Combustion(a process of energy release ) in living beings was first described by Lavoisier(1743-1794).This brilliant chemist discovered the true nature of oxygen and how its combination (in the body) with carbon and hydrogen results in formation of CO2 and H2O and production of heat.
In 1842,Liebig announced that the substances burned in the body for energy liberation were carbohydrate,fat and protein.
Energy is needed for maintenance of body tissues and body temperature, for growth and also for physical and mental activity as well as for reproduction. In other words energy is needed for all physiological processes that go on in the body. The body expends energy for:
1.Voluntary actions,such as running, walking, swimming,typing and talking.The energy requirement of different activities has been tabulated .
2. Involuntary actions, such as expansion and contraction of the heart, respiration, and digestion.Involuntary actions include energy needed for body maintenance and is known as the Basal Metabolic Rate or BMR .This energy must be supplied to the body first,because energy required by the heart for its normal functioning or for the constant supply of blood to the brain are vital functions upon which survival of a living being depends.
Basal Metabolism, therefore, represents the irreducible minimum of energy required to keep up the life processes,i.e. for the basic internal functioning of the body.It is usually defined as the amount of energy required by the body
Saturday, March 6, 2010
RECOMMENDED DIETARY INTAKES(RDI)
The body stores of vitamins vary from one individual to another according to the general state of nutrition and health. The stores of the fat-soluble vitamins are usually higher than those of the water-soluble vitamins. However, even the stores of the latter are sufficient to protect the well nourished individual for many days or even months. For example, it may take as long as 80-90 days before the symptoms of scurvy appear if one eats a diet without vitamin C.
It is estimated that body stores of vitamin B12 are adequate for more than two years and a diet lacking vitamin A will not lead to clinical signs of deficiency for several months.
Consequently, well nourished individuals are usually able to withstand periods of deprivation or periods of increased need such as occur with pregnancy and lactation. They are also at an advantage when stressed by disease or trauma. Undue concern about particular food preferences, for example about children who seem to want one kind of food and not another for a few days, is unnecessary. As long as a variety of foods are eaten over a period of time, the range of essential nutrients should be provided.
RDI's are the amounts of essential nutrients that are considered adequate to meet the nutritional requirements of healthy people. The RDI's are designed to easily prevent classical nutritional deficiency diseases, such as scurvy, beri-beri, pellagra, rickets and anaemia. Indeed, there is a wide margin of safety. However, they do not address the extra nutrient needs of persons with certain chronic ailments, who smoke, or who are on drug medication.
New research suggests a greater role for vitamins (and minerals) in the prevention or slowing down of many diseases such as heart disease, cancer, cataracts, osteoporosis and birth defects. The total effects of vitamins on the body are still not fully known or understood. Further, there is increasing scientific evidence to suggest that higher levels of certain vitamins (e.g. antioxidants vitamins C, E, and beta-carotene) may be necessary for optimal health, and may provide extra protection against cancer, heart disease and other diseases.
In time, the concept of RDI may well be broadened to include a second set of much higher vitamin levels that optimise their disease-preventing properties. From the medical practitioner's point of view, it is particularly important to remember that RDI's are for healthy people. In illness the requirements for many nutrients are altered. For example, with stress, trauma or surgery, the requirement for vitamin C may be more than 8 times the RDI for healthy adults; zinc requirements increase for wound healing.
It is estimated that body stores of vitamin B12 are adequate for more than two years and a diet lacking vitamin A will not lead to clinical signs of deficiency for several months.
Consequently, well nourished individuals are usually able to withstand periods of deprivation or periods of increased need such as occur with pregnancy and lactation. They are also at an advantage when stressed by disease or trauma. Undue concern about particular food preferences, for example about children who seem to want one kind of food and not another for a few days, is unnecessary. As long as a variety of foods are eaten over a period of time, the range of essential nutrients should be provided.
RDI's are the amounts of essential nutrients that are considered adequate to meet the nutritional requirements of healthy people. The RDI's are designed to easily prevent classical nutritional deficiency diseases, such as scurvy, beri-beri, pellagra, rickets and anaemia. Indeed, there is a wide margin of safety. However, they do not address the extra nutrient needs of persons with certain chronic ailments, who smoke, or who are on drug medication.
New research suggests a greater role for vitamins (and minerals) in the prevention or slowing down of many diseases such as heart disease, cancer, cataracts, osteoporosis and birth defects. The total effects of vitamins on the body are still not fully known or understood. Further, there is increasing scientific evidence to suggest that higher levels of certain vitamins (e.g. antioxidants vitamins C, E, and beta-carotene) may be necessary for optimal health, and may provide extra protection against cancer, heart disease and other diseases.
In time, the concept of RDI may well be broadened to include a second set of much higher vitamin levels that optimise their disease-preventing properties. From the medical practitioner's point of view, it is particularly important to remember that RDI's are for healthy people. In illness the requirements for many nutrients are altered. For example, with stress, trauma or surgery, the requirement for vitamin C may be more than 8 times the RDI for healthy adults; zinc requirements increase for wound healing.
CHOICE OF FOOD
The basic misconception about food is that we crave for the food which our body needs. We very often hear 'Let him eat it (whatever food is likes most).If he likes it so much, may be he needs it more.'
Human beings are considered to be the most advanced when their intelligence is compared to that of animals,but as far as food selection is concerned,man does not retain this position.Choice of foods
relating to the body's requirement is more accurate in case of animals.The food-choice of human beings is influenced by his social life and cultural background as well as his learning.Learning profoundly influences our food selection.It is interesting to note that infants show a natural ability to select foods needed by their body,This ability is lost as the child grows up.
Human beings are considered to be the most advanced when their intelligence is compared to that of animals,but as far as food selection is concerned,man does not retain this position.Choice of foods
relating to the body's requirement is more accurate in case of animals.The food-choice of human beings is influenced by his social life and cultural background as well as his learning.Learning profoundly influences our food selection.It is interesting to note that infants show a natural ability to select foods needed by their body,This ability is lost as the child grows up.
BMI - Body Mass Index
BMI or Body Mass Index, is another method of estimating a person's body fat percentage based upon simple weight and height measurements. While the BMI calculation is an indirect measurement, it has been found to be a fairly reliable indicator of body fat measures in most people. Although some studies still question the accuracy of the BMI method of body fat measurement, especially for athletes.
Ideal Body Weight and Body Fat Percent
The ideal weight and fat-lean ratio varies considerably for men and women and by age, but the minimum percent of body fat considered safe for good health is 5 percent for males and 12% for females. The average adult body fat is closer to 15 to 18% for men and 22 to 25% for women.
Athletes tend to be at low end of this scale due to their increased lean weight (muscle mass). While low levels of body fat seem to be related to improved performance, body composition alone is not a great predictor of sports success. A linebacker needs to have enough body mass (lean and fat weight) to generate high forces and avoid injury. Body fat among elite athletes vary largely by sport. There is little evidence of any benefit when men drop under 8% and women drop under 14 percent body fat.
How Low Is Too Low?
While the average body fat percent in the United States and Europe is increasing, extremely low body fat percent is also a health problem. The female athlete triad highlights the problem. Women athletes who lose too much fat risk injury, decreased performance and health issues.
The female athlete triad refers specifically to three related health problems often found in women athletes:
- Eating disorders and low energy availability.
- Amenorrhea and menstrual disorders.
- Decreased bone mass and increased risk of stress fractures and osteoporosis.
This attempt to reduce body fat by extreme measures not only leads to decreased exercise performance, but can lead to severe health complications. Nutrient deficiencies and fluid/electrolyte imbalance from low food intake can lead to increased risk of fractures, illness, loss of reproductive function and serious medical conditions such as dehydration, and starvation. The medical complications of this triad involve almost every body function and include the cardiovascular, endocrine, reproductive, skeletal, gastrointestinal, renal, and central nervous systems.
Read the updated American College of Sports Medicine Position Stand on the Female Athlete Triad.
How Much Body Fat Is Too Much?
Just as too little body fat can cause physiological complications, too much body fat is also harmful. For men over 25% and women over 32% fat there is a dramatic correlation with illness and disease.
Isn't Body Composition Genetic?
Some aspects of your body composition are genetic (where you store fat), but most fat increase is related to lifestyle.
Can I Change My Body Composition?
Yes. To increase or decrease your percent of body fat you need to create the right balance between the calories in and calories out. The best way to do this is to decrease daily calories by about 500 and increase your exercise. Aerobic exercise along with strength training is ideal. If you are beginning a new exercise program, you are advised to first consult your physician.Body Composition - Fat - Weight
Body composition is the term used to describe the different components that, when taken together, make up a person's body weight. The human body is composed of a variety of different tissue types including lean tissues (muscle, bone, and organs) that are metabolically active, and fat (adipose) tissue that is not.
Underwater Weighing - Hydrostatic Weighing
Body Weight Measurements
Standard body weight scales provide a measure of total weight, but don't determine the lean-to-fat ratio of that weight. Standing on most scales can tell you only if you weigh more than the average person, but not if that weight is fat or muscle. Based only on scale weight, a 250-pound athlete with 8% body fat may be considered "overweight" by a typical weight chart. Such charts are not a good indication of ideal body weight for general health or for athletic performance.Body Composition | Body Fat Measurement
There are many methods of assessing a person's fat and lean mass. The most common methods include the following.
Underwater Weighing - Hydrostatic Weighing
One method of body composition analysis in which a person is weighed while submerged in a large tank of water is called underwater or hydrostatic weighing This method of determining body composition relies on Archimedes' Principle of displacement which states:
- The density of fat mass and fat-free mass are constant
- Lean tissue is more dense than water
- Fat tissue is less dense than water.
- Therefore person with more body fat will weigh less underwater and be more buoyant.
Skinfold Thickness Measurements
Because underwater weighting it is complicated and cumbersome and requires special equipment, most exercise physiologists use simple skinfold measurements to determine body fat percent. The American College of Sports Medicine says that when performed by a trained, skilled, tester, they are up to 98% accurate.Bioelectrical Impedance
Bioelectrical Impedance is another method of assessing body fat percentage. There are a variety of body composition and body fat analyzers and scales available for home use that provide more than just total weight measurements. These devices determine total weight, the percent and amount of body fat, muscle mass, water, and even bone mass. While the readings can be affected by hydration levels, food intake, skin temperature, and other factors, if you follow the directions and take the reading under similar conditions, you will obtain the best results.The chemical analysis of foods
Nutrition analysis - Nutrition analysis refers to the process of determining the nutritional content of foods and food products. The process can be performed through a variety of certified methods. Traditionally, food companies would send food samples to laboratories for chemical testing. Chemical testing involves..
Isotope analysis - Isotope analysis is the identification of isotopic signature, the distribution of certain stable isotopes and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence. Isotope ratios..IMPORTANCE OF CHEMICALS IN FOOD
Chemicals are mainly used in food as flavors, coloring agents and preservatives to increase their shelf life.
What Is a Nutrient?
Macronutrients
"Macro" means big, so the macronutrients are the big nutrients, better known as protein, fats and carbohydrates. Except for zero-calorie foods, everything you eat contains varying amounts of these nutrients. Despite the popularity of some fad diets that require you to drastically reduce any of these macronutrients, all of them are important for your health and you need them everyday.Proteins are necessary for building the tissues in your body including all of the muscles, organs, skin and the parts of the immune system. Your body can use extra protein for energy or can convert it to fat. Carbohydrates include sugar, starch and fiber. Sugars and starches are needed for the energy that your body needs to function. Extra carbohydrates are converted to fat.
Fats are needed for the membranes that surround all the cells in your body, for normal brain and nerve function and for signaling hormones. Just like protein, the extra fat can be used as fuel for the body or can be stored as fat.
Micronutrients
"Micro" means small so the micronutrients are the nutrients that we need in small amounts. These include the 12 vitamins and 13 minerals that we need every day. Vitamins are grouped as water-soluble or fat-soluble depending on whether they can dissolve in fat or water. Minerals are divided into two groups, the major minerals and the trace minerals.Water-soluble vitamins include vitamin C and the seven B-complex vitamins. They have a variety of functions and you need all of them to be healthy. Chronic deficiencies of these vitamins can result in poor health.
Fat-soluble vitamins include vitamins A, D, E and K. Vitamins A and E come strictly from the foods you eat. However your body can make both vitamin D and vitamin K. Your body can store these vitamins in fat tissue. While it is extremely difficult to get too much of these vitamins from the foods you eat, you can build up toxic amounts of these four vitamins if you take massive amounts as dietary supplements everyday.
Major minerals include calcium, phosphorus, chloride, magnesium, potassium and sodium. These minerals are particularly important for healthy bones, teeth, muscles and fluid balance in the body. The trace minerals are chromium, copper, fluoride, iodine, iron, selenium and zinc. Your body needs all of these minerals for a variety of processes to keep it working.
Eating a healthy diet with lots of fruits, legumes, nuts, seeds, vegetables, whole-grains, lean meats, poultry, fish and dairy products should provide you with all of the micronutrients you need. There are people who may need to take additional dietary supplements may be helpful, such as women at risk of osteoporosis or people with age-related eye diseases. Always follow label directions if you take any dietary supplements.
Phytonutrients
"Phyto" refers to plants. Many different phytonutrients are found only in plants. Many of these natural chemicals are found in the colorful skins and flesh of fruits and vegetables. Some of the best known phytochemicals are the carotenoids, such as beta carotene, lutein, lycopene and zeaxanthin and flavonoids such as quercetin and anthocyanins.Phytonutrients have a variety of functions in the body. Some of them may function as antioxidants that protect the cells in our bodies from free radical damage. We don't know exactly how many of these different phytonutrients we need, however a healthy diet including at least five servings of fruits and colorful vegetables every day will supply your body with lots of phytonutrients.
Subscribe to:
Posts (Atom)