NUTRITION FUNCTION & ENERGY VALUE OF FOOD The human body utilizes the potential energy contained in foods for maintaining life & doing work. The energy yielding food factors are: 1.) Carbohydrates. 2.) Fats. 3.) Proteins. within the body, these nutrients are oxidized in the cells with the help of catalysis such as enzymes, Co-enzymes (containing certain vitamins) & harmones the process is one of continuous utilizaton of O 2 & production of CO 2 water & heat: carbohydrates & fats oxidation CO 2 + H 2 O + Heat Proteins oxidation CO 2 + H 2 O + Urea The energy value of food: The energy or calorific value of foods depends on the quantity of carbohydrates, fats & proteins present in them. This can be determine by oxidising a known weight of food an instrument called bomb calorimeter & measuring the heat produced. Energy Units: The energy value of foods can be expressed in terms of kilocalories (kcal) or megajoules(mj). The unit union of nutritional sciences has suggested the use of megajoules (mj) as the energy unit in place of kcal. Kilo calorie: The energy needed to increase the temperature of a gram of water by 1 degree Celsius depends on the starting temperature and is difficult to measure precisely. BASAL ENERGY METABOLISM: The energy metabolism of a subject at complete physical & mental rest & having normal body temperature and in the past absorptive state i.e.
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NUTRITION
FUNCTION & ENERGY VALUE OF FOOD
The human body utilizes the potential energy contained in foods for maintaining life & doing work. The energy yielding food factors are:
1.) Carbohydrates.2.) Fats.3.) Proteins.
within the body, these nutrients are oxidized in the cells with the help of catalysis such as enzymes, Co-enzymes (containing certain vitamins) & harmones the process is one of continuous utilizaton of O2 & production of CO2 water & heat:
carbohydrates & fats oxidation CO2 + H2O + Heat
Proteins oxidation CO2 + H2O + Urea
The energy value of food:The energy or calorific value of foods depends on the quantity of carbohydrates, fats & proteins present in them. This can be determine by oxidising a known weight of food an instrument called bomb calorimeter & measuring the heat produced.
Energy Units:The energy value of foods can be expressed in terms of kilocalories (kcal) or megajoules(mj). The unit union of nutritional sciences has suggested the use of megajoules (mj) as the energy unit in place of kcal.
Kilo calorie:The energy needed to increase the temperature of a gram of water by 1 degree Celsius depends on the starting temperature and is difficult to measure precisely.
BASAL ENERGY METABOLISM:
The energy metabolism of a subject at complete physical & mental rest & having normal body temperature and in the past absorptive state i.e. 12 hours after intake of last meal is known as basal energy metabolism.
a.) Basal Metabolic Rate:
Basal metabolic rate (BMR) is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). The release of energy in this state is sufficient only for the functioning of the vital organs, such as the heart, lungs, brain and the rest of the nervous system, liver, kidneys, sex organs, muscles and skin. BMR decreases with age and with the loss of lean body mass. Increased muscle mass can increase BMR.
BMR is measured under very restrictive circumstances when a person is awake, but at complete rest. An accurate BMR measurement requires that the person's sympathetic nervous system not be stimulated.
A more common and closely related measurement, used under less strict conditions, is resting metabolic rate (RMR).
BMR and RMR are measured by gas analysis through either direct or indirect calorimetry, though a rough estimation can be acquired through an equation using age, sex, height, and weight. Studies of energy metabolism using both methods provide convincing evidence for the validity of the respiratory quotient (R.Q.), which measures the inherent composition and utilization of carbohydrates, fats and proteins as they are converted to energy substrate units that can be used by the body as energy.
BMR estimation formulas:
Several prediction equations exist. Historically most notable was Harris-Benedict equation, which was created in 1919.
The original equations from Harris and Benedict are:
for men,
for women,
where P is total heat production at complete rest, m is the weight, h is the stature (height), and a is the age, and with the difference in BMR for men and women being mainly due to differences in body weight. For example, a 55 year old woman weighing 130 lb (59 kg) and 5 feet 6 inches (168 cm) tall would have a BMR of 1266 kcal per day or 52.8 kcal/h (61.3 watts).
It was the best prediction equation until recently, when MD Mifflin and ST St Jeor in 1990 created new equation:
where s is +5 for males and −161 for female. According to this formula, the woman in the example above has a BMR of 1208 kcal per day.
During the last 100 years, lifestyles have changed and a survey in 2005 showed it to be about 5% more accurate.
These formulae are based on body weight, which does not take into account the difference in metabolic activity between lean body mass and body fat. A more accurate formula is the Katch-McArdle formula based on lean body mass:
where LBM is the lean body mass in kg. According to this formula, if the woman in the example has a body fat percentage of 30%, her BMR would be 1263 kcal per day.
To calculate daily calorie needs, this BMR value is multiplied by a factor with a value between 1.2 and 1.9, depending on the person's activity level.
It is defined as that percentage of absorbed N which is retained in the body. A protein of high biological value contains proper amounts of all the essential amino acids and is utilized in a better way. Collagens, gelatins and proteins of cereals and pulses have low biological values. These are deficient in some essential amino acids. Egg protein, gelatine & maize protein have biological values of 96, 63 & 60. A mixture of several proteins of low biological values may have better BV as an essential amino acid is one of them may be compensated by sufficient amounts of the amino acid in the other proteins. This is known as the supplementary value of proteins. Therefore, eating cereals with pulses improves the biological values of both of them.
Estimation of biological value.biological value can be estimated in a number of ways.
Nitrogen balance studies:To estimate the biological value of a protein, the animals is first kept on a protein-free diet for a couple of days and the faecal N & the urinary N are estimated to obtain the amounts of the metabolic faecal N & endogenous urinary N, respectively. Then the animal is fed with a measured amount of the test protein & the faecal urinary nitrogens are determined again. The biological value is calculated thus:
BV = 100* (Food N – Metabolic Faecal N) – (Urinary N – Endogenous urinary N)
Food N – (Faecal N - Metabolic Faecal N)
c.) Protein Efficiency Ratio (PER):
It is defined as weight gain per gram protein intake when the protein under test is the sole source of dietary protein. PER for casein is taken as 2.5. Total protein intake is determined from the total dietary intake & % composition of protein in the diet (usually, 10%). PER can be calculated from the equation.
PER = Weight gain = (Final body weight - Initial body weight)
Total Protein intake Total protein intake
The common practice to express PER of the test protein as a proportion of the PER obtained with a standard diet containing 10% casein. The advantage of PER is that it eliminates the cumbersome measurement of nitrogen excretion. Its main shortcoming is that PER values vary with test animals, giving higher values when the food appeals to the experimental animals.
d.) Net Protein Ratio (NPR):
NPR was essentially designed to correct the shortcoming of PER. It is determined over a shorter feeding period of 10 days with an additional control fed on a protein free diet.
NPR = Wt. gain on test diet + wt. loss on protein free diet
Total test protein intake
In designing, NPR it is assumed that weight loss by rats on a protein free diet is equivalent to the amount of protein required for maintenance functions & that above maintenance of N balance requirements, protein depositon (or retention) efficiency is directly proportional to intake. Hence, the inclusion of a control on protein-free diet & the shortening of the feeding period of 4 week to 10 days. Like PER, the NPR value is expressed as a proportion of the NPR of standard diet as 2.5.
The assumption of linearity of N deposition has been found to apply only at points just below & just above the maintenance level. Therefore, NPR values are ureliable when protein intakes deviate substantially from maintenance level.
e.) Net Protein Utilization (NPU):
It is concerned with the proportion of dietary protein N intake retained by experimental animal. By definition:
NPU = Retained protein N = PNI – (Faecal N - EFN) – (Urinary - N- EUN)
Protein N intake (PNI) PNI
Where EFN & EUN stands for endogenous faecal N & endogenous urinary N respectively.Again, values are expressed as % of the values obtained for a standard protein. The NPU values obtained with protein concentrations at about maintenance level are often distinguished from those obtained.
DIETARY ALLOWANCES
Recommended Dietary Allowances (RDAs) are the levels of intake of essential nutrients that, on the basis of scientific knowledge, are judged by the Food and Nutrition Board to be adequate to meet the known nutrient needs of practically all healthy persons.
Medical calculators:
Estimate basal energy expenditure using the Harris-Benedict equations.
For men, the B.E.E. = 66.5 + (13.75 x kg) + (5.003 x cm) - (6.775 x age)
For women, the B.E.E. = 655.1 + (9.563 x kg) + (1.850 x cm) - (4.676 x age)
Total Caloric Requirements equal the B.E.E. multiplied by the sum of the stress and activity factors. Stress plus activity factors range from 1.2 to over 2.
The recommended dietary allowance for males & females of different age groups are tabulated as below:
NUTRITIVE VALUE OF INDIAN FOODS
The following table provides you with energy, protein, Carbohydrate and Fat content of most of the Indian foods, classified under different food groups such as:
Cereal grains . Pulses (dals) . Leafy vegetables . Roots and tubers . Other vegetables . Fruits . Milk and milk products . Meat and poultry . Fishes and sea food . Fats and oils . Sugars . Nuts and oil seeds .
CEREALS Energy (KCal) Protein (g) Carbohydrate (g) Fat (g)All values are per 100 g of edible portions.
Bajra 361 11.6 67.5 5.0
Barley 336 11.5 69.6 1.3
Jowar 331 12.3 60.9 1.9
Maize (dry) 342 11.1 66 3.6
Maize (tender) 125 4.7 24.6 0.8
Rice 345 6.8 78.2 0.5
Rice flakes 346 6.6 77.3 1.2
Rice (puffed) 325 7.5 73.6 0.1
Wheat flour 341 12.1 69.4 1.7
Wheat flour Refined (Maida) 348 11.0 73.9 0.9
Semolina (Suji) 348 10.4 74.8 0.8
Vermicelli (Sewia) 352 8.8 78.3 0.4
Brown bread 245 7.8 51.9 0.7
PULSES (DALS) Energy (KCal) Protein (g) Carbohydrate (g) Fat (g)All values are per 100 g of edible portions.
1.) The nutritional status of an individual is often the result of many inter-related factors.2.) It is influenced by food intake, quantity & quality & physical health.3.) The spectrum of nutritional status spread from obesity to severe malnutrition.
Need Of Nutritional AssessmentThe purpose of Nutritional Assessment is to:1.) Identify individuals or population groups at risk of becoming malnourished.2.) Identify individuals or population groups who are malnourished.
3.) To develop health care programs that meet the community needs which are defined by the assessment.
4.) To measure the effectiveness of the nutritional programs & intervention once initiated.
Methods of nutritional assessment1.) Nutrition is assessed by two types of methods; direct & indirect.2.) The direct methods deal with the individual & measure objective criteria, while indirect
methods use community health indices that reflects nutritional influences.
Direct methods of nutritional assessmentThese are summarized as ABCD1.) Anthropometric methods.2.) Biochemical, laboratory methods.3.) Clinical methods.4.) Dietary evaluation methods.
Indirect methods of nutritional assessmentThese include three categories:1.) Ecological variables including crop production.2.) Economic factors e.g. per capita income, population density & social habits.3.) Vital health statistics particularly infant & under % mortality & fertility index.
Clinical Assessment:1.) It is an essential features of all nutritional surveys.2.) It is the simplest & most practical method of ascertaining the nutritional status of a group
of individuals.3.) It utilizes a number of physical signs, (specific & non specific), that are known to be
associated with malnutrition & deficiency of vitamins & micronutrients.4.) Good nutritional history should be obtained.5.) General clinical examination, with special attention to organs like hair, angles of the
mouth, gums, nails, skin, eyes, tongue, muscles,bones & thyroid gland.6.) Detection of relevant signs helps in establishing the nutritional diagnosis.
Clinical Assessment :
Advantages1.) Fast & easy to perform.2.) Inexpensive.3.) Non-invasive.Limitations1.) not detect early cases.CAUSES & PREVENTION OF MALNUTRITION:
Malnutrition is the condition that develops when the body does not get the right amount of the vitamins, minerals, and other nutrients it needs to maintain healthy tissues and organ function.
Malnutrition occurs in people who are either under-nourished or over-nourished. Undernutrition is a consequence of consuming too few essential nutrients or using or excreting them more rapidly than they can be replaced.
Infants, young children, and teenagers need additional nutrients. So do women who are pregnant or breast-feeding. Nutrient loss can be accelerated by diarrhea, excessive sweating, heavy bleeding (hemorrhage), or kidney failure. Nutrient intake can be restricted by age-related illnesses and conditions, excessive dieting, severe injury, serious illness, a lengthy hospitalization, or substance abuse.
The leading cause of death in children in developing countries is protein-energy malnutrition. This type of malnutrition is the result of inadequate intake of calories from proteins, vitamins, and minerals. Children who are already undernourished can suffer from protein-energy malnutrition when rapid growth, infection, or disease increases the need for protein and essential minerals.
Causes and Symptoms:
Poverty and lack of food are the primary reasons why malnutrition occurs in the United States. Ten percent of all members of low income households do not always have enough healthful food to eat, and malnutrition affects one in four elderly Americans. Protein-energy malnutrition occurs in 50% of surgical patients and in 48% of all other hospital patients.
There is an increased risk of malnutrition associated with chronic diseases, especially disease of the intestinal tract, kidneys, and liver. Patients with chronic diseases like cancer, AIDS, and intestinal disorders may lose weight rapidly and become susceptible to undernourishment because they cannot absorb valuable vitamins, calories, and iron.
People with drug or alcohol dependencies are also at increased risk of malnutrition. These people tend to maintain inadequate diets for long periods of time and their ability to absorb nutrients is impaired by the alcohol or drug's affect on body tissues, particularly the liver, pancreas, and brain.
Unintentionally losing 10 lb (4.5 kg) or more may be a sign of malnutrition. People who are malnourished may be skinny or bloated. Their skin is pale, thick, dry, and bruises easily. Rashes and changes in pigmentation are common.
Hair is thin, tightly curled, and pulls out easily. Joints ache and bones are soft and tender. The gums bleed. The tongue may be swollen or shriveled and cracked. Visual disturbances include night blindness and increased sensitivity to light and glare.
Other symptoms of malnutrition include: Anemia. Diarrhea. Disorientation. goiter (enlarged thyroid gland). loss of reflexes and lack of coordination. muscle twitches. scaling and cracking of the lips and mouth.
Malnourished children may be short for their age, thin, listless, and have weakened immune systems.
Prevention:
1.) Breast-feeding a baby for at least six months is considered the best way to prevent early- childhood malnutrition. The United States Department of Agriculture and Health and
Human Services recommend that all Americans over the age of two. Consume plenty of fruits, grains, and vegetables.
2.) Eat a variety of foods that are low in fats and cholesterols and contain only moderate amounts of salt, sugars, and sodium.
3.) Engage in moderate physical activity for at least 30 minutes, at least several times a week.
4.) Achieve or maintain their ideal weight.
5.) Use alcohol sparingly or avoid it altogether.
6.) Every patient admitted to a hospital should be screened for the presence of illnesses and conditions that could lead to protein-energy malnutrition. Patients with higher-than-average risk for malnutrition should be more closely assessed and reevaluated often during long-term hospitalization or nursing-home care.
