Hormones

Peer-Reviewed Scientific Articles​

The ‘carnivore connection’ — evolutionary aspects of insulin resistance

URL: https://www.nature.com/articles/1601351

Journal: European Journal of Clinical Nutrition

Publication Date: 03/2002

Summary: Insulin resistance is common and is determined by physiological (aging, physical fitness), pathological (obesity) and genetic factors. The metabolic compensatory response to insulin resistance is hyperinsulinaemia, the primary purpose of which is to maintain normal glucose tolerance. The ‘carnivore connection’ postulates a critical role for the quantity of dietary protein and carbohydrate and the change in the glycaemic index of dietary carbohydrate in the evolution of insulin resistance and hyperinsulinaemia. Insulin resistance offered survival and reproductive advantages during the Ice Ages which dominated human evolution, during which a high-protein low-carbohydrate diet was consumed. Following the end of the last Ice Age and the advent of agriculture, dietary carbohydrate increased. Although this resulted in a sharp increase in the quantity of carbohydrate consumed, these traditional carbohydrate foods had a low glycaemic index and produced only modest increases in plasma insulin. The industrial revolution changed the quality of dietary carbohydrate. The milling of cereals made starch more digestible and postprandial glycaemic and insulin responses increased 2–3 fold compared with coarsely ground flour or whole grains. This combination of insulin resistance and hyperinsulinaemia is a common feature of many modern day diseases. Over the last 50 y the explosion of convenience and takeaway ‘fast foods’ has exposed most populations to caloric intakes far in excess of daily energy requirements and the resulting obesity has been a major factor in increasing the prevalence of insulin resistance.

Key Takeaways

Humans consumed a high protein low carbohydrate diet during the ice ages. Then, at the end of the last ice age carbohydrate intake increased with agriculture, but it wasn't until industrialization producing large quantities of refined carbohydrates did humans experience problems with insulin resistance and hyperinsulinemia that results in modern day diseases.

Modern Day Diseases Are Caused By Deviation From Our Ancestral Diet

The carnivore connection: dietary carbohydrate in the evolution of NIDDM.

URL: https://www.ncbi.nlm.nih.gov/pubmed/7895958

Journal: Diabetologia.

Publication Date: 12/1994

Summary: We postulate a critical role for the quantity and quality of dietary carbohydrate in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). Our primate ancestors ate a high-carbohydrate diet and the brain and reproductive tissues evolved a specific requirement for glucose as a source of fuel. But the Ice Ages which dominated the last two million years of human evolution brought a low-carbohydrate, high-protein diet. Certain metabolic adaptations were therefore necessary to accommodate the low glucose intake. Studies in both humans and experimental animals indicate that the adaptive (phenotypic) response to low-carbohydrate intake is insulin resistance. This provides the clue that insulin resistance is the mechanism for coping with a shortage of dietary glucose. We propose that the low-carbohydrate carnivorous diet would have disadvantaged reproduction in insulin-sensitive individuals and positively selected for individuals with insulin resistance. Natural selection would therefore result in a high proportion of people with genetically-determined insulin resistance. Other factors, such as geographic isolation, have contributed to further increases in the prevalence of the genotype in some population groups. Europeans may have a low incidence of diabetes because they were among the first to adopt agriculture and their diet has been high in carbohydrate for 10,000 years. The selection pressure for insulin resistance (i.e., a low-carbohydrate diet) was therefore relaxed much sooner in Caucasians than in other populations. Hence the prevalence of genes producing insulin resistance should be lower in the European population and any other group exposed to high-carbohydrate intake for a sufficiently long period of time.

Key Takeaways

Over the course of millions of years, the dietary patterns of humans and our ancestors have gone through some changes. Before the ice ages, it is likely that our ancestors ate a higher carbohydrate diet, but when the ice ages came along we were forced to eat a diet of mostly protein and fat. The ice ages lasted about two million years and therefore made it so individuals who could adapt to this high protein and fat diet were more likely to survive. But, after the ice ages humans began farming and returned to a higher carbohydrate diet. Populations that began farming earlier such as Europeans likely have adapted better to higher carbohydrate diets and are therefore less likely to become diabetic in the modern era.

Two Million Years Of Ice Ages Selected For Humans To Consume A High Protein and Fat Diet

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