4 Nutrition epidemiology

Meenal Dhall and Kshetrimayum Surmala

Contents:

1.  Introduction

2.  History of nutritional epidemiology

3.  Nutritional deficiency diseases

3.1. Malnutrition

3.1.1. Protein energy malnutrition (PEM)

3.1.2. Kwashiorkor

3.1.3. Marasmus

3.2 Micro-nutrient malnutrition

3.2.1. Iron Deficiency Anaemia (IDA)

3.2.2. Vitamin A Deficiency (VAD)

3.2.2.1. Night Blindness (XN)

3.2.2.2. Conjunctival Xerosis (X1A)

3.3.2.3. Bitot’ Spot (X1B)

3.3.2.4. Corneal Xerosis (X2)

3.3.2.5. Cornea Ulceration (X3A)

3.3.2.6. Keratomalacia (X3B)

3.2.3. Iodine Deficiency Disorders (IDD)

3.2.4. Water soluble vitamin deficiency disorders

3.2.4.1. Thiamine (Vitamin B1) Deficiency Diseases

3.2.4.2. Riboflavin (vitamin B12) Deficiency Diseases

3.3. Nutrition and Non Communicable Diseases (NCDs)

3.3.1. Obesity

3.3.2. Type 2 diabetes

3.3.3. Coronary heart disease (CHD)

    Learning Objectives:

To understand:

1.      Definitions and concepts of nutritional epidemiology.

2.      Deficiency diseases due to suboptimal intakes of micronutrients and its dietary management.

3.      Non Communicable Diseases (NCDs) due to excessive intakes of macronutrients (over nutrition) and its dietary management.

Introduction

The word epidemiology comes from two Greek words epi, meaning on or upon, demos, meaning people, and logos, meaning the study of. Several definitions have been proposed, but the underlying principles and public health spirit of epidemiology following is define by the following. “Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems”.

Nutritional epidemiology studies the role of food and nutrition and in relation to disease in human populations. Nutritional epidemiological research involves the role of food and nutrition in etiology of diseases, assess and monitor the food consumption and nutritional status of populations, measures to prevent, control and improvement of health, develop interventions in order to maintain healthy eating lifestyle and also to analyze the association of nutrition and physical activity in relation to diseases.

History of nutritional epidemiology

Epidemiology is the study of the distribution and frequency of diseases in human populations. Nutritional epidemiology examines the association of diet and our health. Earliest epidemiological investigation dates back to more 2000 years ago, when Hippocrates conducted a clinical trial to observe the cause of a disease and belief in notion that health depends on magical influence. Lind in 1753 observed that scurvy was caused by deficiency of vitamin C when he conducted one of the earliest clinical trials with lemons and oranges. Milestones in classic epidemiology include John Snow’s (1813-1858) who studied the spread of cholera due to of polluted water, and suppresses the outbreaks of the disease 44 years even before the discovery of , the causal agent Vibrio cholera. Casimir Funk in 1912 investigated that deficiency of substances which he called “vitamins” may cause diseases such as sprue, beriberi, rickets, pellagra etc.

Another epidemiological investigation of 19th and 20th century include Joseph Goldberger who observed the occurrence of pellagra among poor relying on as staple diet. He suspected the disease could be due to nutritional deficiency. It was later identified as deficiency of niacin, a B-complex vitamin (B3). With the discovery of microorganisms, at the end of the 19th century mark the era of infectious disease epidemiology. Robert Edward Koch work on the etiology of tubercle bacillus in 1882 resulted in improved environmental conditions and interventions for preventing transmission of certain microorganisms. Epidemiological observation thus has provided the insight into the diet-disease relationship and the cause and prevention of diseases. Earlier epidemiologist focused on the etiology of infectious diseases but since early decades of 20th century, they shifted to chronic disease and remarkable contribution have made to the understanding of nutrition-related diseases as well. Band and Dyerberg studied coronary disease in Eskimos and observed that it was uncommon despite their high fat diet and later found that omega -3 fatty acid from fish oil is responsible for low plasma lipid level in their diet. Hospital based case control study in 1950 showed that smoking was associated with lung cancer. So, epidemiology play an increasingly important role and its evolution has led to the development of specialized areas like environmental, clinical, psychiatric, genetic, occupational within the epidemiology.

Nutrition and health related diseases

In developed countries excessive intakes of macronutrients (over nutrition) and suboptimal intakes of micronutrients (hidden hunger), lead to obesity and related non-communicable diseases (NCDs). There is a global burden of diseases in developing countries because of the coexistence of under-nutrition and related deficiency and infectious diseases along with overweight and obesity, or diet-related non-communicable diseases as a result of nutritional transition. Nutrition in addition to other factors such as unhealthy lifestyle and environmental factors influence health and well-being. However, it is important to realize that nutrition is a major, modifiable, and powerful factor in promoting health, preventing and treating disease, and improving quality of life.

Nutritional deficiency diseases

Hunger and malnutrition remain the most widespread devastating problem affecting the health of children and continue to dominate the health of world’s poorest nations. The proportion of malnutrition ranges from 1% of children in developed countries to 27% in developing countries. Report from NFHS3 data shows that 19.8%, 42.5% and 48% children under 5 years are wasted, underweight and stunted. Particularly, children, nursing mothers and pregnant women are vulnerable to malnutrition.

Malnutrition

Malnutrition is a condition resulting from faulty nutrition either due to deficiency or excess of one or more essential nutrients or to a failure of the body to digest or absorb the food from the alimentary tract. It can be classified into three categories from nutritional stand point i.e. under-nutrition, over-nutrition and micro-nutrient malnutrition.

Macronutrient deficiency (under-nutrition)

Under-nutrition occurs due to inadequate calorie intake or due to non-availability of nutrients due to frequent infections, other metabolic issues or endocrine disturbances.

Protein energy malnutrition (PEM)

Protein energy malnutrition is often used as synonyms of malnutrition and under-nutrition. Most important factor resulting to PEM are inadequate diet and infectious diseases affecting all segments of population particularly from the backward and downtrodden communities who do not have proper access to food. PEM covers a wide spectrum of conditions from growth retardation to over marasmus and kwashiorkor.

Kwashiorkor

Diet predominantly deficient in protein often leads to kwashiorkor. Although it occurs in older children and adults, it usually affects children aged 1- 4 years when they are weaned from breast milk to adult diet. Clinical features of kwashiorkor are growth failure, oedema and mental changes. The main sign is oedema usually appear first on the feet and leg and eventually spread to hands and faces. Other symptoms include skin lesions and hypo-pigmentation and in severe cases the epithelium peels off leaving behind depigmented patches. The hair shows changes in texture and curly hair becomes straight easily pluckable. Diarrhoea may occur due to secondary infections and defective digestion.

Marasmus

A diet deficient in calories and prolonged starvation results in marasmus. It may also occur due to chronic infections with marginal food intake. It is more common in children below 2 years of age. Main cardinal features include severe muscle wasting, growth retardation and loss of subcutaneous fat. The child appears very thin because most of the muscles mass and fat have been expended to provide energy. Associated vitamin deficiencies are however very common.

Source Link: (http://lexusorganics.com/blog/protein-energy-malnutrition/)

Dietary management and prevention

An adequate amount of diet with sufficient calories and a good quality protein should be given. High energy intakes (150kcal/kg) and high protein intakes (3-4g/kg) are required for rapid recovery. During infancy and childhood protein requirement is more. In pregnancy protein requirement is increased by another 15-20 gram per day. Liquid diet either fresh milk or dry skimmed milk powder is recommended. Eggs are desirable as sources of protein. Vitamins and mineral supplements are recommended for all malnourished children. Besides, dietary management it is also necessary for health promotion at community and household level. Promotion of breast feeding, measure to improve family diet, distribution of supplements, routine immunization of children, and periodic surveillance of child’s diet should be encouraged. In India, the Integrated Child Development Services (ICDS) is a major national program providing integrated health and nutrition services to preschool children.

Micro-nutrient malnutrition

It refers to a group of conditions caused by deficiencies of essential minerals and vitamins. The most common types of micro-nutrient malnutrition in India and in most developing countries include:

Iron Deficiency Anaemia (IDA):

Nutritional anaemia is a major public health problem affecting all sections of the society. It is defined by WHO as a condition in which the haemoglobin content is low as a result of deficiency of one or more essential nutrients, regardless of the cause of deficiency. The major cause of nutritional anaemia is due to deficiency of iron, vitamin B12 and vitamin C. Burden of anemia are not only confined to pregnant women but affects other segments of the society. Adolescent boys and girls, women in reproductive years, infants and young children and pregnant women are in vulnerable groups Prevalence of anemia in India is high due to low dietary intake, poor iron and folic acid intake, poor bio-availability of iron in phytate fibre-rich Indian diet. NFHS- 3 reported prevalence of anemia as 55%   in women aged 15–49 years, 24% in men aged 15–49 years and 70% among children aged 6–59 months. Deficiency of iron increases incidence of maternal deaths by 20% increases the risk of premature delivery and low birth weight. According to WHO, 12.8% maternal mortality in Asia are attributed to anaemia. Iron rich supplements are a must for prevention of anaemia. Oral iron or low dosage of iron, multivitamin supplements, folic acid, vitamin A and zinc are recommended.

Vitamin A Deficiency (VAD):

Vitamin A deficiency with a variety of manifestations is wide spread in the world today. Deficiency of vitamin A leading to xerophthalmia and night blindness among young children has become a major public health problem in developing countries including India. The term xerophthalmia comprehensively includes all ocular manifestations of vitamin A deficiency. The most contributing factor is due to inadequate of vitamin A or its precursor i.e β carotene. The most vulnerable groups are the pregnant women and infants born particularly in low income groups. According to the estimates of NFHS 2, prevalence of night blindness due to low dietary intake of vitamin A in pregnant women was up to 10-20%. Vitamin a deficiency predominantly occurs in children due to common childhood infections like diarrhea, measles and infestations like giardiasis and ascariasis. Micronutrient Initiative (MI) estimates that around 3, 30,000 children in India die due to VAD. More than 4 million children worldwide exhibit sings of severe deficiency.

WHO recommends the following classification of xeropththalmia:

Night Blindness (XN)

Symptoms include inability to see in dim light, either at dusk or dawn due to impairment in dark adaptation. If vitamin A is not administered properly, the condition may get worse especially when children suffer from diarrhea and other infections.

Conjunctival Xerosis (X1A)

Symptoms of conjunctival xerosis includes dry and non wettable conjunctiva. When the eye is exposed for about 30 seconds, the tear is described as emerging like sand bank at receding tide when the child ceases to cry. Often it may be associated with muddy and wrinkled conjunctiva instead of shiny and smooth.

Bitot’ Spot (X1B)

Symptoms of Bitot’ Spot include dry triangular patches, white or yellowish, foamy spots on the bulbar conjunctiva on either side of cornea.

Corneal Xerosis (X2)

It is characterized by the presence of dry and non wettable cornea and the changes start at the lower level of the eye.

Cornea Ulceration (X3A)

Cornea Ulceration may occur if corneal xerosis is not treated properly. These ulcers may be circular and sharply demarcated, initially appear to be shallow and may lead to perforation resulting in prolapsed of content of eye ball if it becomes deep.

Keratomalacia (X3B)

Keratomalacia is characterized by liquefaction of cornea. Cornea may become soft and may end up in extrusion of intra-ocular contents or complete atrophy of the eye.

Dietary management and prevention

The most sustainable solution is regular intake of adequate food source rich in vitamin A or its precursor β carotene such as dark green leafy vegetable like spinach (palak) drumstick, agathi (Sesbania grandiflora), yellow and orange coloured fruits. Animal foods such as fish liver, dairy products and egg yolk are advisable.

Nutritional education programs are a must at community level to increase awareness and improve consumption of vitamin a foods. Such intervention programs should include aspects such as breast feeding, immunization and utilization of the available primary health care facilities to control infections and infestations. Another strategy is the food fortification or enrichment of widely consumed food with vitamin A. Fortified foods can be integrated into the conventional food system as value added products to reach large sections of the society. However, in India, fortification approach has been limited to few food items like milk and vanaspati.

Iodine Deficiency Disorders (IDD)

Iodine is an essential micro-nutrients and deficiency of which causes a wide variety of neurological and physiological development. The term “Iodine Deficiency Disorders” was introduced by Hetzel in 1987. The major clinical manifestation of iodine deficiency is goiter, defined by non-inflammatory enlargement of thyroid gland. For clinical assessments, goiter size is assessed based on the palpation of thyroid and classified as follows:

Grade 0- No goiter (if it is not visible or palpable, if palpable but the size is less than the distal phalange).

Grade I- Not visible when the neck is in normal position, but palpable (the size of the enlargement of gland should be more than the size of the distal phalange of the thumb of the subject). Grade III– Visible from the minimum distance.

Grade III- Visible from the minimum distance.

Figure. Picture shows the enlargement of thyroid gland.

Source Link: (http://www.uofmhealth.org/health-library/zm6301)

Environmental factors such as environmental iodine deficiency and goitrogens (substances which interfere with the metabolism of iodine in the body) leads to endemic IDD while intrinsic factors like hormonal imbalance, failure to synthesis the thyroid hormone contributes to sporadic cases. Iodine deficiency disorders include a spectrum of disorders such as goiter, retarded physical development, impaired mental function, juvenile hypothyroidism in children and adolescents, psychomotor defects, congenital anomalies in foetus.

Prevention of Iodine Deficiency Disorders (IDD)

Fortification of food items with iodine or by direct supplements is a way out. Fortification of food items like wheat flour, drinking water milk, bread and common salt is still practicing in different parts of the world. The oldest control measure is to iodize the common salt with potassium iodate. Iodized oil is also available for oral or intra-muscular injection.

Water soluble vitamin deficiency disorders

Vitamins are essential for several physiological and biochemical functions. B complex vitamins are water-soluble vitamins and are easily excreted and do not have adequate stores in the body. Some of the water soluble vitamin deficiency disorders are discussed below:

Thiamine (Vitamin B1) Deficiency Diseases

Deficiency of thiamine causes beri-beri and the severity is determined by the degree and duration of deficiency. Cardiac beri-beri or wet beri-beri is characterized by biventricular heart failure, peripheral vasoconstriction, wide pulse pressure and oedema. An acute form documented as pernicious beri-beri is characterized by sudden onset of cardiac pain, restlessness, and peripheral circulatory failure. Atrophic or dry beri-beri is often prevalent in India and its symptoms include numbness, loss of function or paralysis of lower extremities due to multiple neutritis. Both the type of ber-beri show muscle degeneration, loss of motor function and loss of sensation. Aetiology of water soluble vitamin deficiencies includes inadequate due to poverty, faulty cooking habits, losses due to storage, impaired absorption due to chronic diarrhea, metabolic functions such as genetic abnormalities, metabolic stress. Adequate food source of thiamine are sufficient to prevent any of the deficiency. Parboiled rice and un-milled rice are excellent source of thiamine and hence should be encouraged. The most appropriate approach to meet the nutritional needs is to encourage consumption of inexpensive and locally available foods and to educate the public to improve the dietary and cooking habits.

Riboflavin (vitamin B12) Deficiency Diseases

Deficiency of riboflavin is widely prevalent in low income groups of the population in all age groups. Clinical manifestation of riboflavin deficiency includes ocular symptoms with characteristic itching, burning, fatigue and eyestrain. Other symptoms are shiny red mucosa of lips with cracking at the corners of the mouth, known as cheilosis and roughened skin around the mouth and nose. For control and prevention diet rich in riboflavin such as meats, milk, pulses, and other dairy products are recommended.

Nutrition and Non Communicable Diseases (NCDs)

With the economic development, rapid urbanization, food security and increase health care services in developing countries there has been decline in under nutrition-related diseases. However, these factors on the other hand have exacerbated the development of chronic diseases, also known as non communicable diseases (NCDs) due to unhealthy diets, sedentary lifestyles and lack of physical activity. NCDs are now a major global burden in public health. In has been reported that in 2001, 60% of the 56.5 million global deaths were from chronic diseases, such as cardiovascular diseases, hyperlipidaemia, hypertension, cancer, and diabetes. In both developing and developed countries, due to nutritional transition, unhealthy dietary and lifestyle pattern chronic non communicable diseases have become principal global causes of morbidity and mortality.

Obesity

Obesity defined by excessive accumulation of body fat resulting in adverse effect on health is associated with other chronic diseases. The fundamental cause of obesity is excessive consumption of high calorie foods with less physical activity level i.e. when the energy intake is in excess of expenditure. Though obesity can be determined by many other methods, calculation of BMI defined as weight (in kg) divided by height (in meters square), is widely used to classify underweight, overweight and obesity in adults. It is considered as a practical indicator of the severity of obesity.

Obesity has multi-factorial epidemiology such as genetic, environmental, psychological, age, sex and socio-economic factors. The determinant of obesity are urbanization, nutritional transitional, globalization of food production, i.e. the shift towards highly refined foods, meat, dairy products of high level saturated fats have, together with reduced energy expenditure, contributed to rises in the incidence of obesity and non communicable diseases. Obesity is associated with other diseases such as diabetes, cardiovascular diseases, hypertension, cancers and polycystic ovarian diseases. In India, particularly in urban setting, obesity is emerging as an important health problem. According to NFHS 3 report, 9% of Indian men and 13% of women are overweight or obese.

Dietary prevention for obesity include limited intake of fats, elimination of trans fatty acids, increasing physical activity level , reducing intakes drinks high in sugars, limited salt consumption, increase consumption of fruits and vegetables, can prevent unhealthy weight gain.

Type 2 diabetes

Type 2 diabetes often referred to as non insulin dependent diabetes mellitus is characterized by insulin resistance where the body is unable to utilize the glucose derived from carbohydrates food or glycogen store in the tissues. Diagnosis of type 2 diabetes usually occurs on the onset of middle adulthood and is associated with obesity which lead to elevated blood sugar and itself can lead to insulin resistance. This type of diabetes is the most common type and nearly 90-95% of all diabetic belongs to this category and is distinguished from type 1 diabetes and gestational diabetes of pregnancy.

There is increasing reports of children with type 2 diabetes and have become serious health issues. It has been estimated in the adult population that the prevalence of diabetes milletus will raise from 4% in 1995 to 5.4% in 2025. Obesity is a major risk factor for development of non insulin dependent diabetes. Approximately type 2 diabetic patients are either found to be overweight or obese and impaired glucose tolerance is also common in this group. Many epidemiological research revealed that central obesity as assessed by waist hip ratio (WHR) is associate with higher occurrence of diabetes. Diet rich in energy dense food such as carbohydrates which contribute to high calorie and enhance body weight have been associated with diabetes. Other risk factors associated with development of type 2 diabetes include physical inactivity, diet, increasing age, insulin resistance, ethnicity, family history of diabetes, genetic factors.

Global prevalence and projections, 2010 and 2030

Source Link: www. diabetesatlas.org

Weight control, preventing obesity and enhance physical activity level is the most promising approach of preventing diabetes. It can be achieved by modifying nutrient intake and a healthy life style. Diet high in plant food is often associated with a lower incidence of diabetes milletus.

Coronary heart disease (CHD)

Coronary heart disease (CHD) is a condition of impairment of heart function due to obstructive changes of one or more of coronary arteries causing inadequate supply of blood to the heart muscles. Pathological lesion leading to CHD is called atherosclerosis, defined by accumulation of complex carbohydrates and lipids in the blood vessels. This leads to thickening of the arterial vessels of the body in cerebral, abdominal and peripheral circulation and thus interferes with the oxygen supply to the heart muscle (myocardium). Two clinical conditions associated with this process are angina pectoris characterized by chest pain and myocardial infarction (heart attack) characterized by prolong chest pain, shortness of breath, sweating that results from prolonged total occlusion of artery.

Risk factors for CHD can be classified as non-modifiable and modifiable. The modifiable factors are metabolic syndrome such as diabetes, obesity, high blood cholesterol, elevated blood pressure, abnormal glucose tolerance, stress, tobacco smoking and alcohol consumption. Non-modifiable risk factors are increasing age, heredity and masculine gender.

Diet significantly influence the development of CHD and several epidemiological studies have taken up in investigating the role of dietary factors. Quantity and quality of carbohydrates in diet have been documented to influence chronic conditions like obesity, coronary heart diseases and hypertension.

Consuming high glycaemic index foods are at greater risk of developing CHD. Carbohydrates mediated their effects by reducing HDL (high density lipoprotein) and increasing triglyceride, plasma lipids and glycaemia. Consumption of coffee, animal protein and saturated fats is positively associated with CHD date rate. Many other studies conducted on middle-aged men showed that risk of CHD is increased by cigarette smoking, high serum cholesterol and high blood pressure.

Replacement of simple sugar and fat with complex carbohydrates containing foods like pulses, whole cereals, roots, millets, vegetables and fruits is recommended for preventing weight gain, control of high blood sugar and lipids. High calorie dense food, processed foods, sweetened beverage, deep fried foods should be avoided. Increasing physical activity level along with dietary modification can reduce development of cardio-vascular diseases.

Summary

Role of diet and nutrition are important factors for determining, maintenance and promotion of a good health. Malnutrition remains the most widespread devastating problem affecting the health of children and continues to dominate the health of world’s poorest nations. There is a global burden of diseases in developing countries due of the coexistence of under-nutrition and related deficiency and infectious diseases along with overweight and obesity. For example, India, at present faces a combination of chronic diseases and communicable diseases where the burden of chronic diseases exceeds that of communicable diseases. With the economic development, rapid urbanization, food security and increase health care services in developing countries there has been decline in under nutrition-related diseases. However, these factors on the other hand have exacerbated the development of chronic diseases, also known as non communicable diseases (NCDs) due to unhealthy diets, sedentary lifestyles and lack of physical activity. NCDs are now a major global burden in public health. By 2020, the burden of NCDs is expected to increase to 57% and it has been projected that in developing countries, 71% of deaths due to ischaemic heart disease (IHD), 70% of deaths due to diabetes and 75% of deaths due to stroke will occur.

References

1. Last JM, Ed. Dictionary of epidemiology. (2001). 4th Ed. New York: Oxford University Press; p. 61.
2. Langseth, L. (1996). Nutritional epidemiology: possibilities and limitations. International Life Sciences Institute.
3. Alwan A et al. (2010). Monitoring and surveillance of chronic noncommunicable diseases: progress and capacity in high-burden countries. The Lancet376:1861–1868.
4. Gibney,   MJ.,   Lanham-New,  SA.,   Cassidy,  A   and       Hester,   Vorster,   HH,  Eds.   (2009). Introduction to Human Nutrition. Second Edition Edited on behalf of The Nutrition Society. Wiley Blackwell Publication.
5. Chopra, M., Galbraith, S et al. (2002). A global response to a global problem: the epidemic of over nutrition. Bulletin of the World Health Organization, 80 (12).
6. World health report (1997): Conquering suffering, enriching humanity. Geneva.
7. Popkin, BM. (2001). Nutrition in transition: the changing global nutrition challenge.Asia Pacific Journal of Clinical Nutrition; 101:S13-8.
8. World Health Organization (2003). Diet, nutrition, and the prevention of chronic diseases. Report of a Joint WHO/FAO Expert Consultation. WHO Technical Report Series No. 916. Geneva.
9. Truswell, S. (2002). Protein – energy malnutrition in the “Essentials of human nutrition”. Mann, J & Truswell, AS (eds). Second edition. Oxford University Press.
10. The world health report 1998. Life in the 21st century: a vision for all. Geneva,
11. The world health report 2002: reducing risks, promoting healthy life. Geneva.

    Web links

1. www. diabetesatlas.org
2. http://www.uofmhealth.org/health-library/zm6301.
3. http://lexusorganics.com/blog/protein-energy-malnutrition

    Suggested readings

1. Fleck, Henrietta. Introduction to Nutrition. (1976).4th edition. USA: Macmillan publishing Co., Inc.,.
2. Indian Council of Medical Research. (2010). Nutrients requirements and recommended dietary allowances for Indians. A Report of the Expert group of the Indian Council of Medical Research, NIN, Hyderabad.
3. Bamji, MS., Krishnaswamy, K., and Brahman, G.N.V. Eds.(2009) Text book of Human Nutrition. Oxford & IBH Publishing House.