Monday, August 26, 2013

Is Modern Disease Due to Agricultural Foods?

Early Agriculture 

Initially agriculture was a disaster, likely born out of desperation from overpopulation >> food scarcity due to the Holocene Extinction, which occurred between 9,000-13,000 years ago (because, you know, humans were terrible hunters).  The health of early agriculturalists was quite poor:

  • Early agriculturists showed signs of malnutrition and infectious disease.  They were shorter, had an 11% smaller cranial capacity and evidence of poor dental health [1]
  • In addition to arthritis, parasites and some atherosclerosis (not abnormal), Otzi the Ice Man had gallstones, cavities and periodontitis [2]
  • Many ancient Egyptians seem to have had poor dental health [3]
  • The health of the agriculturalists at Hardin village was worse than the neighbouring at Indian Knoll [4] 

“Generally, in most parts of the world, whenever cereal-based diets were first adopted as a staple food replacing the primarily animal-based diets of hunter-gatherers, there was a characteristic reduction in stature, an increase in infant mortality, a reduction in lifespan, an increased incidence of infectious diseases, an increase in iron deficiency anemia, an increased incidence of osteomalacia, porotic hyperostosis and other bone mineral disorders and an increase in the number of dental caries and enamel defects” [5] 

What to Blame 

It would be wrong to compare the disease rates of modern of paleolithic HGs with early agriculturalists or those of the modern world and then solely blame agricultural foods (grains, dairy, legumes) for modern health problems as it’s observational, and just like with any observational study there are confounding variables.  In the early agriculturists potential confounders include increased lack of food, malnutrition (from relying heavily on grains, etc) and population density >> infection.  The modern world has many more confounders, such as refined sugar, seed oils, alcohol, smoking, low physical activity/sedentarism, etc (that list could get really long) 

What’s more, the rates of chronic disease have generally only taken off quite recently, suggesting the later additions to the modern food environment and modern lifestyle are perhaps more responsible: 

  • Coronary heart disease (CHD) only took off in the early 20th century (independent of life expectancy), which coincided with an increase in smoking, refined sugar, refined seed oils and trans fats [6] [7] [8]
  • Cancer death rates in Australia have increased from 7% male, 8% female in 1909 to 31% male, 26% female in 2002 (higher life expectancy would have contributed) [9]
  • The obesity epidemic is fairly recent (see graphs) [10], although there were still a lot of overweight people in the US during the 1960’s (there doesn’t seem to be any data from earlier).  Likewise childhood obesity was almost non-existent in the 1930s [11]
  • In the UK, the prevalence of diagnosed allergic rhinitis and eczema in children have both trebled over the last three decades” and “since 1990, admissions for anaphylaxis have increased by 700%, for food allergy by 500” [12]

Also, there are many societies who consume agricultural foods (grains, dairy and legumes) to various degrees, and these societies have been quite healthy up until adoption of western diet and lifestyle (think Weston A Price and ‘Nutrition and Physical Degeneration’)* 

An example of this is in a paper called How the Mid-Victorians Worked, Ate and Died’, which suggests the health of the mid-Victorians was pretty good.  They had low rates of chronic disease, despite the alcohol, smoking and adulterants in their food, likely due to two main factors: (1) their micronutrient rich, whole food diet based on vegetables, fruit, legumes, nuts, meat, organ meats, fish, eggs and dairy, and (2) high rates of physical activity, which promotes health independently and allows for increased calorie, therefore micronutrient consumption** [13].  There actually doesn’t seem to be too many differences between the mid-Victorian diet and the Paleo diet, just the legumes and alcohol. 

However, Australian Aborigines, Pacific Islanders and Native American groups (like the Inuit and the Pima), etc are generally more vulnerable to chronic diseases than people of other ethnicities living in the same country.  Some of this is probably due to environmental differences such as relative poverty, more junk food and alcohol and less education and access to medical services.  I’m not aware of a study that controlled for those other factors and put a number to genetic risk.  So I can only speculate that they are more genetically vulnerable, and for the sake of the last bit I’m going make that assumption.  Assuming these people are more genetically vulnerable, it may tell us a few things: 

  • We haven’t stopped evolving.  In fact, the harsh conditions at the origins of agriculture exerted strong selective pressures, favouring those who were better adapted to the agricultural diet.  Therefore, people with agricultural ancestry would have more adaptation to agricultural foods.  The cliché adaptations include lactase persistence and amylase copy number, but it probably goes well beyond that
  • If agricultural foods are inherently benign, then why do people with more agricultural ancestry, therefore more adaptation, have a lower risk of disease?  My take is that the modern diet and lifestyle isn’t good, but rather is just ‘tolerated’ more or less by different people.

Based on the links provided it seems that grains are nutrient poor foods and so eating a diet heavily based on grains, especially without much animal foods, was probably a pretty important factor in the poor health of early agriculturalists.  So it shouldn't be surprising then, that there's so much chronic disease in western societies which eat a heavily refined, grain-based diet.  However, over time health improved as people's nutrition got better by food preparation methods (such as soaking/fermenting grains to improve mineral bioavailability), increasing animal foods, etc, which brings us to the Victorian era and Weston A Price's traditional cultures.   So far it seem that healthy people with agricultural ancestry don't have to totally avoid grains, dairy and legumes and that these foods can be in the diet, just not dominate it.
* The Weston A Price Foundation stresses that traditional food preparation methods are important and they also added various nutrient dense foods that we rarely eat 

** The paper mentions whole grains 4 times but doesn't have a sub-heading for whole grains like the other food types, which leads me to suspect they didn't eat them (and ate refined grains instead), or much of them

Further Reading:
(1) Paleopathology at the Origins of Agriculture
(2) Lessons From Ötzi, the Tyrolean Ice Man. Part II
(3) Nutrition and health in agriculturalists and hunter-gatherers
(4) How the Mid-Victorians Worked, Ate and Died
(5) Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part II
(6) Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part III

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