In May of last year I wrote about a study which tested the effects of a so-called paleolithic diet ” a diet based on the foods eaten prior to about 10,000 years when it’s believed some of our ancestors converted from being to hunger-gatherers to agriculturalists. The paleolithic diet is one which contains ‘primal’ foods such as meat, vegetables, fruit and nuts, but is devoid of nutritional newcomers like refined sugar, grain-based foods, dairy products and legumes (beans and lentils).
In the study I reported in May , individuals ate an average of 900 calories less per day than they had been previously for three weeks. Not surprisingly, they lost weight (an average of 2.3 kg/5 lbs). But in addition, there were other benefits for the study subjects in the form of reduced blood pressure and a considerable reduction in the levels of a substance known as plasminogen activator inhibitor-1 (this would be expected to reduce the clotting tendency of the blood, which might translate into a reduced risk of heart attack and stroke).
The effects of the paleolithic diet were once again assessed in a recent study published on-line in the European Journal of Clinical Nutrition . This study subjected 9 men and women to a paleolithic diet for just 10 days. In the preceding 7 days, their usual diet was morphed into the paleolithic diet in the form of three diets which contained steadily more potassium and fibre.
The paleoloithic diet that the subjects ate for 10 days was made up of meat (chicken, pork, turkey), vegetables (e.g. lettuce, spinach, broccoli, salad, parsnips), fruit (pineapple, melon), honey and nuts (almonds). The diet emphasised lean meat (while the true paleolithic diet was unlikely to be particularly lean) also included foods that you can’t imagine our early ancestors eating (tomato soup, guacamole, carrot juice, mayonnaise), but the basic make-up of the diet was, overall, reflective of the foods we ate prior to the agricultural age.
While weight loss is often experienced on a paleolithic-type diet, the authors of this study were most certainly not interested in this: if someone in the study was found to be losing weight they were instructed to eat more to counteract this. The aim was to see if such a diet might produce physiological/metabolic benefits, even in the absence of weight loss.
Weight aside, the subjects experienced significant changes in a number of parameters. These included:
Reduced blood pressure
Lower fasting insulin levels (levels fell from an average of 11.5 to 3.6 µU/ml)
Lower insulin secretion after ingestion of glucose
Lower levels of total cholesterol
Lower levels of LDL-cholesterol
Lower triglyceride levels
These changes, taken as a whole, would be expected to translate into a reduced risk of type 2 diabetes and cardiovascular disease if sustained.
While the number of individuals in this study was relatively small, one perhaps notable finding is that the results were very consistent: 8 or 9 of the group (remember, the group only contained 9 people) were found to experience each of the changes listed above. The suggestion here is that such a diet may have broad benefits for a population, though larger studies would be required to confirm this.
What is also striking, I think, about the results is just how quickly the changes came. There was a run-in of a week, but the full-blown paleolithic diet lasted a mere 10 days. It does seem that returning to the diet of our past can bring about very rapid benefits in terms of our physiology and biochemistry going forward.
1. -sterdahl M, et al. Effects of a short-term intervention with a paleolithic diet in healthy volunteers. European Journal of Clinical Nutrition 2008;62:682″685
2. Frassetto LA, et al. Metabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet. Eur J Clin Nutr 11 Feb 2009 [Epub ahead of print]