Nutrition Overview
The Council on Food and Nutrition of the American Medical Association defines nutrition as "the science of food; the nutrients and the substances therein; their action, interaction, and balance in relation to health and disease; and the process by which the organism (i.e. body) ingests, digest, absorbs, transports, utilizes, and excretes food substances." The purpose of our diet is to consume foods that provide the six essential nutrients: carbohydrates, protein, fat, vitamins, minerals, and water. The correct amount and variety of food provides the correct amount of nutrients for health and weight management.
Dietary Reference Intakes
Research to determine the appropriate amount of nutrients for health began in the 1940s. This need arose after men were being rejected from the military during World War II due to the effects of poor nutrition on their health. The first Food and Nutrition Board was formed to evaluate the nutrition intakes of large populations. Since then, the Food and Nutrition Board has undergone many changes and published comprehensive guidelines on nutrition for disease prevention.
The latest and most comprehensive nutrition recommendations are contained in the so-called Dietary Reference Intakes (DRIs). DRIs were created in 1997 and have changed the way that diets are evaluated. The primary goal of these guidelines was to not only prevent nutrient deficiencies but also reduce the risk of chronic diseases such as cancer, cardiovascular disease, and osteoporosis. DRIs have been set for macronutrients (carbohydrates, proteins, and fats), micronutrients (vitamins and minerals), electrolytes and water, the role of alcohol in health and disease, and bioactive compounds such as phytoestrogens and phytochemicals.
There are four types of DRI reference values:
- Estimated Average Requirements (EARs): the nutrient intake that is estimated to meet the needs of 50% of the individuals in a given gender and age group
- Recommended Dietary Allowances (RDAs): These tend to be the most well-known guidelines. They were set for the nutrient intake that is sufficient to meet the needs of nearly all individuals (about 97%) in a given gender and age group. Many people often incorrectly refer to these as the recommended "daily" allowances and believe that it is their goal to reach the RDA each day. It was not meant to be used as a guide for an individual's daily needs. The RDAs were established to be used in setting standards for food-assistance programs, for interpreting food record consumption of populations, and for establishing guidelines for nutrition labels.
- Adequate Intakes (AIs): the nutrients for which there is not enough information to establish an EAR
- Tolerable Upper Limits (Upper Levels or ULs): a nutrient's maximum level of daily intake that is unlikely to cause adverse health effects in nearly all individuals (97% to 98%) of the population
You do not need to reach the guidelines for every nutrient, every day of the week, so do not be alarmed when you fall short or go over in nutrients every now and then. But when you are consistently having a problem reaching your recommendations, it's best to work with a
Dietary Guidelines for Americans
The key recommendations are:
Adequate nutrients within calorie needs:
- Consume a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol.
- Meet recommended intakes within energy needs by adopting a balanced eating pattern, such as the USDA Food Guide or the DASH Eating Plan.
- To maintain body weight in a healthy range, balance calories from foods and beverages with calories expended.
- To prevent gradual weight gain over time, make small decreases in food and beverage calories and increase physical activity.
- Engage in regular physical activity and reduce sedentary activities to promote health, psychological well-being, and a healthy body weight.
- Achieve physical fitness by including cardiovascular conditioning, stretching exercises for flexibility, and resistance exercises or calisthenics for muscle strength and endurance.
- Consume a sufficient amount of fruits and vegetables while staying within energy needs. For a reference 2,000-calorie intake, 2 cups of fruit and 2½ cups of vegetables per day are recommended, with higher or lower amounts depending on the calorie level.
- Choose a variety of fruits and vegetables each day. In particular, select from all five vegetable subgroups (dark green, orange, legumes, starchy vegetables, and other vegetables) several times a week.
- Consume three or more ounce-equivalents of whole-grain products per day, with the rest of the recommended grains coming from enriched or whole-grain products. In general, at least half the grains should come from whole grains.
- Consume 3 cups per day of fat-free or low-fat milk or equivalent milk products.
- Those who choose to drink alcoholic beverages should do so sensibly and in moderation -- defined as the consumption of up to one drink per day for women and up to two drinks per day for men.
- Alcoholic beverages should not be consumed by some individuals, including those who cannot restrict their alcohol intake, women of childbearing age who may become pregnant, pregnant and lactating women, children and adolescents, individuals taking medications that can interact with alcohol, and those with specific medical conditions.
The guidelines are extensive, but you do not need to meet every recommendation all at once. To establish a healthy eating plan, the goal is to begin to make gradual changes to your eating and activity. You can select one or two guidelines a week or month to focus on. Over time, you will be able to make most, if not all, of the guidelines a part of your life.
health-care professional
The Food Guide Pyramid
Food guides have been categorizing foods into food groups since 1916 and have undergone many changes:
- 1916 Caroline Hunt buying guide: five food groups were milk and meat; cereals; vegetables and fruits; fats and fat foods; and sugars and sugary foods
- 1930's H.K. Stiebeling buying guide: 12 food groups were milk; lean meat, poultry and fish; dry mature beans, peas, and nuts; eggs; flours and cereals; leafy green and yellow vegetables; potatoes and sweet potatoes; other vegetables and fruit; tomatoes and citrus; butter; other fats; and sugars
- 1940's Basic Seven foundation diet: seven food groups were milk and milk products; meat, poultry, fish, eggs, dried beans, peas and nuts; bread, flour, and cereals; leafy green and yellow vegetables; potatoes and other fruit and vegetables; citrus, tomato, cabbage, and salad greens; and butter-fortified margarine
- 1956-1970's Basic Four foundation diet: milk group; meat group; bread and cereal; and vegetable-fruit group
- 1979 Hassle-Free foundation diet: five food groups were milk-cheese group; meat, poultry, fish, and beans group; bread-cereal group; vegetable-fruit group; and fats, sweets, and alcohol group
- 1984 to present Food Guide Pyramid: six food groups were milk, yogurt, and cheese; meat, poultry, fish, eggs, dry beans, and nuts; breads, cereals, rice, and pasta; vegetables; fruit; and fats, oils, and sweets
Another feature of the MyPyramid Plan is the food-gallery section. This section provides images of the serving sizes of foods in each of the food groups. Many people complain about serving sizes being too small. Serving size is a standard unit of measurement, not the amount that you are supposed to consume. The amount, or number of servings that you consume, is your portion. For example, if the serving size for pasta is ½ cup and you consume 2 cups, that means that your portion is 2 cups and you consumed 4 servings.
The food guides have been separating food into food groups for nearly a century. The current Food Guide Pyramid still emphasizes eating a balanced diet with foods from each of the food groups, but with today's version of the plan, you can get a personalized plan instead of just general recommendations. This is everyone's chance to learn how to eat a well-balanced diet.
Food Labels
The food label provides information about
- serving size,
- calories,
- calories from fat,
- total fat,
- saturated fat,
- monounsaturated fat,
- polyunsaturated fat,
- trans fat,
- cholesterol,
- sodium,
- total carbohydrates,
- dietary fiber,
- sugars,
- protein,
- vitamins, and
- minerals.
The information listed below the serving size is listed in grams and percentages. You will learn how to interpret the grams for each nutrient later on in the article. In an attempt to help people determine if the food will reach their nutritional needs, the FDA developed a set of generic standards called Daily Values. You will only find Daily Values listed on food labels. The standard DRIs could not be used because they vary by gender and age, so they are too specific for a food label. The limitation of the Daily Values is that they are based on a 2,000-calorie diet. This means that the percentages are only relevant to someone who is consuming 2,000 calories. For everyone else, these percentages will either be too high or too low. For this reason, it's best to focus on grams and ingredients.
Calories
Your sources of calories comes from three of the essential nutrients: carbohydrates, protein, and fat. Each of these nutrients has a set number of calories:
- 1 gram of carbohydrates = 4 calories
- 1 gram of protein = 4 calories
- 1 gram of fat = 9 calories
- 1 gram of alcohol has 7 calories
The FDA and United States Department of Agriculture (USDA) regulations require that ingredients be listed in order of their predominance in a food. This means that the ingredient used in the highest amounts will be listed first. This poses a problem when a perceived unhealthy ingredient was the predominant ingredient. For example, when people see sugar as the first ingredient in a cereal, they may be more likely to consider it unhealthy. The way that food manufacturers have gotten around this is to use different sources of sugar in smaller quantities. For example, a food containing 1 cup of sugar may have to have the sugar listed as the first ingredient, but smaller amounts of different sources of sugar could be listed throughout the ingredients.
Carbohydrates
Carbohydrates are the primary source of fuel for your body. Your red blood cells and most parts of your brain derive all of their energy from carbohydrates. An adequate consumption of carbohydrates also allows your body to use protein and fat for their necessary requirements, it prevents ketosis, it provides fiber, and it's the source of sweetness in your foods.
Carbohydrates are all made up of carbon, hydrogen, and oxygen, but they are not equal in terms of their nutritional value. This is where the concept of good and bad carbohydrates probably began. Based on the structure, carbohydrates are divided into two categories:
1. Simple carbohydrates
- Monosaccharide
- Fructose (fruit sugar)
- Glucose (blood sugar)
- Galactose (part of milk sugar)
- Disaccharide: two monosaccharides combined
- Sucrose: a combination of fructose and glucose (table sugar)
- Maltose: a combination of glucose and glucose
- Lactose: a combination of galactose and glucose (milk sugar)
- Polysaccharide: a combination of thousands of glucose units (starch, glycogen, fiber)
Contrary to what many people believe, carbohydrates are found in the majority of the food groups. They are found in
- grains,
- fruits,
- milk/yogurt, and
- vegetables.
- Choose fiber-rich fruits, vegetables, and whole grains often.
- Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts suggested by the USDA Food Guide and the DASH Eating Plan.
- Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and starch-containing foods and beverages less frequently.
- Adults and children should get 45%-65% of their calories from carbohydrates.
- Added sugars should comprise no more than 25% of total calories consumed. Added sugars are those incorporated into foods and beverages during production which usually provide insignificant amounts of vitamins, minerals, or other essential nutrients. Major sources include soft drinks, fruit drinks, pastries, candy, and other sweets.
- The recommended intake for total fiber for adults 50 years and younger is set at 38 grams for men and 25 grams for women, while for men and women over 50 it is 30 and 21 grams per day, respectively, due to decreased food consumption.
Proteins
Protein has numerous functions in the body:
- Regulates and maintains body functions: blood clotting, fluid balance, and enzyme and hormone production
- Supports growth and maintenance: hair, skin, nails, and cells
- Builds antibodies necessary for your immune system
- Provides energy
- kwashiorkor, which occurs when a diet has a marginal amount of calories and an insufficient amount of protein; and
- marasmus, which occurs when a diet has an insufficient amount of calories and protein.
- beans and rice,
- peanut butter and bread, and
- cereal and milk.
- Adults and children should get 10%-35% of their calories from protein.
- Using new data, the report reaffirms previously established recommended levels of protein intake, which is 0.8 grams per kilogram of body weight for adults; however, recommended levels are increased during pregnancy.
Fats
Dietary fat is required for
- energy: Fat is the most concentrated source of calories in the diet, providing 9 calories per gram compared with 4 calories per gram from either carbohydrates or protein;
- transport of fat-soluble vitamins: A, D, E, and K and carotenoids;
- maintenance of healthy skin;
- regulation of cholesterol metabolism; and
- precursor of prostaglandins (hormone-like substances that regulate many body functions).
- monounsaturated: olive oil, olives, peanut oil, canola oil, avocado, and nuts;
- polyunsaturated: safflower oil, sunflower oil, corn oil, fish, flaxseeds, and walnuts; and
- saturated: butter, lard, red meat, poultry skin, whole milk, coconut oil, and palm oil.
- olive oil: 15% saturated fat, 10% polyunsaturated fat, and 75% monounsaturated fat;
- lard: 43% saturated fat, 10% polyunsaturated fat, and 47% monounsaturated fat; and
- flaxseed oil: 9% saturated fat, 73% polyunsaturated fat, and 18% monounsaturated fat.
Trans fat has been found to be the most dangerous for our health. It's so dangerous that the guidelines are not to consume any in your diet. Recently, trans fat has been added to the food labels so that you can now determine if there is any present in the food. The one limitation is that you will only see foods with over 0.5 grams of trans fat per serving list any trans fat on their label. This means that if the serving size is two cookies and there is .4 grams of trans fat in two cookies, the trans fat content will be listed as 0 grams. However, if you eat eight cookies, you will actually be consuming 1.6 grams of trans fat. The way to determine if there is any trans fat present is to read the list of ingredients and look for hydrogenated or partially hydrogenated oil.
The cholesterol in your blood comes from your liver and your diet. The dietary sources are animal foods like meat, poultry, fish, and dairy products. The reason our livers produce cholesterol is because our body needs it. Cholesterol is used for producing cell membranes and some hormones, and serves other needed bodily functions.
The effects that dietary fat has on your blood cholesterol levels will help you choose which ones to consume. According to the American Heart Association, LDL (low-density lipoprotein) is the "bad" cholesterol because when too much of it circulates in the blood, it can slowly build up in the walls of the arteries that feed the heart and brain. HDL (high-density lipoprotein) is the "good" cholesterol because it helps remove "bad" cholesterol from arteries and prevent blockage. The goal is to have a
- total blood cholesterol less than 200 mg/dL;
- LDL less than 100 mg/dL; and
- HDL greater than 40 mg/dL for men and 50 mg/dL for women.
- saturated fat increases total cholesterol and LDL levels: the goal is for this to be less than 7% of your fat;
- trans fat increases total cholesterol and LDL levels and lowers HDL levels; and
- cholesterol over 300 mg/day can raise total cholesterol and LDL levels.
Dietary Guidelines for Fat
- Consume less than 10% of calories from saturated fatty acids and less than 300 mg/day of cholesterol, and keep trans fatty acid consumption as low as possible.
- Keep total fat intake between 20%-35% of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.
- When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free.
- Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose products low in such fats and oils.
- Adults should get 20%-35% of their calories from fat.
- Infants and younger children should get 25%-40% of calories from fat.
- The report doesn't set maximum levels for saturated fat, cholesterol, or trans fatty acids, as increased risk exists at levels above zero; however, the recommendation is to eat as little as possible while consuming a diet adequate in important other essential nutrients.
- Recommendations are made for linoleic acid (an omega-6 fatty acid) and for alpha-linoleic acid (an omega-3 fatty acid).
Fat-Soluble Vitamins
Vitamins fall into two classes: fat-soluble and water-soluble. Their solubility will determine how the vitamin is absorbed and transported by the bloodstream, whether or not it can be stored in the body, and how easily it can be lost from the body. Requirements for each of the vitamins are based on age, gender, pregnancy, and lactation. You can find them at http://www.iom.edu/Object.File/Master/7/296/
webtablevitamins.pdf.
The fat-soluble vitamins are A, D, E, and K. Adequate absorption of these vitamins is dependent on efficient fat intake and absorption. Except for vitamin K, fat-soluble vitamins are not easily excreted from the body, so they can be toxic at excessive levels. The only way to reach toxic levels would be through taking supplements, not through your diet. This is another case when balance is the key, and excessive amounts can cause harm.
Vitamin A is abundant in our food supply, so there is little risk of a deficiency. It is needed for regulation of the immune system, vision, reproduction, bone growth, cell division, and cell differentiation. A deficiency will result in night blindness and a decreased immune system, resulting in a decrease in the ability to fight infections. This can occur from an inadequate diet, chronic diarrhea, and an excess intake of alcohol. Dietary sources of vitamin A include
- whole eggs,
- milk,
- liver,
- fortified cereals,
- sweet potatoes,
- cooked spinach,
- fresh mango,
- cooked acorn squash,
- cooked kale,
- cooked broccoli, and
- margarine.
Vitamin D is needed for healthy bones by maintaining normal blood levels of calcium and phosphorus and for maintenance of a healthy immune system. A deficiency in children can result in rickets, and a deficiency in adults can cause osteomalacia. An inadequate diet, limited exposure to sunlight, and malabsorption can cause the deficiency. Dietary sources of vitamin D are
- cod liver oil,
- baked herring,
- salmon,
- canned tuna in oil,
- sardines in oil,
- milk,
- fortified cereals, and
- whole eggs.
- almonds,
- sunflower seeds,
- sunflower oil,
- wheat germ,
- peanut butter,
- avocado,
- hazelnuts,
- broccoli, and
- kiwi.
- kale,
- spinach,
- turnip greens,
- collards,
- Swiss chard,
- parsley,
- mustard greens, and
- Brussels sprouts.
Water-Soluble Vitamins
There are numerous B vitamins. Each one of them facilitates energy release in every cell, so a deficiency affects the entire body. Fortunately, deficiencies are rare when a diet is well balanced. These are the various B vitamins:
- Thiamin: Also known as vitamin B1, thiamin is involved in nervous-system and muscle functioning, the flow of electrolytes in and out of nerve and muscle cells, carbohydrate metabolism, and the production of hydrochloric acid. Very little thiamin is stored in the body, so depletion can occur in a little as 14 days. Chronic alcohol intake and an inadequate diet can lead to a thiamin deficiency. Beriberi is the deficiency disease for thiamin. Sources of thiamin are pork chops, sunflower seeds, green peas, baked potatoes, and enriched and whole grain cereals and pastas.
- Riboflavin: This B vitamin also plays a role in energy metabolism. It has similar function and sources as thiamin, so a deficiency in one usually means a deficiency in the other. Additional sources of riboflavin are milk and milk products and beef liver.
- Niacin: Along with its role in energy metabolism, niacin is also responsible for the synthesis and breakdown of fatty acids. Pellagra is the deficiency disease for niacin. Because the primary source of niacin is dairy products, poultry, fish, lean meats, nuts, and eggs, deficiencies can be found among the poor as well as in alcoholics.
- Folate: This vitamin became a mandatory addition to certain foods due to its role in producing and maintaining new cells. The folate fortification project was implemented for the protection of developing fetuses. A folate deficiency in a woman who is pregnant can cause neural tube defects that result in malformations of the spine (spina bifida), skull, and brain (anencephaly). Since the fortification of foods with folate began, the incidence of these defects has declined. Dietary sources of folate are fortified cereals, beef liver, pinto beans, lentils, spinach, asparagus, avocados, and broccoli.
- Vitamin B12: Like folate, vitamin B12 is needed for producing and maintaining new cells. It is also needed to maintain the sheaths that surround and protect nerve fibers. An inadequate amount of B12 causes pernicious anemia. Signs of vitamin B12 deficiency are fatigue, weakness, constipation, loss of appetite, weight loss, and numbness and tingling in the hands and feet. An excess intake of folate can mask the symptoms of B12 deficiency, so it's important to have your levels checked by a blood test, especially if you consume a vegetarian diet. Vitamin B12 is found in animal products like trout, salmon, beef, and dairy foods. There are fortified cereals that provide B12 as well.
Minerals
The primary functions and sources of the major minerals are
- Calcium: The primary mineral in bones and teeth is also needed for normal muscle contraction and relaxation, nerve functioning, and blood clotting. The dietary sources are milk and milk products, oysters, small fish, tofu, greens, and legumes.
- Phosphorus: This mineral makes up about 1% of your body weight. It is needed for bone and tooth strength, and it plays an important role in the body's utilization of carbohydrates and fats and in the synthesis of protein and in the maintenance and repair of cells and tissues. The dietary sources are dairy products and meat.
- Magnesium: This is required for nerve and heart function, bone strength, and to maintain a healthy immune system. The dietary sources are halibut, nuts, spinach, cereal, oatmeal, potato, peanut butter, and yogurt.
- Sodium: This is critical for nerve impulse transmission and helps to maintain cells' normal fluid balance. The guidelines for sodium consumption are to consume less than 2,300 mg (approximately 1 tsp of salt) of sodium per day and to choose and prepare foods with little salt. At the same time, consume potassium-rich foods, such as fruits and vegetables.
- Potassium: This is essential for the body's growth and maintenance and the contraction of muscles. It's also necessary to maintain a normal fluid balance between the cells and body fluids. Dietary sources are potato with the skin, prunes, raisins, lima beans, orange juice, tomato juice, acorn squash, bananas, spinach, and sunflower seeds.
- Chloride: Chloride is a part of the hydrochloric acid in the stomach that is necessary for proper digestion. The dietary sources are salt and processed foods.
- Sulfur: This is the only mineral that aids in drug detoxification. The dietary sources are all protein-containing foods.
- Iodine: This mineral is a component of thyroid hormones. The dietary sources are iodized salt, seafood, and dairy products.
- Iron: Iron deficiency is considered the number-one nutritional disorder in the world. It is needed to make hemoglobin, which is used to carry oxygen in the blood. When oxygen can't get to the cells, the symptoms will be fatigue, poor work performance, and decreased immunity. The dietary sources are liver, oysters, beef, turkey, chicken, and tuna.
- Zinc: This mineral is involved in normal growth and development, it's needed for a healthy immune system, it helps maintain your sense of taste and smell, and it is needed for wound healing. The dietary sources are seafood, meat, poultry, and whole grains.
- Fluoride: Pick up your toothpaste and you will see that it contains fluoride. The reason for this is because it increases resistance of tooth enamel to dental caries. Water is also fluoridated for this reason.
- Chromium: This mineral enhances the action of insulin. It also appears to be involved in carbohydrate, protein, and fat metabolism. Dietary sources are meat, unrefined grains, broccoli, garlic, and basil.
- Copper: Copper aids in forming hemoglobin, which is needed to carry oxygen to the cells. It is also involved in protein metabolism and hormone synthesis. The dietary sources are liver, cocoa, beans, nuts, whole grains, and dried fruits.
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