The new dietary wisdom

Carbs are out.  Fats are in.  

We seem to be bombarded by messages these days warning of the evils of carbs, particularly sugar.  The recently released documentary, Fed Up, produced by Katie Couric presents one conspiratorial, over-wrought perspective on the issue.

In their indictment of farm policies, somehow the makers of Fed Up, failed to look at some of the best economic research on the topic, which shows that sugar import quotas, among other policies, make US sugar prices 2-3 times higher than the world price.  Moreover, ethanol policies have driven up the price of corn and have made high fructose corn syrup (HFCS) more expensive as well.  Here, for example, is USDA data on the price of HFCS over the past 14 years.  As you can see, prices have more than doubled since 2005.

Of course, that's just one example.  This week in the Sunday Review edition of the New York Times ran an editorial by David Ludwig and Mark Friedman, which a argued that over-eating is actually making us hungrier.  They seem to place the blame mainly on carbs, writing:

By this way of thinking, the increasing amount and processing of carbohydrates in the American diet has increased insulin levels, put fat cells into storage overdrive and elicited obesity-promoting biological responses in a large number of people. Like an infection that raises the body temperature set point, high consumption of refined carbohydrates — chips, crackers, cakes, soft drinks, sugary breakfast cereals and even white rice and bread — has increased body weights throughout the population.

One reason we consume so many refined carbohydrates today is because they have been added to processed foods in place of fats — which have been the main target of calorie reduction efforts since the 1970s. 

Last week, the Wall Street Journal also ran an editorial on the issue by Nina Teicholz, who has a recently released book, The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.  In the editorial, she argues that past nutritional guidelines that emphasized carbs and demonized fat were a major cause of the rise in obesity, writing:

Seeing the U.S. population grow sicker and fatter while adhering to official dietary guidelines has put nutrition authorities in an awkward position. Recently, the response of many researchers has been to blame "Big Food" for bombarding Americans with sugar-laden products. No doubt these are bad for us, but it is also fair to say that the food industry has simply been responding to the dietary guidelines issued by the AHA and USDA, which have encouraged high-carbohydrate diets and until quite recently said next to nothing about the need to limit sugar.

Indeed, up until 1999, the AHA was still advising Americans to reach for "soft drinks," and in 2001, the group was still recommending snacks of "gum-drops" and "hard candies made primarily with sugar" to avoid fatty foods.

Teicholz does a good job describing how previous dietary guidelines were based on tenuous scientific evidence and largely represented group think and a desire to "do something."  

Here's my question: How can we be so sure we now know more?  It seems to me this history lesson would cause us to be much more cautious about what we know about nutritional science and about the ability of public policy to beneficially affect food choice, weight, and health.  Yet, the aforementioned writings, and others, often contain as much hubris as ever.  It is unhealthy to eat too many carbs (or too much fat for that matter), but do we really know enough to design policies that will have intended effects?  I'm skeptical.

One reason is that writings by medical doctors and nutritionists on carbs often narrowly focused and miss larger "macro" issues.  Here, for example, is USDA data on per capita sugar consumption.  I've added in the recent trend lines, which show a strong downward trend in consumption over the past decade.

I suspect some of the downward trend is due to increased public awareness of the dangers of over-consumption of sugars, but also because of market conditions and aforementioned government policies.   

Another factor that many of these writers seem to overlook is that we grow a lot of carb-producing grains not just because of nutritional guidelines but because of economic forces.  The reality is that, by far, the most cost efficient producers of calories and protein are crops like corn, wheat, soybeans, and rice.  Historically, the challenge has been (and it remains a current challenge in many parts of the world), producing enough food and calories to keep pace with a growing population.  Moreover, if you're concerned about environmental issues, you also want to get as many calories and nutrients using the least amount of land and other resources, and that's precisely why economic forces lead farmers choose to grow so much corn, wheat, soybeans, and rice (not to mention these can be stored and will not spoil and waste soon after harvest).  I'm not saying we shouldn't re-think how much of these types of grains we eat, often in processed food, but I think it is useful to have some perspective on why these crops are so prevalent on our farms and in our diet.

I'll conclude with this passage I recently read from Sara Hara, a nutritionist who was dismayed by what she saw in Fed Up.   

An important note for those who are earnestly trying to sort through the abundance of the information and misinformation about "good foods" and "bad foods" in search of the truth: know the source of the information being promoted and the difference between a real nutrition expert and a self-proclaimed "expert". Most medical doctors are well trained in medicine, but have less than a semester of nutrition education in the entirety of their training (there are a few rare exceptions). Medical doctors are smart, but are not typically experts in nutrition. Investigative journalists are also a talented lot, but rarely have formal education in nutrition.Registered Dietitians/Nutritionists (RD or RDN) have at least a 4 year degree in nutrition (many have an additional 2 year master's degree), have completed a clinical nutrition internship, and maintain continuing education requirements to retain their credential. THESE are the nutrition experts... along with researchers and other professionals who have advanced degrees in Nutrition. I was struck by the fact that the new film Fed Up has a list of "experts" that includes medical doctors, a psychologist, politicians and journalists...all very intelligent and respected professionals, but none with extensive training in nutrition. There are no RDN's among their "experts"... and for good reason. Most true nutrition experts do not agree with the propaganda being promoted by this film. The RDN experts know that the issue is multi-faceted and cannot be reasonably blamed on a single factor. Nutrition needs to be viewed in context of lifestyle habits, genetics, personal preferences, and so much more. Sensationalism sells... but healthy living and common sense are what will fix our nation's failing health.