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close this bookSCN News, Number 13 (ACC/SCN, 1995, 68 p.)
close this folderFEATURES
View the documentInterview with Dr A Horwitz, SCN Chair, 1986-1995
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View the documentPoor Nutrition and Chronic Disease - Part I

Poor Nutrition and Chronic Disease - Part I

The first of a two part report of the proceedings of the ACC/SCN Symposium on Nutrition in the Epidemiology and Prevention of Cardiovascular Disease, Diabetes Mellitus, and Obesity in Developing Countries.

At the SCN’s 22nd Session held at the Pan American Health Organization, Washington, D.C., a Symposium was held on “Nutrition in the Epidemiology and Prevention of Cardiovascular Disease, Diabetes Mellitus, and Obesity in Developing Countries” on 12 June 1995. Bringing this topic to the attention of the SCN and the other participants aimed to serve four purposes. The first was to provide a review of the evidence that there may be an emerging complex of problems in developing countries with respect to these non-communicable diseases, and to examine how these problems - which are more commonly regarded as affecting affluent populations - are distributed across income groups. The second was to give an insight into the potential economic implications of these trends, particularly as they may impact on health systems. The third aim was to examine the causal factors behind these trends, including dietary, behavioral or life-style factors, and introduce the intriguing notion that malnutrition itself may be among the causes of these problems. And the fourth was to encourage participants to consider what could be done to help prevent these trends from continuing, and particularly how UN agencies could be involved in this.

The Symposium began with an overview of the topic by Dr J Jervell, member of the AGN and President of the International Diabetes Federation. Presentations then followed on “The Emergence of Chronic Diseases in Developing Countries” by Dr T Byers of the University of Colorado; “The Role of Foetal and Infant Growth and Nutrition in Causality of Cardiovascular Disease and Diabetes in Later Life” by Dr J Hoet, Professor Emeritus at Louvain University, Belgium; “The Contribution of Urbanization and Lifestyle Changes to Cardiovascular Disease, Diabetes Mellitus and Obesity in Developing Countries” by Dr A Wielgosz, Division of Cardiology, University of Ottawa; and “Prevention and the Role of Nutrition” by Dr G Beaton, Department of Nutritional Sciences, University of Toronto.

In Part I of this report of the Symposium proceedings, the introductory presentation by Dr J Jervell, and papers by Dr T Byers and Dr A Wielgosz on the epidemiology and causes of non-communicable diseases in adulthood, are reproduced. Part II, to be published in the next issue of SCN News, will cover the role of foetal and infant malnutrition in increasing the risk of cardiovascular disease and diabetes in later life.

INTRODUCTION: OVERVIEW AND IMPLICATIONS FOR THE FUTURE

by Dr J. Jervell, President, International Diabetes Federation

Too much or too little of a good thing is deleterious. Too little food leads to malnutrition, undernutrition and micronutrient deficiencies. That we have come to address the consequences of overnutrition in developing countries is a measure of some success in combating undernutrition. We may even learn, during this symposium, that early undernutrition and later overnutrition are a particularly dangerous combination.

Non-communicable diseases are emerging not only with the same strength as they have done in the industrial world, but perhaps even more strongly, in the developing countries - especially those which are developing fast.

What are the diseases we are speaking of? We have a group of diseases which we call sometimes the “metabolic syndrome” in the western world, and this is because if you have one of them, you are more likely to have one of the others (see figure 1). If you have diabetes, you are more likely to have hypertension, you are more likely to get coronary heart disease and stroke, and your blood lipids are more likely to be deranged.

Figure 1. The Metabolic Syndrome or Syndrome X

Coronary artery disease

angina pectoris
myocardial infarction
sudden death

Stroke

Diabetes mellitus type II and impaired glucose tolerance

Hypertension
Dyslipidemia
Central Obesity

These diseases apparently have a common causation. In western medicine, today we talk about insulin resistance or hyper-insulinaemia, which may provide a link. Perhaps they may also be joined together as a consequence of earlier under-nutrition, and as a consequence of changing lifestyles.

We talk about diseases and we talk about risk factors. Diabetes, in addition to being a disease in itself, is also a risk factor for coronary heart disease. If you have diabetes you are three to four times as likely to get coronary heart disease and myocardial infarction, angina, and sudden death. If you have hypertension you get more stroke and more coronary heart disease. If you have dyslipidemia?, it’s the same way.

But diabetes in itself is also a disease with symptoms and with specific complications. I was asked earlier today why do you talk so much about diabetes, is a little high blood glucose really dangerous? I repeat, it causes specific complications. Diabetes is the most common cause of blindness in adults in America; it’s also the most common cause of amputations. In Japan it’s the most common cause of renal failure in adults. So it’s not only causing coronary artery disease and stroke, but specific complications as well.

These diseases may have a common preventive aspect, but once they have developed, you need very specific management plans to control their impact. So sometimes we say the primary prevention of these diseases is probably much the same, but the management, once they appear, is very costly and very different.

There are two main types of diabetes. One is insulin-dependent diabetes, an auto-immune disease which destroys the beta cells in the pancreas, the cells which produce insulin. It’s called insulin-dependent because without insulin the patient dies. It is also known as type I diabetes.

As far as we know today, it is probably not particularly common in developing countries. This may be in part because it is undiagnosed - we do know that there is a lot of type I diabetes which is not diagnosed in developing countries. But this is not the main type of diabetes that we are talking about today. That is the non-insulin dependent diabetes, due to an insulin resistance and a reduced capacity to produce extra insulin to overcome this resistance. Sometimes this is called type II diabetes.

A pre-diabetic stage is called impaired glucose tolerance. WHO has decided that you have diabetes if 2 hours after having drunk a solution with 75 grams of glucose, you have a blood glucose of more than 200 milligrams per deciliter. If it is below around 140 mg/dl you are normal, but if it is in between 140-200 mg/dl you have impaired glucose tolerance, unpaired glucose tolerance is a risk factor for developing diabetes, and also increases the risk of getting a myocardial infarction.

Now there is also malnutrition related diabetes which occurs in some developing countries. There are two types of this. One is due to a pancreatitis, perhaps - it has been suggested due to inadequately processed cassava. The other is related to severe undernutrition throughout childhood and adolescence, and Joseph Hoet will talk more about this later today (see part II).

How common is diabetes in the world? I am talking about diabetes because we have good criteria for making the diagnosis, and a lot of good surveys have been done. It is much harder to get good data on causes of death from myocardial infarction in developing countries. Results of a study on the prevalence of diabetes in adults, by standardized criteria and age corrected are shown in figure 2. There is a wide range of prevalences. In the Pima Indians in Arizona, about 50% of the adults are diabetic, at the survey time: at the age of 40, 50% of Pima Indians have diabetes. They were described about a century ago as a population where diabetes was not seen; then they were poor agricultural people, now they live in the reservation and are very obese. What is striking in figure 2 is that high diabetes prevalence is either in developing countries or in under-privileged groups in developed countries, such as the Hispanics or the Indian populations in the U.S. Diabetes is extremely high in people who go directly from a hunter-gatherer existence, and skip the agricultural part of our development going directly into an urbanized life-style.

Some recent examples come from Pakistan. Surveys in Karachi have shown a prevalence in the adult population, about 25 years of age, of 16.5% diabetes. In my own country, which is Norway, the prevalence in a similar population would be 3%, and I can tell you we are fatter than the Pakistanis that we studied! Impaired glucose tolerance - the pre-diabetic state - in Pakistan was 10.4%, adding up to more than a quarter of the adult population having some form of glucose intolerance. This leads to increased risk of coronary heart disease, and indeed when we talked to cardiologists in Pakistan, they said that myocardial infarction in young men around 30-40 years was much more common than seen in the western world.

In Shikapur, up to one quarter of the population has glucose intolerance; in rural Baluchistan (a tribal area) the prevalence is 17%. So even there they have more glucose intolerance than in urbanized northern Europe.

Why are these non-communicable diseases, including diabetes, becoming so high? Is it due to genetics? Obviously, if you go on an individual basis, and ask a person who has non-insulin dependent diabetes or coronary heart disease or hypertension, or obesity, these conditions are commoner in their relatives, in their parents and grandparents. It is not just due to family life-style, there are definite genetic factors. But are the genetic factors responsible for the differences between ethnic groups? Probably some. Pima Indians are probably genetically disposed to get diabetes to a higher degree than most other populations of the world. But from all other continents and all other ethnic groups there are subgroups of populations who have diabetes incidences like these. For example, the Chinese at present have a prevalence of 2% of diabetes in their adult population; the Chinese in Mauritius have 13%. So they are not protected, they have just not become urbanized yet. The north Hong Kong Chinese population has a prevalence of diabetes of 5%, so it’s developing there, and is higher than in Europe, for example.


Figure 2. Prevalence (%) of total glucose intolerance (diabetes and IGT) in selected populations in the age range of 30-64 yr.

(Source: (1993). Diabetes Care, 16(1), 170)

We sometimes talk about urbanization as the causal factor. What do we mean when we talk about urbanization? I would rather call it an urbanized life-style, because certainly in my country you don’t have to live in a city to lead an urbanized life-style. I believe that to really have a rural life-style you actually have to till the earth. You can live in the rural areas and lead very urbanized life-styles. There is a definite urbanization going on in the world. Probably something like 40-50% of the population is now living in cities, and there are marked changes in diet, varying from place to place. There is definitely less physical activity. There is more smoking. There are higher salt intakes - there have been studies showing that Africans moving from rural areas, changing to the higher salt intake of the Sub-Saharan African cities, get an increase in blood pressure within 6-8 weeks. There is a higher alcohol intake. People who are living in cities in the developing worlds say that there is definitely more stress than their parents had when they were rural.

Obesity is a risk factor. Obesity minus physical activity is more dangerous than obesity with physical activity. There are many good studies showing this, both for coronary heart disease, diabetes, and hypertension. So obesity is the risk factor but physical inactivity is equally risky. When I go to cities such as Karachi, or Accra in Ghana, I wonder how are people going to have physical activity programmes there - especially in Karachi, which is a city of 11 million inhabitants.

Humanity developed as hunter-gatherers, probably a couple of hundred thousand years before we discovered agriculture. Then there was another 10,000 to 5,000 years before we became urbanized, but we are supposed to be hunter-gathers. Kierin O’Dea, in Australia, has collaborated with a group of Aborigines who had become extremely urbanized and then taken them out to the hunter gatherer existence for short periods.

The 10 Aborigines were diabetic, living in an urban environment, but had had a childhood in the outback and had lived the traditional existence as hunter-gatherers. There were 5 men and 5 women - all had diabetes, and they spent 7 weeks together in the hunter-gatherer existence. They had a marked weight reduction, their body mass index went down and their diabetes improved. Their fasting blood glucose and 2 hour glucose after 75 grams (which is a glucose tolerance test) went down and their fasting insulin levels went down so they became more insulin sensitive. They also lowered their cholesterol, their triglycerides which are all risk factors for coronary heart disease, their blood pressure and the bleeding time went up which means that their blood was not so likely to coagulate. They were less likely to get thrombosis.

There are three survival factors if you are a hunter-gatherer, according to O’Dea. You should have a strong preference for energy dense food, honey and fats - but there is little honey available and wild animals have much less fat than domesticated animals, so these are scarce, but you survive better if you like these foods because you then store them as fat. You should have a great capacity to gorge, because when food is there you should get as much as you can inside yourself, to store it for later use, and then you should minimize physical activity as much as possible, only be physically active when it is necessary. I asked Dr O’Dea how much time these hunter-gatherers spend actually hunting and gathering and preparing food and she said about 4-5 hours per day. It’s not natural to work as much as 8 hours a day for humanity, but still we do it. These beneficial tendencies for hunter-gatherers to gorge - to prefer energy-dense food and to be physically inactive when it is not necessary to be physically active - are not a good life-style in our society. It is too easy to be a hunter-gatherer in Washington.


Figure 3a. Correlation between mortality from diseases (total) 1964-67, in men aged 40 to 69 years (standardised rates/100,000 population) and infant mortality rates 1896-1925.


Figure 3b. Correlation between mortality from arteriosclerotic heart disease, 1964-67, in men aged 40 to 69 years (standardised rates/100,000 population) and infant mortality rates 1896-1925.


Figure 3c. Correlation between mortality from arteriosclerotic heart disease, 1964-67, in women aged 40 to 69 years (standardised rates/100,000 population) and infant mortality rates 1896-1925.

(Source: (1977). British Journal of Preventive and Social Medicine, 31, 92.)

Studies of changes in diet in rural and urban Cameroon have found that the rural diet is very high starch, high fibre and very low fat; moving to the city, fat increases, starch goes down, sugar is introduced to a large extent. We had a meeting of diabetologists in Ghana recently to give advice on diet for diabetes there, and all agreed that the standard traditional African diet is the correct diet for people with diabetes (and the other non-communicable diseases), very high in fibre and complex carbohydrates.

Now are there other factors? A friend of mine Anders Forsdahl suggested in 1977 that perhaps if you were poor in childhood you were more likely to get coronary heart disease and premature death from arterial sclerosis in later life. He said this because he grew up in a very poor community in the 1930’s in northern Norway, where his father was the district physician, and he later came back as a district physician himself and saw that there was an awful lot of myocardial infarction and high cholesterol levels. He then did a very simple study. He compared the infant mortality between 1895 and 1925 with later total death and death from coronary heart disease. You can see that there is a pretty good correlation, in figure 3.

This could be a nouveau-riche phenomenon, that you are poor in childhood, you just eat more of the wrong things, but it could also be some sort of programming going on and this is what Joseph Hoet is going to talk about later today, and which Barker and Hales have suggested. They have done studies of the birth weights and the 1-year-old weights of children in a county in England, and found that the lower the birthweight, and the 1-year-old weight, the higher the coronary mortality later in life. A low birth weight and for some reason high placenta weight, leads to higher blood pressure later. You get more diabetes in those who have low birth weights, and low weights at one year. The hypothesis that early under-nutrition is so important for developing the non-communicable diseases of the metabolic syndrome later in life is based on studies done in developed countries, and no good studies have yet been done in a similar fashion in developing countries.

If, however, this is true, we can expect an epidemic once development occurs, and perhaps that is what we are seeing in Pakistan. The prevalence of low birth weight in 1990 was more than 30% in South Asia, and it is between 10 and 20% in very many areas of the world.

Of course, there are other changes which cause higher prevalences of these diseases, not the least one being the demographic changes that are occurring. The World Bank’s World Development Report (1993, p.32) compares the median age of death in various areas of the world: up to 1950, half the population died before they reached 20 years; in many countries this median had risen to around 40 or more by 1990, and the expectation is that this will continue. A totally different population pyramid will result, and we will therefore get a marked increase in the non-communicable diseases. So the success in preventing childhood mortality and morbidity leads to problems later, even though it is also a measure of success.

What we can wonder is perhaps whether the epidemic that we are seeing in the industrialized countries will come with even more force in the developing countries. Perhaps if the early undernutrition hypothesis is right, it may be a temporary phenomenon - hopefully - but not in our lifetime I think.

The expectation is that the communicable diseases will dominate the picture in the future. This is going to put a major strain on the resources of the health care system. In the developing countries today, meetings are being held by physicians and public health officials on how to actually manage these diseases when they occur. The primary prevention is, of course, the great challenge and should be high priority. I think we do know some of the lessons, although we need more research. Implementing these measures is difficult, but we have to start now.

THE EMERGENCE OF CHRONIC DISEASES IN DEVELOPING COUNTRIES

by T. Byers, M.D., M.P.H. and Julie A. Marshall, Ph.D., University of Colorado School of Medicine, Denver, Colorado.

The burden of chronic diseases now nearly equals that of communicable diseases, even in many developing countries (1). There is increasing evidence that chronic conditions such as coronary heart disease, cerebrovascular disease, diabetes, and many cancers, are in part a result of nutritional problems that have occurred years before. In this paper we will review some of the epidemiologic evidence about the emergence of nutrition-related chronic diseases in developing countries and will address the question of whether people in developing countries might have a special vulnerability to nutrition-induced chronic diseases.


Figure 1. Changing Age at Death in Developing Countries

WORLD BANK, WORLD DEVELOPMENT REPORT, 1993 (REFERENCE #1)

A common theme in the literature is the phenomenon of a transition, variously called the “epidemiologic” or “demographic” or “health” transition, occurring in developing countries. As a result of declining mortality in early life, the population of developing countries is rapidly aging. The changes in chronic disease mortality are rather striking just within a generation. Fewer than 20% of deaths in 1950 were in the age group 60 and older, but over 40% of deaths will occur in this age group in the year 2000 (figure 1). Chronic disease deaths are increasing both because there are more older people, and because of the increasing prevalence of chronic disease risk factors. Today, two thirds of the chronic disease deaths occur in developing countries and only one third in the so-called industrialized nations (1). If we think in a politically and economically neutral way, then, about preventing chronic diseases in the world, it is within the developing countries that the biggest potential already exists for preventing unnecessary premature suffering and death from chronic diseases.

Disability-adjusted life-years (DALY’s) are a measure of the combined effects of mortality and morbidity in a population (1). DALY’s are computations of the years of life “lost”, both because of premature mortality and because of disability, scaled to the severity of the disabilities due to incident diseases. DALY’s lost in a particular year in a population are discounted for the relative value of future years (3% per year). The World Bank has estimated DALY’s based on both direct measures of health and on expert judgment, which is critical in making estimates for developing countries, where good data often do not exist. Cardiovascular diseases, cancer, and diabetes already have equivalent or higher risks on a per-population basis for disability adjusted life years in developing countries compared to industrialized countries (figure 2).


Figure 2. Disability-adjusted Life Years Lost (DALY’s) per 1000 Population per year by Age and Economic Development

WORLD BANK, WORLD DEVELOPMENT REPORT, 1993 (REFERENCE #1)

The epidemiological data needed to fully assess trends in disease incidence in developing countries is limited, but there are some informative survey data from some countries that have undergone rapid transitions. In Singapore, in contrast to the rapidly declining trends in the industrialized countries, ischemic heart disease mortality has increased over 90% among men and over 135% among women over the period 1959-1983 (2). We know less about trends in risk factors in developing countries, but there are some data being collected now by the International Clinical Epidemiology Network (INCLEN), a network of epidemiologists conducting standardized surveys of chronic diseases and their risk factors in developing countries (3,4). These surveys measure risk factors cross-sectionally, but will have the capacity to examine trend data in the future. These surveys have shown that risk factors for cardiovascular diseases and cancer are already highly prevalent and variable across countries (3).

Obesity is a very important chronic disease risk factor to consider in detail because it is tied to many chronic diseases, and it is easy to measure. Obesity, a useful indicator of caloric imbalance, has been increasing in nearly all countries in recent decades among both men and women (5). Almost all anthropometric surveys in industrialized countries that have repeated results over time show that an increase in BMI is occurring (5) (figure 3).

In developing countries good trend data are usually absent, but within country contrasts in lifestyle and in diets are often reflected by contrasts in urban versus rural cultures. Fairly consistent patterns are seen in countries where surveys have been done showing the prevalence of obesity is considerably higher and the mean body mass index higher in urban than in rural areas (6). A survey in Costa Rica of urban versus rural dwellers has shown not only higher BMI in urban than in rural-dwellers, but also adverse trends for diastolic blood pressure, saturated fat intake, smoking, blood glucose and blood cholesterol concentrations (7). Migrants from developing to more industrialized countries show rapid increases in body weight. Japanese men migrating from Japan to Hawaii or California showed increasing prevalence of obesity and higher body mass index with “westernization” of the diet and physical activity habits (8). The same phenomenon has been seen in the Western Pacific where Samoans from more traditional areas have migrated into progressively more “western”, “industrialized” areas, with a progressive increase in the prevalence of overweight (9) (figure 4). The “nutritional transition” is now underway in developing countries. The most prominent features of the changes in the “nutritional transition” are increases in the intake of fats in the diet, along with decreases in the intake of complex carbohydrates and fiber, accompanied by a decrease in physical activity.


Figure 3. Percent Change in BMI per Decade in Countries with Repeat Surveys

BYERS ET AL (REFERENCE #5)

A metabolic syndrome, often referred to as “syndrome X”, defined by the combined occurrence of hyperinsulinemia, hypertriglyceridemia, hypertension, and central adiposity (fatness in the abdominal area out of proportion to fatness in the rest of the body), may be a particularly common manifestation of the nutritional transition in developing countries (10). Considerable anecdotal evidence from many populations suggests that “syndrome X” poses a special risk for peoples and populations previously undernourished (11, 12). But there may be a latent period, a “honeymoon generation” in which we can be fooled into thinking adverse physiologic changes are benign. In the United States, for instance, in considering the emergence of diabetes as a significant health problem in Native Americans, we have been fooled before. A paper published in 1965 described a “benign” form of diabetes in Navajos (13). These Native Americans had experienced changes in diet and physical activity, followed by increases in body weight, then the emergence of diabetes. But in the 1960’s their diabetes was regarded as a benign condition because the blindness, amputation, and renal failure had not yet begun to occur. Now a generation later, in retrospect, we can see that there was a “honeymoon generation”, a latency period between the onset of diabetes in the population and the occurrence of serious diabetic complications (14). The recent emergence of diabetes mellitus as an increasingly common problem in developing countries likely predicts a future wave of diabetes-related morbidity and mortality (15).


Figure 4. BMI in Samoans According to Their Degree of Western Acculturation

MC GARVEY ET AL. (reference #9)

An important question arising from the epidemiologic patterns that we are beginning to see and that we will clearly see in the future, is whether a special biological vulnerability might be present among populations that have previously been under-nourished, either in their own lives or in the lives of their ancestors, that might be placing them at higher risk for chronic disease in middle age and adulthood (16). How might such a special biologic vulnerability emerge? Our ancestors were metabolically and genetically mixed, and when they went through hard times, either traveling between the Pacific Islands, experiencing intermittent famines in the American southwest, or surviving the Caribbean hurricanes, those who were metabolically thrifty were able to survive (ie, they had a “thrifty genotype”) (16). Those who were genetically vulnerable then died off, so by natural selection we now have some populations who have undergone hard times in the past who are particularly vulnerable to adverse effects of overnutrition for their level of physical activity because they are genetically thrifty and metabolize foods in a more efficient way (16).

Nutritional deprivation can also happen in utero, where either genetic selection or phenotypic re-programming can occur (17). Low birth weight has been shown to be associated with many of the physiologic conditions that define “syndrome X” (18,19) (figure 5). The intrauterine environment, or perhaps other critical periods in early life (20), may not just select out certain fetuses for survival, but may actually program us nutritionally to have a particular metabolic phenotype. The data to support the conclusion of a thrifty genotype versus a thrifty phenotype is limited, but the common thread is that the ancestors of some peoples, or in fact their own early life environments, may have resulted in the creation of populations that are metabolically vulnerable to overnutrition.


Figure 5. Relative Risk of Syndrome X Among Adult Men, According to Birth Weight

* Relative Risk for syndrome x (non-insulin-dependent diabetes mellitus, hypertension, and hyper-triglyceridemia), adjusted for adult BMI.

Reference: Barker, reference # 18

What data do we have to suggest that there is a particular special vulnerability with the nutritional transition that we are clearly seeing in developing countries? In England, where mortality rates have been stable or slightly declining in recent years, Indian migrants from South Asia have had increasing mortality risk for heart disease (21,22). Their body mass index is not particularly different from Englanders, but the waist to hip ratio of the South Asians versus the Europeans in England is substantially different: more central adiposity in South Asians, even though their total body mass index is very similar (21, 22). Central adiposity is thus much higher, as are diabetes prevalence and insulin levels among the South Asian immigrants. The migrants from South Asia in England then seem to have higher heart disease risk as part of “syndrome X”, and therefore they seem to have a special vulnerability to adverse effects from their changed diets. More research is needed on the question of special biologic vulnerability for peoples in developing countries. This special vulnerability may lead to much higher levels of premature morbidity, mortality and unnecessary suffering than would be predicted by the adverse changes in risk factors alone among middle aged adults in developing countries in the years to come.

There are two public health nutrition revelations of note. First, the control of nutrition deficiency diseases has been mostly completed in industrialized countries, but is still evolving in developing countries. The second is the control of nutrition-induced chronic diseases. We have not done a good job yet in industrialized countries with this second problem. Developing countries that are still trying to deal with the first challenge will now have to deal as well with the second one, which is rapidly emerging as the primary problem in terms of deaths and disability.

How can developing countries deal with, on the one hand, micronutrient deficiencies (eg, iodine deficiency, vitamin A deficiency, iron deficiency) that are still plaguing large parts of populations, while chronic diseases are emerging as well? Often this plays out as a rural problem for micronutrient deficiencies and an urban problem for caloric overload. What is the commonality in public health strategies for fortification, infection-control, and nutritional supplementation, that deal with micronutrient deficiencies, and for fat reduction, fiber promotion, and physical activity promotion, that relate to chronic disease-relevant nutrition? There is a potential common link in the promotion of fruits, vegetables, and whole grains in the diet.

Clearly, as we eat more fruits, vegetables, and whole grain in the diet we can substitute these for high fat foods. In addition, it is increasingly clear that the micronutrients in whole foods have profound effects on heart disease and cancer risk. Our clinical trials have thus far been unsuccessful in giving high doses of single micronutrients to prevent chronic diseases, but it is clear that there is a powerful effect in fruits and vegetables that reduces chronic disease risk. At the same time we cannot, of course, forget infection control, supplementation and micronutrient fortification, but the promotion of fruits and vegetables in the diet may be a useful commonality between strategies for preventing micronutrient deficiency and chronic diseases that can he a basis for food policy and education in the future. Because of the importance of caloric balance, and the emerging problem of obesity in developing countries, nutritional interventions should always include the promotion of regular physical activity, which can allow for greater intakes of foods, and thereby also prevent micronutrient deficiencies that can lead to chronic diseases.

We need to decide how we are going to educate people and what kinds of food policies we are going to promote. What kind of actions can we suggest that be taken? We need to improve surveillance of adult health risks and risk factors in developing countries. But in isolation surveillance is not going to be particularly informative unless we link our future surveillance to intervention policies and to intervention programs. So how do we strategically develop collection systems for surveillance data linking it to policies and interventions’? We need to develop, of course, culturally relevant interventions. In the case of foods, it is particularly important to develop interventions and educational approaches for developing countries that play on the strengths of their heritage and their history and their culture and really build on the roots of their civilizations.


Figure

Finally, in developing countries, as well as in industrialized countries, we need to find out how to implement policies to promote healthy diets and physical activity. How can we really have policies that promote fruit and vegetable and whole grain intake, and how can we build and design our cities and our lifestyles to promote regular physical activity? These are important challenges for all countries (23,24). Price supports can encourage the production and consumption of some foods in preference to others, but price support systems can cause inefficiencies in free markets. If countries choose not to engage in price supports for promoting healthy commodities, they should at least be careful to avoid hidden subsidies for high fat diets, such as subsidies for the production of high fat meats or high fat dairy products. The challenge that faces developing countries is that with the emergence of obesity and chronic diseases due to changes in diet and physical activity in some segments of the society, undernutrition and poor economic development continue to lead to the opposite problems of starvation and physical stress in other areas. There must be a social balance between feast and famine, and between sedentariness and over-exertion. Otherwise, the future economic and social burden of high rates of heart disease and cancer will become a costly burden for developing countries.

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24. WHO Study Group. Diet, nutrition and the prevention of chronic diseases: A report of the WHO Study Group on diet, nutrition and prevention of noncommunicable diseases. Nutrition Reviews 1991, 49-291-301.

THE CONTRIBUTION OF URBANIZATION AND LIFESTYLE CHANGES TO CARDIOVASCULAR DISEASES, DIABETES MELLITUS, AND OBESITY IN DEVELOPING COUNTRIES

by Dr A Wielgosz, Head, Division of Cardiology, University of Ottawa

First I would like to review the epidemiology of urbanization. Then I will discuss some of the relevant lifestyle changes that are associated with development and urbanization, pointing out how they affect cardiovascular diseases, diabetes mellitus and obesity in developing countries. Finally, I would like to examine obstacles or barriers that need to be overcome in order to maintain health and prevent the rise of these non-communicable diseases.

Table 1. Project growth of megacities

Population in millions

1992

2000

Tokyo

25.8

28.0

Sao Paulo

19.2

22.6

New York

16.2

16.6

Mexico City

15.3

16.2

Shanghai

14.1

17.4

Bombay

13.3

18.1

Los Angeles

11.9

13.2

Buenos Aires

11.8

12.8

Seoul

11.6

13.0

Beijing

11.4

14.4

Rio de Janeiro

11.3

12.2

Calcutta

11.1

12.7

Jakarta

10.1

13.4

Tianjin

9.8

12.5

Manila

9.6

12.6

Cairo

9.0

10.8

New Delhi

8.8

11.7

Lagos

8.7

13.5

Karachi

8.6

11.9

Bangkok

7.6

9.9

Dacca

7.4

11.5

Urbanization

Most remarkable about the epidemiology of urbanization, is the rate of its occurrence. In 1960 about 30% of the world’s population was urbanized. In four years’ time, it will reach 50%. The fastest rate of urbanization is occurring in Africa, at 10% per year. In the Eastern Mediterranean region the population has doubled over the last two decades and in the 5 year span from 1985 to 1990, urbanization increased from 39% to 44%. It is likely to reach 50% by the turn of the century.

In some, urbanization is proceeding at an unprecedented rate and most of the growth is taking place in developing countries. Of 21 megacities (more than 10 million population) projected for the year 2000, 18 will be found in the developing world, as shown in table 1.

Lifestyle Changes

Along with urbanization come a number of lifestyle changes. Over the course of thousands of years, populations have struggled to achieve a balance between food intake and energy expenditure, for the most part, trying to avoid a caloric deficit. This is true whether the lifestyle was nomadic or settled. In many developing countries, we can still see traditional food sources and food types, that have not changed over the millennia. However, significant changes have occurred in the availability of food, its caloric value, and in energy expenditure.

Table 2. Comparison of American and Rural Chinese Diets

American

Rural Chinese

Total fat (% of kcal)

38-40

15

Dietary fibre (g/day)

10-12

34

Soluble carbohydrate (g/day)

240

470

Calcium (mg/day)

1140

540

Protein (g/day, 70 kg male)

90-95

64

Animal protein

70

7

Iron (mg/day)

18

34

Thiamin (mg/day)

1.4

2-3

Retinol (RF/day)

990

30

Total carotenoids (RE/day)

429

836

Vitamin C (mg/day)

73

140

Riboflavin (mg/day)

1.9

1.8

Energy Intake (k-cal/day)

2360

2640

One of the significant innovations associated with development and urbanization is mechanized transportation. The consequence of this is a decrease in physical activity. Furthermore, modern food production, processing and storage require less expenditure of human energy, thus contributing to the imbalance between consumption and output. I consider energy expenditure relative to food intake a crucial aspect of nutrition.

Sometimes the lifestyle changes brought on by innovation and development are overlooked because of an overriding “greater good”. Mass education is an example. We take young children and constrain their physical activity in classrooms over the course of 10 or 15 years. Granted, they become educated but at the same time they develop lifestyle habits that diminish their expenditure of energy. Of course, education can and should include physical activity but all too often it is neglected and as children become adults they become accustomed to a lesser degree of activity. Passive entertainment, facilitated by attractive technologies also contributes to a culture of decreased energy expenditure. An increase in salt and sugar intake is associated with modern food production, food storage, processing and marketing. Total fat consumption increases and the balance between saturated and unsaturated fat is altered, while the intake of anti-oxidants is decreased. Table 2 shows a comparison between a typical American diet and a traditional, rural Chinese diet. Perhaps the most striking difference here is the total fat as percent of calories, which is significantly higher in the Western industrialized diet (38% to 40% compared to 15% in the Chinese diet). The “urbanized” Western diet has much less dietary fibre and the intake of total carotenoids and vitamin C are half that of the Chinese diet. Yet interestingly, the energy intake in terms of kilocalories per day is higher among the rural Chinese who appear to burn off more calories than the average American.

Development brings about a change not only in the constituents of nutrition, but also in the culture of eating. Food is marketed with compelling messages to eat. The public is bombarded by advertising that encourages consumption. At the same time lifestyles are changing with less energy expenditure. The consequence is an imbalance in energy intake relative to output. This can only result in obesity and disease.

The poster shown in figure 1, from North Karelia (in Finland) advocates intake of fresh fruits, particularly berries. There is an interesting story behind this poster and behind the public health message. North Karelia until recently had the highest rate of cardiovascular disease mortality among men in the world. Although the initiative for change came from the public, when it became obvious that one of the things that had to change was the diet, many people resisted, complaining that their traditional diet was being tampered with. Anthropologists and sociologists were called in to study the traditional diet. They found that the so-called traditional diet, which had a high content of dairy products and animal fat, was consequence of the Second World War, a form of compensation for hard times, and that the pre-war traditional diet had included a lot of berries rich in vitamin C. Finland is heavily forested and has abundant berries. The public began to respond to the message to get back to heart healthy diets. Many societies in developing countries are distancing themselves from their own heart healthy diets as they become urbanized and industrialized and start to adopt Western ways of eating. It is imperative that those traditional diets at least be documented so that they can be referred to and their continued consumption can be encouraged.


Figure 1

I would be remiss in talking about the consequences of modernization without mentioning the problem of tobacco, its production and marketing. There is no question that tobacco leads to premature death from non-communicable diseases, but it also has other effects, including some that impact on nutrition. Tobacco cultivation results in environmental spoilage and competition for limited resources, occupying up to 70% of the land available for agriculture in some developing countries. In Malawi and Tanzania, there is wide-spread destruction of forests to provide fuel for flue curing of tobacco. Unfortunately, such behaviour is motivated by short-term economic gains. Zimbabwe for example derives most of its foreign exchange from tobacco. No wonder then, that smoking is increasing in the developing world. In Jakarta, Indonesia, the prevalence is as high as 60% among men. This is a serious problem and it is not enough to talk about tobacco control. The objective must be tobacco eradication.

Urbanization and Adaptation

We heard earlier about the famous study of Japanese men who were examined and compared in Japan, Honolulu and California. We know that the prevalence of risk factors as well as the prevalence of coronary heart disease increased across a gradient of change. But I do not think the degree of change refers to the extent of urbanization. I do not believe that California is any more urbanized that Japan or Hawaii. What these findings reflect is the impact of migration and of undergoing a rapid change in lifestyle particularly to one that fosters non-communicable diseases.

The complexity of urban life requires adaptation i.e. survival skills. To succeed both individually and collectively, requires time. Newly urbanized or urbanizing societies have not had time to adapt. While Western societies still have problems of urban living to reckon with, they have had a head start in adapting. Societies in developing countries are much more vulnerable because they have not had the same opportunity to fully adapt and they are urbanizing at an unprecedented faster rate.

The transition to urban life involves changes in social relationships. These include changes in the structure of the family unit and in the roles of its individual members, particularly women. Research in social medicine is pointing out the importance of personal control, control of one’s work and home environments. Social isolation and the lack of social support add to the stress and increase risk of disease and death. Much of the mortality difference within society is explained by the social gradient from rich to poor, advantaged to disadvantaged and educated to uneducated.

While many Western industrialized countries are beginning to enjoy a decline in mortality from cardiovascular diseases, there are indications of an epidemic rise in diabetes, obesity and cardiovascular diseases in the developing world. Over half the deaths caused globally by cardiovascular diseases occur in developing countries. Admittedly in most of these countries there are significant problems with disease surveillance, making the validity of data often suspect. But I fully endorse the comments made earlier this morning, that we need to take the data that we have at hand, allow for best estimates and work with them. When we do that, we see that in 1990 there were about 8 to 9 million cardiovascular deaths the developing world. That represents about 70% more than the 5.3 million death that occurred in the developed world. Cardiovascular deaths in developing countries still represent a much smaller fraction of total mortality (15-30%) than the approximately 50% experienced in developed countries. But that is changing and the contribution of non-communicable diseases to total mortality is expected to rise in the developing world in an epidemic fashion.

Again I come back to the contribution of smoking. Peto and Lopez have estimated that smoking kills about 6 people a minute world-wide: one in the European Union one in the United States, one in other developed countries, one in the former USSR, one in China and one in other developing populations. Taking the former USSR as a rapidly industrializing part of the world and adding China and other developing nations, results in about half the mortality coming from the developing world. That is a significant toll. Unfortunately tobacco consumption is being driven by the forces of development.

Table 3 Barriers to Prevention

competing priorities
technology - based interventions
inadequate epidemiological data
poor presentation of messages to policy-makers and the media
failure to recognize the importance of prevention and cost-effectiveness
anonymity
economic and social constraints
vested interests
lack of community mobilization

Barriers to Prevention

The problems I have outlined call for action and in many places a response has begun. But there are barriers to preventive action and I would like to go over some of them, listed in table 3. One is competing priorities. Each developing nation has to determine its own priorities. Donor countries and donor agencies also have competing priorities. The global agenda is full. In the face of multiple requests to help out with a range of problems, often the responses are not proportional to the size of the problem. The need to treat seems more compelling than the need to prevent so we end up with the all too familiar “too little, too late”. Technology based interventions are favoured. They are more glamorous. They are the quick fix and that is why we see such heavy investments in interventions. It is often argued that there is inadequate epidemiologic data and as an epidemiologist I cannot but agree. However, I think there are enough data to support the initiation and implementation of preventive actions.

Another barrier is the poor presentation of messages to policy-makers and the media. We have to talk their language. We have to talk in ways that policy - makers understand and are sensitive to. In that regard, the economic burden of disease provides a compelling argument. The messages have to be clear and consistent. Discordant messages from the scientific community greatly undermine attempts to influence policy. The public can only resist change if they perceive that we ourselves are not even sure whether butter or margarine, both or neither are harmful, or that we keep changing the message. There is an urgent need to develop ethical guidelines on the dissemination of early scientific findings.

Encouraging leadership in the realm of preventive action is beset with barriers. There is often a failure to appreciate the importance of prevention and its cost-effectiveness. The effects are not immediate. Whoever embarks on a career of disease prevention is guaranteed anonymity. It does not bring quick results nor credit for what is done. Consequently, there are not too many heroes in this arena.

Even when the public is informed about heart healthy lifestyle choices, there may be economic and social constraints. Vested economic interests can block availability or impede necessary policy implementation. To effect change, the community must be mobilized. I mentioned North Karelia - there, the initiative came from the people themselves. When the population is mobilized to action, politicians fall in line and start to pay attention.

Who in the developing world is demanding change? Who even recognizes the problems and issues? Prevention of non-communicable diseases starts with education and heightened awareness that a problem exists. For many in all sectors, it is not apparent that a problem even exists, let alone that there are effective strategies available. We heard earlier today about physicians who do not prescribe an appropriate diet for their diabetic patients. Clearly a lot of work needs to be done.

There is a need to place health high on the list of national priorities. This can be achieved in a meaningful way only by a multi-sectorial partnership. The Victoria Declaration on Heart Health emphasizes the importance of a partnership of the community, of its various sectors, both political as well as non-governmental including international organizations and agencies concerned with health and economic development.

Conclusion

I would like to close with a thought about guiding the process of development. Countries in transition have a unique opportunity to profit from innovation and development while avoiding many of its detrimental effects including disability and premature death from non-communicable diseases. This can be achieved only if the lessons learned by already developed nations are made known and brought to the fore as part of the process of aiding development itself. To achieve this requires a code of behaviour that obligates investors and donors as well as recipients. Such guidelines would govern urban planning, introduction of new technologies, implementation of policies - in fact everything that we put under the banner of development.

Suggested Reading

1. World Health Statistics Quarterly. 1993, Vol 46, No 2 (A. Wielgosz, ed)

2. Health Promotion Research: towards a new social epidemiology. WHO Regional Publications. European Series. No 37, 1991 (B. Badura and I. Kickbush, eds)

3. The Victoria Declaration on Heart Health 1992, Health and Welfare Canada.

4. Peto R, Lopez AD, Boreham J, Thun M, Heath C Jr. Mortality from Smoking in developed countries 1950-2000. Indirect estimates from national vital statistics. Oxford University Press 1994.