Saturday, October 4, 2008

Paleolithic Diet Clinical Trials

If Dr. Ancel Keys (of diet-heart hypothesis fame) had been a proponent of "paleolithic nutrition", we would have numerous large intervention trials by now either confirming or denying its ability to prevent health problems. In this alternate reality, public health would probably be a lot better than it is today. Sadly, we have to settle for our current reality where the paleolithic diet has only been evaluated in two small trials, and medical research spends its (our) money repeatedly conducting failed attempts to link saturated fat to every ill you can think of. But let's at least take a look at what we have.

Both trials were conducted in Sweden. In the first one, lead by Dr. Per Wändell, 14 healthy participants (5 men, 9 women) completed a 3-week dietary intervention in which they were counseled to eat a "paleolithic diet". Calories were not restricted, only food categories were. Participants were told to eat as much as they wanted of fruit, vegetables, fish, lean meats, nuts, flax and canola oil, coffe and tea (without dairy). They were allowed restricted quantities of dried fruit, potatoes (2 medium/day) salted meat and fish, fat meat and honey. They were told not to eat dairy, grain products, canned food, sugar and salt.

After three weeks, the participants had:
  • Decreased their caloric intake from 2,478 to 1,584 kcal
  • Increased their percentage protein and fat, while decreasing carbohydrate
  • Decreased saturated fat, increased dietary cholesterol, decreased sodium intake, increased potassium
  • Lost 2.3 kg (5 lb)
  • Decreased waist circumference, blood pressure and PAI-1
Not bad for a 3-week intervention on healthy subjects. This study suffered from some serious problems, however. #1 is the lack of a control group as a means for comparison. Ouch. #2 is the small study size and resulting lack of statistical power. I consider this one encouraging but by no means conclusive.

The second study was conducted by the author of the Kitava study, Dr. Staffan Lindeberg. The study design was very interesting. He randomly assigned 29 men with ischemic heart disease, plus type II diabetes or glucose intolerance, to either a "Mediterranean diet" or a "paleolithic diet". Neither diet was calorie-restricted. Here's the beauty of the study design: the Mediterranean diet was the control for the paleo diet. The reason that's so great is it completely eliminates the placebo effect. Both groups were told they were being assigned to a healthy diet to try to improve their health. Each group was educated on the health benefits of their diet but not the other one. It would have been nice to see a regular non-intervention control group as well, but this design was adequate to see some differences.

Participants eating the Mediterranean diet were counseled to focus on whole grains, low-fat dairy, potatoes, legumes, vegetables, fruit, fatty fish and vegetable oils rich in monounsaturated fats and alpha-linolenic acid (omega-3). I'm going to go on a little tangent here. This is truly a bizarre concept of what people eat in the Mediterranean region. It's a fantasy invented in the US to justify the mainstream concept of a healthy diet. My father is French and I spent many summers with my family in southern France. They ate white bread, full-fat dairy at every meal, legumes with fatty pork, sausages and lamb chops. In fact, full-fat dairy wasn't fat enough sometimes. Many of the yogurts and cheeses we ate were made from milk with extra cream added. 

The paleolithic group was counseled to eat lean meat, fish, fruit, leafy and cruciferous vegetables, root vegetables (including moderate amounts of potatoes), eggs and nuts. They were told to avoid dairy, grain products, processed food, sugar and beer.

Both groups were bordering on obese at the beginning of the study. All participants had cardiovascular disease and moderate to severe glucose intolerance (i.e. type II diabetes). After 12 weeks, both groups improved on several parameters. That includes fat mass and waist circumference. But the paleolithic diet trumped the Mediterranean diet in many ways:
  • Greater fat loss in the the midsection and a trend toward greater weight loss
  • Greater voluntary reduction in caloric intake (total intake paleo= 1,344 kcal; Med= 1,795)
  • A remarkable improvement in glucose tolerance that did not occur significantly in the Mediterranean group
  • A decrease in fasting glucose
  • An increase in insulin sensitivity (HOMA-IR)
Overall, the paleolithic diet came out looking very good. But I haven't even gotten to the best part yet. At the beginning of the trial, 12 out of the 14 people in the paleo group had elevated fasting glucose. At the end, every single one had normal fasting glucose. In the Mediterranean group, 13 out of 15 began with elevated glucose and 8 out of 15 ended with it. This clearly shows that a paleolithic diet is an excellent way to restore glucose control to a person who still has beta cells in their pancreas.

This post is getting long, so I think I'll save the interpretation for the next post.

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