Public Health Aspect of Nutrition, Malnutrition and Infection
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Introduction
· There is enough food to feed everybody in the world now.
· Yet many million people remain malnourished. In the third World that protein energy malnutrition (PEM) affects 500 million people and kills 10 million every year.
· Most child deaths are caused by the combination of malnutrition and infection.
· No other cause of mortality has a comparable impact.
· The saddest thing is that previous views held that malnutrition had a very small effect on mortality.
· This truth has has major implications for primary health care.
What is an infection and how are we caught by it?
· Infection means the entry and development of an infectious agent in the body in which the body responds either by defending itself through its immune (defense) mechanism or disease.
· The disease organism may be transmitted from the reservoir or source of infection to a susceptible individual in many different ways.
Transmission of infectious agents
Direct transmission
Direct contact: e.g., STD and AIDS, leprosy, skin and eye infections.
Droplet infection: e.g., respiratory infections, tuberculosis, whooping cough, measles etc.
Contact with soil: e.g., tetanus, hookworm infestation, etc.
Indirect transmission
Vehicle-borne: via water, food (including fruits and raw vegetables), blood, or other biological products; e.g., acute diarrheal diseases, cholera, typhoid fever, polio, hepatitis A, food poisoning, etc.
Vector-borne: via living carrier like mosquito, fleas, cockroaches, bugs and mites, etc. e.g., malaria, plague, encephalitis, etc.
Air-borne: by "droplet nuclei"; e.g., measles, chickenpox, and tuberculosis.
Fomite-borne: Inanimate objects like soiled clothes, towels, linen, handkerchief, books, toys, door handles, cups, drinking glasses, syringes, surgical instruments, etc. are called fomites; e.g., diphtheria, typhoid, eye and skin infections, hepatitis A, etc.
Unclean hands and fingers: provide the most common medium for transfer of infectious agents to food.
Transplacental
e.g., STORCH agents (syphilis, toxoplasma, rubella, cytomegalovirus and herpes virus), and AIDS and hepatitis B.
· Body becomes unable to defend itself.
· Decreased ability produce antibody.
· Decreased cellular immunity.
· Decreased phagocytic power of macrophages.
· Infectious organisms can take upper hand.
· Vitamin C cause small vessels in the body to become fragile; the skin then breaks down more easily, facilitating the entry of infectious organisms
· Niacin deficiency causes pellagra, with its associated skin breakdown.
· Vitamin A deficiency reduces epithelial protection ability. There is at least 2-fold increase in incidence of infection and 4-12 fold increase in incidence of mortality in children with even mild vitamin A deficiency.
Figure-1. The downward spiral of malnutrition and infection.
How malnutrition occurs in infection
· Malnutrition makes infection more severe.
· The more prolonged and severe the infection, the worse the malnutrition (because of loss of appetite).
· Infection causes loss of appetite.
· Body temperature is increased (fever) demanding more calorie intake. Fever increases caloric requirements. Each degree rise increases caloric needs by 7%.
· Thus, the body badly suffers from deficient food intake.
· This is further compounded by traditional methods of treatment, such as “starving a fever.”
· The body loses increasing amounts of nitrogen into the urine, usually as a result of the breakdown of protein in muscle tissue.
· On recovery, more protein is needed to replace the lost amino acids.
· In Third World countries, children suffer from many different infections, often having some kind of infection for 200 days of the year.
· Thus, the baby fails to grow.
The mechanisms of malnutrition in infection are summarized below:
1. Alteration of absorption and availability of nutrients.
2. Compromise of defense mechanisms: humoral and cellular immunity.
3. Increase of body temperature causing increase in caloric requirement (Fever increases caloric requirements. Each degree rise increases caloric needs by 7%).
4. Alteration of hormone secretion, liver synthesis of acute-phase reactant proteins.
5. Increase of gluconeogenesis/lipogenesis. Most infections alter carbohydrate, lipid and protein metabolism, electrolyte balance, and trace mineral/vitamin levels.
The effects of malnutrition and infection are synergistic
§ The effect of the presence of both malnutrition and infection at once is greater than the sum of the effects of malnutrition plus the effects of infection.
§ The cause of death in diarrhea is not the infection itself, but dehydration from the resultant water loss.
§ Some parasitic infestations are a direct cause of nutritional deficiencies. Hookworms, prevalent in Third World countries, suck blood from the lining of the gut, thereby causing iron deficiency anemia.
§ Measles severely affects those whose immune systems have already been eroded by malnutrition.
§ Recent data indicate that, at least for an RNA virus, host nutriture can influence the genetic make-up of the pathogen and thereby alter its virulence.
§ Increased virulence of coxsackievirus B3 due to vitamin E or selenium deficiency was recorded.
Predominant causes of persistent diarrhea could be persistent infection, malabsorption and enteric infection. It is more common in malnourished infants and young children.
Malnutrition and respiratory tract infections
§ Respiratory tract infections particularly pneumonia are major causes of illness and deaths in children.
§ RTIs are caused due to infection by micro-organisms i.e. bacteria, viruses or sometimes even fungus.
§ The incidence of infection increases when the child is malnourished, is of low-birth weight or is exposed to low temperatures.
Malnutrition and HIV infection
§ Malnutrition is common in HIV-infection and plays an independent and significant role in its morbidity and mortality.
§ The development of malnutrition is multifactorial, and includes alterations in intake, absorption, or metabolism.
§ Malnutrition is a very serious problem in AIDS, since the timing of death is directly related to the degree of body mass depletion.
Preventive measures against infection and malnutrition
· Immunization (vaccination)
· Barrier protection, like covering body parts by appropriate clothing, mosquito-net, etc.
· Improved water supply, sanitation and hygiene.
· Routine deworming projects may be undertaken until a community’s sanitation is improved sufficiently to eliminate the worm.
· Improved food-hygiene, health education for a healthy diet, and improved access, by the poor, to adequate amounts of healthy food.
§ Choosing bottle feeding by a poor mother in a developing country means greater chances of sickness and death for the baby.
§ Four different influences can bring a tragedy: economic, hygienic, nutritive and immunologic.
§ The effects are threefold: the infants literally starve, they are more exposed to infection, they do not have the immunological protection that comes in breast milk.
§ Formula is relatively expensive: for a three-month-old child, it can cost 50 to 60 per cent of the minimum wage in some developing countries.
§ Because of the high cost there is a tendency to stretch the formula by overdiluting it leading to nutritional marasmus.
§ Contamination leads to infectious diarrhea.
§ Breast milk comes sterile from the breast. And anti-infective properties cannot be put into formula.
§ Conversely, at least a dozen anti-infective factors are found in breast milk, including antibodies, lysozyme, lactoferrin and interferon.
· Food or water introduces health risks if it is contaminated with pathogenic organisms, toxins, pesticides or poisons.
· Any of these can lead to illness, sometimes in a few hours and sometimes a long time after their consumption.
More than 25 organisms, including bacteria, viruses and parasites, infect humans and cause specific disease after being consumed in contaminated foods.
Viruses: cause outbreaks of diarrhea, particularly in children. e.g., rotavirus or Norwalk virus, measles virus.
Bacteria: cause gastro-enteritis and other diseases. e.g., salmonella, staphylococci, clostridium (Clostridium perfringens or Clostridium welchii), Clostridium botulinum, four Shigella species (S. sonnei, S. flexneri, S. dysenteriae and S. boydi)i, Vibrio cholerae, Escherichia coli, Campylobacter species; Bacillus aureus; and other vibrios such as Vibrio parahaemolyticus.
Parasites: Ascaris lumbricoides (roundworm), which infects about 1200 million people worldwide, Whipworm (Trichuris itrichiura,) protozoan, Giardia lamblia, Taenia solium (pork tapeworm) or Taenia saginata (beef tapeworm), Diphyllobathrium latu, The tapeworm in the human gut competes with the host for vitamin B12 so the infection may lead to macrocytic anaemia.
Latrine and faeces disposal
Personal hygiene
Household hygiene
Food preparation and storage
Four steps to improve food hygiene
· Buy fresh food that looks clean and uncontaminated with good appearance and no bad smell, mould or discoloration.
· Store the food in a safe cool place out of reach of rodents and other pests.
· Prepare the food for eating in a clean environment, with clean hands and clean utensils, and cook foods such as meat thoroughly to kill all organisms. For uncooked foods, eat peeled; if not peeled, washing thoroughly.
· After the meal, leftover food should be stored safely, and some foods that cannot be stored may be fed to domestic animals. Food areas should be cleaned, utensils well washed and garbage buried or burned some distance from the house.
Tips for consumers in choosing fast food
· Choose a food that is served at a very high temperature. If it is cold, ask the vendor to heat it more. Heat kills many organisms.
· Of uncooked foods, choose only those that are eaten peeled. Choose a banana rather than a slice of watermelon, for example.
· Ask for a drink that comes in a bottle or can that can be opened by the consumer, or order tea or coffee that is served very hot.
Dr. Abul Kalam Azad, Professor & Head, Department of Nutrition & Biochemistry, National Institute of Preventive and Social Medicine (NIPSOM), Mohakhali, Dhaka