The Road to RDville: More Med diet

Whoops…missed yesterday’s post. Isn’t it Murphy’s Law that the amount of schoolwork you have to do expands to fill the amount of time you intended to spend blogging? No…well, maybe that’s just my law. Or my lot (in life)!
Anyhoo, on Sunday I posted my original version of my latest column in The Seattle Times. You can now see it in its native online habitat here. How did I choose the Mediterranean diet for a column topic, you ask? Well, I’ll tell you: I spent an intense week of my life back in March writing a 20-odd page paper about this way of eating for my Nutrition & Metabolism class. It was our final exam (we usually have 5-6 tough questions for our take-home exams in this class, so when he told us there would be only one question for the final, we were a little scared).
Specifically, we were asked to explain whether or not the Mediterranean diet was the optimal diet for the prevention and treatment of heart disease, type 2 diabetes, obesity, chronic inflammation, cancer and Alzheimer’s disease. Naturally, we had to support our contention with evidence.
I can’t even tell you how many scientific journal articles I read about the Med diet. Piles and piles and piles. I have a tendency to, as I put it, fall down the “research rabbit hole,” especially when I’m personally interested in a topic, and not simply writing about it because I have to. I was still reading articles and cramming in more info up until the moment I hit “send” to e-mail it to my prof.
What I found really exciting, and I touched on this in the Times column, was the direction that nutrition research is starting to go. For decades (nay, centuries), nutrition research has been ruled by the “one nutrient, one disease” philosophy. In other words, a deficiency of a specific nutrient causes a specific disease. For example, vitamin C and scurvy, thiamine and beriberi, vitamin D and rickets, niacin and pellegra. Now, the one-nutrient rule has been very important and useful–it’s how many nutrients were even “discovered.” But the rule doesn’t quite do the job when trying to explain how food and nutrition are related to the multi-factorial chronic diseases that are of concern in the modern world (not that beriberi and scurvy never happen any more, but they aren’t very common, and we’ve got them figured out!).
Many people would like a definitive answer to questions like, “What foods should I eat to prevent cancer?” The truth is that anyone who gives you a list of foods and says “Eating these WILL prevent cancer” is lying. The answer is just not that clear cut. Here’s what happens, generally, when scientists investigate the role of diet in chronic disease. 

  1. They do epidemiological studies (population studies) in which they look at dietary habits of a population, as well as the presence of existing disease (prevalence) and/or new cases of disease that crop up during the study (incidence). They look at whether there is an association between diet and disease (i.e., people who eat a lot of vegetables are less likely to get cancer), and then look further to see if maybe people who eat a lot of vegetables happen to have other lifestyle habits that could explain why they are less likely to get cancer.
  2. They do randomized control trials (RCT), in which people are randomly assigned to, say, eat a vegetable rich diet or a diet low in vegetables. They follow up and see if the vegetable group is less likely to develop cancer. RTCs are the research “gold standard,” but they are very difficult, and very expensive, to do well in free-living human populations.
  3. They look at how certain nutrients function in a lab setting. For example, scientists know how antioxidants function biochemically, because they can observe it in a test tube.

In many cases, when science sees definite diet-disease associations in epidemiological studies, and those associations are backed up by what is known to be true about biochemical mechanisms, that makes for some pretty solid evidence. But it doesn’t show cause-and-effect, which can be frustrating.
Nevertheless, the movement toward looking at how people eat in the big picture, rather than fixating on how much beta-carotene they are ingesting, is a good thing. It makes more sense in the real world. And coming back to the Mediterranean diet, so many large, long-term studies all around the world are finding that people who eat in a way that closely matches the traditional Mediterranean diet have lower rates of all the disease I mentioned above. Now that’s some food for thought!