MICROBIOLOGY AND IMMUNOLOGY
LEARN THROUGH YOUR COURSE AND FORTIFY ALL YOUR WEAKNESS WITH KNOWLEDGE
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Topic 1: Modern Nutritional Dietetic Practice
These modern practices in nutrition include but not limited to:
i) Nutraceuticals / functional foods-Provides additional physiological benefits beyond that of meeting basic nutritional needs.
Examples:
- Citrus fruits- protective against a variety of human cancers.
- Fish- fish contains omega 3 (n-3) fatty acids which plays a major role in cardiovascular disease risk reduction.
- Dairy products- contain probiotics which help improving its intestinal microbial balance
Nutraceuticals- chemicals found as a natural component of foods or ingestible forms that have been determined to be beneficial to the human body in preventing or treating one or more disease or improving physiological performance
ii) Food supplements- They are concentrated sources of nutrients or other substances with nutritional or physiological effect, whose purpose is to supplement the normal diet.
Note: Excessive intake of vitamins and minerals may be harmful or cause unwanted side effects, maximum levels are necessary to ensure their safe use in food supplements.
iii) Enteral nutrition-It refers to nutrition support using liquid formula ducts via oral intake or by tube feeding.
iv) Parentral nutrition-This is nutrition directly into the veins hence by passing the GIT. Nutrients must therefore be in liquid form (solution or emulsion and monomolecular). It is indicated for patients with inability to eat and absorb nutrients via the GIT due to:-
§ Non-functioning GIT
§ Diseases of the small intestines
§ Massive small bowel resection
§ Chemotherapy reaction
Contemporary issues in nutrition and dietetics.
a) Fortification
Addition of one or more nutrients such as vitamins, minerals and amino acids to food so that it contains more of the nutrients than were originally present. In Kenya example include fortification of blue band with vitamin A, some maize flour have also been fortified with vitamin A.
b) Public awareness
This is making the people to be aware of nutrition hence increasing nutrition knowledge to help deal with nutrition related problems. This is done through nutrition education.
c) Diabetes
This is a metabolic disease due to absolute or relative insulin deficiency. Diabetes mellitus is a common clinical condition. Nutrition is very important in managing diabetes.
d) Cancer
It is common term for a malignant cellular growth that tends to spread due to the inability of the DNA to normal physiologic stimuli. The observation that cancers of the stomach and liver are prevalent types is of interest, as these organs are directly involved in nutrient utilization.
e) Obesity
Obesity and overweight are on the rise in Kenya. Like several public health challenges, it should be tackled and prevented early as envisioned in the WHO global strategy on diet, physical activity and health.
f) HIV/AIDS
The HIV/AIDS epidemic poses an inescapable challenge to the world at large and Africa in particular. A massive effort is needed to cushion the impact of the epidemic, and nutritional care and support should be integral elements of any action taken. Under nutrition is common among people living with HIV/AIDS.
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Topic 1: Principles of Dietetics
Meaning of terms
Estimated Average Requirement (EAR) is the average daily nutrient intake level estimated to meet the requirement of half of the healthy individuals in a particular life stage and gender group.
Recommended Dietary Allowance (RDA) is the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.
Adequate Intake is the recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people, that are assumed to be adequate — used when an RDA cannot be determined. In the Indian context, this is referred to as acceptable Intake.
Tolerable Upper Intake Level (UL) is the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects increases
Recommended dietary allowances/nutrient and adequate intakes
The RDA is derived from the individual variability, and (ii) the nutrient bio-availability from the habitual diet.
I. Individual variability:
Definition of RDA takes into account the variability that exists in the requirement of a given nutrient between individuals in a given population group. The distribution of nutrient requirement in a population group is considered normal and the RDA corresponds to a requirement, which covers most of the individuals (97.5%) in a given population.
II. Bio-availability:
Bio-availability of a given nutrient from a diet, that is, the release of the nutrient from the food, its absorption in the intestine and bio response have to be taken into account. It is the level of the nutrient that should be present in the diet to meet the requirement. This bioavailability factor is quite important in case of calcium and protein and trace elements like iron and zinc.
The RDA of an individual depends upon various factors which are as follows:
Age: Adults require more total calories than a child, whereas a growing child requires more calories per kg of body weight than an adult.
Sex: Males with high Basal Metabolic Rate (BMR) require more calories than females.
Activity: The type of activity also determines the energy requirements. The activities are classified as sedentary, moderate and heavy based on the occupation of an individual.
Physiological Stress: Nutrient requirements are increased in conditions of physiological stress such as pregnancy and lactation
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Topic 1: Factors Influencing Nutrient Intake
Factors influencing nutrient intake
There are many physiological and psychological mechanisms affecting our daily patterns in consumption of food. Appetite is co-ordinated through the interaction of various complex systems within the body involving the gut and the brain. Genetic factors and the environment also have a role to play in food intake. The factors therefore include:
Physical activity: higher food intake is associated with increased physical activity. However, regular exercise will help regulate appetite and help limit excess food consumption.
Metabolism: people with naturally high metabolic rates have higher appetites. If you are dieting it is important to maintain your metabolic rate by eating and exercising regularly.
Hormones: there are many different hormones at play within the body – ghrelin is secreted by the stomach to tell you that you are hungry and insulin is secreted by the pancreas to tell you that you are full.
Temperature: cold climates has a tendency to be associated with an increase in appetite – this could be due to the body needing to warm itself up quickly, or because dark days mean that people are not getting enough sunlight which causes depression and people eat out of comfort.
Palatability: the tastier the food, the greater the pleasure derived from the food and the greater the appetite will be. On the other hand, it is argued that having food that is very bland will cause overeating because one does not feel satisfied from the food.
Psychology: stress and boredom often result in increased food intake. The best way of avoiding this is to exercise regularly – this will help you to relax and to reduce boredom.
Social influences: eating habits are often influenced by one’s upbringing – the three meals a day routine is often a cause for eating out habit rather than out of hunger. Many social events, such as Christmas celebrations, revolve around eating, drinking or both.
a growing child requires more calories per kg of body weight than an adult.
Sex: Males with high Basal Metabolic Rate (BMR) require more calories than females.
Activity: The type of activity also determines the energy requirements. The activities are classified as sedentary, moderate and heavy based on the occupation of an individual.
Physiological Stress: Nutrient requirements are increased in conditions of physiological stress such as pregnancy and lactation
Factors influencing food choice
Food choices for a balanced diet depend on many factors, such as:
Individual energy and nutrient needs- The amount of energy, carbohydrate, fat, protein, vitamins and minerals needed differs between different age groups and between males and females
Health concerns- Diets which exclude many foods due to a person’s health concerns or for medical reasons need to be planned carefully.
Cultural or religious practices-Ethical and religious practices, such as avoiding meat, may limit the range of foods people eat.
Cost- Cost of food is a particularly important factor for people with low incomes. Food prepared food at home is often cheaper than eating out or buying take-away.
Food availability- Most foods are grown in a particular season of the year. These are called ‘seasonal foods’. Buying foods when they are in season will often ensure the food price is lower.
Food preferences- Not everyone likes the same food, but some foods are particularly popular or unpopular. The taste, texture or appearance of foods can affect people in different ways.
Social considerations- Human welfare and fair trading, where growers or producers in developing countries are paid a good minimum price to cover their costs, can be a high concern for some people
Environmental considerations- Scientific intervention in the food chain also causes concerns for some people. Genetically modified (GM) ingredients changing a plant, animal or micro-organism's genes or inserting one from another organism. These foods are labeled so people may decide to choose non-genetically modified food products.
Advertising and other point of sale information- Advertisements encouraging people to choose certain foods often appear on the television, internet, radio, posters, magazines and newspapers. The point of purchase information and product placement are strategies often used to provide information to consumers. This can assist people in making healthier choices.
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Topic 2: Factors Influencing Nutrient Availability
The following sections will illustrate the different stages at which nutrient bioavailability can be influenced:
a) Effects of food matrix and chemical form of nutrients
The first step in making a nutrient bioavailable is to liberate it from the food matrix and turn it into a chemical form that can bind to and enter the gut cells or pass between them. Collectively this is referred to as bio accessibility. Nutrients are rendered bio accessible by the processes of chewing (mastication) and initial enzymatic digestion of the food in the mouth, mixing with acid and further enzymes in the gastric juice upon swallowing, and finally release into the small intestine, the major site of nutrient absorption. Here, yet more enzymes, supplied by the pancreatic juice, continue breaking down the food matrix.
b) Enhancers of nutrient bioavailability
Nutrients can interact with one another or with other dietary components at the site of absorption, resulting in either a change in bioavailability or if enhancers and inhibitors cancel each other out. Enhancers can act in different ways such as keeping a nutrient soluble or protecting it from interaction with inhibitors.
c) Impact of inhibitors on nutrient bioavailability
Inhibitors may reduce nutrient bioavailability by: binding the nutrient in question in a form that is not recognized by the uptake systems on the surface of intestinal cells, rendering the nutrient insoluble and thus unavailable for absorption, or competing for the same uptake system. Phytic acid is highly abundant in certain plant foods
d) Host factors
Internal or host-related factors can be subdivided into gastrointestinal and systemic factors. The role of gastrointestinal factors is illustrated by the absorptive pathway of vitamin B12. This vitamin requires gastric acid to be released from the food matrix and then it undergoes a sequence of binding to R protein, release from R protein, binding to the protein “intrinsic factor” (IF) and finally absorption of the intact IF-vitamin B12 complex in the lower intestine.
e) Impact on nutrient recommendations
For several nutrients – primarily calcium, magnesium, iron, zinc, folate and vitamin A – knowledge of their bioavailability is needed to translate physiological requirements into actual dietary requirements.
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Topic 3: Factors Affecting Nutrient Utilization
Factors Affecting Nutrient Utilization
Sickness
Nutrients can be lost because of illness. The illness may inhibit the absorption/drain the nutrients away through diarrhea and vomiting.
Bioavailability
Bioavailability indicates the amount of a nutrient that is absorbed in the intestine from the diet and is available to the body for its biological functions. The amount of a nutrient that is consumed is not fully absorbed and available for its metabolic function in the body. Bioavailability of a nutrient is governed by external and internal factors. Some nutrients enhance nutrient absorption while others hinder the absorption. The absorption rate of some nutrients can be enhanced when paired with other nutrients.
For instance, iron that is found in plant source is less bioavailable than iron found in animal sources. To enhance the absorption of iron, consume vitamin C alongside a serving of iron sources especially from vegetarian sources.
Vitamin C is a strong enhancer of iron absorption. This means having a glass of orange juice with a bowl of breakfast cereal helps the body use more of the iron in the cereal.
Inhibitors reduces nutrient bioavailability in three ways:
a. Binding the nutrient in question in form that is not recognized by the uptake systems on the surfaces of the intestinal cells
b. Rendering the nutrient insoluble and thus unavailable for absorption
c. Competing for the same uptake system e.g. interaction between calcium and non-haem iron.
d. Both minerals bind to a transporter on the surface of intestinal absorptive cells
Use of medication
Nutrient needs may be altered because of long-term medication use for instance use of drugs such as anticonvulsants and /phenobarbital for epilepsy, antacids, anti-inflammatory drugs, and laxatives can interfere with calcium and vitamin D absorption, which negatively influences bone metabolism
Alcohol affects the absorption of nutrients in a number of ways:
a) It acts as a diuretic, which promotes excretion of stored minerals like calcium, zinc and magnesium
b) Impairs nutrient absorption by damaging the cells lining the stomach and intestine and disabling the transport of some nutrients into the blood.
Biological value
Is a measure of the
proportion of absorbed protein from a food which becomes incorporated into the
proteins of the organism’s body. It captures how readily the digested protein
can be used in protein synthesis in the cells of an organism. When a protein
contains the essential amino acids in a proportion similar to that required by
the body, it has high biological value. When one or more essential amino acids
are missing or present in low numbers, the protein has low biological value.
Proteins from animal sources generally are of high biological value while those
from plant sources are of low biological value
