What is the world’s healthiest diet?

This is a question that researchers, clinicians and consumers have been attempting to answer for the last 50 to 100 years. Should it be low fat? Fat free?  Good fats, bad fats?  High carb, low carb? High protein? ….  You could be forgiven for being confused.   We need to go back and look at old customs, and how we have arrived at current thinking on what is thought to be a healthy diet, in order to make an informed decision.  We attempt to review this history for you in this article, Part 1, of: What is a healthy diet?

Western societies have been part of a large, uncontrolled and chaotic experiment to determine the health benefits of various methods of eating. This started in the mid 20th century with the pioneering research of Dr Ansel Keys. He compared heart attack rates around the world to various dietary components and found that in general, where there was a lower fat intake, there was lower heart attack risk. He did find one exception to this, which was the Greek island of Crete where there was an elevated fat intake, but a lower risk of cardiovascular disease. As this did not agree with the bulk of his data, it was excluded as an anomaly. This turned out to be an unfortunate decision as the growing body of research around the Mediterranean diet now shows. From this research grew the identification of various lipids (fats), and especially cholesterol, as risk factors for cardiovascular disease. The orthodox recommendation as typified by the original American Heart Association diet then became a low fat, high carbohydrate, high cereal diet, out of which the first of the food pyramids was born.

Cracks in this theory started to appear however, when Danish researchers Bang and Dyerberg conducted studies on the Greenland ‘Innuits’  in the early 1970’s, showing that they had extraordinarily low levels of cardiovascular disease, despite a diet where fat contributed up 70% of the calories.  From this idea was born the concept of ‘good’ and ‘bad’ fats, and the emergence of the recommendations to consume less saturated fats, more unsaturated and essential fatty acids (omega 3’s).

Competing Theories

Around the same time, a contrary view was being developed by Dr Robert Atkins and others who advocated a low carbohydrate diet, with higher levels of protein and fat. These diets included the ‘Stillman diet’, the ‘Airforce Diet’ and the little-known work of Austrian physician Dr Wolfgang Lutz in his book ‘Leben Ohne Brot’ (Life without Bread). Atkins’ work was the most popular and controversial, as it flew completely in the face of the accepted medical orthodoxy of the time. Despite this controversy, the concept of a low carbohydrate diet was appealing to the public and found many devotees. This eventually led to further research on the benefits of a low carbohydrate eating program.

 An important concept was developed by Dr David Jenkins in 1981 – that of the Glycaemic Index (GI). This concept did for carbohydrates what Bang and Dyerberg did for fats – it showed that there were healthier and less healthy choices. This related to the impact of a particular carbohydrate food on the blood glucose level, which is determined by how quickly the carbohydrate is digested and absorbed. Research was starting to emerge that showed that foods with a higher GI were associated with increased blood sugar levels, insulin secretion and potentially weight gain and risk for type 2 diabetes. Following this concept, Barry Sears published and popularised the ‘zone diet’, which focused on creating the right ratio of low GI carbs, fat and protein to achieve optimal insulin and other hormonal levels.

 Human Biochemical individuality

Another development in the diet debate was the idea that no one diet is suitable for all people, and that as people are metabolically unique, their diet should, to a certain extent, reflect this. The concept of ‘biochemical individuality’ goes back to the important work of Dr Roger Williams in his book Biochemical Individuality: ‘The Basis for the Genetotrophic Concept’ published in 1956.

Notable examples of diets that try to reflect this concept include the Blood Type Diet by Dr Peter D’Adamo, and then as an expansion of the concept, the development of Metabolic Subtyping by various Authors, which included blood type, nervous system function and a number of other parameters that are claimed to allow the development of an individualised eating approach. Many Health practitioners and nutritionists through their patients have also successfully utilised various forms of exclusion diets, designed to remove foods which an individual or group are thought to be sensitive to, or object to from philosophical grounds. Gluten and dairy have been commonly excluded from the diets of many patients, as have salicylates and amines. Vegetarianism in its many forms has also been recommended as a healthy and ethically sound approach. There is a substantial amount of evidence to show that vegetarianism when followed as part of a traditional dietary approach is associated with substantially lower risk for many common Western diet related diseases.

Man-Made Diets are Limited by the Knowledge of Their Inventor

It is apparent from this brief, and by no means exhaustive review of the history of ‘man made’ diets that there are multitudes of theories, some of them scientific, but some also political, philosophical or even religious in basis. It is also apparent that our level of understanding of the nutritional requirements of a healthy human is still quite poor. We have identified many nutrients, but still only have a basic knowledge of how these nutrients function in our complex biological systems. For example, we only recently learnt that requirements for vitamins such as folate can vary 1000 fold between individuals due to genetic polymorphisms in enzymes that make use of folate, and can also be impacted by other dietary factors, medications, lifestyle and exposure to chemicals and new-to-nature molecules.

Emerging research fields such as epigenetics also point to the likelihood of further variation in our requirements for nutrients and response to foods. Agricultural techniques such as the hybridisation of plants and differing growing conditions can lead to the production of various subtypes of proteins such as gluten which have the potential to have widely differing levels of ‘immune response’. Many people who would be identified as gluten intolerant have had the experience of travelling to Europe and consuming gluten-based products which do not trigger their usual symptoms. Presumably this is due to a different cultivar of wheat, with different chemical structures and break down of the protein, leading to a modification of the components  that normally trigger an intolerance, allergy or autoimmune reaction.

Perhaps the most consistent conclusion that can be drawn from this examination is that when people set about changing a food, or designing a diet, they often do it with a goal in mind, but are not always able to predict the consequences of these changes. In addition, as can be seen from this brief history, each diet tends to build on perceived weaknesses of previously promoted eating plans and is modified to suit current, sometimes short-lived health goals.

It is interesting to consider what other components of the ‘ideal’ healthy diet we may be overlooking given our current level of knowledge. An obvious area is the discovery of the role of ‘phytochemicals’ in our food. We are just beginning to see the many beneficial effects of exposure to small levels of compounds for example: Turmeric and Resveratrol (found in grape skins) found to be ‘antioxidants’ that may retard aspects of the ageing process and offer many other benefits to health.

There are over 4000 flavonoids alone, many of which we have no clear idea what if any effect they have in the body. It is inevitable that many more components of foods will be shown to be important for optimal health in ways which we have not yet considered. This makes the designing of a diet and its recommendation an inherently risky practice, which often creates as many problems as it solves. It also leads to entrenched political positions being taken by advocates of particular eating programs, which has the potential to stifle the acceptance of new evidence as it emerges.

The Wisdom of Traditional Diets

It is ironic that what some of the latest research seems to be showing is that the answer has been in front of us all along, that people who follow a traditional diet tend to be healthier than those who have adapted to a more modern, Western-style diet. Studies of people largely following their traditional diets around the world consistently show better health outcomes and lower risks of chronic, degenerative disorders such as cardiovascular disease, cancer, dementia, osteoporosis and metabolic syndrome. Whilst these diets vary depending on the ecological niche that the populations occupy, they share many similarities. These include a large amount of plant based foods, a high omega-3 to omega-6 fatty acid ratio, a lower level of saturated fats, a higher level of fibre, a low level or absence of refined carbohydrates, processed foods, artificial foods and chemicals, and a naturally high level of phytochemicals from seasonally fresh, locally grown produce.

Perhaps the best known and researched example of a traditional diet that provides these health benefits is the Mediterranean diet, based on the usual diet of the people bordering the Mediterranean Sea. There have now been over 50 clinical studies published on the effect of the Mediterranean diet on various health outcomes. In a recent meta-analysis by Sofi et al, published in the British Medical Journal in 2008, the researchers concluded the following.

“This meta-analysis shows, in an overall analysis comprising more than 1.5 million healthy subjects and 40,000 fatal and non-fatal events, that greater adherence to a Mediterranean diet is significantly associated with a reduced risk of overall mortality, cardiovascular mortality, cancer incidence and mortality, and incidence of Parkinson’s disease and Alzheimer’s disease. The cumulative analysis of 12 cohort studies shows that a two point increase in the score for adherence to a Mediterranean diet determines a 9% reduction in overall mortality, a 9% reduction in mortality from cardiovascular diseases, a 6% reduction in incidence of or mortality from neoplasm, and a 13% reduction in incidence of Parkinson’s disease and Alzheimer’s disease.”

It seems that the Western dietary ‘experiment’ of the last 50 to 100 years has come full circle. It is now becoming clear that consumption of a traditional diet contains many benefits, and certainly more will come to light as further research is conducted. It is also clear that there is a direct and real consequence to the manipulation of our diets that has happened to satisfy the industrialisation of the food supply. Foods that are heavily processed, laden with artificial ingredients, grown in soils that are stripped of nutrients, and are loaded with fats and sugars to stimulate cravings are clearly only benefiting those that manufacture and sell them, not those that consume them. It is also fuelling the spiraling healthcare costs that Western nations are becoming increasingly burdened with. What is most disturbing is that many of the companies that produce these foods, also own ‘healthcare’ companies and benefit from the increased illness they cause.

The evidence of the impact of dietary change is written in our genes a number of pioneering thinkers have promoted this concept of traditional eating for some time. Dr Weston Price, a dentist from Cleveland in the US, travelled the world studying traditional cultures, their diets and their patterns of health. His book, Nutrition and Physical Degeneration – A comparison of primitive and modern diets and their effects, was initially published in 1939. He found that without exception, the people following their traditional diets had an absence of dental decay, had well formed jaws with no dental crowding and also a striking absence of many of the allergic and chronic degenerative diseases common in more civilised populations. His most important observation was that within a single generation of these people adopting a Western diet and lifestyle, their risk to cardiovascular disease, diabetes, arthritis and dental caries rose sharply to match the levels seen in Western populations. A single generation is clearly not long enough for genetic change to take place, and this rapid shift in health outcomes represents the interaction of our genome with an unfamiliar environment.

How Traditional is Your Traditional Diet?

A fascinating and recent twist on this debate is the concept that the traditional diet that an individual or society is eating may in itself be a relatively recent change. In fact, a growing number of scientists argue that even traditional diets such as the Mediterranean diet, the traditional Japanese diet or vegetarian diets are all newcomers on the diet scene, and that the diet that humans are really best suited to consume is more primitive still. Anthropological records show that agriculture (i.e. the growing of crops such as grains) and animal husbandry only began around 10,000 years ago in what is now the Middle East, and spread to the rest of the world over the subsequent several thousand years. While 10,000 years is a substantial period, from an evolutionary point of view it only represents approximately 300 to 500 generations, which is too short a time on an evolutionary scale for substantial adaptation to take place at a genetic level. These researchers have suggested that the diet that may be most suitable for modern humans to consume is the hunter-gatherer diet that characterised the vast majority of our evolutionary history. In fact, it is suggested that the time spent consuming the modern agriculture based diet represents less than 1% of total hominin evolution, with 99% being devoted to a hunter-gatherer lifestyle.

US Researchers such as Loren Cordain, S Boyd Eaton and Australians including Neil Mann and Jenny Brand-Miller have studied and written extensively on what they term ‘Paleolithic Nutrition’, so named after the diets common in the late Stone Age before the beginning of the agricultural revolution. They speculate that humans, like all other animals, are genetically adapted to the diets, lifestyles and environments that they were exposed to during their evolution. They attribute the rise of chronic, degenerative disease to the misalignment between the ancient genomes that humans possess and their modern diets and lifestyles. In a sense, we are cavemen and cavewomen living a modern life.

Composition of a Paleolithic or ‘Hunter-Gatherer’ Diet

Careful research shows that whilst many pre-agricultural populations had quite varied diets, the basic nutritional components that were present and absent are very similar. A Paleolithic diet includes lean meat, fish, shellfish, fruits and vegetables (seasonal), roots and tubers, eggs, nuts and seeds. It excludes all other foods, including grains, dairy products, salt, refined sugars and fats which became staple foods long after the appearance of fully modern humans. Analysis shows that over 70% of the current typical US diet would not have been consumed by pre-agricultural people, and is thus relatively foreign to our ancient genomes.

 The consumption of milk and dairy products beyond infancy would have been nearly impossible for pre-agricultural peoples, due to the inherent difficulties of milking wild mammals. Whilst domestication of sheep, goats and cows began around 10,000 years ago, the first evidence of dairy consumption dates to only 6,000 years ago.

 The first evidence for consumption of cereals on a regular basis was in the Natufian culture in the Levant (modern day Middle East) approximately 13,000 years ago. Domestication of emmer and einkorn wheat by the descendants of the Natufians about 11,000 years ago heralded the beginning of early agriculture. During the ensuing period until very recently, cereal grains were rarely consumed as year-round staples by hunter gatherer groups. Another important difference is that prior to the industrial revolution all grains were ground with stone milling tools and generally contained the entire contents of the cereal grain (germ, bran and endosperm). With the invention of steel roller mills and automated sifting devices in the second half of the 19th century, the nutritional characteristics of milled grain changed substantially as  refined, white flour that was produced, mainly from the endosperm. The widespread consumption on a daily basis of refined, uniform particulate size white flour represents a very recent phenomenon of the last 150 to 200 years.

 Evidence for Benefit from a Paleolithic Diet

Somewhat surprisingly, there are still some populations in the world that habitually consume a hunter-gatherer diet and follow a traditional, physically active lifestyle. These populations have been studied over the last 10 to 20 years to identify what, if any, differences they have in disease risk compared to Western populations. To provide some context, approximately 60% of adults in the USA and Australia are overweight or obese. More than 60 million Americans have cardiovascular disease, 72 million have dyslipidaemia, 50million are hypertensive and 10 million suffer from type 2 diabetes. These represent the vast majority of risk factors for all deaths in the USA. Astonishingly, these conditions are either rare or virtually nonexistent in hunter-gatherer societies such as the Kitavan Islanders in Papau New Guinea, living and eating in their traditional manner.

More recent evidence also suggests that insulin resistance and hyperinsulinaemia as a result of a Western diet is also a major trigger or driver of many other common Western diseases that are also rare or absent in more primitive societies. These include acne, the trend to early menarche and increased stature, juvenile myopia, skin tags, polycystic ovarian syndrome, male pattern balding and certain epithelial cell cancers including breast, prostate and colon. Insulin is a strong promoter of tissue growth, as are the insulin-like growth factors that are also produced in response to the consumption of modern diets. Lifelong exposure to abnormally high levels of these growth-promoting hormones is thought to be a key reason for the increase in prevalence of many conditions.

Most of this evidence is of an epidemiological or theoretical nature, which is suggestive of a causative relationship, but not conclusive. The gold standard of evidence in this regard is a ‘prospective intervention trial’, comparing one diet to another to see what sort of difference is achieved. A number of these trials have recently been conducted on Paleolithic diets, and the results, while preliminary, are encouraging.  Some examples are:

Paleolithic Diet v’s Standard Diabetes Diet : A newly published study in Cardiovascular Diabetology (July 2009) by Jonsson et al compared the effects of a Paleolithic diet to the current diet recommended for diabetic patients, and looked at cardiovascular risk factors for type 2 diabetes patients. The study concluded that a Paleolithic diet improved glycaemic control and several cardiovascular risk factors as compared to a diabetes diet.

Paleolithic Diet Compared to Mediterranean-Like Diet :This 12 week randomised controlled study published in Diabetologia (2007) by Lindberg et al involved 29 men with ischaemic heart disease and impaired glucose tolerance or type 2 diabetes. The first group was randomised to a Paleolithic diet based on lean meat, fish, fruit, vegetables, root vegetables, eggs and nuts. The second group was allocated a Mediterranean diet based on whole grains, low-fat dairy products, vegetables, fruits, fish, oils and margarines. Over 12 weeks there was a 26% decrease for glucose in the Paleolithic group and a 7% decrease in the Mediterranean group.

For more information on a 'Paleolithic' style diet you may refer to the Gut Matters 'Optimal Digestive Health diet' E Guide.

Eat for Happy Genes

It is easy to get lost in the detail when studying various diets, eating plans and strategies to help us lose weight, reduce our risk for disease and improve our health. When you take a longer-term view of our dietary history however, it becomes clear that we have moved a long way from our optimal diets.

As we have moved away from the diet and lifestyle that our ancient genes expect, we have reaped the progressive disease and disability that this mismatch engenders. One of the primary goals of us practitioners at Gut Matters is to educate our readers about how profoundly abnormal and unnatural the current Western diet really is, and assists them to move back to a diet more in harmony with what their body requires.

‘You cannot break the laws of nature; you can only break yourself against them’.

 Adapted from:  Metagenics Update – December 2009 (Paul Mannion).

Part 2 will explore how many of our modern chronic diseases can be attributed to the typical Western diet.