Part I - Nutritional Review Of The Macro & Micro Nutrients

Nutritional Review Of The Macro & Micro Nutrients
MacroNutrients
Carbohydrates
Protein
Fats
Micro Nutrients
Vitamins
Minerals
Free Radicals and Antioxidants
The Role of Supplements in a Healthy Diet

Nutritional Review Of The Macro & Micro Nutrients
Replenishment of micronutrients is a more delicate matter than the replenishment of macronutrients. No uncomfortable hunger pains come along with the process of cobalamin depletion. But these micronutrients are used up and excreted from the body as part of the continuous processes of metabolism, and they must be replaced at regular short intervals, preferably daily, so they are always available when they are needed.

Essential Nutrients
Most of the compounds (molecules) required by the body to sustain life and health are made (synthesised) within the various tissues and organs of the body, using the compounds obtained from the diet. The term "essential" applied to nutrients means that the body requires the compound for good health, but cannot synthesise it. The biochemical reactions that create this compound take place in some plant or animal species, and humans obtain it by eating food made from those plants or animals. The best-known example is vitamin C, which is absolutely necessary for a number of reactions in the human body but synthesised only in certain plants. Some essential nutrients can be obtained from dietary supplements. Our example, vitamin C, is an essential nutrient obtained from fruits and vegetables, or from supplements. Vitamins and minerals are, by definition, essential. There are also essential amino acids and essential fatty acids. Refer to The macronutrients section for more information about amino acids and fatty acids.

The Elements of Life
All of the molecules that make up all forms of life are composed of huge numbers of atoms of very few chemical elements: mainly carbon, oxygen and hydrogen, with lesser amounts of nitrogen and phosphorous. All of these elements are very abundant in the environment. Plants obtain them mainly from the air. Atoms of other elements can also be very important in nutrition but are required in much smaller numbers. For example, a hemoglobin molecule contains thousands of atoms of carbon, oxygen, and hydrogen, and exactly 4 atoms of iron. But without those 4 atoms of iron, hemoglobin is non-functional.

Polymers
The structural tissue and chemical entities in all organisms are composed of very complex molecules. Although the subject of "similarity" and "uniqueness" in biochemical molecules is a long and complicated one, a great many of these complex molecules can be grouped into a few large categories, based on structure and function, such as carbohydrates, fats and proteins. Many of these complex molecules are very large and are actually chains of similar, relatively small molecules (called monomers) tied together chemically. These chains are called polymers. Polymers made of certain types of molecular sub-units can have more specific names: e.g., proteins are polymers of amino acids; polysaccharides are polymers of sugar sub-units. All organisms, whether plants, animals, fungi, or bacteria, build their polymers out of similar monomers (e.g., amino acids, sugars). To a large extent, digestion is the process of breaking the polymers of the food substance into their constituent monomers; metabolism is, to a large extent, the process of reassembling those monomers into the particular polymers required by the body. When the required monomers are present in sufficient quantity; the body can renew itself structurally and carry on its life processes.

MacroNutrients - Carbohydrates or Protein and Fats

Carbohydrates
Carbohydrates are molecules made up of one, two, or many sugar molecules (saccharides). They contain only carbon, oxygen and hydrogen atoms. They are found primarily in foods of plant origin; however, milk contains lactose, a kind of sugar molecule. Refer to The Elements of Life and Polymers above for more details.

Simple and Complex Carbohydrates
In the context of nutrition, carbohydrates are categorised into simple carbohydrates (sugars), complex carbohydrates (starches), and fibre. Most plant-derived foods contain all three types. Starches and fibre are both polysaccharides. Plants make sugar molecules by photosynthesis, and then use them to fuel their metabolism. They store any excess sugar as starch. Grains (grasses) lay down starch in their seeds for use by their emerging offspring. Other plants store starch in their roots (turnips) or in underground stems (potatoes) for their own use when conditions impair photosynthesis. Much of the time, that starch is diverted to human or animal use. Note that, whether the plant or animal uses the starch, it is mostly broken down into its constituent sugar molecules, which are burned to fuel metabolism.

Fibre
Cellulose ("fibre") is also a polysaccharide, but those bonds between the saccharide monomers are of a different and much stronger type than in starch: whereas starches are easily broken down into their constituent sugars (nearly every organism can do this), cellulose cannot easily be disassembled and used for fuel even by the plant. Humans cannot digest cellulose. The cellulose humans consume passes though the digestive system and is eliminated from the body chemically unchanged. Fibre is the only indigestible substance that plays an important role in human health and nutrition.

Fibre stimulates the actions of the stomach and intestines and holds water, keeping the stool soft and mobile. This makes an inestimable contribution to quality of life. Optimal amounts of dietary fibre can increase the speed at which fecal matter passes though the intestine and is eliminated from the body, which appears to reduce the risk of some lifestyle and nutrition diseases. Soluble fibre can be broken down by the bacteria in the gut and include pectins hemicellulose and gums. Insoluble fibre includes cellulose, which is broken down to a limited extent and lignin, which can be broken down to by the intestinal flora. Certain types of fibre are "soluble", other types "insoluble." They have somewhat different actions: soluble fibre helps lower blood lipid levels and helps regulate blood glucose levels. Both types are beneficial to health.

Dietary Requirements for Carbohydrates
The average adult is advised to consume about 200 to 300 grams of carbohydrates every day. Carbohydrates are found in every balanced meal (and in many unbalanced ones). They are and always have been a major component of the human diet everywhere around the world except in the Arctic. Good sources of carbohydrates are grains and grain products, potatoes, fruits, and vegetables. For optimal nutrition, most dietary carbohydrates should be in the form of complex carbohydrates rather than sugars, and be accompanied by adequate fibre to assist digestion. Unrefined or (minimally refined) grain products are an ideal source of dietary carbohydrates.

Protein
Proteins are long, complex polymers of amino acids. Refer to The Elements of Life and Polymers, previous, for more details. Proteins from the diet are digested into their amino acids monomers, which are metabolised in different ways. Some are used more or less "as is" sub-units to synthesise molecules of the animal's own proteins. Others participate in various biochemical reactions that can change them (e.g., they can be made into a different substance by the addition or removal of atoms or groups of atoms).

Individual amino acid molecules or short chains of them participate in many ways in metabolism.

Like carbohydrates, amino acids are mainly composed of carbon, oxygen, and hydrogen; but they also contain atoms of other elements as well, notably nitrogen. The molecular structure of amino acids is much larger and more complex than the structure of saccharides. All structural tissues of the body are made largely of proteins: muscle, skin, bone, organs, blood vessels, brain. Proteins are also very chemically active in the body: enzymes are proteins, as are antibodies, some hormones, and some "transport molecules," which carry substances into and out of cells.

Special Proteins: Enzymes
Enzymes are proteins that function as biological catalysts. Each enzyme catalysts one specific reaction; each reaction requires its specific enzyme, and can take place only when that enzyme is present.

Dietary Requirements for Protein
There are many amino acids in nature, but the human body uses only 22 of them, combined in thousands of different ways, to make proteins. Of these 22 amino acids, 9 are "essential" (refer to Essential Nutrients, previous). Foods containing all 22 amino acids are called "complete proteins." These are usually from animal sources. Plant protein is usually "incomplete" (it is missing one or more of the essential amino acids). Different plant foods contain different amino acids, and can be combined to provide complete protein. Animal protein (meat) always contains a fairly large proportion of saturated fat as well (30-60 percent or more). Plant proteins contain much less fat; almost none of it saturated, and also provides fibre to help digestion. Plant protein foods includes legumes and some grains. Egg white is mostly protein, with no fat at all. Adults are advised to obtain 12-15 percent of their daily calories in the form of protein, about 60 grams per day. There have been no benefits demonstrated from consuming larger amounts. It is simply stored as fat or converted to sugar and burned. It is not converted to extra muscle mass, as some believe.

Fats
Dietary fats are an important component of nutrition. Fats are used extensively in metabolism for many purposes and serve other physiological functions such as energy storage and heat insulation.

Fatty Acids
Fats are made up of fatty acids, long chain carbon atoms with oxygen and hydrogen atoms attached. Three fatty acid chains attached to one molecule of a substance called glycerol comprise one "triglyceride," the form in which fat is found in food. Triglycerides are made and used in our bodies as well. Fats, also known as lipids, have many important roles in metabolism: they are components of cell membranes and of many classes of bioactive molecules such as hormones, lipoproteins and prostaglandins. They transport the fat-soluble vitamins.

Saturated and Unsaturated Fats
A molecule of fat (triglyceride) is saturated when it contains all the hydrogen molecules that it can carry. An unsaturated fat has one or more hydrogen "positions' unoccupied. In general, saturated fats tend to be of animal origin, and unsaturated fats are of plant origin. Although there are important exceptions both way, if a fat substance is liquid at room temperature, it is of plant origin and unsaturated. If a fat substance is hard at room temperature, it is of animal origin and saturated. Vegetable oil can be artificially saturated (hydrogenated). The product of the process is margarine or vegetable shortening. It was thought at one time that these fats did not bring the detrimental health effects of naturally saturated fats. Then it was acknowledged that the same health risks came with the same degree of saturation. In recent years, researchers have concluded that the hydrogenation process creates a substance called a "trans fat," which may actually be more detrimental to health than naturally occurring saturated fats. Saturated and trans fats have certain harmful effects in the body that unsaturated fats do not have: they are best known for raising lipid levels in the blood.

Dietary Requirements for Fats
Today's "prudent diet" gets no more than 30 percent of daily calories from fat. For most adults, that is about 60 to 70 grams per day. Of this, no more than one-third should be saturated fats (no more than 10 percent of total calories). Fats in the diet come from more than just the butter or mayonnaise you add to the food on the plate. Lean beef trimmed of all visible fat gets between 30 to 40 percent of calories from fat. Partly skimmed milk gets about 34 percent of calories from fat. Certain fatty acids are essential (refer to Essential Nutrients, previous), including linoleic acid, important for growth and development in infants. In developed countries there is very little chance of the diet being deficient in fat. In fact, many of our worst health problems are directly or indirectly caused or worsened by too much fat in the diet e.g. diabetes.

Micro Nutrients

Vitamins
Vitamins are essential micronutrients (ie, they are required by the human body for health; they cannot be synthesised in the human body and they are required in minute quantities). Vitamins can function as coenzymes; compounds necessary for certain enzyme-catalyzed reactions. About one third of all enzymes require a cofactor. In contrast to the enzyme, the coenzyme is destroyed in the reaction and must be replaced.

Water-soluble and Fat-soluble Vitamins
For organic chemicals and biochemicals, a major factor in their ability to participate in different kinds of reactions and processes is their "solubility," ie, whether the molecule dissolves in water, in fat, or neither. Some vitamins are fat-soluble; some are water-soluble.

The water-soluble vitamins are vitamin B and C vitamins. Water-soluble vitamins are absorbed directly from the intestine into the blood for delivery to the cells. They are filtered with the blood through the kidneys and eliminated in urine. They cannot be stored in the body and must be replenished frequently, preferably with every meal. The fat-soluble vitamins, A, D, E and K are absorbed into the lymph and can travel in the blood only when associated with protein carriers. These vitamins can be stored in body fat, and can reach toxic levels if over-consumed. Refer to Part II: Nutrient Review for more details on each of these vitamins.

Minerals
Minerals are the other major class of essential micronutrients. They too function as coenzymes in many reactions. Some minerals are required in daily quantities measured in milligrams (mg, one-thousandth of a gram), for example calcium, iron, phosphorous, potassium and sodium. Others, called trace minerals, are required in microgram quantities (mcg, one millionth of a gram): chromium, copper, fluoride and iodine. Excessive consumption of a mineral (megadosing) may have serious side effects. Most experts recommend staying within 1 to 2 times the RDA (Recommended Daily Allowance) for minerals.

Free Radicals and Antioxidants

Two Aspects of Oxygen
Oxygen, in the form of O2 (molecular oxygen found in air) is absolutely necessary for the life processes of nearly all organisms. For humans, oxygen deprivation causes death in just a few minutes. By contrast, we can live without water for several days, and without food for several weeks. The cellular infrastructure of nearly all organisms (and the infrastructure of much of "energy technology" from primitive fire pits to steam engines to coal-fired power plants) functions by using the awesome chemical power of oxygen in a very controlled way. This is usually referred to as burning. Cells burn glucose for energy by combining molecules of glucose with molecules of oxygen in a very controlled way.

Oxygen appears in other forms besides O2. Some biochemical reactions generate as a byproduct known as "free radicals": unstable oxygen-containing molecules with unpaired electrons. Hydrogen peroxide (H2O2), a by-product of numerous cellular reactions, is a molecule that differs from the ordinary water molecule in having an extra oxygen atom. It is a free radical. Four more free radicals are generated whenever the body is exposed to ultraviolet light rays, which are always present in sunlight. Free radical molecules are very reactive (hyperactive) ie; they will combine chemically with many different substances. These oxidation reactions sometimes create substances that are detrimental to health. Oxidised cholesterol is much more damaging to arteries. These oxidation reactions can also damage structural proteins, enzymes, or nucleic acids. Most of the reactions that generate free radicals are normal metabolic reactions. They are occurring every minute of every day the organism is alive. The exogenous (originating outside of the body) inducers of free radicals (UV light) are part of the normal environment and are to some extent inescapable. The damage free radicals can cause is minute but cumulative. Many of the processes we call "aging" can be considered manifestations of the minute, cumulative damage done by free radicals to tissue.

Countering Free Radicals
It is the essence of free radicals that they react with many different kinds of chemical substances. Certain substances have come to be regarded as antioxidants because the reaction of these substances with free radicals, continually being generated in the cellular environment, does no damage to the cell and prevents potential harmful, damaging chemical energy of the free radical and render it harmless to the cell. Some of these are endogenous (synthesised within the body), e.g., antioxidant enzymes; are available from the diet (betacarotene), some are both endogenous and available from the diet (vitamin A).

There has been much research in recent years into the medical and health effects of free radical reactions and the role of antioxidants in preventing much cellular damage. With only rare exceptions all studies have shown significant health effects from optimal levels of antioxidants. A much greater quantity of some vitamins is required for effective antioxidant activity as opposed to other benefits associated with the vitamin.

The current roster of nutrients considered "antioxidants" includes the following vitamins and minerals: betacarotene, vitamin A, vitamin C, vitamin E, and selenium. Refer to Part II: Nutrient Review for more detailed information on their antioxidant properties.

The Role of Supplements in a Healthy Diet
It is and has always been difficult to get optimal levels of some nutrients from the diet. Vitamin C is nutritionally obtainable mainly from fresh plant sources, which were, until recent decades, largely unavailable for several months of every year in many parts of the world. People expected to lose teeth as they aged, and they did.

Even now, with fresh citrus crops shipping nearly everywhere through the winter, it is very difficult to consume in food the antioxidants of vitamin C recommended by some experts. Four or five oranges a week provide enough vitamin C to prevent tooth loss from scurvy, but a dozen oranges a day would be required for effective antioxidant activity.

It is difficult to consume in food the levels of vitamin E now being recommended by some experts for the protective effects against disease-800mg daily. Vitamin E, a fat-soluble vitamin, comes dissolved in fatty food, so achieving the feat of getting 800mg daily from food would merely be substituting one health risk for another-morbid obesity. Supplementation is the only practical way.

Supplementation is the best way to ensure optimal levels of B vitamins as well. Many physicians and nutritional experts recommend that all women who are capable of becoming pregnant should consume 400mcg of folic acid daily to reduce the risk of certain birth defects (spina bifida, cleft lip, cleft palate, heart anomalies). Supplements are the surest way. Refer to Part II: Nutrient Review for more specific information on folic acid. The ability to absorb B vitamins from food decreases with age. Many elderly persons, even those consuming seemingly very good diets, are chronically deficient in niacin, folic acid, cobalamin (B12), and pyridoxine (B6). As research into the connection between nutrition and medicine continues, supplementation is ever more widely recommended at the top levels of medical science and policy.

[ back ]::[ next ]