The Role of Nutrition in Human Evolution

The Role of Nutrition in Human Evolution: Highlights and Implications Iver Mysterud Trial lecture Dr.philos. degree Department of Biology, University of Oslo June 16, 2005 Hardin’s figure Outline    Natural diet Food and brain growth Paleolithic diet – General – Health  Non-Paleolithic diet – – – – Health Grains Milk Sugar  Conclusions and advice Zoo animal  What does the good animal keeper do when a zoo animal becomes unhealthy or misbehaves? Zoo animal  Recreate the environment to which it is adapted What is the natural diet for a lion?  Carnivore – Adapted to meat (animal foods) What is the natural diet for a moose?  Herbivore –Adapted to plant foods What is the natural diet for a brown bear?  Omnivore – Adapted to both plant and animal foods What is the natural diet for a human? ? What is the natural diet for a human?  What can an evolutionary perspective offer? The main lines of diet adaptation in hominin evolution  Insectivore  Frugivore/ Herbivore  Omnivore The importance of meat  Two important parts of human evolution – The progressive incorporation of more meat into the early human diet – Going from scavenging to hunting   Meat provides easy access to the full complement of nutrients our body needs More closely adapted to a meat based than a plant based diet Hominin brain size evolution   How can we explain this? The brain is an expensive organ A metabolically costly organ  Brain tissue has 16 times greater energy demands per unit weight than muscle tissue How can we explain this brain size expansion? Two central questions  Why did the brain expansion happen? – What selective pressures lead to a steadily larger brain?  How was it possible to expand it? The large human brain     Much larger brain per body weight than other terrestrial mammals Still the total (resting) energy demands for the human body are no more than for any other mammal of the same size Humans allocate a larger share of their daily energy budget to “feed their brains” Brain metabolism in adult humans – 20-25% of resting energy demands – 8-10% in other primates – 3-5% in other (non-primate) mammals How have humans evolved to support the very high nutritional needs of our large brains? The expensive tissue hypothesis    Aiello & Wheeler 1995 Both gut and brain are metabolically expensive Reduction in gut size may account for the lack of increase in resting metabolic rate (RMR) among humans and other primates The expensive tissue hypothesis  Severely criticized – Primates do not have systematically smaller gastrointestinal sizes that other non-primate mammals – Energy costs of a large brain are compensated for by a reduction in the proportions of most body parts rather than by a mere reduction in gut size How have humans evolved to support the very high nutritional needs of our large brains? Changes in two major domains 1. 2. Improvements in dietary quality Changes in body composition 1. Improvements in dietary quality Diet quality = energetic and/or nutrient density of the diet  Increases in diet quality may result from  – changes in diet composition » i.e. what you eat  or – the ways in which food is modified » processing, cooking or genetic manipulation General primate food pattern Small primates •Low total energy needs but very high energy demands per unit mass •Eat foods that are limited in abundance but high in quality Large primates •High total energy needs, but low mass-specific costs •Eat large volumes of widely available, but low in nutritional density foods What about humans? The exceptional primate   Humans have higher quality diets than expected for a primate of our size  We need to eat less volume of food to get the energy and nutrients we require Humans in primate perspective   Bigger brains require better quality diets Humans are the extreme example of this. – The largest relative brain size and the highest quality diet relative to body weight  Brain size expansion during human evolution – Has necessitated a sufficiently high quality diet to support the elevated energy demands Evidence from the fossil record   First major increase in brain size with emergence of the genus Homo 2.0-1.7 mya Teeth and jaws  KNM-ER 3733  Homo erectus was consuming a richer, more calorically-dense diet with less low quality plant material and more animal foods Evidence – Smaller teeth and jaws, but a bigger body than the australopithecines A dietary change alone cannot explain the evolution of large hominin brains, but a sufficiently high quality diet was probably necessary for supporting the increased energy demands of larger brains 2. Changes in body composition  Changes in relative proportions of adipose and muscle tissue may help accommodate the metabolic demands of larger brains – More fat – Less muscle Humans – an under-muscled species  Relatively low levels of skeletal muscle for a primate of our size – At the same body weight, humans have systematically lower levels of muscle mass than other primates  Primates as a group are relatively under-muscled compared to other mammals Fatter than other mammals  Brain metabolism is stable – May not be downregulated to conserve resources during periods of starvation or negative energy balance    How to get enough energy to the brain in infancy, at weaning and in early childhood? Maintain a larger energy reserve at birth Continue to gain body fat after birth Percent body fat at birth of 15 mammalian species  At 15-16% humans have the highest body fat level – of the 15 species shown Improvements in dietary quality with Homo erectus  Likely resulting from – More animal foods – Improved tool technology – Food sharing associated with a hunting and gathering lifeway  Other improvements – Use of fire and development of cooking? » Makes food more digestible » Provides more usable calories than if the same food had been consumed raw Alternative brain expansion scenario   Whatever the changes in meat intake, plants would have remained critical, especially during times of resource stress Calculations – A diet of raw food could not supply sufficient calories for a normal hunter-gatherer lifestyle Richard W. Wrangham, PhD Tubers    Tubers would have been abundant on the African plains 2 mya Digging sticks to get access to deeply buried tubers Controlled use of fires to cook them – Turns hard-to-digest carbohydrates into sweet, easy-to-absorb calories  Evolution of – – – – large brains smaller teeth modern limb proportions male-female bonding Criticisms 1  No convincing evidence of digging sticks for gaining access to tubers Criticisms 2  Would have found evidence of cooking if tubers were important in hominin brain expansion Criticisms 3   When did hominins control fire? Unquestionable evidence only 250000 years ago Conclusion brain expansion   1. Improvements in dietary quality probably resulted from – changes in diet composition » more meat   2. Changes in body composition What happened in the body? – Increased body fatness – Reduced muscle mass   combined with – the ways in which food is modified » improved food technology » use of fire and development of cooking Benefits for brain expansion – Ready supply of stored energy to feed the brain – Less muscle and more fat means reduced total energy costs of the rest of the body » Muscle is more metabolically expensive than fat  and – food sharing 2 requirements for brain expansion   Dietary need of a more concentrated energy source Dietary need of enough of the structural building blocks – Fatty acids » DHA and AA  Both must simultaneously be accomplished How did our ancestors get enough fatty acids for the brain expansion? Source of fatty acids 1   Freshwater fish and invertebrates available at land/water interfaces Both energy and fatty acids for brain expansion Michael Crawford, PhD Evaluations  Fish – – A rich source of DHA and AA, but not energy Fishing increased later in human evolution Of low energetic density, little or no DHA and AA No reliable fossil evidence of cooking Of high energetic density, with trace amounts of DHA and moderate amounts of AA Unlikely to have been encountered Good sources of AA, but not of DHA or energy Concentrated energy, but no DHA and AA Rich in DHA and AA, moderate energy source  Plant foods – –  Subcutaneous fat of large ruminants – –  Muscle tissue of large ruminants –   Marrow of large ruminants – – Brain of large ruminants No single food simultaneously fulfills both of these requirements  Lauren Cordain, PhD Source of fatty acids 2  Brains of scavenged sculls – Main source of DHA and AA  Marrow from scavenged ruminant longbones – Main energy source Field study from Serengeti, Tanzania     260 large herbivore carcasses Consumption patterns of large carnivores Marrow and head contents the last items to be consumed Defleshed marrowbones and defleshed heads were the items most likely to be abandoned How do we explain the creative explosion in human culture 100.000-30.000 ago? The cultural/creative explosion at the Middle/Upper Palaeolithic transition      Sudden emergence of creativity, religion, war, art and perhaps music Started 50.000-100.000 years ago Not linked to increase in brain size per se Better connectivity Fatty acids essential David F. Horrobin, MD, PhD The importance of fatty acid metabolism  Mutations in certain genes before 100000 years ago – Before the spread of humans from Africa    New biochemical variants related to changes in fatty acid metabolism The same changes can be identified today in the range of high-achieving and disordered individuals to be found in the families where schizophrenia is present Variations in phosopholipid biochemistry are responsible both for schizophrenia and our humanity  Madness, badness, creativity and leadership goes together in the same family trees – In all populations Paleolithic nutrition Paleolithic nutrition      Long history Momentum after 1985 S. Boyd Eaton, MD, and Melvin J. Konner, MD Seminal paper in New England Journal of Medicine ”Paleolithic nutrition” S. Boyd Eaton, MD The prevalence in modern societies of many chronic diseases is the consequence of a mismatch between modern dietary patterns and the type of diet that our species evolved to eat as prehistoric hunter-gatherers Humans have evolved not to subsist on a single, Paleolithic diet, but to be flexible eaters Paleolithic nutrition    Seminal paper from 2000 229 hunter-gatherer societies 73% obtained 56-65% of the energy from animal foods Loren Cordain, PhD Critical decisions for hunter-gatherers     Get more energy from hunting or gathering than the energy expended to obtain it Prioritize food choices relative to their energy return rate Optimal foraging theory Data – – Large animals are preferred over small animals Animal foods are almost always preferred over plant foods » because of their increased energy yield Whenever and whereever it was ecologically possible, hunter-gatherers always preferred animal food over plant food No doubt that hunter-gatherers favored the fattiest part of the animals they hunted and killed  Conclusion –  Also – Paleolithic diet: Variations  Variations due to differences in geography, season and glaciations Paleolithic diet       Meat, fish, fowl, vegetables, berries, fruits, nuts, roots, insects and seafood Approximately 20% more energy More nutritious food More protein-rich food Less carbohydrates (from <5 E% to 40 E%) High intake of fiber/phytochemicals Paleolithic diet: Fats   Fats of high quality – Between 10 and 80 E%  More long-chain polyunsaturated fatty acids C20-C22 Much lower n-6:n-3 ratio – – – – 1-2:1 Paleolithic 10:1 USA 6-7:1 Norway? 1:1 optimal? What Paleolithic people didn’t eat         Cow’s milk, cereal grains (after 10 000 BP) Table salt (NaCl) White sugar (after 1800) Potatoes (after 1750) Highly processed foods (mostly after 1800) Pesticide residues (after 1930), radioactive foods (after 1945) Artificial/synthetic additives (mostly after 1950) Genetically modified food (since the 1990s) How is human health when eating Paleolithic diet and unprocessed foods? What happens when humans start eating a modern and processed diet? Historical experience of indigenous/traditional peoples  No cancer, cardiovascular diseases, type 2 diabetes or dental caries – Independent observations of anthropologists, physicians, missionaries, explorers, etc. – E.g. !Kung San people in the Kalahari desert  Appears as soon as such humans change environment and lifestyle, particularly diet Nutrition and health among people on traditional diets in the 1930s 14 human groups –From isolated Irish and Swiss, to Eskimos and Africans every member enjoyed superb health –Free of chronic diseases –Free of dental decay –Free of mental illness –Strong, sturdy and attractive –Produced healthy children with ease Weston A. Price, D.D.S. Almost Comparison groups of the same racial/ethnic groups who had become ”civilized” Ate the products of the industrial revolution –Refined grains –Canned foods –Pasturized milk –Sugar Weston A. Price, D.D.S. Members Highly valuable data     ”Civilized” humans in comparison groups Infectious disease Degenerative illness Infertility Tooth decay Children with – Crowded an crooked teeth – Narrow faces – Deformities of bone structure – Susceptibility to many medical problems    Malnutrition affects all human groups in similar ways Seminole Indians in Everglades (FL) on traditional (left) or ”white man’s diet” Adult Melanesians at Kitava   Tubers, fruits, vegetables, fish and coconuts Unaffected by western diet – No oils, margarine, cereals, sugar and salt Adult Melanesians at Kitava   PhD study 1994 Apparent absence of – – – – – stroke and heart attacks hypertension overweight malnutrition acne Staffan Lindeberg, MD, PhD Paleolithic diet      A natural point of departure Not something which needs to be tested at the outset This is parsimoneous and compatible with evolutionary biology Important implications for nutrition science Burden of proof How well do we tolerate our most important foods that was not eaten by our Paleolithic ancestors? Grains From meat-dominated to grain-dominated diet  Reduction in stature – Ca. 15 cm in the Middle East 10000 years ago      Increase in infant mortality An increased incidence of infectious diseases An increase in iron deficiency anemia An increased incidence of osteomalacia and other bone mineral disorders An increase in the number of dental caries and enamel defects From meat-dominated to grain-dominated diet Conclusions A general decline in tooth health and general health  Probably caused by a diet dominated by cereal grains  Humanity’s doubleedged sword     Cereal grains made it possible to provide enough food for an increasing population May have been a necessary condition for technological and cultural evolution in many parts of the world Nutritional needs cannot fully be met by grains Hypothesis: – Many humans became ill/functioned at a lower level as a direct consequence of eating too much grains  Many grain-eaters developed significant dietary deficiencies Some main problems with cereal grains  Insufficient content of many key nutrients – – – – No vitamin A, C, D, K or B12 Low level of key amino acids, e.g. lysine, isoleucine Unfavorable n-6:n-3 fatty acid ratio (7-18:1) No long-chain unsaturated fatty acids » Arachidonic acid (AA), EPA, DHA    Low bioavailability of many vitamins and minerals May be contaminated by mycotoxins – – – E.g Claviceps, Fusarium Alpha-amylase inhibitors, lectins, protease inhibitors, alkylresorcinols May be reduced by ferentation/processing Increased by breeding More problematic (higher GI), the higher the extraction rate after refining Hyperinsulinaemia and insulin resistance Lectins in wheat and corn Contain many antinutrients   High gluten content – – – High starch content  Insulin mimics in foods – Loren Cordain, PhD Hyperinsulinaemia the big bad wolf   Carbohydrate-dominated diets with high glycaemic index (GI)  hyperinsulinemia  insulin resistance May lead to – – – – – – – – – cancer: breasts, prostate, colon/rectum acne polycystic ovaries myopia obesity type 2 diabetes hypertension high blood triglycerides cardiovascular disease  High-glycaemic foods is a novel environmental factor which humans are not well adapted to Tip of the iceberg?  Gluten -problematic proteins in grains  Autoimmune diseases – Celiac disease, skin problems, type 1 diabetes, Sjögren’s syndrome and reumatoid arthritis  Psychopathological diseases – Epilepsy, autism, schizophrenia and depression  Norwegian pioneer: – Karl-Ludvig Reichelt Karl-Ludvig Reichelt, MD 187 gluten diseases/problems   Review of research and clinical experience Controlled research urgently needed! James Braly, MD Ron Hoggan, PhD Emergence of agriculture  Middle/Near East – 10 000 years ago » 400-500 generations  Scandinavia, England – 5 500 years ago » 220-275 generations 3 reasons for lack of adaptation to grains as a staple food    Too few generations Diseases of civilization affect people late in life Diseases of civilization involve many genes  Conclusion: – Present-day humans are genetically similar to Paleolithic people – Reasonable assumption Milk Domestication    Sheep – 11000 BP Goats and cows – 10000 BP Chemical evidence for dairying – 6100-5500 BP in Britain – Residues of dairy fats on pottery Milk use an exception  Only Europeans and some African tribes  Lactose tolerance in adults – In populations with a history of dairying – Co-evolution of dairying and lactose tolerance genes  Fermentation the norm in all cultures Casein -problematic proteins in milk  Psychopathological diseases – Epilepsy, autism, schizophrenia and depression  Norwegian pioneer: – Karl-Ludvig Reichelt Karl-Ludvig Reichelt, MD Why cow’s milk intolerance in modern European populations? Milk intolerance  Pasteurization the problem?  Chemical residues in milk?  Raw milk better? Milk intolerance big is the problem?  Cause of what diseases?  Research urgently needed  How Sugar Why are we attracted to sugar?    Proximate mechanism for sweetness Ripe fruits and berries Useful nutrient content – Energy substrates, vitamins, minerals, antioxidants  Co-evolution – Mutually beneficial – The plants get their seeds spread, we get useful nutrients In an ever more rapid cultural evolution, the initial sweetness response became maladaptive Sugar consumption  Any refined sugar intake is new in human evolution  A high intake of refined sugar only for ~100 yrs  Average sugar intake in Norway: 43 kg/capita/yr The main problems with sugar     Upsets the hormone balance Depletes us of key vitamins and minerals Weakens the immune system Contributes to – lifestyle diseases – behavioral problems – mental diseases Conclusions and advice            Fatty acids are important for the brain – Both in the past and today Paleodiet as a point of departure – Not modern foods Grains – Problematic for many Milk – Problematic for many, even people with lactase as adults Sugar – Problematic for all, particularly when eaten in excess Adaptation in local populations? – Same advice to everybody? Individual focus – Genetic/biochemical individuality Organic produce Unprocessed foods Traditional food preparation techniques – Fermentation, milk culturing, sprouting, soaking, roasting, cureing Decide what is healthy – Then discuss how as many as possible can eat that way