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    in general, minerals in plant foods have an absorption rate that is _______ than that in animal foods.

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    get in general, minerals in plant foods have an absorption rate that is _______ than that in animal foods. from EN Bilgi.

    CHAPTER 3: CALCULATION OF THE ENERGY CONTENT OF FOODS

    CHAPTER 3: CALCULATION OF THE ENERGY CONTENT OF FOODS - ENERGY CONVERSION FACTORS

    As stated in Chapter 1, the translation of human energy requirements into recommended intakes of food and the assessment of how well the available food supplies or diets of populations (or even of individuals) satisfy these requirements require knowledge of the amounts of available energy in individual foods. Determining the energy content of foods depends on the following: 1) the components of food that provide energy (protein, fat, carbohydrate, alcohol, polyols, organic acids and novel compounds) should be determined by appropriate analytical methods; 2) the quantity of each individual component must be converted to food energy using a generally accepted factor that expresses the amount of available energy per unit of weight; and 3) the food energies of all components must be added together to represent the nutritional energy value of the food for humans. The energy conversion factors and the models currently used assume that each component of a food has an energy factor that is fixed and that does not vary according to the proportions of other components in the food or diet.

    3.1 JOULES AND CALORIES

    The unit of energy in the International System of Units (SI)[8] is the joule (J). A joule is the energy expended when 1 kg is moved 1 m by a force of 1 Newton. This is the accepted standard unit of energy used in human energetics and it should also be used for the expression of energy in foods. Because nutritionists and food scientists are concerned with large amounts of energy, they generally use kiloJoules (kJ = 103 J) or megaJoules (MJ = 106 J). For many decades, food energy has been expressed in calories, which is not a coherent unit of thermochemical energy. Despite the recommendation of more than 30 years ago to use only joules, many scientists, non-scientists and consumers still find it difficult to abandon the use of calories. This is evident in that both joules (kJ) and calories (kcal) are used side by side in most regulatory frameworks, e.g. Codex Alimentarius (1991). Thus, while the use of joules alone is recommended by international convention, values for food energy in the following sections are given in both joules and calories, with kilojoules given first and kilocalories second, within parenthesis and in a different font (Arial 9). In tables, values for kilocalories are given in italic type. The conversion factors for joules and calories are: 1 kJ = 0.239 kcal; and 1 kcal = 4.184 kJ.

    3.2 THEORETICAL FRAMEWORK FOR AN UNDERSTANDING OF FOOD ENERGY CONVERSION FACTORS

    As described in detail in the report of the most recent Expert Consultation on Energy in Human Nutrition (FAO, 2004), humans need food energy to cover the basal metabolic rate; the metabolic response to food; the energy cost of physical activities; and accretion of new tissue during growth and pregnancy, as well as the production of milk during lactation. “Energy balance is achieved when input (or dietary energy intake) is equal to output (or energy expenditure), plus the energy cost of growth in childhood and pregnancy, or the energy cost to produce milk during lactation” (FAO, 2004).

    The total combustible energy content (or theoretical maximum energy content) of a food can be measured using bomb calorimetry. Not all combustible energy is available to the human for maintaining energy balance (constant weight) and meeting the needs of growth, pregnancy and lactation. First, foods are not completely digested and absorbed, and consequently food energy is lost in the faeces. The degree of incomplete absorption is a function of the food itself (its matrix and the amounts and types of protein, fat and carbohydrate), how the food has been prepared, and - in some instances (e.g. infancy, illness) - the physiological state of the individual consuming the food. Second, compounds derived from incomplete catabolism of protein are lost in the urine. Third, the capture of energy (conversion to adenosine triphosphate [ATP]) from food is less than completely efficient in intermediary metabolism (Flatt and Tremblay, 1997). Conceptually, food energy conversion factors should reflect the amount of energy in food components (protein, fat, carbohydrate, alcohol, novel compounds, polyols and organic acids) that can ultimately be utilized by the human organism, thereby representing the input factor in the energy balance equation.

    3.3 FLOW OF ENERGY THROUGH THE BODY - A BRIEF OVERVIEW

    Food that is ingested contains energy - the maximum amount being reflected in the heat that is measured after complete combustion to carbon dioxide (CO2) and water in a bomb calorimeter. This energy is referred to as ingested energy (IE) or gross energy (GE). Incomplete digestion of food in the small intestine, in some cases accompanied by fermentation of unabsorbed carbohydrate in the colon, results in losses of energy as faecal energy (FE) and so-called gaseous energy (GaE) in the form of combustible gases (e.g. hydrogen and methane). Short-chain (volatile) fatty acids are also formed in the process, some of which are absorbed and available as energy. Most of the energy that is absorbed is available to human metabolism, but some is lost as urinary energy (UE), mainly in the form of nitrogenous waste compounds derived from incomplete catabolism of protein. A small amount of energy is also lost from the body surface (surface energy [SE]). The energy that remains after accounting for the important losses is known as “metabolizable energy” (ME) (see Figure 3.1).

    Source : www.fao.org

    Food processing and nutrition

    betterhealth.vic.gov.au

    Healthy eating

    Food processing and nutrition

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    Food processing and nutrition Actions for this page Summary

    The nutrient value of food is almost always altered by the kind of processing it undergoes.

    The water-soluble vitamins are the most vulnerable to processing and cooking.

    Careful cooking and storage will help retain the nutrients in your food.

    Excessive consumption of ultra-processed foods can result in weight gain in the short term and diet-related disease in the long term.

    On this page

    About food processing

    Effects of processing and storage of food

    Processes affecting food nutrient content

    Preparation of vegetables

    Losing nutrients through cooking

    Benefits of cooking food

    Preserving the nutrient value of vegetables

    Ultra-processed foods

    Where to get help

    About food processing

    Almost all food is processed in some way before it is eaten. Commercially, the main reasons to process food are to eliminate micro-organisms (which may cause disease) and to extend shelf life.

    Simply cooking or combining a food with other foodstuffs to create a recipe is also considered a form of food processing. Whatever the case, the nutrient value of any food is often altered by the processing.

    Effects of processing and storage of food

    Some vitamins are more stable (less affected by processing) than others. Water-soluble vitamins (B-group and C) are more unstable than fat-soluble vitamins (K, A, D and E) during food processing and storage.

    The most unstable vitamins include:

    folate thiamine vitamin C.

    More stable vitamins include:

    niacin (vitamin B3) vitamin K vitamin D biotin (vitamin B7)

    pantothenic acid (vitamin B5).

    Processes affecting food nutrient content

    A variety of things can happen during the growing, harvesting, storage and preparing of food that can affect its nutritional content. Processes that expose foods to high levels of heat, light or oxygen cause the greatest nutrient loss.

    Fertilisers

    Most plant crops are produced with the aid of fertilised soils. High use of nitrogen fertilisers tends to reduce the vitamin C content in many fruit and vegetable crops. It does not seem to make any difference to the plant’s nutrient value whether the fertiliser is organic or not.

    Milling

    Cereals such as wheat can be ground to remove the fibrous husks. The husks contain most of the plant’s dietary fibre, B-group vitamins, phytochemicals and some minerals.

    That is why products such as white bread are less nutritious than wholemeal varieties, even if they have been artificially fortified with some of the nutrients that were lost after milling.

    It is impossible to add back everything that is taken out, especially the phytochemicals. The ‘fibre’ that is added back to some products is often in the form of resistant starch, which may not be as beneficial as the fibre removed.

    Blanching

    Before a food is canned or frozen, it is usually heated very quickly with steam or water. The water-soluble vitamins, including vitamin C and B-complex, are sensitive and easily destroyed by blanching.

    Canning

    Food is heated inside the can to kill any dangerous micro-organisms and extend the food’s shelf life. Some types of micro-organisms require severe heat treatment and this may affect the taste and texture of the food, making it less appealing. Preservatives are generally not needed or used in canned foods.

    Water-soluble vitamins are particularly sensitive to high temperatures. Many people believe that canned foods are not as nutritious as their fresh counterparts, but this is not always the case, as fresh food often deteriorates more rapidly than canned foods.

    Freezing

    The nutrient value of a food is retained when it is frozen. Any nutrient losses are due to the processing prior to freezing and the cooking once the frozen food is thawed.

    Pasteurisation

    Pasteurisation involves heating liquid foods such as milk and fruit juices to specific temperatures to destroy micro-organisms. The nutrient value of milk is generally unaffected. In the case of pasteurised fruit juices, some losses of vitamin C can occur.

    High pressure processing

    This alternative preservation method subjects a food to elevated pressures, with or without the use of heat to kill micro-organisms. This method has been used in foods such as fruit juices. As heat is not required, this process impacts less on the vitamin content, flavour and colour of foods.

    Dehydrating

    Drying out foods such as fruits can reduce the amount of vitamin C they retain, but it can also concentrate other nutrients, particularly fibre in plant foods. Dehydrating food also makes food products more energy dense, which may contribute to weight gain.

    If a dehydrated food is reconstituted and cooked with water, further nutrients are leached out of the food and lost in the cooking water.

    Preparation of vegetables

    Most vegetables are peeled or trimmed before cooking to remove the tough skin or outer leaves. But most nutrients, such as vitamins, tend to lie close to the skin surface, so excessive trimming can mean a huge reduction in a vegetable’s nutrient value.

    Losing nutrients through cooking

    Some vitamins dissolve in water, so you lose your vitamins to the cooking water if you prefer to boil your vegetables. For example, boiling a potato can cause much of the potato’s B and C vitamins to migrate into the boiling water.

    Source : www.betterhealth.vic.gov.au

    Magnesium

    Magnesium overview for health professionals. Research health effects, dosing, sources, deficiency symptoms, side effects, and interactions here.

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    Source : ods.od.nih.gov

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