Introduction to Nutrition Part 1 PDF

Lectures are: 1. Introduction to nutrition. 2. Assessment of obesity 3. Facts and myth about nutrition. 4. Diet planning I 5. Diet planning II Dr. Nada Ahmed Hussein Lecturer of medical biochemistry Faculty of medicine  “the science that interprets the relationship of food to the functioni...

Lectures are: 1. Introduction to nutrition. 2. Assessment of obesity 3. Facts and myth about nutrition. 4. Diet planning I 5. Diet planning II Dr. Nada Ahmed Hussein Lecturer of medical biochemistry Faculty of medicine  “the science that interprets the relationship of food to the functioning of living organism” Nutrition is a science of food and its relationship to health. Nutrition refers to nourishment that sustains life. The study of nutrient requirements and the diet providing these requirements is also known as ‘nutrition’. It includes the uptake of food, liberation of energy, all the processes of synthesis essential for maintenance, growth and reproduction and elimination of wastes.  Eating can be People eat for one of life’s enjoyment and greatest to obtain energy pleasures. and nutrients. Although many genetic, Over the past decades, environmental, behavioral, attention has been and cultural factors affect focused increasingly health, diet is equally on the relationship of important for nutrition to chronic promoting health and diseases (CHD, DM & preventing disease. cancer).  Balanced diet meets all the nutritional needs of an individual for maintenance, repair, living processes, growth, and development. An appropriate diet is considered one that helps reduce the risk of developing chronic diseases: for prevention of illness as well as for treatment of the illness. The amount of food needed to meet the daily dietary requirements will differ according to age, gender, physiological status and level of physical activity.  It includes energy and all nutrients in proper amounts and in proportion to each other. The presence or absence of one essential nutrient may affect the availability, absorption, metabolism, or dietary need for others. It is achieved by carefully selecting and combining food items from different food groups. It provides little extra nutrients to withstand short duration of illness (safety margin).  Adequate nutrition or good nutrition is a diet that provides all dietary nutrients in combination or balance, so that the organism can meet exogenous and endogenous stresses, whether in health or disease, with a minimal demand or strain on the body’s natural homeostatic mechanisms”  A balanced diet also ensure that a person is consuming sufficient amounts of functional food constituents that, although not defined as nutrients, have biologic effects and may influence health and susceptibility to disease : - dietary fiber and carotenoids (beneficial antioxidant), - Phytochemicals: compounds that are produced by plants ("phyto" means "plant"): they protect cells from cancer such as isothiocyanates in broccoli or other cruciferous vegetables and lycopene in tomato products.  Chemical substances found in food that are required by the body to provide energy, give the body structure, and help regulate chemical processes. There are six classes of nutrients: 1. Carbohydrates 2. lipids 3. Proteins 4. water 5. Vitamins 6. minerals They are classified as: 1. macronutrients or micronutrients. 2. Organic or inorganic, 3. whether or not they provide energy to the body. Choosing a variety of foods (from the different food groups) should provide adequate amounts of nutrients.  Several countries have developed food-based dietary guidelines (appropriate for the circumstances and needs of their population) that are illustrated using images including a pyramid, a house, a staircase, or a palm tree, for planning and evaluating diets and food supplies (what to eat each day). These guidelines have been developed over the years as educational tools, grouping foods of similar nutrient content together to help facilitate the selection of a balanced diet. in 1992 the five major food groups of the Food Guide Pyramid was introduced by the United States Department of Agriculture (USDA) as a tool recommending a daily pattern of wise food choices, ranging from liberal consumption of grain products, as represented in the broad base of the pyramid, to sparing use of fats, oils, and sugary foods, as represented in the apex. In 2011 the USDA abandoned MyPyramid and introduced MyPlate, which divided the four basic food groups (fruits, grains, protein, and vegetables) into sections on a plate, with MyPyramid, introduced by the USDA in the size of each section representing the relative 2005, represented the major food groups in dietary proportions of each food group. A small circle shown at the edge of the plate was vertical bands and used a figure climbing used to illustrate the dietary inclusion and steps to illustrate the importance of daily proportion of dairy products. exercise. Japanese Food Guide Spinning Top (The Plate of Good Eating). (Courtesy of Mexico Ministry of Health The Wheel of Five (Netherlands)  The relatively simple dietary guidelines discussed above provide guidance for meal planning. Standards for evaluating the adequacy of specific nutrients in an individual diet or the diet of a population require more detailed and quantitative recommendations. The Recommended Dietary Allowances (RDAs), first published by the U.S. National Academy of Sciences in 1941 and revised every few years until 1989, established dietary standards for evaluating nutritional intakes of populations and for planning food supplies. The RDA: the amount of a nutrient needed to meet the requirements of almost all the healthy population.  MACRONUTRIENTS: Nutrients needed in large amounts are called macronutrients. There are three classes of macronutrients: carbohydrates, lipids, and proteins. Water is also a macronutrient in the sense that you require a large amount of it, but unlike the other macronutrients, it does not yield energy.  I- Carbohydrate: Carbohydrates are broadly classified into two groups based on their chemical structure: simple carbohydrates (often called simple sugars) and complex carbohydrates: Complex carbs are usually whole foods that contain fiber. Simple carbs most often contain added sugar, and many are void of fiber, with the exceptions that include whole fruit. They are a major fuel source for all cells of the body, and certain cells, like cells of the central nervous system and red blood cells, rely solely on carbohydrates for energy.  Carbohydrate: Complex Carbohydrate: Complex carbohydrates are different from simple carbohydrate in that they’re made up of longer chains of sugars. Because of this, they take more time to break down, which allows for a slower, more gradual release of energy. Whole grains, beans, legumes, and starchy vegetables are all examples of complex carbohydrates. Most complex carbs have fiber and vitamins, minerals, and phytonutrients in addition to providing energy in the form of calories.  I- Carbohydrate: Simple carbs are short-chained groups of sugars. Because they’re made up of shorter chains, it’s easier for them to break down in your body, which results in a sudden rush of energy (potential spike in blood sugar) soon after you eat them.  I- Carbohydrate: Simple carbs are short-chained groups of sugars. Mostly, they’re carbohydrates that are quickly digested, low in fiber and nutrients, and potentially high in added sugar. Refined overly processed “white” grains and foods or drinks with added sugars. They’re basically carbs that aren’t whole foods found in nature.  I- Carbohydrate: This doesn’t mean that all simple carbs are refined; some are found in whole foods. Fruit and milk are made up of naturally occurring simple sugars, but they also provide vitamins and minerals (and, in the case of whole fruit, not fruit juice, contain fiber).  I- Carbohydrate: On the other hand, more processed foods and beverages like candy bars and soda are simple sugars that come from added sugars. These “junk foods” don’t offer many added nutritional benefits beyond the calories (or energy) they provide. Simple carbs are usually treats, not foods that you should not include in your everyday diet. The carbs we eat should mainly fall under the complex category, along with naturally occurring simple carbs (fruit, vegetables, and milk) instead of refined carbs (white bread, pasta, etc.) or foods with added sugars (candy, soda, and baked goods).  Glycemic index: The glycemic index (GI) is a ranking system for foods containing carbohydrates. It is a value used to show how quickly each food increases blood glucose levels compared with eating a standard amount of glucose (50g). Low GI foods are foods with a GI less than 55. Intermediate GI foods are foods with a GI between 55 and 70. High GI foods are foods with a GI greater than 70.  Glycemic index: The lower the GI, the slower the rise in blood glucose levels will be when the food is consumed. Carbohydrates with a low GI value (55 or less) are more slowly digested, absorbed and metabolized and cause a lower and slower rise in blood glucose and, therefore usually, insulin levels. It include most fruits and vegetables, milk, some wholegrain cereals and bread, pulses and basmati rice. Glycemic index: Research shows that both the amount and the type of carbohydrate in food affect blood glucose levels. Studies also show that the total amount of carbohydrate in food, in general, is a stronger predictor of blood glucose response than the GI. Glycemic index: The amount of carbs you eat has a bigger effect on blood glucose levels than GI alone. For example, pasta has a lower GI than watermelon, but pasta has more carbs than watermelon (per weight), so if you eat similar amounts (weight) of either of these two foods, the pasta will have more of an impact on your blood glucose levels. The most important thing to do is get your portion size right – once you do this, you will get an added bonus for choosing low GI alternatives.  Your blood glucose rises and falls when you eat a meal containing carbs. How high it rises and how long it remains high depends on the quality of the carbohydrates (the GI) and the quantity (the serve size). Glycemic load or GL combines both the quality and quantity of carbohydrate in one ‘number’. It’s the best way to predict blood glucose values of different types and amounts of food. The formula is: GL = GI x available carbohydrate in a 100g serving 100 Recommendations for using GI in your diet Aim to include at least 3 low GI foods throughout the day, ideally one with each meal or snack. When eating high GI foods, try to combine these with a low GI food in order to decrease the overall GI of a meal. Factors that can affect the GI of a food: 1. The type of sugar present: fructose (fruit sugar) and lactose (milk sugar) both have a lower GI than sucrose (table sugar). 2. Ripeness and storage time: the more ripe a fruit or vegetable is, the higher the GI. 3. Processing: juice has a higher GI than whole fruit; mashed potato has a higher GI than a whole baked potato. 4. Cooking methods: how long a food is cooked, frying, boiling and baking. Cooking and processing food will usually increase the GI as there is less work required by the body to break the carbohydrates down. 5. Fiber: wholegrains and high-fiber foods act as a physical barrier that slows down the absorption of carbohydrate. 6. Fat lowers the GI of a food. For example, chocolate has a medium GI because of it’s fat content, and crisps will actually have a lower GI than potatoes cooked without fat. 7. Protein lowers the GI of food. Milk and other diary products have a low GI because they are high in protein and contain fat. 8. Adding acidity to the food will lower the GI (e.g. adding lemon juice).  Remember, GI is not a reflection of how healthy a food is. Fat content: Foods high in fat often have a low GI (e.g. chocolate or corn chips) and should only be included occasionally. The amount of food eaten: a small amount of a high GI food e.g. watermelon may only have a small effect on blood sugar levels. The quality of food: always aim to eat a wide range of carbohydrate containing foods including wholegrain breads and cereals, fresh fruit and vegetables and dairy which provide important nutrients and fiber.  The GI value relates to the food eaten on its own and in practice we usually eat foods in combination as meals. Bread, for example is usually eaten with butter or margarine, and potatoes could be eaten with meat and vegetables. Therefore relying solely on the glycemic index of foods could result in eating unbalanced and un-healthy diets high in fat, salt and saturated fats. An additional problem is that GI compares the glycemic effect of an amount of food containing 50g of carbohydrate but in real life we eat different amounts of food containing different amounts of carbohydrate.