I remember once being startled during a conversation with my boss, a pharmacist, because his response to my points about getting vitamins from diet was basically "why worry about that, just take a vitamin pill". To me, the idea that health comes from a pill rather than from living properly is bizarre. But to someone with a doctorate in pharmacy, which in many ways is applied chemistry, it is an obvious path.
This conversation from a couple of years ago came back to me as I read Michael Pollan's latest book In Defense of Food: An Eater's Manifesto. Mr. Pollan begins his manifesto by identifying nutritionism, the idea that we should "understand and engage with food and our bodies in terms of their nutritional and chemical constituents and requirements..." because "foods are essentially the sum of their nutrient parts."

After years of health classes in public school, learning about the four food groups (or the seven) and the USDA food pyramid, (not to mention the alternate food pyramids that have been suggested by Harvard University, the University of Michigan, and vegetarian groups), stints in restaurant and hospital kitchens, and many years of cooking and gardening, I have to admit that the obvious problem with a lot of my thinking about food and diet wasn't so clear to me until I read this book. That obvious problem is that we've let the inmates take charge of the asylum!
Science is not a body of knowledge...it's a process for adding to our knowledge. And the results of scientific investigation are, by their very nature, tentative--always waiting to be supplemented or supplanted by further investigation. Yet, we put the scientists in charge of food long before they were ready. And if you look at some of the foods that have been created since nutrition science came along, things like margarine and egg beaters, it's pretty obvious that something's wrong. Of course, as a hospital cook I had the same idea when I was working under a nutritionist; some of the stuff that was being pushed on patients was basically inedible. But it conformed to the nutrient tables and prescriptions, and so that was what counted...even if the food got sent back to the kitchen uneaten.
Mr. Pollan's book is not a book for gourmands, however. It's a plea for real food, not manufactured edibles. It's a slender volume and well worth a read. It's available at Amazon, of course, and likely most book stores. (I got mine from the library.) There's also an essay on Mr. Pollan's web site that reproduces some of the beginning and ending of his book that is a great introduction to the work.
I'm now reading his earlier (and longer work) The Omnivore's Dilemma.