A Paleolithic diet confers higher insulin sensitivity, lower C-reactive protein and lower blood pressure than a cereal-based diet in domestic pigs

Abstract

Background: A Paleolithic diet has been suggested to be more in concordance with human evolutionary legacy than a cereal based diet. This might explain the lower incidence among hunter-gatherers of diseases of affluence such as type 2 diabetes, obesity and cardiovascular disease. The aim of this study was to experimentally study the long-term effect of a Paleolithic diet on risk factors for these diseases in domestic pigs. We examined glucose tolerance, post-challenge insulin response, plasma C-reactive protein and blood pressure after 15 months on Paleolithic diet in comparison with a cereal based swine feed.

Methods: Upon weaning twenty-four piglets were randomly allocated either to cereal based swine feed (Cereal group) or cereal free Paleolithic diet consisting of vegetables, fruit, meat and a small amount of tubers (Paleolithic group). At 17 months of age an intravenous glucose tolerance test was performed and pancreas specimens were collected for immunohistochemistry. Group comparisons of continuous variables were made by use of the t-test. P < 0.05 was chosen for statistical significance. Simple and multivariate correlations were evaluated by use of linear regression analysis.

Results: At the end of the study the Paleolithic group weighed 22% less and had 43% lower subcutaneous fat thickness at mid sternum. No significant difference was seen in fasting glucose between groups. Dynamic insulin sensitivity was significantly higher (p = 0.004) and the insulin response was significantly lower in the Paleolithic group (p = 0.001). The geometric mean of C-reactive protein was 82% lower (p = 0.0007) and intra-arterial diastolic blood pressure was 13% lower in the Paleolithic group (p = 0.007). In evaluations of multivariate correlations, diet emerged as the strongest explanatory variable for the variations in dynamic insulin sensitivity, insulin response, C-reactive protein and diastolic blood pressure when compared to other relevant variables such as weight and subcutaneous fat thickness at mid sternum. There was no obvious immunohistochemical difference in pancreatic islets between the groups, but leukocytes were clearly more frequent in sampled pancreas from the Cereal group.

Conclusion: This study in domestic pigs suggests that a Paleolithic diet conferred higher insulin sensitivity, lower C-reactive protein and lower blood pressure when compared to a cereal based diet.

Figures

Figure 1

Average weight during study and final weight. The curves representing mean group weight started to diverge after 3 months of feeding the different diets. Spread of individual weights at the end of the study displayed some overlap between groups (insert).

Figure 2

Glucose response during glucose tolerance test. No significant difference was observed between groups in average glucose response after an intravenous bolus of glucose (0.5 g/kg body weight) at age 17 months.

Figure 3

Insulin response during glucose tolerance test. Average insulin area under the curve from 0 to 120 minutes was significantly lower by 47% in the Paleolithic group as compared to the Cereal group after an intravenous bolus of glucose (0.5 g/kg body weight) at age 17 months (p = 0.001).

Figure 4

Immunohistochemical staining of pancreatic islets. Immunohistochemical staining of pancreatic islets showed no obvious difference between Cereal (A and C) and Paleolithic (B and D) groups regarding the frequencies or intraislet distribution patterns of cells storing insulin (A and B), glucagon (C and D), somatostatin and pancreatic polypeptide, nor was the islet size or islet frequency overtly different.

Figure 5

Frequency of pancreatic leukocytes. Leukocytes, as revealed by their unspecific binding of the secondary antibodies, their small size, and their characteristic nuclei, were clearly more frequent (more than doubled by cell counting) in all the sampled pigs from the Cereal group (A and C, n = 5) as compared to all the sampled pigs from the Paleolithic group (B and D, n = 5), with no overlapping between groups. These cells usually occurred scattered throughout the exocrine pancreatic parenchyma or clustered around pancreatic ducts (A and B) and blood vessels (C and D).