Tuesday, August 27, 2013

What Can Our Nutrient Requirements Tell Us About Diet?

We can infer some of the foods/dietary patterns we are better adapted to by using evolution in the context of our nutrient requirements 

* Just so people are aware this blog post isn’t about the optimal amount/ratio/whatever of a given nutrient or food.  Please don’t take ‘required amount’ to mean ‘optimal amount’ (and in what context?) 

An Omnivorous Diet 

Not all of the recommended daily intakes are based on requirements or on ‘optimal’ amounts.  Even so, they can be a good guide as to what we need.  One of the purposes behind doing my nutrient database was to look at which nutrients various food groups were good and poor sources of.  One thing I found was that animal foods tend to rich sources of some nutrients and plant foods tend to be rich sources of other nutrients, which suggests we should eat both animal and plant foods.  As an omnivorous species, this shouldn’t be particularly surprising. 

Vitamins and Minerals
Animal but not Plant Foods
Plant but not Animal Foods
Zinc*
Calcium
Selenium*
Potassium
Riboflavin
Copper*
Niacin
Manganese*
Vitamin B5
Vitamin C*
Vitamin B6
Thiamine
Biotin
Folate*
Choline*
Vitamin E*
Vitamin B12*
Vitamin K1
Vitamin K2*
Other Nutrients
Animal but not Plant Foods
Plant but not Animal Foods
Carnitine, Carnosine, Creatine, Taurine
Phenolic Compounds
Long Chain Omega 3 Fatty Acids*
Carotenoids
Conjugated Linoleic Acids
Soluble Fibre
Coenzyme Q10

* The nutrients with an asterisk are those that carnivores or vegans would most likely or certainly become deficient in 

Calcium

The RDI for calcium is 1,000 mg per day, which was based on calcium balance experiments that found calcium balance occurs at 840 mg.  The most common way of meeting the 1,000 mg per day target is through dairy consumption.  Yet, given the lack of dairy throughout evolution the idea that we need dairy for calcium is a bit absurd.  Rather than a biological need for dairy there might be other explanations for the high calcium requirement: 

  • Historically other high calcium foods may have been eaten such as fish bones, the bones of small animals, more calcium-rich plants, etc
  • Plant foods probably used to be higher in nutrients like calcium [1]
  • The subjects in those calcium balance studies probably had lower than ideal levels of vitamin D and K2 (given sun and SFA/cholesterol phobia) 

Choline 

The adequate intake for choline in men is 550 mg.  This is based on an amount of choline that didn’t increase ALT levels (500 mg), +10% [2] [3].  Like calcium, we seem to have a pretty high requirement for choline that is quite difficult to meet without the inclusion of certain foods.  Non-starchy vegetables, meat, shellfish, organ meats, eggs and wheat are pretty much the only good sources of choline.  Although you need a lot of non-starchy vegetables, meat or shellfish for 550 mg of choline. 

Food
Amount of Food to Needed for 550 mg of Choline
Non-starchy vegetables
Few kgs of vegetables (depending on which ones)
Spinach
450g
Meat
~200g of protein (~1kg of meat)
Shellfish
Roughly several hundred grams
Wheat
8.5 slices (240g) of whole wheat bread [4] [5]
Beef Liver
160g
Eggs
220g (~3 eggs)

With most other food sources being pretty poor sources (<50%) or barely/nearly adequate (low fat dairy and legumes).  I would guess that historically the major source of choline was organ meats such as liver, seeing as the sheer quantity of vegetables is unrealistic, eggs would have been smaller and an unreliable source and wheat used to only be found in NE Africa and the Middle East 

Non-Essential Amino Acids 

In Beyond Good and Evil, Chris Masterjohn discusses how many diets are low/deficient in glycine and the need to balance glycine and methionine to prevent excess methylation and promote adequate glutathione synthesis.  Good glycine sources are skin and bones 

Creatine is tri-peptide found in meat and can be synthesised using arginine, glycine and methionine.  Even though we can synthesise creatine vegetarians have lower levels of creatine [6], which seems to negatively affect their memory (as creatine improved memory in the vegetarians but not the meat eaters) [7].  Vegetarians have lower levels of some other non-essential amino acids (carnitine [6], carnosine (vegetarians have more AGEs and carnosine inhibits formation of AGEs, but other factors could be involved) [8] and taurine (vegans) [9]) and those nutrients are beneficial, although at this time no studies suggest vegetarians are worse off because of their lower levels (like ref 7) 

Carbohydrate 

Carbohydrates aren’t technically an essential nutrient, but outside of ketosis it kind of is in practice.  Most of our carbohydrate needs aren’t genetically determined (unlike the stuff in this post) but rather are largely determined by our brain’s need for glucose.  The US DRI has set an EAR of 100g and an RDA of 130g of carbohydrate per day to cover our basic glucose needs [10] 

In Perfect Health Diet (PHD) the Jaminets find 150-480 glucose calories are required for the central nervous system (150 only when offset by ketones), 200-300 for glycoproteins and 100 for other uses, which comes to 780-880 *.  Fat in food comes in the form of triglycerides.  The glycerol in triglycerides can be converted to glucose, so some of the glucose calories can be met through fat.  The amount of glycerol can be determined by the percentage of glycerol calories in triglycerides (12%) multiplied by the total fat calories in the diet.  A 2,400 calorie PHD provides 187.2 glucose calories from glycerol, reducing the glucose needs to 600-700 calories or 25-29% of total calories (outside of gluconeogenesis from amino acids, which doesn’t contribute much anyway) [11]. 

* The need will be higher with intense exercise 

Long Chain Omega 3’s 

There’s lots of talk about the benefits of omega 3s, but not all omega 3s are equal.  In order to have much effect the shorter chain omega 3s like ALA (18:3) need to have more double bonds (desaturation) and become longer (elongation) to EPA (20:5) and DHA (22:6) and then get incorporated into cell membranes and form eicosanoids or docosanoids 

The conversion rate of ALA to EPA and especially DHA is extremely poor.  One review suggests ~5% of ALA is converted to EPA and only <0.5% of ALA is converted to DHA.  For this reason large amounts of ALA have a negligible impact on plasma DHA levels [12] 

ALA is mainly found in plants and plant oils while EPA and DHA are almost exclusively found in animal foods (algae contains DHA).  Healthy vegans have lower plasma DHA, but have no symptoms of DHA deficiency * [12]. 

* It’s suggested that vegans must be synthesising more DHA and/or reducing DHA turnover.  However, the plasma level of DHA doesn’t increase much with ALA supplementation [12]. 

Summary 

Our genetics and physiology suggest we should be better adapted to an omnivorous diet that includes at least meats, organ meats, skin, >25-30% of total calories from carbohydrate and perhaps bone or calcium rich plants. 

(I realise this post was quite meat/animal food focussed, which wasn’t my intention.  I actually planned to have a section on vitamin C, but I realised our very low ‘requirement’ tells us very little as it can be met with a piece or two of fruit) 

Further Reading:
(1) Meeting the Choline Requirement -- Eggs, Organs, and the Wheat Paradox
(2) Beyond Good and Evil
(3) Extremely Limited Synthesis of Long Chain Polyunsaturates in Adults: Implications for their Dietary Essentiality and use as Supplements

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

Monday, August 12, 2013

Applying Mismatch Theory to Diet

  • In 2007, 67.4% of Australian adults were overweight.  In 2005, 20% of Australian adults were obese, which was projected to rise to roughly 29% in 2010 [1]
  • Cardiovascular disease is the leading cause of death in Australia, causing 31% of all deaths in 2011 [2]
  • Cancer is the second leading cause of death in Australia, causing ~30% of all deaths in 2010 [3]
  • In 2007, 45% of Australians (aged 16-75) had suffered from a mental illness at some point in their life and about 20% were/are suffering from a mental illness in the last 12 months [4]*

These statistics are pretty grim, worse still when you consider that this doesn’t include all the other diseases, disability adjusted life years (DALYs) and the CV events and cancers that don’t kill people.  I think it’s a fair call that we aren’t well adapted to the modern world. 

Let’s apply mismatch theory: what are humans better adapted to? 

The earliest evidence for anatomically modern humans is from some incomplete fossils which date to ~200,000 years ago.  For most of human history we lived as hunter-gatherers, up until about 10,000-13,000 years ago (11,000-8,000 BC) when people living in the Fertile Crescent developed agriculture.  We have been hunter-gatherers for ~95% of our evolutionary history as humans**. 

Hunter-gatherers seem to be mostly free of the chronic, non-communicable diseases that are so common in the modern world.  Biomarkers of disease such as obesity, IR and high BP are rare among modern day hunter-gatherers*** [5] 

Given the history and rates of chronic disease, I think it’s a fair call that we are well adapted to a hunter-gatherer diet and lifestyle.  One could say our genes may ‘anticipate’ these things from us. 

Diet has perhaps the most important effect on health and disease, which is why I’ll focus on it, but we shouldn’t ignore the potential consequences of mismatches related to lifestyle (exercise, sleep, sun exposure, stress, etc) and the environment. 

There’s a lot of debate as to what paleolithic hunter-gatherers actually ate because modern hunter-gatherers aren’t a perfect analogy to paleolithic hunter-gatherers and the diet of hunter-gatherers would vary a fair bit by location, season, etc.  That being said, I don’t think a perfect accounting is necessary for the following reasons: 

  • Modern hunter-gatherers are good enough.  We can use a bit common sense, for example: if modern HGs have refined sugar, refined grains and alcohol they would have gotten it from an industrialised society
  • The commonalities between HGs tribes are probably more important than the differences
  • The diet of HGs is only a starting point and re-enactment is not the end goal.  Let’s use the information to generate some hypotheses, conduct some studies (clinical trials that compare diets or foods, and looking at what’s contributing to the mismatch) and use what’s effective.

Cordain, et al found the following****: 

  • On average modern HGs get 45-65% of their calories from animal foods and 35-55% from plant foods.  And 19-35% of their calories from protein, 29-48% from fat and 22-40% from carbohydrates [6]
  • Modern HGs got most of their calories from meats, fish/shellfish, fruits, roots, tubers, nuts and seeds [6]
  • Modern HGs had low amounts of or no: dairy foods, cereal grains, refined sugars, refined vegetable oils, alcohol, salt, fatty domestic meats [7]
  • Modern HGs on average had a lower GL diet, a lower proportion of SFA and a lower n-6:n-3 ratio (2-3:1 vs. 10:1), higher protein, higher micronutrient density, a neutral acid-base balance, a lower sodium:potassium ratio and higher fibre [7]

“Although dairy products, cereals, refined sugars, refined vegetable oils, and alcohol make up 72.1% of the total daily energy consumed by all people in the United States, these types of foods would have contributed little or none of the energy in the typical preagricultural hominin diet” [7]

* It should go without saying that those are old Australian statistics and may not reflect the rates of disease in Australia currently or those in other developed countries. 

** I drew the line at anatomically modern humans, which is a little later than where most in the Paleo community draw the line (2.5 million years ago, when early hominids ate more animal food).  Drawing the line at anatomically modern humans makes the point well enough (that we are likely well adapted to a HG diet and lifestyle).  You have to draw the line somewhere, if you go back 2.5 million years, why not 3.5 million years, 5, or even 55?

*** One could argue that HGs are genetically protected against chronic diseases, but this is unlikely seeing as they are usually more susceptible to chronic diseases when exposed to the western diet and lifestyle 

**** This is just a summary of what they found.  It doesn't mean that it's optimal, although is a move in the right direction.  I disagree with the lean meat, low salt, high protein and low SFA, and don't think acid-base and GI is important.

Further Reading:
(1) An Evolutionary Approach to Chronic Disease
(2) Evolutionary Health Promotion: A Consideration of Common Counterarguments
(3) Guest Post – Professor Gumby - essay 001
(4) Origins and evolution of the Western diet: health implications for the 21st century
(5) Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets
(6) The western diet and lifestyle and diseases of civilization

Monday, August 5, 2013

What Is Evolution, Is It True, And Why Do We Care?

Where to begin?  Evolution is the ‘guiding principle’ of biology.  As a subset of biology, evolutionary thinking can help us understand diet/nutrition.  So I will begin with evolution, but I won’t end there.

What is Evolution?

I would like to assume that everyone (with access to the internet and other first world sources of education) would have a basic understanding of what evolution is, but after listening to some of the questions directed to Richard Dawkins it’s clear that many people don’t have a clue. 

For longer and more detailed explanations see the Wikipedia articles on Introduction to Evolution and Evolution, or you can read a biology textbook, etc.  For a quick explanation of evolution see either one of these two videos


What evolution is not: 

  • Evolution doesn’t explain how life on earth began, abiogenesis does
  • Evolution doesn’t explain how the universe began, the Big Bang does (maybe it doesn’t, but this blog isn’t about theoretical physics)
  • Evolution is not random.  There are random mutations, random gene recombinations and a random allele in gametes (eggs and sperm), but there is non-random selection (natural selection*)
  • Humans didn’t descend from chimpanzees.  Humans and chimpanzees shared a common ancestor several million years ago
  • Evolution (in the real world) isn’t like Pokemon evolution (where a chimp could turn into a human).  “Evolution is the change in the inherited characteristics of biological populations over successive generations” 


* Also referred to as ‘survival of the fittest’ where fitness is reproductive fitness rather than athleticism (though in the natural world the two are often related). 

Is It True? 

Yes.  Rather than bombard you with arguments I would rather take one logical, common sense approach. 

  • Do you agree there are traits organisms possess that are hereditary (such as height, eye colour, hair colour, etc) and that there is variation in a population with regards to these traits?
  • Do you agree that selection pressures in the environment can select for desirable traits (such as people with lactase persistence in agrarian societies having access to more food sources, therefore increasing their chance of survival and reproduction)?
  • Do you therefore agree that the next generation of this species would have more of the desired trait than the previous (the next generation of people having a higher proportion of lactase persistence than the previous generation)?  If you have you have just agreed with evolution 

Evolution simply follows from there being: 1) variation in a population due to heritable traits and 2) certain heritable traits being more successful than others.  If you agree with (1) and (2) you agree with evolution.  No divine intervention necessary 

You can see evolution in the world, for example: 

Antibiotic resistance and related: A small number of bacteria (bacteria X) in a given species have mutations that allow them to survive antibiotic Y.  Upon exposure to antibiotic Y all the bacteria die except for bacteria X, which then multiplies rapidly without much competition from other bacteria and become very successful.  As a larger part of the bacterial population is now comprised of bacteria X the overall bacterial population has become more antibiotic resistant. 

Rapid changes apply to all organisms under strong selection pressures (even including some populations of elephants who are increasingly become more tusk-less as a result of poaching), but particularly in organisms that reproduce rapidly.  A similar kind of 'resistance' can also apply to tumour cells in cancer, see Genes and Cancer 

Breeders: Animal and plant breeders select desirable traits in their own little population and only allow those animals/plants to reproduce.  Consequently the population of offspring have a higher proportion of those desirable traits than the previous generation (whether its making a shorter dog, the spontaneously hypertensive rat or a chicken that lays lots eggs). 

If the knowledge of evolution was somehow magically erased from our minds then biologists and clever breeders would simply rediscover it again because they will see the patterns, and understanding those patterns is so important for their area of work. 

Why Do We Care?

Evolution helps us understand biology.  One way in which it does so, that's quite relevant to the blog, is mismatch theory.

Just as evolution follows from there being 1) variation in a population due to heritable traits and 2) certain heritable traits are more successful than others, so too does mismatch theory (or genetic/evolutionary concordance/discordance) follow from evolution.

Mismatch theory essentially suggests that due to selective pressures species are more adapted to certain environments and less adapted to others.  And that problems may occur when species are placed in environments that they are poorly adapted to.  Again, common sense.  I'll continue with mismatch theory next week.

* I'm not religious and I don't mind whether you are or not, that's not the point.  Evolution is a useful tool for asking questions and improving our understanding on matters related to biology.  I simply want to draw attention to its usefulness and clear up any misconceptions.