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Nutrition — The New Dismal Science

Posted Jul 08 2009 11:44am

There are few areas of preventive health care and in fact medicine as difficult to get a firm grasp on as nutrition. It seems that everyone has a different take on nutrition and advocates a different approach to healthy eating. Some pursue specific diets — the Mediterrenean diet, Atkins or low-fat diets. Others advise calorie counting and strict measurement. And still others nutritional supplementation, organic or locally grown foods, or behavioral approaches.

The implications of nutrition cannot be understated. Unhealthy eating is a significant risk factor for major diseases such as cardiovascular disease, cancer and dementia. Obesity, a major consequence of unhealthy eating, is a leading cause of death in the United States today.

As advocates for health, doctors are somewhat at a loss for how to advise their patients. Despite my interests in preventive health I am reluctant to advise my patients about nutrition or even apply what I understand about nutrition to my own life. I know that excess dietary salt is bad and feel comfortable counseling my patients about lowering their salt intake. I know obesity is bad but besides calorie restriction and exercise do not advise patients about particular diets to adopt. I used to feel comfortable counseling patients about what fats are bad (trans fats and saturated fats) and which are good (unsaturated fats) but have recently called this advice into question and stopped giving it.

So what makes the nutrition field so challenging? Here are some of the problems I have identified:

1) Counseling in any area of preventive health is difficult and subject to wide variations. Unlike prescription medications which are given for specific diagnoses and are themselves uniform, counseling methods vary widely in their use and their application. At least with smoking cessation, the end-message is unanimous — stop smoking. However, nutrition not only is subject to wide variations in how and when the message is delivered but what message is delivered. Some doctors recommend particular diets or suggest foods to avoid or adopt, while some simply refer their patients to nutritionists, dietiticians, or nurse practitioners.

2) Nutrition education in medical school and residency training is wholly inadequate. As a recent medical graduate, I can tell you that nutrition comprised a mere few hours during my entire 4 year, thousands of hours plus medical school curriculum. At my institution, nutrition was addressed under “Biochemistry and Nutrition”; however most of our time was spent drawing cellular pathways of metabolism or memorizing the number of ATPs (energy molecules) produced for various metabolites, rather than learning nutrition science as it pertains to real people. Thus far in my first year of residency nutrition has not once been a topic of our daily lectures and conferences. Most doctors it seems are left to their own devices to learn about nutrition, yet are seen by their patients as learned experts.

3) If the ties between the pharmaceutical industry and academia are problematic for medications, then conflicts of interests and biases within the nutrition field are even graver. In addition to the usual players, the nutrition industry includes farmers and food manufacturers, fast food chains and corporate restaurants, and the nutritional supplement industry — to name a few. Even trusted government sources such as the well-known USDA food pyramid are criticized for being biased against new developments in nutrition science.

4) Nutrition by its nature is less tractable. Unlike a medication which can be produced in mass to have consistent properties, foods differ from each other. Carrots from a local farmer’s market are different from carrots from a large grocery chain. Furthermore, their properties change with their preparation — uncooked vs pan-fried vs boiled. Breaking food down into their relevant properties — calories, fat content, carbohydrates — is also problematic. Foods have micronutrients such as phytochemicals that are not captured by these simplistic models. At the same time, absorption of foods is highly variable. A milligram of iron consumed is not a milligram of iron absorbed. Finally, the effects of nutrition on the body are multifactorial. In medicine we tend to study the effects of one drug on one clinical entity. However, nutrition effects many aspects of health at the same time in an interrelated way.

One of my goals over the next several months is to face this uncertainty and these challenges up front. I am starting with a book by Gary Taubes called “Good Calories, Bad Calories” and will periodically report on what I learn. Anyone who has any other recommendations for good reading please send my way. Nutrition it seems is the new dismal science. Let’s see if we can’t make it a little less so.

- Shantanu Nundy, M.D.

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