all things in moderation,” which has been promoted in diet books since at least the fifteenth century, is the best advice about food intake.
I doubt that the average person refers to randomized clinical trials when making decisions about nutrition. Most of us follow any advice that reinforces our current lifestyle (i.e. bacon is good for you!), and accords with our knowledge of our own bodies. Since my own body responds well to a decrease in carbs, I tend to think that low-carb diets will be the most effective. Yet every body is unique. In my opinion, the real challenge for nutrition based research is that food is not a “scientific” topic. Most of us are invested emotionally with food, and are rather irrational about it. That is why we can say one thing (“I will eat more vegetables today”) and then immediately go and order a caramel brulee latte at Starbucks. This illogical kind of decision making—which informs everything we do, not just health decisions—fuels my doubts about both the “natural eating” movement and the notion that there is a “natural resting point” for a body’s weight. If I ate what my body told me to eat, I would be full of high-fat European yogurt, nutty granola drenched in brown rice syrup, and spice cake. I would then “naturally” weigh about 50 pounds more than I do right now. Sigh. Can I end with giving you some of my nutrition advice? When you go to a noon-hour talk that promises free snacks and find only boxes filled with large, soft, chocolate chunk cookies, ask yourself the following questions: 1) How much do you really like this particular kind of cookie? 2) What would it score from 1-10 in a taste test? At Dr. McCormack’s talk I analyzed my answers (not that much and maybe a five?) before putting the cookie down. Now that’s a successful nutrition test.