Chapter 1: Discerning the histories encoded in our bodies

By Dagmar
In Interesting stuff
Oct 5th, 2014
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After the Introduction to the book Why some like it hot: Food, Genes and Cultural Diversity, Gary (the author) will take you to the American desert where Pima Indians have been living for a long time and got adapted to the environment, diet and a lifestyle on which they have evolved over centuries. There he had a friend called Gabriel, also a Pima man.

How people became lactose tolerant

The story starts how Gabriel asked Gary to help him delivering some commodity food to a village. It was powdered milk. Normal powdered milk delivered to the community possessing a lactase deficiency. This ethnic group cannot digest normal milk containing lactose without the unpleasant consequences in form of bloating, indigestion or even cramping or diarrhoea. The funny part of this was that the milk was actually not destined for consumption in this case, but to mark the fields on the baseball playground. Those families who previously received this milk for consumption did not know what to do with it, so it just aged in their homes and went wasted over time. But the government kept providing them with this stuff further.

Gary later summarizes the research on prevalence of lactase deficiency, aka lactose intolerance, among the world population. It started with a cultural geographer Frederic Simons about 40 years ago (as per 2014) and how he noticed that the distribution of populations that were able to digest milk in their adult age (extended lactose tolerance – beyond the weaning age) correlated with ancient herding people in Europe, Asia or North Africa, while in other world locations people are generally lactose intolerant. It was found that a mutation occurred in DNA around 10 000 years ago among some isolated northern European populations. This mutation is thought to be evolutionary advantageous in terms that when there was scarcity of food, those that had this new trait were able to digest milk without the side-effects and thrive. As such they were having a greater chance for survival, mating and passing their new hereditary trait to their offspring, while those that did not have this advantage, slowly became a minority within that milk drinking society.

Egg or chicken?

Gary also talks about other uses of milk among the herding people before the lactose tolerance became more widespread: they probably consumed small amounts of milk when performing some rituals or preferred consuming fermented milk foods such as cheese or yogurt, in which the fermenting bacteria convert most of the lactose (milk sugar) into lactic acid and that is also the reason why lactose intolerant people can actually consume these acidified milk products in small amounts. It is not know for sure whether the change in DNA happened in response of this practice among herding people or whether the mutation occurred spontaneously in one or more societies across the globe. Both could have been true simultaneously. What is for sure is that only in those herding populations this lactose tolerance could have become apparent because they consumed the milk and milk products beyond the weaning age. In contrast, hunter-gatherers weaned their offspring much earlier and did not keep the livestock for milk, so any lactase deficiency did not pose a problem for them. Interestingly, Gary mentioned that among the herding people within as little as ‘15 generations of eating cheese and yogurt the frequency of lactose tolerance increased dramatically’.

When looking for the causal mechanism of the genetic variations with the changed environment and exposure to varying conditions, Gary referred to a food psychologist Paul Rozin that it is possible to go from culture to biology (not just the vice versa when a certain biology profiles the culture), when the ‘practices of drinking raw milk and dairying provided the selection pressure for genetic change’. Another man, Matt Ridley, supported in 2000 this direction of effect: “The evidence suggests that such people took up a pastoral way of life first, and developed milk-digesting ability later in response to it.” And continues: “It provides an example of a cultural change leading to an evolutionary, biological change. The genes can be induced to change by [several generations of] voluntary, free-willed conscious action… human being creating their own evolutionary pressures.” Although this sounds impressive, it still remains probable, that there must have been the ‘lactose tolerance gene’ to begin with, even if in low frequency among the particular society. And now we are at the beginning of the dilemma: was it the egg first or a chicken? We cannot say for sure whether the attempts to drink the milk caused the genes to change, or that there was this potential which occurred by a random mutation in some individuals and when they drunk the milk, they became a seed that created a field over several generations. I would say that the second scenario was more probable. However, I am not trying to disprove the mechanism by which the food we eat directly affects our genes, or, at least, their transcription. This will be discussed later.

An interesting point was mentioned in the book: One of the reasons why the non-herding people weaned their offspring earlier was that the gradually reduced synthesis of lactase over early years of the childhood had discouraged the offspring to consume mother’s milk. As a result, there were more births spaced more closely among these societies (breastfeeding has some contraceptive effect, although unreliable), which meant better nutritional status for the mother on one side (less nutrient depletion due to shorter breast feeding), but there was a higher infant mortality, because the breast milk is very nutritious, nurturing and virtually sterile. Overall, the longer the child is breast fed, the better for it. Learn more about the benefits of breast feeding here. In contrast, the herding societies had a high childhood survival rate and grew in size of population quite rapidly. This subsequently led to overcrowding with its own issues, but it is another story.

Getting back to Gabriel, Gary points out that the refusal of consuming the provided dried milk was embedded in their genetic make-up (unable to digest it), but also the cultural history, because they were not accustomed to consumption of any milk beyond the weaning age.

Good or bad program?

The milk for the village, mentioned at the beginning, came from the ‘federal government surplus commodity food program, providing it to low-income families. Other such support stock included greasy beef, white flour or processed cheese of Velveeta style – so nothing particularly healthy. All these were the surplus of the agricultural and food processing industry which would probably go wasted if not bought off by the government and provided to the poor folks elsewhere. While such schemes are useful for people facing an economic hardship, preventing them from going hungry, from the listed items you can see that a healthy diet is not something that plays a role here. Even more, none of these items were part of the traditional diet of these people, which thrived on a completely different diet for centuries, until they were introduced to the modern western diet quite recently and when their health started to deteriorate on a massive scale. Gary calls these federal food aids the kiss of death for Native American communities already suffering from nutrition-related diseases. This kind of support basically only worsens the already bad situation. Even the food banks existing today contain mostly tinned and packed food items with a long shelf-life, hence not promoting health and productivity of the supported social groups.

Why alcohol destroys some people easier than others

The chapter continues with discussing another sad event – the untimely death of Gabriel. This was in connection with drinking alcohol, in addition to an abundant diet and subsequently developed ill health in which the type 2 diabetes played a major role. Pima Indians, as some other cultures, metabolize alcohol differently, which means that they are facing more deleterious consequences and much earlier than we can see among other populations. The gene interaction with the diet of Gabriel was behind his diabetes. While ‘only’ up to 9.3% of the U.S. population suffered diabetes in 2012 (ADA, 2014), among Pima Indians it was 50% of the adults in that particular Gila River community at the time of writing the book. We can expect that this rate has only increased if no effective intervention took place to reverse the trend.  In the world, this disease is mainly affecting the adults, too, but there has been recorded an alarming juvenile onset of this kind of diabetes, hence before the 18 years of age. About 80-90% of all diabetes cases is type 2 and therefore it is largely preventable.

Gary recalls how he spent a lot of time with Gabriel when they were in their twenties and how they were unaware of their physiological differences, ‘acting as if they were equally invincible’. They worked hard together, they socialized together, ate and drank together… recalling eating ‘bowls of chile Colorado con carne, piles of pinto beans, huge flour tortillas or fry breads and then wash it all down with a beer or two’. They both were little overweight at that time, but they were also very physically active. Although physical activity is one of the preventative factors from type 2 diabetes, this was not enough for Gabriel. He occasionally joined friends in binge drinking, ‘disappearing for several days’. Nonetheless, Gabriel was aware of his weakness about alcohol and asked Gary to look after him and to stop him when it was apparent he had enough, because Gabriel would not be able to do it himself. This was not only about drinking, but ‘wolfing down the food’ as well. Gabriel continued: “It is not like getting a little buzz off a beer, you know… For us, it’s like going into an entirely different space… we’re in there by ourselves, not ever wanting to come out.”

This was in their twenties as mentioned earlier. Then Gary talks how it took only months for the health of Gabriel to deteriorate and how he had been dividing his life between ‘parties, hangovers and the hospital’. Gabriel had liver problems, sky-high blood sugar and also ulcerated stomach – a result of excessive drinking. Towards his end of life he lost a lot of weight and met the end in the hospital bed. And if that was not enough, his teenage daughter had metabolic problems as well, even without having a history of drinking like her father, all just the result of abundant food of wrong kind and perhaps less physical activity.

In fact, whole Gabriel’s family experienced problems with alcohol – because their genetics was different from others. This brings the light into the stereotyping of the Indians as ‘fat lazy Indians who can’t keep their jobs’. They were simply not made/adapted for our diet rich in calories, comfortable lifestyle with little exercise and drinking a lot of alcohol, which most of us can easily handle. Those Native Americans, that kept active and continued eating the ‘nutritious, savoury foods that their ancestors had eaten’, remained fit and healthy.

Interaction of the wrong environment and otherwise perfect genes – a problem

One thing should be noted here and the author discussed this as well. It is commonly being said that these populations are predisposed to certain health issues but it is not that simple. They do not get ill when following their traditional diet, so it is not only the predisposition of some individuals for particular diseases. Instead, this is a result of interaction of their genes perfectly synchronized with their traditional diet when clashing with the modern lifestyle of western civilization. Gabriel’s community carry different traits on their chromosomes 4 and 11, controlling for dopamine and metabolism of alcohol via a crucial enzyme called alcohol dehydrogenase. This explains why consumption of alcohol took Gabriel and his akin to a ‘different space’, giving him a higher level of buzz, euphoria and other physiological responses. According to the author, at least eight genes influence how alcohol is handed in an individual and these can help to predict the consequences. But this problem would not exist if people carrying these genes were not introduced to alcohol, which was almost non-existent in their traditional diet. This is the case for many other societies across Eastern Asia, such as Taiwanese, Chinese, Korean or Japanese, Gary says. The tolerance to alcohol, due to a sufficient synthesis of alcohol oxidizing enzymes in the liver, again correlate with the history of our ancestors, who settled in the areas and bred livestock. This lifestyle of densely populated areas had such consequences that the drinking water was polluted by various faecal bacteria, either from the livestock or the people and dysentery and other water-borne illnesses were quite common, especially in the cities. Therefore, it is not that Pima Indians have bad genes, it is about how WE have adapted to consumption of alcohol because our ancestors kept consuming it over centuries.

Therefore, it is not far from truth to say that: “we are what our ancestors drank and ate”. Furthermore: “The longer the chain of ancestors who lived in one place … – the greater the probability that selection was both for a diet and for genes that worked well with that …” and “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.”

Here we come to Matt Ridley again. Sharing his observations makes us aware that nomadic people, such as Gabriel’s ancestors, evolved as ‘hunter gatherers in an unpredictable desert environment rather than by herding cattle or sheep’. They often faced a food scarcity and they had a high level of physical activity, which made them very efficient in utilizing the little energy they consumed. Half of this energy was from wild desert foods. No wonder that they face such negative consequences when adopting the modern western lifestyle and diet, rich in calories, low in nutrients and with reduced energy expenditure, creating a positive energy balance. This lifestyle does not even make us very healthy, so how about the Pima Indians and similar societies?

I would end my talking about the first chapter of the book here. The author further discussed the wrong premise of gene therapy to fix the genes instead of focusing on what diet is the best for different ethnics on which they have evolved over many generations. This sounds logic and I tend to agree with that in a certain context. I will return to this matter later on.

Index:

Introduction

Chapter 1: Discerning the histories encoded in our bodies

Chapter 2: Searching for the ancestral diet

Chapter 3: Finding a bean for your genes and a buffer against malaria

Chapter 4: The shaping and shipping away of Mediterranean cuisines

Chapter 5: Discovering why some (don’t) like it hot

Chapter 6: Should we change places, diets or genes?

Chapter 7: Rooting out the causes of disease

About "" Has 48 Posts

Graduated at London Metropolitan University: BSc (Hons) Human Nutrition in 2014. Working as a research assistant at the MRC, The University of Cambridge.

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