Showing posts with label dietary guidelines. Show all posts
Showing posts with label dietary guidelines. Show all posts

Sunday, June 19, 2011

MyPlate

Source:  www.chosemyplate.gov

The USDA has recently released its newest dietary food guide: MyPlate.  The side-ways and striped MyPyramid that replaced the upright and grains-at-the-bottom pyramid has now, in-turn, been replaced by another info-graphic.  You can read an LA Times article here.  MyPyramid was a modest update to the original pyramid as it was an internet-only food guide, and even advocated some so-called "healthy" fats such as avocado and salad oils.  But the icon didn't actually contain any information regarding food, and instead relied on the interactive website.  This created an obvious deficit - that we need to see what we should eat - so the USDA is trying yet another design.

I have to commend them for using a single meal representation since few of us think of an entire day's worth of food in one thought.  It gives us some idea of what a meal should look like.  You might laugh at the notion that we have forgotten what a meal looks like, but clearly, as a society we have lost something.  Although I personally prepare my meals in a similar component-derived way (protein, some veggies, plenty of fat, maybe some fruit), this icon doesn't lend it self well to traditional meals such as curries, pots of beans with rice and veggies, or a dinner salad and soup.  And many cultures have thrived without breaking up their meals into various proportions.  But this is only a symptom of the actual problem - the untenable notion that we can summarize our entire diet into a single image.

Nutrition is in a unique position because it is both a science and a public health issue - unlike, say, particle physics.  A major goal of the science of nutrition is to reduce diet down to some fundamental level that allows us to explain our observations of diet, health, and disease.  And as a public health issue, the authorities want to communicate the healthiest diet in the shortest message.  This is a double-wammy of reductionism, which is one of the concerns of the current "food movement."

I recently listened to a lecture by Michael Pollan where he outlined the principles of his book In Defense of Food.  One of his main arguments against our current food culture is that of nutritionism.  Nutritionism, as opposed to nutrition, is the psuedo-science ideology that focuses on building a healthy diet from our current understanding of individual nutrients - antioxidants, omega-3's, fiber - that have been completely isolated from the foods, meals, and diets that they are components of.  In essence, it is an overly simplified and hubristic view of the complexities of nutrition.  And so we have guideliness that consist of discrete dietary components - dairy, protein, fruit - that should all be consumed in correct proportions and all at the same time.  No other culture has viewed diet in such a way, so why should we?  Pollan offers a more fluid algorithim-like recommendation for food: "Eat food.  Not too much.  Mostly plants."  And let culture fill in the rest.  I agree that Pollan's is probably best, albeit vague, but both guidelines make a flawed assumption.

The second major problem with dietary guidelines is that they attempt to be applicable to everyone - even the obese and diabetic.  As of 2010, one third of the U.S. is considered obese while another third is considered overweight (Flegal JAMA 2010); and roughly 11% of adults over the age of 20 have diabetes (CDC Fact Sheet).  Given that our population is no longer "normal" and that the preponderance of these cases, both obesity and diabetes, are directly related to diet, we cannot assume that one set of guidelines is remotely appropriate for everyone.  Although to be fair, those who are effortlessly lean may avoid obesity by following these guidelines as long as they follow the recommendations to "drink water instead of sugary drinks" and notice there is no section for dessert.  After all, not everyone needs to restrict carbohydrates.  But we need to change how we view obesity before addressing dietary guidelines, whether to everyone or to individuals.

The conventional wisdom suggests that obesity is simply the far end of a weight spectrum, and therefore obese people just need to eat like lean people do.  Or as the USDA recommends "enjoy your food, but eat less."  We don't tell smokers to simply smoke less, or alcoholics to simply drink less, or people with depression to simply "cheer up."  In these conditions, we acknowledge that there is a disorder or pathology, and that we need to change behavior in order to return to normality - by tapering off of cigarettes, absteining from alcohol, or going to therapy and taking medication.  Obesity is unique in that we ignore the disorder - as Taubes puts it, "a disorder of excess fat accumilation" - and plead for normality.  We need to acknowledge that a large number of people fatten differently than others, and therefore need a different diet if they want to control their weight.

Again, the USDA has made a modest improvement.  But it won't stop publishing dietary guidelines in info-graphic format any time soon, nor will it offer something that is removed from the economic responsibilities of the USDA (good article here).  So as someone who can't simply follow the USDA's guidelines without gaining weight, I'll combat obesity with what works for me.  Cheers to MoosePlate.
Bison steak with herb-butter.  Caprese salad of heirloom tomatoes and basil purée.

Monday, March 21, 2011

Symposium on reducing dietary saturated fat

     The latest issue of the American Journal of Clinical Nutrition has a perspective article highlighting topics discussed at an international nutritional symposium (Nutrition Symposium).  The goal of the symposium was to reach an expert consensus on the current state of research regarding the evidence for the reduction of dietary saturated fat for the prevention of cardiovascular disease (CVD).  There were several notable researchers.  This included Walter Willett, the nutrition research juggernaut who leads the ongoing Nurse's Health Study, and Ronald Krauss, whose research describes the deleterious effects of high carbohydrate diets on LDL particle and subsequent atherogenicity.
     The article seemed oddly cold and ambiguous.  While this may seem like an odd criticism of a scientific article, I usually characterize scientific writing as calculated and skeptical.  Perhaps it was just strange to see how little confidence the experts had on the available data which have been used to establish a very specific and rigorous public health message; that is, "reduce your saturated fat intake.  I don't care how you do it. Good God! Why aren't you reducing your saturated fat intake?!"
    Regardless, there were some interesting and important topics discussed:

1.  Given that some evidence, but certainly not all (my words), indicates that it is beneficial to reduce saturated fat intake, there is insufficient research examining what nutrients should replace it.  Thus, replacing saturated fat with transfats or carbohydrates, especially refined carbohydrates, likely offers no benefit and may increase the risk of CVD.

2.  There is actually little to no direct human evidence that monounsaturated fats (think olive oil) offer a beneficial replacement for saturated fats to reduce the risk of CVD.  The recommendations given are based on animal studies, epidemiological studies, and risk factors (cholesterol) and not intervention studies with hard CVD outcomes.

3.  There is no consistent epidemiological evidence that dairy products adversely effect CVD risk and no intervention research indicating that it actually does.  Although I would not have this perception given the nutritional Zeitgeist.  


4.  Research needs to address the role of individual saturated fats in the diet (although whole foods never contain them in isolation).  Single biomarkers for CVD risk, such as LDL, HDL, triglycerides, LDL particle size, and many more, may be insufficient to judge the effects of diet on actual CVD risk (although by my count, most of these markers are adversely affected by refined carbohydrates and unaffected or improved by fat).  Also, genetics appear to play an important role, but there isn't enough data to clarify this role.

     I'm not sure what the impetus was to have all of these researchers convene and address this issue.  I can only imagine (hope?) that it has been the mounting skepticism for the current dietary recommendations given by numerous organizations; and thus, an opportunity to reevaluate the evidence.  I'm happy to see that refined carbohydrates are being put under the microscope not only for obesity, but now also for heart disease.

(Side note:  I'm doing my best to avoid becoming a sarcastic or overtly critical blogger who constantly points out perceived flaws in what I share.  But I have to say that I'm concerned that eight of the eleven organizations that provided (unrestricted) grants were industrial food groups, most of which were dairy groups.)