Palaeolithic Nutrition?

By John Coleman

Introduction

The Palaeolithic Diet has been popularised primarily because of research by S.B. Eaton and M. Konner that advocates a hunter-gatherer diet for humans. A large volume of literature has been produced out of this hypothesis, one of many which are arising through the logical application of evolutionary theory to nutrition. The idea is that humans are adapted to the higher animal product diets that they ate as "cave men" for hundreds of thousands of years. It quite rationally proposes that humans have not adapted to the Standard Western Diet (SWD), or indeed to any of the diets that are a consequence of Neolithic developments - that is, ones including the consumption of cultivated grains, dairy products, over fatted animal carcasses, salt and so forth. The traditional Australian aborigines and the !Kung San peoples of the Kalahari dessert are often suggested as contemporary models for the diet.

The Weak Hypothesis of Anthropologists

One well known advocate of the diet, Dr. Loren Cordain, author of "The Paleo Diet" (1) claims that hunter-gatherer populations have much lower incidence of chronic degenerative diseases than modern Westerners, for example cardiovascular events are much more rare in contemporary hunter-gatherer societies than in peoples eating the SWD. The suggestion is that this is a result of superior nutrition. The Palaeolithic diet was characterised by wild game which is generally lower in fat than modern commercial meat, and has preferential fatty acid and vitamin profiles. Palaeolithic wild gathered fruit and plant matter was suposedly nutritionally superior to modern day grain type plant foods, and plant foods grown under commerical conditions in general. The case for this is fairly convincing, although quite how one properly takes into account the many very different lifestyle factors between modern humans and Palaeolithic ancestors, is not clear. Indeed, a general lack of clarity and precision characterises the whole topic of Palaeolithic nutrition, which is inevitable given the nature of the available information - i.e. very little. So projecting from the Palaeolithic experience to modern humans, is fraught with potentially serious issues of interpretation and extrapolation.

Although we may be lead to believe that the Palaeolithic diet has a scientific basis, Loren Cordain makes a rather poor case for the diet in his book. The scientific reader given a "hypothesis" can reasonably expect to be provided with precise definitions, supporting facts and logic, and an unbiased approach that appraises all the relevant data and makes well reasoned assumptions. The opening prose explain the basis of the hypothesis along the lines that modern humans are clearly not adapted to their modern diets because of the high prevelence of diet related diseases. However, this fact does not demonstrate that Palaeolithic peoples were adapted to their diet. Cordain fails to define what dietary adaptation actually is, and how we might test for it. He fails to provide any specifics in his hypothesis, which of course makes it hard to test. He claims that people don't realize "how healthy Paleolithic ancestors were" and then fails to provide evidence that they were healthy. Instead he claims they were free from heart disease and other chronic ailments that plague modern Westerners, but that does not demonstrate that Palaeolithic people were healthy, anymore than does his claims that hunter-gatherers look lean and fit in the many photographs that Cordain has seen. Even modern day world class athletes have competed successfully with advanced cancer. Cordain cites the Yanomamo Indians for their low blood pressure, but of all the hunter-gatherers, these perhaps eat the least animal products and are sometimes said to be close to vegetarian. The Yanomamo also practice forest gardening, a primitive form of agriculture. So the intoduction that Cordain gives us to his ill defined hypothesis is a series of non sequiters and unsupported claims. The book then follows with one after another of unsupported claims and logical fallacies. Cordain often displays his own personal prejudices in the material presented in the book. Cordain does not tell us why humans had to wait to develop technology before they could eat the diet they were allegedly "designed" to eat.

Cordain repeats the oft made claim of anthrpologists that meat is "brain food", and goes even further suggesting that our our ancestors meat habit somehow lead him to become a scientist. However, scientific philosophy only arose after the Palaeolithic era, and is not present in any stone age society, and of course it cannot be so. Science arose along with the develoment of agriculture, which is almost a science, and the eating of less meat. So does Cordain demonstrate that the hunter gatherer high meat diet necessitated the development of agriculture and science? That hunting and gathering necessarily lead to the development of agriculture is also questionable, given the existence of hunter-gatherer societies up until recently. It is possible that the high pressure that over hunting and gathering places on the environment with a growing population necessitated agriculture, but that is no case for meat eating, or meat as a brain food. The need for humans to develop tools in order to process animal foods is perhaps a rather better theory. While the historical basis of the argument seems weak (correlation doesn't identify causation), the case for DHA, a fatty acid, sounds more scientifically plausible. As yet though, DHA is not recognised as an essential fatty acid, except parhaps in growing children who may obtain it from breast milk. On the web site Cordain does mention some studies that show better outcomes when developing children have access to DHA, but this could be suggestive that a prolonged period of breast feeding is beneficial, or simply that the standard diet does not promote sufficient DHA synthesis - and that could be for a variety of other reasons beyond DHA provision in the diet. In any case, the point simply is not proven by any of Cordain's works. Furthermore, there is no exploration of the possible detrimental effects of meat consumption on brain development and function.

As we shall see later, there is evidence that stone age dieters suffer from gastric ailments that are common nowadays. However, Cordain believes that a diet high in animal products is not constipating. If this were true, then this would be a major blow to the idea that humans were adapted to a Palaeolithic diet. The case he presents though, is remarkably unconvincing, and relies on weak evidence and some flawed reasoning. Cordains first piece of evidence relates an anecdote about Arctic explorer Vilhjalmur Stefansson who sometimes lived exclusively on animal products. He had found that constipated men who had been eaten refined cereal foods were relieved of their condition when they tried the menu of the "Eskimos". However, this diet is unusual in that it includes a lot of oily fish and blubber, which are of course excellent lubricants. Even so, the Innuit are no strangers to constipation. One of the most powerful spirits in Innu mythology is Matshishkapeu (translated "fart man"), who can control other spirits by inflicting deadly bouts of constipation upon them. The Innu people of Labrador also have herbal remedies for constipation, colds and other ailments common to more civilised peoples.

In citing Stefansson, Cordain uses a worst case scenario comparison, and of course this always presents things in a biased fashion. A fair comparison is not between a person on an entirly unnatural diet of refined cereals such as a sailor or arctic explorer, but rather, with people eating a diet high in natural plant fibres who then add meat to their diet. It is common knowledge that red meat is constipating, for example The Constipation Resource Center gives the advise to "Limit your consumption of meat" in cases of constipation. How then is meat a cure for constipation? Clearly it is not. Perhaps Stefansson and his men could have got the same result if they just ate grease or oil, or of course some fruit or other source of plant fibre. To further support his claims, Cordain then reports how Stefansson returned from his arctic exploration and then repeated his all-meat diet and was observed by physicians to have "normal" bowel function. (Stefansson died at age 83 due to stroke.) Furthermore, in the experiment with Stefansson and his friend, they confirmed that they only had satisfactory bowel function when they ate a meat only diet including all the fat. They reported that when they cut the fat out, they had digestive problems. Cordain advocates removing the fat to cut the risks of atherogenous diseases. The Paleo choice seems to be constipation or arterial disease.

Cordain also suggests that humans are not intended to eat a plant based diet because of the evolutionary evidence and the anthropological record. As we shall see later, human evolution is clearly indicative of a herbivorous lineage. Using the anthropological record is flawed reasoning ("argumentum ad antiquitatem"), what was done isn't necessarily what should have been done. Furthermore, we don't really have any precise evidence of what our evolution actually was. Instead we have some bone fragments of which rather subjective, and often changing interpretations are made - what Jared Diamond referred to as "paleopoetry" (The Rise And Fall of The Third Chimpanzee, Jared Diamond, p.70, Vintage Science).

While the above is not an exhaustive critique of the ideas presented by Cordain, it is at least enough to expose his fundamentally unscientific approach. That Cordain claims to be a scientist, and presents this kind of clearly prejudicial selection biased evidence, should be reprehensible to any reasonable person. Cordain could be forgiven for not presenting a blow by blow account of his research findings in what is austencibly a recipe book, but the kind of rubbish he does present is hardly worthy of repeating. Cordain fails to link the reference material in his bibliography to the many claims he makes in the main text.

The Problem of Uncertainty

We have no medical records (no morbidity data) from the Palaeolithic era, so no way of telling whether Palaeolithic man was really healthy or not. Looking at bones and teeth may show that these humans were often well nourished, but that is all. If they died of cancer, heart disease, gall bladder complications or other organ pathology, we would not expect to see evidence of that in the bones. In any case, these diseases tend to kill outside the expected lifespan of Palaeolithic man, so we could never discover their real susceptibility, even if we had soft tissues to examine. Modern humans live longer in a different world, and may require a more carefully chosen diet in order to remain free from degenerative diseases. The Palaeolithic diet is akin to a creationist ideology. It is devoid of robust definitions, a testable hypothesis, and finds its basis in the personal beliefs and prejudices of its authors. Huge claims are made which are unsupported by factual evidence, while at the same time facts that crack the dogma open, are either ignored or papered over.

Human Dietary Adaptations

The Paleo diet rather assumes that we "adapted" to what our alleged ancestors ate during the Palaeolithic period. What about the prior billions of years of evolution of eating a totally raw diet without the higher meat availability from hunting and the related technology? What strong evidence is there of any adaptations to Palaeolithic eating patterns? A paper by Caleb E. Finch and Craig B. Stanford, published in the The Quarterly Review of Biology (2), suggests that humans have indeed made some small biochemical inroads into adapting to a diet including more meat. They suggest that up to eight genes in humans allow for greater protection from the degenerative effects of consuming meat. From this study, we may infer that humans will suffer less damage from meat eating than they would otherwise, but this is far away from suggesting that it is beneficial overall for humans to eat meat, rather the adaptation is alleged to offset degenerative disease events. The existence of a protective mechanism isn't evidence of benefit from the chemical insult it protects against. For example, the existence of a protective mechanism against cyanide in our liver, does not mean we should ingest cyanide, although it does mean we are "adapted" to cyanide in the diet. The same principle applies to this meat eating/adaptive hypothesis, and the researchers make it very clear that these are protective adaptations in their work.

Above is the best evidence in favour of humans being meat eaters. What is the evidence against the idea? On page 280 of Harper's Biochemistry 24 Ed., a medical students text, we discover that "The rabbit, pig, monkey, and humans are species in which atherosclerosis can be induced by feeding cholesterol. The rat, dog and cat are resistant." Therefore, it seems there is something fundamentally different between human biochemistry and that of species that naturally consume high amounts of animal products, and of course, humans do suffer from atherosclerosis. Much of this will be because of the high intake of saturated fats and a low intake of protective vitamins in SWD, which would not be such an issue for Palaeolithic humans. However, without medical evidence that they were free of the disease - what are we to assume? We don't even have in depth medical studies on the diseases of contemporary hunter-gatherers, let alone long deceased ones. Although dietary cholesterol isn't as great a problem it was once thought to be to most of us, cholesterol oxidises in animal products, and oxidised cholesterol is still thought to be problematic (3) as well as saturated fats. Meat also contains small amounts of trans-fats (4) that would raise LDL cholesterol slightly, thus increasing risk of heart disease. Therefore, we would expect to find heart disease amongst the hunter-gathereres who eat the most meat. Cordain however, suggests that the paleo diet improves blood lipid profiles when compared to a Western diet, because of factors such as better essential fatty acid intakes, and because in Western diets refined carbohydrates and high fat intakes both work together to elevate serum cholesterol. He also suggests that calorific restriction (i.e. lack of food), as well as greater physical activity helps to lower cholesterol levels in hunter-gatherer societies. These factors need teasing out in order to make a case for the diet outside that of the overall lifestyle.

"Although saturated fat is the main dietary culprit that raises LDL, trans fat and dietary cholesterol also contribute significantly. ... Dietary cholesterol also raises LDL cholesterol and may contribute to heart disease even without raising LDL. ... Health experts recommend that you keep your intake of saturated fat, trans fat, and cholesterol as low as possible while consuming a nutritionally adequate diet." (4)

The big question is of course, just how good is a hunter-gatherer diet at lowering cardivascular risk in reality? Does the theory really work? In a paper called "Diet of Aboriginal hunter-gatherers" Kerin O'Dea (5) reveals that traditionally fed Aborigines had cholesterol concentrations of about 3.9 mmol/l (about 150 mg/dL vs. 210 mg/dL for an average American) . O'Dea also reports that traditionally living Aborigines have inappropriately elevated insulin and tryglyceride levels, and that this is consistent with insulin resistance. This could be because of iron overload, which is discused below. However, there was no evidence of diabetes or coronary heart disease. When cholesterol levels are below 150 mg/dL, then coronary heart disease is virtually unknown (T.C. Campbell, personal communication). In this respect Palaeolithic diet seems to be a success. However, it would be misleading to suggest that it is necessary to follow a Palaeolithic diet to get these results. Similar results can also be achieved using a low fat, plant based diet with without or with minimal animal products such as fish or fish oil or a source of plant omega-3 fats such as flax oil. This program has been used by Dr. Dean Ornish, and is actually effective in reversing atherosclerosis without drugs. Cholesterol levels below 150 mg/dL, average for 130 village 127 ± 15 mg/dL, were also normal in rural Chinese populations according to a large ecology study (6), and in these populations, heart disease and other diseases of afluence where the lowest in the world.

Primary hyperoxaluria type 1 (PH1) is a recessive disease in which an enzyme, alanine:glyoxylate aminotransferase (AGT), is mistargetted from the peroxisomes where it functions in the glyoxylate pathway, to the mitochondia (7) where it is inefficient. It can be caused by defects in at least two glyoxylate-metabolizing enzymes and leads to excessive urine oxalate excretion resulting in kidney stones and/or calcification of the kidney which can occur in childhood or adolescence. Patients used to die on average at age 36 (8), however modern therapeutics can help to increase lifespan in certain forms of the disorder. According to Christopher Danpure and associates, "One molecular adaptation to diet that is spread widely across Mammalia is the differential intracellular targeting of the intermediary metabolic enzyme alanine:glyoxylate aminotransferase (AGT), which tends to be mitochondrial in carnivores, peroxisomal in herbivores, and both mitochondrial and peroxisomal in omnivores." (9) As humans normally express this gene effectively in their peroxisomes only, humans are classed along with herbivores in respect of AGT expression, as are chimpanzees. AGT assists in the detoxification of glyoxylate, the precursor of which is thought to be glycolate from plant foods, and hydroxyproline in meat. Glyoxylate forms in the peroxisomes from glycolate and in the mitochondria from hydroxyproline. If glyoxylate oxidises, it becomes oxalate which is prone to crystallise out in the kidneys, where it causes blockages.

Further evidence that humans don't seem to have adapted to meat eating is the higher prevalence of diabetes and heart disease amongst meat eaters in modern populations. In modern populations, controlled studies show that increasing plant foods tends to decrease mortality, whereas increasing animal foods increases mortality from the common degenerative diseases. Studies comparing vegetarian and meat eating populations have shown that a vegetarian diet can lower risk of diabetes (10). One factor linked to the risk is the type of iron found in red meats, "heme-iron". When the body builds up excessive stores of this form of iron from red meat, then risk of diabetes increases (11), particularly when intakes of protective nutrients are low. The human body is ultra efficient in its preservation of iron status, and has no natural means of excreting any excess absorbed. Daily losses of iron are so low, normally around 1 milligram, that it is necessary to keep meat intakes low in order to avoid excess. This may be less an issue for Palaeolithic humans, because of intestinal parasites that also take up dietary heme-iron and even iron directly from the gut of the host (see CDC discussion below). A 100 gram cut of beef may contain as much as 1.9mg of iron, much of which is highly absorbable heme-iron, wild game probably contains more. The heme-iron found in meat is not subject to the tighter regulatory control that non heme-iron is, through binding proteins and other control mechanisms. These mechanisms are effective in preventing iron overload even when large quantities of iron is ingested from plant foods, or even contaminating soil. However, when red meat is eaten as part of a SWD, the risk of fatal heart attack rises proportionally (12). The availability of iron from plant foods can be improved significantly (300-400%) when vitamin C intake is high, because vitamin C neutralises the inhibitory effects of polyphenols and phytates found in some plant foods, particulalry grains. Therefore failure to absorb sufficient iron from plant foods can indicate inadequate vitamin C OR iron intake. Unfortunately, the practice of cooking food reduces vitamin C content of foods by between 20-90%. Palaeolithic humans probably ate more fresh and raw plant foods than typical modern humans, so ensured a greater intake of protective nutrients such as vitamin C.

Doesn't the presence of a heme-iron receptor in humans suggest that we are adapted to eat animal products? This hypothesis certainly does not appear in any credible research literature. However, a very different explanation is provided by the CDC (13). Each day the digestive system loses thousands of its surface cells, and the heme-iron in these cells potentially becomes available as a crucial nutrient for gut pathogens. Effective absorption of heme-iron in the digestive system is probably a necessary part of our immune system, and known as the "iron withholding defence system ". The CDC specifically lists excessive consumption of red meats as a condition that can compromise iron withholding, and therefore resistance to invading pathogens. This iron withholding system is common to all mammals (i.e. includes all herbivores), and so is nothing to do with a specific dietary adaptation. A further blow to this idea is the fact that plant polypeptides called cytochromes, such as cytochrome f contain heme iron. Finally, guinea pigs are ranked second after dogs in their ability to absorb heme iron(16), yet they are strict herbivores. Perhaps the ability to absorb heme iron well, is also a beneficial adaptation for herbivores?

Longevity

Another issue is longevity. Palaeolithic humans are not thought to have lived so long as modern humans, but it is hard to know how long Palaeolithic humans lived. Even eating a SWD, you might expect to live into your 70s, or rather longer as happens in some Asian populations, who incidentally, eat very little food of animal origin. The same cannot be said for the lifespans of hunter-gatherers in the recent past or present. For example, some estimates suggest a life expectancy of Pleistocene humans as well under 25 years (The Cambridge Encyclopedia of Human Evolution, p. 406). Modern hunter-gatherer societies may not be realistic models for Palaeolithic humans either, because of contact with modern culture, and further development of their own cultures since Palaeolithic times. Modern hunter-gatherer societies are the result of Palaeolithic developments. If they are used as models, their average life expectancy and upper life expectancy compared to modern humans is still rather poor. These differences might not be so much to do with diet, but then maybe they are?

Diseases of Contemporary Populations Eating Stone Age Diets

While we don't have any good data on the real state of health of Palaeolithic humans, we do know that contemporary hunter-gatherer peoples are not healthy. Human cultures seem to have a variety of bizarre healing systems (a.k.a. "witchcraft", "black magic", "herbalism"), some of which have useful treatments, but most of which are ineffectual (or highly dangerous) and based on false beliefs. For example, the Australian aborigines traditionally live a hunter-gatherer lifestyle and have a herbal medicine (14) that predates Western contact, and is probably quite ancient. It has treatments for symptoms of colds and flu, gastro-intestinal disorders (bad diet?), congestion, coughs, generally feeling unwell, sore throat and so forth. The traditional North American aboriginal medicine also has remedies for diseases of the digestive systems such as hemorrhoids (see below), which is now a very common disease in modern populations, yet is almost non existent in wild animals. This demonstrates that hunter-gatherers suffer from many of the ailments common to contemporary populations, including those undoubtedly caused by inappropriate diet, such as hemorrhoids. As with any other species eating its correct diet, healthy humans have no need of these complex medical cultures or any of these remedies. Means of dealing with accidental injuries is all the medical culture a healthy human society would develop.

"Witch hazel preparations have a long history of traditional use in North America (Der Marderosian, 1999; Duke, 1985). The aqueous infusion of the bark was used in aboriginal medicine to treat hemorrhages, inflammations, and hemorrhoids (Millspaugh, 1974)"
Witch Hazel leaf and bark, herbalgram.org, American Botanical Council

"Sanguinaria canadensis L.
Bloodroot; Papaveraceae
Iroquois Drug (Hemorrhoid Remedy)
Decoction of roots used to push piles back into intestines.
Herrick, James William 1977 Iroquois Medical Botany. State University of New York, Albany, PhD Thesis (337)"
Native American Ethnobotany Database

What about the !Kung San as a model for hunter-gatherer health? Again the evidence for health isn't convincing. The !Kung San believe that everyone is inherently ill, and it is common for a large proportion of tribal members to be shamanic healers. When you read about the !Kung San, it seems that they have a culture that is paranoid about illness. This is perhaps not surprising as survival in the remote and often extremely arid areas they live in, must be far from easy. These conditions may not model the Palaeolithic human condition at all well, but whether they do or not, no evidence of good health has been produced. We simply cannot translate their experiences into a modern human world.

A more representative picture of how cave men probably lived is given by the Andamanese peoples as theirs is the most ancient surviving way of life on earth. For example the Onge tribe of the Andaman Islands, until recently, lived an almost undisturbed way of life that fits the Palaeloithic model. The men hunt wild boar, but they also fish, and women gather wild tubers and burries. They tend to boil their food in large pots, in this respect they must differ from the earliest Palaeolithic ancestors, however food must be relatively abundant when compared to other contemporary hunter-gatherer societies from arid regions. According to a source quoted by The Andaman Association Switzerland (15), the Andamanese suffered most from "coughs and cold, ague, fever, and severe headache", and they also mention that diseases known to have been common in the Andamanese before 1800 were malaria, catarrh, coughs, rheumatism, tuberculosis, pneumonia, and perhaps most signifcantly heart disease. Some of these ailments may be a consequence of outside contact, but not all. The Andamanese seem unaware of good hygiene practices, so presumably are also like cave men in this regard. Once again, it is difficult to project these findings into a contemporary situation. However, it is notable that these peoples suffered from diseases associated with the Standard Western Diet, and in particular it seems, of high meat consumption.

Conclusions

The "empirical method" is the hallmark of contemporary science. That is, a hypothesis such as the Palaeolithic diet needs to be tested experimentally in controlled conditions in order to develop a convincing theory. At present there is no empirical evidence to suggest that modern day humans who adopt a Palaeolithic diet will have good health, or significantly reduce their chances of degenerative diseases in the same way as hunter-gatherers are sometimes alleged to have. Modern humans live in very different environmental conditions to traditional hunter-gatherers, and it simply does not follow that we can adopt hunter-gatherer nutrition and be healthy.

In summary: 1) no evidence that a Palaeolithic diet is healthy, 2) no real evidence of adapting properly to a high meat diet, 3) some good evidence that humans didn't adapt to the diet and 4) are unhealthy on hunter-gatherer diets, as well as on modern diets including high meat consumption. Taking these points into account, the "cave man" diet really looks like a discreditable hypothesis. Perhaps the "Paleo" diet is rather better than a Standard Western Diet, but there is no case for it being natural, or optimal for us, by a long way.

References

1. The Paleo Diet, Loren Cordain
   http://www.thepaleodiet.com
2. The Quarterly Review of Biology, March 2004, Vol. 79, No. 1, Meat-adaptive Genes And The Evolution Of Slower Aging In Humans, Caleb E. Finch, Craig B. Stanford
   http://www.journals.uchicago.edu/QRB/journal/issues/v79n1/790101/brief/790101.abstract.html
3. Dietary Cholesterol Makes LDL Cholesterol More Radical, Judy McBride, April 4, 2000, USDA Agricultural Research Centre
   http://www.ars.usda.gov/is/pr/2000/000404.htm
4. Revealing Trans Fats, FDA Consumer magazine, September-October 2003 Issue, Pub No. FDA03-1329C
   http://www.fda.gov/fdac/features/2003/503_fats.html
5. Phil. Trans. R. Soc. Lond. B (1991), Diet of Aboriginal hunter-gatherers, K. O'Dea, p. 74
6. Chen J, Campbell TC, Li J, Peto, R. 1990. Diet, life-style and mortality in China. A study of the characteristics of 65 Chinese counties. Oxford, UK; Ithaca, NY; Beijing, PRC: Oxford University Press; Cornell University Press; People's Medical Publishing House, 896 pp.
7. J Nephrol. 1998 Mar-Apr;11 Suppl 1:8-12, The molecular basis of alanine: glyoxylate aminotransferase mistargeting: the most common single cause of primary hyperoxaluria type 1, Danpure CJ
   http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db;=PubMed&list;_uids=9604801&dopt;=Abstract
8. Primary Hyperoxalurias, Mayo Clinic College of Medicine
   http://mayoresearch.mayo.edu/mayo/research/nephrology/hyperoxaluria.cfm
9. Mol. Biol. Evol. 21(4):632-646, 2004, Differential Enzyme Targeting As an Evolutionary Adaptation to Herbivory in Carnivora, Birdsey GM, Lewin J, Cunningham AA, Bruford MW and Danpure CJ
   http://mbe.oupjournals.org/cgi/content/abstract/21/4/632?ct
10. Eur J Clin Nutr. 2004 Feb;58(2):312-6, Insulin sensitivity in Chinese ovo-lactovegetarians compared with omnivores, Kuo CS, Lai NS, Ho LT, Lin CL
    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db;=pubmed&dopt;=Abstract&list;_uids=14749752
11. Am J Clin Nutr. 2004 Jan; 79(1): 70-5, Dietary iron intake and blood donations in relation to risk of type 2 diabetes in men: a prospective cohort study, Jiang R, Ma J, Ascherio A, Stampfer MJ, Willett WC, Hu FB
    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db;=pubmed&dopt;=Abstract&list;_uids=14684399
12. Am J Epidemiol. 1999 Mar 1;149(5):421-8, Dietary iron and risk of myocardial infarction in the Rotterdam Study, Klipstein-Grobusch K, Grobbee DE, den Breeijen JH, Boeing H, Hofman A, Witteman JC
    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db;=pubmed&dopt;=Abstract&list;_uids=10067901
13. CDC, Iron Loading and Disease Surveillance, Eugene D, Weinberg, Indiana University, Bloomington, Indiana, USA
    http://www.cdc.gov/ncidod/EID/vol5no3/weinberg.htm
14. Traditional Aboriginal Medicine Practice, Dr Dayalan Devanesen AM, MBBS, DPH (Syd) Grad. Dip MGT, MHP (NSW) FRACMA, FAFPHM, FCHSE
    http://www.nt.gov.au/health/comm_health/abhealth_strategy/Traditional%20Aboriginal%20Medicine%20-%20Japan%20Paper.pdf
15. In Sickness and in Health, Chapter 19, The Andaman Association, Switzerland
    http://www.andaman.org/book/chapter19/text19.htm
16. PHYSIOLOGY ANDMOLECULAR BIOLOGY OF DIETARY IRON ABSORPTION, Silvia Miret, Robert J. Simpson, and Andrew T. McKie, Annu. Rev. Nutr. 2003. 23:283-301
    http://www.micronutrient.org/idpas/pdf/2489Physiology.pdf