It is ingeniously convenient that eating is one of life's great pleasures. Besides providing a reason for culinary artistry and entertaining our taste buds, the consumption of food equips our bodies with the necessary carbohydrates, proteins and fats we need to create energy. Converting gastronomic fuel into energy, the process of metabolism, is how we grow and replace cells, fight infection and disease, preserve good health and remain psychologically fit. Every calorie (a unit of measurement expressing the energy-producing value in food when oxidized in the body) consumed influences health.

How does this metabolic process work? First of all, just like your car in the driveway, your body needs a regular supply of fuel to keep running. Interestingly, the ultimate source of fuel in living organisms is the sun. Remember photosynthesis? That's when sunlight shines on the leaves of plants, stimulating their chlorophyll-containing tissues to convert carbon dioxide and hydrogen into glucose. Protein, fats and carbohydrates are synthesized from glucose, so when we eat plants and plant-fed animals, we obtain these nutritive fuels needed for energy synthesis. Energy synthesis in turn powers the maintenance of body tissues, electrical conduction in nerves, mechanical work of muscles, hear production to maintain body temperature-all the vital functions our bodies instinctively perform to sustain life.

It's important to understand the components of advanced nutrition so you may energize your body most effectively. As in the case of the car, which must be filled with specially designed fuel in order to protect engine health we need to make educated dietary decisions since every ounce we ingest has such a significant job to do. If you've ever seen the effects of sugar or diesel introduced into an unleaded gas tank you are acquainted with the results of incorrect fueling! The following nutritional tutorial was designed to identify and explain the fundamental ingredients that, when consumed in correctly balanced proportions, amount to a nourishing and beneficial diet.

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Carbohydrates

Fifty to seventy percent of all calories ingested in the human diet come from carbohydrates. Carbohydrates come in the form of simple sugars, complex carbohydrates (starches) or dietary fibers (celluloses), depending on their varying composition of carbon, hydrogen and oxygen. Some examples of simple sugars are table sugar, honey, high fructose corn sweetener (found in soft drinks and other manufactured sweetened products,) maltose, and lactose. Starches include whole grains, potatoes, cereals and pasta; dried peas and beans, vegetables, and fruits are all forms of celluloses.

When carbohydrates of all forms are digested, the end product is glucose. Absorbed from the digestive tract, glucose enters the bloodstream, is oxidized (combined with oxygen) and delivered as energy to the cells or stored in muscle or liver tissue in the form of glycogen. Under normal conditions, glucose is the lone fuel source for the central nervous system.

It's the time it takes to digest a carbohydrate that determines its significance as a fuel to nutritionists. When a simple sugar is ingested, it swiftly elevates blood sugar levels because digestion time is minimal. Normal blood glucose levels range from 70 to 100 mg/100ml. However, glucose derived from simple sugars burns quickly, requiring a continual input to keep blood sugar control mechanisms steady. Because complex carbohydrates such as starches, glycogen and cellulose are a series of linked simple sugar molecules, they take longer to digest, producing a slower and more stable supply of glucose and keeping us functioning effectively for longer periods of time than simple sugars. Starch and glycogen are generally completely digestible; cellulose and other complex carbohydrates, if indigestible, provide fiber in the intestines.

Dietary fibers can be categorized into two types: soluble and insoluble. Soluble fibers include pectins, gums, and mucilages. Pectins are found mostly in fruits and vegetables, especially apples, oranges and carrots. Other forms of soluble fiber occur in oat bran, barley and legumes. Soluble fiber absorbs water and forms gels, becoming bulky in the stomach and remaining so throughout the intestinal track. This promotes good intestinal health by increasing mobility and transit time, and creating an environment that enhances the growth of "'good bacteria." Soluble fiber acts as Liquid Plumber does in your clogged drain-breaking up and sweeping away congestion-keeping the pipes clean and running smoothly. Research proposes that increased soluble fiber in the diet correlates with controlling blood sugar and cholesterol levels, decreasing the incidence of colon cancer, and aiding in weight control. Insoluble fiber, on the other hand, absorbs little water and adds bulk only in the lower intestine. A major source of insoluble fiber is from whole grain breads and cereals. Insoluble fiber increases transit time of material in the colon.

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Protein

Protein is a fundamental building block of the world around us and is the most plentiful substance in the human body second to water. The body uses protein to shape the major cellular structural elements for blood, bone tissue, muscles, skin, hair, nails and internal organs like the brain and heart. Vital for the creation of enzymes (biochemical catalysts) and antibodies (proteins which help fight foreign substances in the body) as well as hormones, which regulate growth, sexual development and rate of metabolism. As the food we eat digests, protein molecules are disintegrated into small units called amino acids. The human body requires approximately 22 amino acids in a specific pattern to synthesize body protein and other tissues, and the body itself can produce all but eight of these amino acids. The eight that must come from an outside source are termed "essential amino acids," and in order for the body to effectively process and produce protein from the amino acid building blocks, all essential amino acids must be supplied in the diet in proper proportions. If just one is missing or in insufficient amounts, protein synthesis becomes sluggish or ceases entirely.

Therefore, just because one eats foods containing protein does not guarantee intake of all the essential amino acids. A "complete protein" refers to foods rich in all 8 essential amino acids, while an "incomplete protein" lacks one or more. Eggs, meat, fish and dairy products are complete protein foods, while fruits and vegetables are incomplete. That is why is it so necessary to carefully combine these foods to create a balanced meal, mixing two or more sources of protein so that they will complement each other and provide in one source an amino acid lacking in another. For example, in the familiar combination of rice and beans, the essential amino acid absent in rice is abundant in beans.

Your minimum daily protein requirement depends on a variety of factors, including the type of protein, your body size and activity level. Getting the balance right for optimal health and cellular growth can be difficult and entails attentive planning. The National Research Council's Recommended Dietary Allowance was formulated to help individuals calculate proper protein intake amounts, suggesting a consumption of .42 grams of protein per pound of body weight each day. To gauge the right amount, divide your body weight by 2 and this is the approximate number of grams of protein you need each day; for instance, if you weigh 120 pounds, you need about 60 grams of complete proteins daily. However, this amount fluctuates depending on the essential amino acid composition of the foods you eat.

Fats

Fats, or lipids, are the most concentrated sources of energy you can eat - when oxidized, fats provide twice the number of calories per gram furnished by carbohydrates or proteins - one gram of fat generates 9 calories in the body. Since dietary fats pack such a punch, it's important to consume them in limited amounts - a little fat goes a long way. But we definitely need them since not only do fats act as carriers for fat-soluble vitamins such A, D, E and K and are necessary to the conversion of carotene to vitamin A; fats also help the body absorb vitamin D, thus making calcium accessible to body tissues, especially teeth and bones. The layer of fat under our skin protects us from external environments and regulates our body temperature and internal fat deposits cushion and hold the organs in place. Moreover, fats slow the digestion process by slowing the stomach's secretions of hydrochloric acid, thus extending fullness sensations longer.

It' helps to know a bit of the biochemistry behind fats in order to consume the right kind and avoid dietary fats that are harmful to the body in excessive amounts. The molecules that formulate fats and influence their flavor, texture and melting point are called the "fatty acids." The three types of fatty acids, monounsaturated, polyunsaturated and saturated, are determined by the number of hydrogen molecules connected to the basic fatty acid and glycerol (a type of alcohol) that make up dietary fat molecules known as triglycerides.

Saturated fatty acids contain the maximum number of hydrogen molecules the triglyceride chain can hold. Although all foods contain some sort of mixture of saturated fatty acids, the largest concentration of these can be found in animal products such as beef, chicken or pork and dairy products, and in the vegetable products of palm oil, palm kernel oil and coconut.

This is where cholesterol comes into the picture. Cholesterol is a necessary lipid-related substance, present in our cells and body fluids, that regulates membrane fluidity and functions as a precursor molecule in various metabolic pathways. However, there are two very different types of cholesterol. High density lipoprotein (HDL) is a cholesterol-poor and protein-rich lipoprotein of blood plasma, while low density lipoprotein (LDL) is cholesterol-rich and protein-poor. Numerous studies have confirmed that HDL ( called good cholesterol) reduces and LDL (called bad cholesterol) contributes to the build up of these blood plasmas in our veins that lead to arteriosclerosis.

The more saturated fatty acids an individual consumes, the higher their serum cholesterol levels are, increasing risk of heart disease. In fact, medical studies concerning populations and nutrition have consistently found that countries with the highest saturated fatty acid consumption also had the highest serum cholesterol levels and coronary heart disease mortality. Thus, nutritionists strongly recommend that no more than 7% or less of total fat calories come from saturated sources.

However, this doesn't mean that all lipids should be avoided. On the contrary, just like essential amino acids, there are three fatty acids that cannot be produced by the body and therefore must be consumed in the diet. Linoleic, arachidonic and linolenic, collectively known as vitamin F, are essential unsaturated fatty acids necessary for healthy blood, arteries and nerves as well as lubricating the skin and internal tissues.

Monounsaturated fatty acids (MUFAs) contain one double bond, meaning that they are less flooded with hydrogen than saturated fatty acids. Oleic acid is the most common monounsaturated fatty acid, and olive oil, canola oil, peanut oil, peanuts, pecans, almonds and avocados are concentrated food sources. MUFAs are believed to help lower LDL cholesterol (the bad kind), while maintaining levels of HDL cholesterol (the good kind). It is recommended that in a diet with no more than 30% of the calories coming from fat, 10% of the fat be from sources of MUFAs.

Polyunsaturated fatty acids (PUFAs) contain the least hydrogen. The predominant PUFA in the diet is Linoleic acid and from sources such as vegetable seeds and the oils they produce, such as corn, soybean, safflower and sunflower oils. More important are the two groupings of PUFAs, Omega 3 and Omega 6. These fatty acids are not interchangeable, and have very different biochemical roles in the body. Linoleic acid, an omega-6 fatty acid, and linolenic acid, an omega-3 are the parent compounds for other biologically active fatty acids such as those that play a role in early brain development, in hormones that regulate blood pressure, blood clotting, immune responses and other functions.

Derivatives of the essential omega-3 fatty acid linolenic are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Fish oils and shellfish are rich in EPA and DHA and have been proven to lower total cholesterol and triglycerides in the presence of saturated fat intakes, reducing the risk for heart disease. Omega-3 fatty acids affect many other stages of artheroma (fatty deposits in an artery), including interfering with blood clotting. High consumption of omega-3 prolongs bleeding time; a factor observed among Eskimo populations who consume large amounts of fish and have a low incidence or coronary artery disease. However, since PUFAs lower both LDL and HDL cholesterol levels, nutritionists advise that of the 30% caloric intake of fat in the diet, less than 10% be from PUFAs.

Manufacturing margarines from oils produces trans-fatty acids, another lipid grouping. In the process of hydrogenation, unsaturated oils are converted to a more solid form of fat. The harder the fat (as in stick margarine vs. tub margarine), the higher the amount of trans-fatty acids. Snack foods, cookies and crackers containing hydrogenated vegetable oils are a source of trans-fatty acids in the typical American diet. Research has shown that consuming trans-fatty acids in high amounts such as this will raise LDL cholesterol levels, but to a lesser extent than saturated fatty acids. Therefore, in terms of your LDL/HDL intake, using margarine as a spread on French bread is an improvement over regular butter, but using olive oil would be better.