A diet hacker's lesson digest

Some of the best lessons are learned the hard way. In this post, I mention four I picked up while getting to know myself from the inside out. These are:

1. There is no such thing as a one-size-fits-all diet
2. Diet is just one component of a healthy lifestyle
3. If dieting causes you stress, ditch it
4. Food and eating should be treated as sacred

Lesson 1: there is no such thing as a one-size-fits-all diet

Anyone who has ever heard anyone say “I can't eat the way he does” intuitively knows this one. In saying this, I'm looking particularly at the proselytisers of the Paleo and Atkins diets because it was they who shouted the loudest when I was hacking my diet. But the lesson applies across the board. Not every body will benefit from eating a diet that is, say, high in protein and low in carbs and fat, or a macrobiotic diet à la the Japanese.

According to one school of thought, this is because the diet(s) that elevates your wellbeing is determined by the interaction between your genes and the environmental conditions that figured predominantly in your formative years. You may be 99.9% genetically similar to your human neighbour but (a) researchers have shown that the 0.1% of a genetic difference is significant enough when it comes to variations in biological constitution (Nabhan, 2013) and (b) this difference is exacerbated by the diversity of environments and cultures in which the both of you were brought up. Throw in the differences in your current lifestyles (e.g. how much exercise the two of you get), it is highly likely that the two of you have appreciably different metabolic constitutions and therefore nutritional needs.

Gary Paul Nabhan, an author and ethnobotanist, takes this thesis a giant leap further. In Food, Genes and Culture, he eloquently describes his decades-long research that led to him concluding that We Are What Our Ancestors Ate. He pooh-poohs the Paleo Dieters' thesis that every single one of us living on this planet are adapted to eat the diets that the first generations of Homo Sapiens ate. The thesis is based on the premise that biological evolution is so slow that there is no appreciable biological difference between us and our hunter gatherer ancestors. But to Nabhan, pace Darwin, there is such a thing as microevolution that can effect significant genetic changes among populations in a matter of just a few generations. In other words, natural selection can occur over millennia, not just millions of years as Darwin had theorised. As Nabhan says (p.49):

“Our bodies' responses to particular diets were not fully shaped 2.5 million years ago during the emergence of the genus Homo, nor were they fixed during the period when mitochondrial Eve roamed the savannas of East Africa between 150,000 and 200,000 years ago.”

Paleo Dieters grossly underestimate the small but significant amount of diversity in our collective gene pool. Since members of our species fanned out across the entire planet, they would have needed to adapt to different climates and the distinct array of flora and fauna (some of which would have been edible) offered by various parts of the world. As a result, the group of humans who colonised Australia would have evolved slightly different biological constitutions from those who colonised northern Europe because of the location specific foods that were available to each group, among other environmental factors.

“While about 85 percent of human genetic diversity can be represented by different individuals in the same ethnic population, as much as 15 percent appears as differences among or between various ethnic populations.” (Nabhan, p.9)

Nabhan is one of a growing number of scientists interested in epigenetics, an exciting movement in biology that neutralises the age-old Nature Versus Nurture debate. Put simply, epigenetics stresses the interaction between environmental stimuli (which includes cultural products like diet) and our genes. More specifically, it looks at how this interaction can affect gene expression in a population. As the cell biologist Bruce Lipton says in his remarkable book The Biology of Belief, genes can't switch themselves on or off. It is up to environmental stimuli to do this. So imagine for a moment a person who has inherited the hereditary trait for 'tallness'; but due to a poor, malnourished upbringing, he is shorter than he would otherwise be had he been weaned on a nourishing diet.

Nabhan cites the work of food psychologist Paul Rozin that demonstrates this interaction in an area particularly relevant and interesting to people like me. He showed that over several generations, a population can gradually override a genetic predisposition for lactose intolerance simply by drinking more milk. Conditions for this phenomenon are a) if a genetic mutation for lactose tolerance is present in small frequencies in the population group and b) if the genetic ability to tolerate dairy products gives those endowed with it reproductive advantages. It is no coincidence that population groups with the greatest frequency of the gene for the digestive enzyme lactase are also traditional herding populations. In this example, selective pressures don't just occur at the biological level (selection for lactose tolerance) but also at the cultural/environmental level (selection for a diet containing dairy). This is what is known as co-evolution.

Moral: our biological constitutions are intimately tied to the climate and land that our ancestors eventually settled on.

“The less that our ancestors intermarried with individuals from other lands, the greater the probability that we still carry genes that allow us to survive, thrive and successfully reproduce under those particular environmental conditions.” (Nabhan, p.30)

As mentioned above, evolutionary selection happens on at least two levels. The human genes that are selected for by a particular location (whether the tropical savanna of Sub-Saharan Africa or the lush Northern European lowlands) are those that enable its carriers to thrive and reproduce in that environment. Selective pressures also happen at the level of food and diet so that what a group of people ate in a certain location would have enabled them to thrive and reproduce in that environment.

“There are no less than twenty-six genes on sixteen chromosomes that interact with various environmental factors, namely with the foods and beverages characteristic of certain ethnic diets rooted in particular places around the world.” (Nabhan, p.7)

Our biological diversity reflects the diversity of cuisines, which in turn reflects the planet's environmental diversity. It is therefore no accident that people from the Indian subcontinent love their spices and that Navajo Indians like it chilli (capsaicin) hot. These foods are what these groups of people have evolved to eat over thousands of years. It is a well-known fact that my ancestors have been cultivating and eating rice for over 10,000 years. Rice eating is literally in my DNA. So, in a snub to the Paleo diet, I have reintroduced rice (albeit the brown kind) into my diet and have instantly felt more human because of it!

“There is something profoundly functional in the mix of ingredients, cooking techniques, and preservation strategies characteristic of each ethnic cuisine, for each traditional cuisine has evolved to fit the inhabitants of a particular landscape or seascape over the last several millennia.” (Nabhan, p.31)

There is therefore a case to be made for preserving traditional cuisines, which, before the widespread globalisation of today, would have been passed down the generations relatively undiluted.

The co-evolution of our genes and diet, of course, has health implications in the 21^st century. Ever wondered why migrants to the UK from the African continent and the Caribbean are disproportionately at greater risk of developing heart disease and diabetes and other conditions collectively and ominously known as Syndrome X than the white British? Migration is essentially a displacement of peoples from the land and environment from which they are adapted. The novel foods and novel climate offer a profound shock to the system for migrants that can have plenty of maladaptive side effects, especially if they are struggling socioeconomically as well.  

“Because some people have been untethered from the foods to which their metabolisms are best adapted, some 3 to 4 billion of your neighbours on this planet now suffer nutritional-related diseases.” (Nabhan, p.32)

To demonstrate the healing power of traditional location-specific diets, Nabhan describes a community nutritional project undertaken in the nineties that helped native Hawaiians reign in the skyrocketing rates of obesity and diabetes mellitus afflicting their people. This epidemic was kickstarted by the wholesale invasion of the islands by American fast food and the near extinction of the local culture, language and cuisine. The project found that the most effective way to help people to lose weight, keep it off and even reverse the deleterious effects of Syndrome X was to reintroduce the traditional Hawaiian diet and re-cultivate traditional crops locally. One notable traditional food is taro, the native sweet potato and ancient staple crop, which is high in calcium, potassium, iron, A B and C vitamins. Its high fibre content means it is a source of 'slow release' carbohydrates, which protects against sudden spikes in insulin, a precursor to diabetes mellitus. In other words, eating taro protects native Hawaiians from Syndrome X. The communities that took part in the project returned to the foods that had nourished their ancestors, allowing them to adapt to life on the islands.

Nabhan's overall message is that if you want optimal health, it doesn't make sense to separate your nutritional needs from your genetic makeup, and your genetic makeup from your cultural roots.

Of course, the story isn't complete. When I retold Nabhan's message to a perceptive friend of mine, she made the remark that the world now has a great many people who are 'mixed-race'. Far from a rebuttal of Nabhan's thesis, though, I think the observation drives home the importance of finding out what diet suits you as an individual given your current lifestyle while always keeping in mind what your grandmothers fed you. Which brings me on to:

Lesson 2: diet is just one aspect of a healthy lifestyle

Yes, lifestyle counts. For the longest time, I focussed primarily on maintaining a good level of physical activity without looking closely at what I was eating. Then with the detox, all I could think about was what I was eating. But as any good doctor will prescribe, optimal health rests on a diet of fresh foods, regular exercise, sleep and manageable levels of stress.

Lesson 3: if dieting causes you stress, ditch it

As alluded to in Part II, stress can reverse all the hard work you've put into restricting what you eat. Studies have shown that a chronic increase of the stress hormone, cortisol, fires up your body's fight-or-flight sympathetic nervous system. Not only does it put you on edge as if danger is lurking around every corner, the hormone stimulates your appetite and encourages your body to store energy (that is, accumulate fat stores) in preparation for fuelling your body when danger does come pouncing out at you.

A fired-up sympathetic nervous system also diverts nutrients and oxygen, via blood flow, from your visceral organs – your life support in other words – to your limbs so that you can bolt when the danger approaches. That's why stress suppresses the immune system. When you're in danger of being mauled by a lion, your body's got more urgent things to attend to than to fight bacteria.

Lesson 4: treat food and eating as sacred

I'm a huge proponent of eating without distraction, chewing food properly and savouring the texture of food. In his book The Story of the Human Body, Daniel Lieberman explains how, of all the hominids, it us humans who have exclusively evolved the ability to talk and chew at the same time. It's a talent that comes with a potentially fatal risk: choking. So don't talk with your mouth full or read scandal-filled papers like the The Daily Mail while enjoying your salad. I believe that mindful eating isn't just a fad but a critical component for maintaining wellbeing and sanity in this world of fuss-free liquid diets.