This paper was published in the American Journal of Clinical Nutrition 2005 Feb;81(2):341-54
Study title and authors:
Origins and evolution of the Western diet: health implications for the 21st century.
Cordain L, Eaton SB, Sebastian A, Mann N, Lindeberg S, Watkins BA, O'Keefe JH, Brand-Miller J.
Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523, USA. firstname.lastname@example.org
This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/15699220
In this review Professor Cordain notes that humans are genetically adapted to the diet of their ancestors. The massive changes in diet that has occured with the development of agriculture in the last 10,000 years or so has occured too rapidly for humans to genetically adapt. This, combined with modern nutitional trends have led to the emergence of the diseases of civilisation such as diabetes, heart disease and cancer.
In the US 11 million people have diabetes, 64 million people suffer from cardiovascular diseases and cancer is responsible for 25% of all deaths.
Professor Cordain investigates the diets of pre-agricutural man and modern man and the diets effects on health.
Types of food in pre-agricultural diets and modern diets.
(i) Before agriculture our diets would of consisted of mimimally processed animal food and plant food.
(ii) 72% of the daily food consumed today such as cereals, refined sugars and vegetable oils would not have been consumed in the pre-agricultural era.
(iii) The yearly intake of sugar was 6.8 kg in 1815 and had risen to 54.5 kg in 1970. Since 1970 sugar consumption has increased by a further 24%.
(iv) The consumption of fructose (mainly from high fructose corn syrup) has increased by 25% since 1970.
(v) Since 1909 vegetable oil consumption has increased by 130% and margarine consumption has increased by 410%.
What are the health effects of the modern diet?
(a) Consumption of refined cereals and sugars cause an acute rise in the levels of blood glucose and insulin which leads to insulin resistance and the metabolic syndrome which is a precursor to heart disease and diabetes.
(b) High fructose consumption has been shown to induce insulin resistance.
(c) 39% of the typical US diet is made up of high fructose corn syrup, sugars and refined cereals (foods which were not consumed by most people as recently as 200 years ago). These foods promote the causes of insulin resistance:
(i) High blood glucose levels.
(ii) High insulin levels.
(iii) High levels of very low density lipoprotein (VLDL) cholesterol.
(d) A high ratio of the consumption of omega-6 fats compared to omega-3 fats are implicated in chronic diseases such as diabetes, heart disease and cancer. The ratio of omega-6 to omega-3 was estimated to be around 2.5:1 in the pre-agricultural diet. Vegetable oils and margarine are high in omega-6 and low in omega-3, thus with the massive rise in the consumption of vegetable oils and margarine the modern diet provides a ratio of around 10:1 of omega-6 to omega-3.
(e) In the pre-agricultural era, carbohydrate consumption may have been as low as 22% of the diet, whereas the modern diet contains about 60% as carbohydrates. Studies in patients with type II diabetes have shown that diets low in carbohydrate decrease the risk of diabetes and heart disease by lowering the levels of harmful triglycerides and very low density lipoprotein (VLDL) cholesterol, and increasing the levels of the beneficial high density lipoprotein (HDL) cholesterol.
(f) High homocysteine levels are linked to an increase in heart disease and diabetes. Meat eating populations have lower homocysteine levels than non-meat eaters.
(g) 36% of the typical US diet is made up of refined sugars and vegetable oils which are virtually devoid of vitamins and minerals. Because of the high consumption of these products in the modern diet, people are now deficient in many vitamins and minerals such as zinc, calcium, magnesium, vitamin A and vitamin B12. Vitamin and mineral deficiences are implicated in many of the diseases of civilisation such as diabetes, heart disease and cancer.
The review by Professor Cordain shows that the change of diet since the advent of agriculture and the introduction of modern foods such as cereals, refined cereals, sugars, vegetable oils and margarine may produce nutritional factors that underlie or exacerbate vitually all chronic diseases such as diabetes, heart disease and cancer. Our genetic make-up is still rooted in the pre-agricultueal era and has not adapted to the new foods in the modern diets such as cereals, sugar, vegetable oils and margarine.