Nutrition — The New Dismal Science

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. Some pursue specific diets — the Mediterrenean diet, Atkins or low-fat diets. Others advise calorie counting and strict measurement. And still others support nutritional supplementation, organic or locally grown foods, or behavioral approaches to healthy eating.

The importance of nutrition cannot be overstated. 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 and accounts for 300,000 deaths each year.

As advocates for health, doctors are somewhat at a loss for how to advise their patients about nutrition. Despite my interests in preventive health I am reluctant to give my patients nutrition advice. The science of nutrition seems to change daily and generally accepted mantras fall weekly. I know that excess dietary salt is bad and am comfortable counseling patients about lowering salt intake. I know obesity is bad but besides calorie restriction and exercise do not advise patients about what eating habits to adopt. I used to counsel 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 key problems:

1) Counseling in any area of preventive health is difficult and subject to wide variation. 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 message is clear — 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 others simply refer patients to nutritionists 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 energy molecules produced for various metabolites, rather than learning nutrition science as it pertains to real people. In my first year of residency training nutrition was not once a topic of our daily lectures and conferences. Most doctors it seems are left to their own devices to learn about nutrition.

3) If the ties between the pharmaceutical industry and academia are problematic for medicines, 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. Even trusted government sources such as the well-known USDA food pyramid are criticized for their biases.

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 components. 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 uncertaintyup 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 is the new dismal science. Let’s see if we can’t make it a little less dismal and a little more science.

- Shantanu Nundy, M.D.