Tuesday, November 18, 2008

The healthiest diet in the world

Is the Mediterranean diet the healthiest diet in the world? Better than the 7th Day Adventists? Better than the diet of those 100-year-olds on Okinawa? The New York Times Health Experts seem to think so.

Writer Dr. Peter Libby, professor of medicine at Harvard Medical School and chief of cardiovascular medicine at Brigham and Women’s Hospital in Boston, bases this conclusion on a study released in September by the British Journal of Medicine. The NYT article says that, compared to other diets, individuals who eat a Mediterranean Diet are at a decreased risk of developing heart disease and cancer. Dr. Libby hypothesizes that the reason the diet works compared to others is that 1.It has genuine health benefits and 2.People can actually stick with it long term.

One important point: Although the NYT article makes it sound like the Mediterranean diet is being compared to other diets like Atkins, South Beach, DASH, etc., what is really being compared is adherence to the Mediterranean diet vs. non-adherence. Right now we'll have to suspend disbelief that there isn't a One True Mediterranean Diet.

Adherence to the diet was defined as doing more Mediterranean things (like eating fruits and vegetables, cereals, olive oil, a little red wine), and abstaining from non-Mediterranean things (like red and processed meats and dairy) than the average (median) person in the study. So say the median number of fruits eaten per day by study participants was 2. A person in the study who ate 3 fruits per day would earn a "Mediterranean point". If the median number of servings of red meat per week was 4and a participant ate 7, he or she would not get a "Mediterranean point". The idea is that people in the study with the most "Mediterranean points" were the healthiest.

Although the whole "studying diet as a whole rather than individual nutrients" movement is great, the part of the study design that interested me the most was its focus on compliance. One of the most difficult parts of doing a randomized controlled study on diet is figuring out what to do with the people who go off their diets- and many do.

If you randomize someone to Atkins, and they eat cookies everyday anyway and gain a bunch of weight, do you keep them in the Adkins group for analysis purposes or do you move them in the no-diet group? One argument says, "They sure weren't acting like they were on Atkins so we don't want their weight gain to mask the effects of Atkins on the people who actually complied." The other argument says, "If Atkins wasn't such a crappy diet, then that person would have complied. We need to know that there are people who try Atkins and gain weight because they can't/won't follow the rules."

All this does seem to lead to the conclusion that the benefits of the Mediterranean diet come from 1. Actual health benefits particular to the foods (from what we do know about the micronutrients, etc.) and 2. The fact that eating fruit, vegetables, cereal, olive oil and drinking wine is enjoyable, actually.

So what about the Adventists and the Okinawans? Maybe being vegetarian or eating seaweed and bean curds are just as healthy as the Mediterranean diet, but are not as easy to comply to. I don't think that's the real answer to why these diets weren't found to be the "world's healthiest", but I'll get to that in a minute.

A major limitation to the study is the way the study authors defined the Mediterranean diet. There are a lot of differences in the cultures and cuisines in that region. There is no One True Way. The authors say these regional/cultural differences wash out compared to the difference between what they call Mediterranean and non-Mediterranean.

However, when you get down to the fine print, what is really being studied here is compliance to a diet that these researchers have defined as good and have called Mediterranean. Maybe because the term is already mainstream? I'm not saying the diet of that region is didn't influence the selection of the study diet, but I am saying that those dietary practices are not exclusive to that region. If you look at other groups with low cardiovascular disease and cancer mortality rates, you see the same things: lots of fruits, veggies and grains, few red and processed meats and dairy.

So what's the healthiest diet in the world? The one you've heard about 1000 times before. Call it the no crap diet. There is a healthy way to eat, but I don't think this study shows that at any particular region "owns" it.

7mi with .75, .65, .5, .35, .25 mi intervals
2 sets stairs
upper body weights