Energy Source PDF

ENERGY SOURCE  The source of energy for all muscle contractions is adenosine triphosphate (ATP).  The central limitation on one's capacity to exercise lies in the ability to maintain the availability of ATP; it's not stored in large amounts in skeletal muscle.  Viable sources of ATP com...

ENERGY SOURCE  The source of energy for all muscle contractions is adenosine triphosphate (ATP).  The central limitation on one's capacity to exercise lies in the ability to maintain the availability of ATP; it's not stored in large amounts in skeletal muscle.  Viable sources of ATP come from both anaerobic (doesn't require O2) and aerobic (requires O2) means.  Theprimary energy source for a given activity mostly depends on the intensity of the muscle contractions. Where does the energy for muscle contraction come from?  The source of energy that is used to power the movement of contraction in working muscles is adenosine triphosphate.  Adenosine triphosphate (ATP) A chemical used by cells to store and transport energy (ATP) , So once muscle contraction starts, the making of more ATP must start quickly.  ATP is so important, the muscle cells have several different ways to make it.  When the muscle’s supply of ATP is exhausted, it can be resynthesized from ADP in three ways: 1. via phosphorylation by phosphocreatine 2. via anaerobic metabolism 3. via aerobic metabolism PHOSPHOCREATINE  Phosphocreatine is a secondary reserve of energy that can quickly generate more ATP from ADP.  In this reaction, a phosphate group is transferred from phosphocreatine to ADP to form ATP very rapidly, allowing muscle contraction to continue for about 10 seconds.  When phosphocreatine is depleted, the muscles must turn to metabolism of fuel molecules to produce more ATP to power physical activity. Aerobic versus Anaerobic Activity  At the molecular level, we can divide all exercise into two general categories aerobic and anaerobic exercise.  Aerobic activity, which involves sustained effort such as distance running and walking, occurs when the body has sufficient oxygen available to oxidize fuel molecules for energy.  Anaerobic activity, which involves quick bursts of effort like weightlifting and sprinting, occurs in the absence of sufficient oxygen for the aerobic pathway.  The types of fuels that can be used differ, depending on the type of exercise that we’re doing.  Within two minutes of exercise, the body starts to supply working muscles with oxygen.  When oxygen is present, aerobic respiration can take place to break down the glucose for ATP. ENERGY SOURCES & SYSTEMS There are three type of sources  Carbohydrate- glycogen  Fat - fatty acid  Protien - amaino acid There are two type of energy system  Aerobic  Aenarobic ENERGY SOURCES CARBOHYDRATE  Carbohydrate have Sugar, vegetable, bread, fruit.  Animals store carbohydrates as glycogen, a polysaccharide consisting of thousands of glucose units covalently linked together.  Glycogen reserves, which represent the body’s “quick” form of energy, are found in the muscles and the liver  They are first broken down to glucose before undergoing further metabolism.  Glucose can then be further processed to release energy under both anaerobic and aerobic conditions.  FAT  Butter, oils, nuts.  Fats are stored as triglycerides, molecules that contain a single glycerol unit linked to three fatty acid units.  Most of our fat stores are found in adipose tissue, but other organs, including muscles, also have small reserves to fuel their ongoing needs.  Triglycerides, which account for about 84% of the total energy stores in the average individual, are degraded to fatty acids (and glycerol) before being further metabolized  Fatty acids can undergo only aerobic metabolism.  PROTEIN  Protein have Meat, fish, eggs.  Protein growth & repair of the body.  While dietary protein can also be degraded for energy, we have very little expendable protein reserves.  Skeletal muscle will actually be broken down despite potentially disastrous consequences.  This occurs primarily to fuel the brain, which needs a constant source of energy in the form of glucose.  Animals lack a metabolic pathway that can make glucose from fats, but most amino acids can undergo conversion to glucose. Summary of Energy Sources  ATP and phosphocreatine are the first energy sources to fuel ,the muscles during physical activity but are depleted very rapidly.  Glucose then follows, degraded by glycolysis and then either fermentation (anaerobic metabolism) Finally, under conditions of sustained aerobic activity.  The abundant fats are mobilized. Amino acids from proteins are also metabolized aerobically but make only a modest contribution to the energy demands of exercise. Relative Advantages of Anaerobic versus Aerobic Metabolism  Anaerobic metabolism has the distinct advantage of proceeding very quickly in theabsence of oxygen,this is the pathway that provides the energy needed to power their muscles.  Aerobic metabolism oxidizes glucose completely to obtain the maximum amount of energy possible. For endurance athletes, this is the pathway that provides the necessary ATP until fat mobilization begins to supplement energy production. Recommended Dietary Allowances  Recommended dietary allowances RDA is defined as the nutrients present in the diet which satisfy the daily requirement of nearly all individuals in a population.  Recommended dietary allowances , This implies addition of safety factor amount to the estimated requirement to cover Variation among individuals Losses during cooking Lack of precision in estimated requirement Recommended Dietary Allowances = Requirements + Safety factor Factors that effects RDA  RDA of an individual depends on many factors like: 1.Age 2. Sex 3. Physical work a. Sedentary b. Moderate c. Hard (Heavy) 4. Physiological stress a. Pregnancy b. Lactation  Factors that effects RDA For all the nutrients (except energy) estimates of allowances are arrived at by determining the average.  The value will meet more than 97.5% of the population which is composed of individuals with a satisfactory normal distribution of requirements.  ICMR’s Reference Woman 1. between 20-39 years of age 2. healthy and weighs 50kg. 3. may be engaged 8 hours in general household work or in light industry or in any other moderately active work. 4. 8 hours in bed 5. spends 4-6 hours sitting or moving around in light activity 6. 2 hours walking or active recreation or household chores. ICMR’s Reference men 1.between 20 – 39 years of age 2. weighs 60 kg 3. free from disease and physically fit for active work. 4. employed for 8 hours 5. 4-6 hours sitting and moving about 6. 2 hours in walking or in active recreation or household duties 7. 8 hours in bed  Scientists have prescribed RDA for adults, depending on the level of activity of individual. 1.Sedentary workers: Those who sit and do work using brain and hands. Ex: teachers; clerks, typists, officers  2. Moderate workers:  Works vigorously for a few hours using many parts of the body like hands, feet and muscles. Ex: postman; mali; maid servant; housewife doing all household work. 3. Heavy workers:  Use different parts of body for several hours. Ex: rickshaw pullers; coolies; workers in mines; sports persons, masons etc. Energy Requirements  The unit of energy, which has been in use in nutrition for a long time, is Kilocalories (kcal).  physical activity ratio (PAR) is expressed as the ratio of the energy cost of an individual activity per minute to the cost of the basal metabolic rate (BMR) per minute.  Physical Activity Ratio (PAR) = Energy cost of an activity per minute Energy cost of basal metabolism per minute  SIGNIFICANCE/USES OF ‘RDA’  RDA, we know, represents the level of the nutrient to be consumed daily to meet all the requirements of most of the individuals in a given population.  RDA's help us plan balanced diets which include a variety of foods derived from diverse food groups which help meet the nutrient requirements.  APPLICATIONS OF ‘ RDA’  Comparison of individual intakes to the RDA allows an estimate to be made about the probable risk of deficiency among individuals.  Modifying nutrient requirements in clinical management of diseases.  To help public health nutritionists to compose diets for schools, hospitals, prisons etc.  For health care policy makers and public health nutritionists to design, develop nutrition intervention programmes and policies. Recommended Dietary Allowances (RDA) for Indian Population  For the Indian population, the dietary standards have been computed by the Indian Council of Medical Research (ICMR).  These recommendations have been published as "Nutrient Requirements and Recommended Dietary Allowances for Indians" (ICMR 2010). 1.Note, the RDA for Indians are presented for the different age categories: 0-6 months, 7 to 12 months, 1 – 3 years, 4 – 6 years, 7 – 9 years, 10 – 12 years, 13 – 15 years,16 – 18 years, adult man and women.. 2. Recommendations are given for energy and all other nutrients including proteins, visible fat, calcium, iron, retinol, Beta Carotene, thiamine, riboflavin etc. 3. Recommended dietary allowances for adults are based on sex (male, female), body weight and physical activity level (i.e. Sedentary, Moderate and Heavy work). 4. RDA for energy is expressed in kilocalories (Kcal), for proteins, fats in grams (g), and for calcium, iron, vitamins and minerals in milligram (mg) or microgram 5. RDA for protein is based on body weight. The relationship can be expressed as 1g protein per kg body weight in the case of adults. It varies for other age categories. 6. RDA for energy and protein are given as additional intakes in pregnancy and lactation, indicated by a ( " + " sign). 7. In infancy RDA's for energy, protein, iron, thiamin, riboflavin and niacin are expressed as per kg body weight (expected for a healthy, normal growing infant of a particular age) 8. RDA for Vitamin A have been given in terms of retinol or alternatively in terms of Beta Carotene. DIETARY GUIDELINES 1.Eat variety of foods to ensure a balanced diet. 2.Ensure provision of extra food and healthcare to pregnant and lactating women. 3.Promote exclusive breastfeeding for six months and encourage breastfeeding till two years or as long as one can. 4.Feed home based semi solid foods to the infant after six months. 5.Ensure adequate and appropriate diets for children and adolescents, both in health and sickness. 6. Eat plenty of vegetables and fruits. 7. Ensure moderate use of edible oils and animal foods and very less use of ghee/ butter/ vanaspati. 8. Avoid overeating to prevent overweight and obesity. 9. Exercise regularly and be physically active to maintain ideal body weight. 10. Restrict salt intake to minimum. 11. Ensure the use of safe and clean foods. 12. Adopt right pre-cooking processes and appropriate cooking methods. 13. Drink plenty of water and take beverages in moderation. 14. Minimize the use of processed foods rich in salt, sugar and fats. 15. Include micronutrient-rich foods in the diets of elderly people to enable them to be fit and active. IMPORTANCE OF DIET DURING DIFFERENT STAGES OF LIFE DIET  Diet is the sum of food consumed, i.e. one which provides a mixture of foods which include enough of all the essential nutrients for living.  It is also concerned with the eating patterns of the individual or a group.  It may also be modified and used for medically ill persons as part of their therapy (therapeutic diets). What is Balanced Diet  A balanced diet is one which provides all the nutrients in required amounts and proper proportions  It can easily be achieved through a blend of the four basic food groups.  The quantities of foods needed to meet the nutrient requirements vary with age, gender, physiological status and physical activity.  Should provide around 50-60% of total calories from carbohydrates, preferably from complex carbohydrates  about 10-15% from proteins and 20-30% from fat.  should provide other non-nutrients such as dietary fiber, antioxidants and phytochemicals Antioxidants such as vitamins C and E, beta-carotene, riboflavin and selenium protect the human body from free radical damage.  Other phytochemicals such as polyphenols, flavones, etc., also afford protection against oxidant damage. Nutritional needs of specific groups Nutritional needs can vary depending on a number of factors: Different life stages – childhood, adulthood, female (pre/postnatal, pre/post menopausal), later adulthood; Medical conditions – diabetes (type 1 or 2), anaemia, lactose intolerance, coeliac disease; Culture – religious beliefs, vegetarians, lifestyle choices. Nutritional needs at different life stages Early childhood The Department of Health recommends exclusive breastfeeding for the first 6 months.  Weaning or complimentary feeding should begin at around 6 months.  The aim of weaning is to gradually introduce babies to a wide range of new tastes and textures. After 6 months of age, the baby must be given other foods in addition to breast milk or infant formula. This process is called weaning.  Weaning too soon (before 4 months) can increase the risk of infections and allergies.  Solids must be semi-fluid and soft, since the baby has no teeth and cannot chew.  Supplements of vitamins A, C and D in the form of drops are recommended for children aged from 6 months to 5 years.  Cows’ milk is not suitable as a drink before 12 months of age. CHILDHOOD Children aged between 2 and 5 should gradually begin to follow the proportions illustrated in the Eatwell Guide. The Eatwell Guide does not apply to children under the age of 2, as their nutritional needs are different. ADOLESCENCE Eating a healthy, varied diet and keeping active will be good for teenagers’ health. Your teenage years are a time of rapid growth and development, and the requirements for some nutrients, like calcium and phosphorus, is fairly high. Boys need more protein and energy than girls for growth. Girls need more iron than boys to replace menstrual losses. Pregnancy During pregnancy, some extra nutrients are needed (mainly in the last three months) to: Help the development of the uterus, placenta and other tissues; Meet the needs of the growing foetus; Lay down stores of nutrients and energy (as fat) for the growth of the foetus and in the mother for lactation. This equates to an extra 200 kcal/day during the third trimester only (last three months). LACTATIONING MOTHER  Lactation is the period following pregnancy when the women nourishes a full ydeveloped and a rapidly growing baby with brest milk.  Most of the nutrients required by the baby are supplied by the breast milk. BREASTFEEDING When breastfeeding it is recommended to follow a healthy, varied diet as depicted in the Eatwell Guide. Pregnant and breastfeeding women should aim to restrict their caffeine intake to less than 200mg a day. While breastfeeding, women should have no more than two portions (140g each) of oily fish a week. Breastfeeding women should not drink more than one or two units of alcohol, more than once or twice a week when breastfeeding. Breastfeeding can have health benefits for both the baby and mother. BREAST MILK Breast milk provides special proteins, antibodies and white blood cells which help to protect the baby against infection. In the first three days after birth, the mother produces a special form of breast milk called colostrum. It contains less fat, more protein and is rich in antibodies, proteins that play a key role in the baby’s immune system. GERIATRIC POPULATION Our risk of chronic conditions such as heart disease, cancer and dementia increases as we age. Older people may eat less for different reasons, for example: 1.difficulty in chewing and swallowing; 2.dental problems; 3.changes in sense of smell and taste; 4. difficulty in shopping, preparing and cooking food; 5. living alone; financial problems and illness. Older adults are advised to stay active and follow the basic principles of the Eatwell Guide. Later life and bone strength After menopause (when menstruation stops), women gradually lose bone strength. This can also happen in older men. Osteoporosis may occur when bones become weak, brittle and break easily. This may lead to fractures in the wrist, back and hip. Older adults should have plenty of calcium intake from milk and dairy products, green leafy vegetables, beans, pulses, and products made from flour. They should also remain active and have adequate vitamin D from foods such as oily fish, or through the action of sunlight on the skin. Adults over 65 years who are housebound should take a daily supplement of vitamin D as skin synthesis of this vitamin requires sunshine.