In honor of TwinTown Crossfit I am re-posting this January post in which I reviewed some of the recent scientific studies about the paleo diet. I’m doing this because I am planning to talk about this research tonight, and I am sure I will forget some of the details:
“The information cascade, or what I think should be called ‘the misinformation cascade’ is when people see someone else doing something and then they do the same thing, even though it goes against their instincts. It’s what has caused us all to keep buying low-fat foods even though they don’t actually improve weight loss. Eventually that sort of mis-information gets repeated so many times that it is taken to be true, even without any real evidence.” Dave said. I sat in his office snacking on a red bell-pepper. I was telling him about how hard it is for me to change my perception of animal fats as being evil, and grains as being good. It’s like a scooby doo ending, where the bad guy removes his mask to reveal that he was really the friendly neighbor that you had been trusting all along.
For the past 3 weeks Christina and I have been adhering to a palaeolithlic diet. I didn’t do too much research before we started (mainly because we are both healthy and can afford to play around with our diet for the sake of experimentation) but after being a vegetarian for so long, and now eating a diet heavily laden with meat, I decided to dig into the literature to see what potential damage I might actually be causing.
What I have been finding out has totally blown my mind.
Here is a summary of what I read this afternoon. The field of palaeolithic nutrition begins with observational studies of hunter-gatherer cultures, a few scattered studies comparing modern “western” diets with traditional diets and such. In the past few years, however, a number of small clinical trials have been done comparing the palaeolithic diet with various other “healthy” diets.
In 2007, Lindeberg et al compare the palaeolithic diet of lean meat, fish, fruits, vegetables, root vegetables, eggs, and nuts with a “Mediterranean-like diet” comprised of whole grains, low-fat dairy, vegetables, fruit, nuts, fish, oils, and margarine, in ischaemic heart disease patients with either type 2 diabetes or glucose intolerance. The study lasted 12 weeks, after which comparisons of body weight, waist circumference, and glucose tolerance were made. Both groups lost comparable amounts of weight, and reduced waist circumference, however the palaeo group had significantly improved glucose tolerance over the Mediterranean-like diet:
(the light grey is baseline glucose area under the curve (AUC) the medium grey is after 6 weeks and the dark grey is after 12 weeks (Lindeberg et al., 2007). The shorter the bar, the better the glucose tolerance.)
Okay, so this study shows that the palaeo diet might be slightly better than the Mediterranean diet if you have ischaemic heart disease and glucose intolerance. What about the rest of us?
In 2008, Osterdahl et al performed a dietary intervention on a small group of healthy individuals as part of a pilot study. They tested the effects of 3 weeks of a palaeolithic diet on several metabolic endpoints. They found significant reductions in body weight, BMI, waist circumference, systolic blood pressure, and plasminogen activator inhibitor-1 (used as a marker of several disease states, including cancer, obesity, and metabolic syndrome). Although the palaeo diet was higher in cholesterol, it did not cause increased blood cholesterol of the subjects. The subjects ate far less calories on the paleo diet than they had prior to the start of the study.
In 2009 Frassetto et al investigated the effects of a palaeo diet on different outcome variables used to measure circulatory health, and carbohydrate and lipid metabolism. The diet was controlled in that the researchers portioned out food and kept the calories constant to prevent the patients from losing weight. They wanted to see if the diet could be of benefit independently of the reduced body weight. The paleo diet REDUCED blood cholesterol, LDL cholesterol, VLDL cholesterol, and triglycerides, without affecting HDL cholesterol. They also found that it improved results of an oral glucose tolerance test, as well as reducing diastolic blood pressure. These results are extremely impressive given the small size of the group (9) and the short length of the study.
In 2009 Jönsson et al. performed a study where patients with type-2 diabetes ate either a palaeolithic diet or a “diabetes diet” which was designed in accordance with current guidelines. This was a randomized cross-over study, which basically means that each participant consumed both diets, and the order in which they completed each trial was random. Thus some patients ate palaeo for 3 months, then were switched to the “diabetes diet” and vice versa. The conclusion of the study was that the palaeo diet significantly improved glycemic control as well as body weight, BMI, diastolic blood pressure, triacylglycerol, and raised HDL compared with the “diabetes diet”.
These studies were all small, pilot type studies. I imagine it is incredibly difficult to find funding for something that is so contrary to what has been en-grained in our minds for years. When someone speaks to me about heart health, I think oatmeal. This is not due to any sort of research that I have seen, but instead to this little icon:It says “As part of a heart healthy diet, the soluble fiber in oatmeal helps reduce cholesterol.” If it’s only the soluble fiber that makes oatmeal a heart healthy food, a person would actually be better off skipping the oatmeal and having a cup of blackberries for breakfast instead, as blackberries have nearly twice the soluble fiber of oatmeal. In fact, most fruits and vegetables are high in soluble fiber, so why does my brain instantly think of oatmeal when people start talking fiber?
For more information about the politics of food labeling, check out the amazingly awesome Marion Nestle’s website
For more information about the paleo diet, check out the site of Dr. Loren Cordain, PhD by clicking here
..and for an awesome community of people who are eating primal (similar to paleo, but with a few delicious differences) click on Mark Sission’s site here
Lindeberg S, Jönsson T, Granfeldt Y, Borgstrand E, Soffman J, Sjostrom K, Ahren B. “A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease” Diabetologia, 50(9): 1795-807, Sep 2007.
Osterdahl M, Kocturk T, Koochek A, and Wandell PE. “Effects of a short-term intervention with a paleolithic diet in healthy volunteers” European Journal of Clinical Nutrition 62, 682-5; 2008.
Frassetto LA, Schloetter M, Mietus-Synder M, Morris Jr RC, and Sebastian A. “Metabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet” European Journal of Clinical Nutrition. 63, 947-55; 2009.
Jönsson T, Granfeldt Y, Ahren B, Branell UC, Palsson G, Hansson A, Soderstrom M, and Lindeberg S. “Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetics: a randomized cross-over pilot study” Cardiovascular Diabetology. 8:35; 2009.