Carbohydrates are the main energy source, comprising at least 50-60% of the dietary intake. Each gram of glucose releases 4 calories of energy.
Carbohydrates can be further subdivided into simple and complex compounds. Simple carbohydrates are converted to glucose very rapidly, resulting in a rise in blood sugar levels after consumption. Examples include sweets, sugar, biscuits and other confectionery products.
Complex carbohydrates have more complicated molecular structures, so the energy released from metabolism is spread over a longer period of time. Examples include rice and pasta, particularly if they have not been refined. Complex carbohydrates are the best source of energy for endurance athletes as they provide an immediate and sustained source of energy.
Carbohydrates are needed for the regulation of protein and fat metabolism.
Food containing high levels of both carbohydrates and fiber, like fruits and vegetables, help in optimal colonic function. This is thought to help prevent diseases like colon cancer and diverticular disease.
The liver converts excess glucose into glycogen. Once the body's glycogen stores are full, the remainder is converted to fat. As a result, the consumption of excessive carbohydrate calories even in combination with a low-fat diet and inadequate exercise can result in weight gain.
Twenty percent of our body composition is protein. Proteins and their peptide precursors are essential for healthy musculoskeletal and hormonal function. The consumption of adequate dietary protein is particularly important during childhood, pregnancy and lactation.
Like carbohydrates, each gram of protein releases 4 calories of energy.
Proteins are complex molecules made up of 22 amino acids. Some amino acids are considered as essential, which are obtained from the diet. The consumption of a purely vegetarian diet may lead to deficiencies in a couple of these essential amino acids. Proteins from animal sources contain 8 essential amino acids.
Around 60-70% of the amino acids used in metabolism are recycled from old tissue proteins.
Amino acids are used to build enzymes, hormones and muscles.
Excess proteins are converted to fat. Starvation will cause muscle breakdown and the release of muscle protein for energy. This in turn reduces the basal metabolic rate.
Protein deficiency results in weight loss and a multitude of functional problems.
Fats are the energy storing substance. Each gram releases 9 calories of energy.
The main source of dietary fat is meat and dairy products. However, some vegetable products also have a high fat content. These include nuts, seeds, avocadoes and olives.
Fat stores not only provide energy in times of lack, they also provide insulation from cold and trauma. Fat absorption is necessary for fat-soluble vitamin absorption. These include vitamins A, D, E and K. Fats are also essential components of cellular membranes.
Dietary fats comprise of triglycerides and cholesterol. Excessive fat consumption results in obesity. The maximum calorie contribution from fat should not exceed 25%. In the presence of cardiovascular disease, a dietary intake of 10-20% fat may slow down disease progression by a corresponding reduction in blood lipid levels.
The current accepted wisdom for weight loss, maintenance of healthy body weight and general good health involves a diet that is low in dietary fat whilst maintaining adequate protein and carbohydrate intake.
Nonetheless, the consumption of a minimal amount of fat, particularly the essential fatty acids, is essential for the normal function of the central nervous system and the production of hormones and other cellular messengers.
Vitamins are classified as micronutrients that are essential in human nutrition. They are organic in that they contain the element carbon and are found in plant and animal substances in small amounts. We obtain them by eating the plants and animals that produce them.
Most vitamins cannot be manufactured in our body, except for some of the B vitamins, which can be made by our intestinal bacteria, and occasional biochemical conversions from a precursor to the active form of the required vitamin, as when beta-carotene is converted to vitamin A.
Vitamins are not a source of energy which we obtain from macronutrients such as carbohydrates, proteins and fats. In fact vitamins help to convert these macronutrients into more bioavailable or metabolically useful forms.
We need food and certain minerals to best absorb any vitamin supplement we take. Vitamins are essential for growth, vitality, and health and are helpful in digestion, elimination of and resistance to disease. Depletion of vitamins can lead to a variety of both specific nutritional disorders and general health problems, depending which vitamin is lacking in the diet.
Vitamins are usually classified as water-soluble and fat-soluble and further categorized by letters, groups and individual chemical names.
Water-soluble vitamins include mainly the many B vitamins and vitamin C. They are stable in raw foods but may be lost easily during the cooking and processing. Commonly found in the vegetable foods, these vitamins are contained less so in most animal sources. The water-soluble vitamins are mostly not stored in the body, so they are needed regularly in our diet; this makes them much less potentially toxic than the fat-soluble vitamins, which are stored when taken in higher dosages. Most of the water-soluble vitamins function in the body as coenzymes in combination with an inactive protein to make an active enzyme.
Fat-soluble vitamins are vitamins A, D, E and K that are found in the lipid component of both vegetables and animal source foods. These fat-soluble vitamins can be stored in the body tissue so they can function for a longer period of time than the water-soluble ones. For this reason, toxic levels can occur more easily from a regular increased intake of these vitamins, especially vitamin A. Vitamins D and K can also cause problems when taken in high dosages. Toxicity is less likely with vitamin E, since it is used readily by the body as an antioxidant to help protect against the harmful by-products of metabolism and against outside pollutants. Vitamin A adds cellular protection as well as resistance to infection, while vitamin D aids in the absorption of calcium from the gut and thus is important to skeletal health. Vitamin K promotes blood clotting and prevents bleeding.
Uses of Vitamins
Vitamin supplements to our diet can be used as a preventive approach to maintain or improve health -- characterized as a basic state of vitality and involvement with life.
Vitamins may also be used in the primary treatment or in the support of other treatment for a variety of symptoms, short-term illnesses, and chronic diseases.
Nutritional supplements are being used increasingly by nutritionists, GPs, and individuals as treatment for a multitude of ailments. And many are helpful. An extra positive benefit is that vitamins rarely ever make matters worse, although they may produce effects such as diarrhea or other detoxification symptoms.
Since vitamins and minerals are essential constituents of vegetable and animal foods, it is important that they are viewed as "food supplements" -- best to be digested and assimilated when taken with or following food. The B vitamins, Vitamin C and the minerals, all of which are water-soluble, especially need to be dissolved and digested with food before they can be assimilated and thereby used by the body.
The fat-soluble vitamins can be utilized when taken alone either in the morning before breakfast or at bedtime. They can be taken after meals consisting of fat-containing foods.
For people who have energy related problems, such as fatigue, hyperactivity, or insomnia, it is advisable to have a supplement plan where they take their B vitamins early in the day with breakfast and lunch and their minerals, such as calcium and magnesium, later in the day and before bed. The B vitamins tend to be stimulating, while the minerals tend to be relaxing and balancing to the muscles and nervous system.
Minerals or elements come from the earth and eventually return to the earth and can most simply be defined as chemical molecules that cannot be reduced to simpler substances.
Approximately 4-5% of our body weight is mineral matter, and most of that is in our skeleton. Minerals are also present in tissue proteins, enzymes, blood, some vitamins and so on.
If the human body were left to decompose completely, most of the organic tissues which are made up of proteins, carbohydrates, and fats would break down into water, carbon dioxide and nitrogen that either evaporate into the atmosphere or enter the soil. What is left would be about five pounds of elemental mineral ash. Of this, about 75% would be calcium and phosphorous, mostly from the bone; there would be about one teaspoon of iron, a couple of teaspoons of salt, and a little more of potassium; and the rest of the ash would contain numerous other elements.
Most of the calcium and phosphorous are in the bones, but some are also present in the blood and in every cell. Calcium particularly is vital to the heart and muscle function and nerve conductivity.
Other elements contained in the body include some of the toxic metals, which may cause harm in relatively high concentrations.
Metal poisoning primarily affects the metabolic enzymes, brain, and nervous system, but it can affect many other bodily functions as well. In addition to these toxic metals, some essential elements such as copper, arsenic, iodine, selenium, chromium and even iron and calcium are more likely than other minerals to cause health problems when high levels are present in the body, resulting from either an excessive intake or a reduced ability to eliminate them.
What Can Minerals Do for Us
Like vitamins, they contain no calorie or energy in themselves but assist the body in energy production. Although our bodies can manufacture some vitamins, we make no minerals. Natural minerals come from the earth. If a mineral nutrient is not contained in the soil, it will not be in the food grown there. Fruits and vegetables grown in rich, well-nourished soils obviously will have more of the essential minerals we need for our health and vitality.
Like vitamins, minerals are essential to our physical and mental health and are a basic part of all cells, particularly blood, nerve and muscle cells, as well as our bones, teeth, and all soft tissues. Minerals offer us both structural and functional support. The special electrolyte minerals -- sodium, potassium and chloride -- help regulate the fluid and acid-base balance of our bodies. Other minerals are part of enzymes that catalyze biochemical reactions and aid the production of energy or participate in metabolism. Some minerals also help in nerve transmission, muscle contraction, cell permeability, and blood and tissue formation.
Our basic body acid-base balance is slightly alkaline, so more of our diet should consist of alkaline-forming foods, primarily the fruits and vegetables. Interestingly enough, these foods usually have a relatively high mineral content. Even though many people think of citrus foods as "acidic", they are actually alkaline in function -- that is, they create an alkaline residue. Meats, dairy foods, and most nuts, seeds, and grains decompose with an acid residue, so too much of these may throw off the body's pH.
Most minerals are not destroyed by heat, but some are soluble in water and therefore are lost or leached out during the cooking process.
Many minor and major problems can arise from mineral deficiencies. A well-known condition is osteoporosis -- a loss of bone minerals due to a long-term, low-calcium intake. Low calcium and probably low magnesium levels may contribute to hypertension, as do high sodium with lower potassium levels. Magnesium deficiency has also been associated with muscular spasms and nerve-related pain and, more recently, with acute heart attacks. Low zinc or selenium levels may hinder the immune system and make us prone to infection. The list goes on.
The healthiest approach for ensuring optimum mineral levels is to get the majority of them from wholesome foods. Eating a variety of foods, with a lot of organic, local produce and grains is a good start.
Avoiding refined and processed foods that have poor mineral content or high-sugar foods, caffeine, and alcohol, all of which can "flush" or deplete body minerals, is also helpful.
Eating a calcium-rich diet has been confused with drinking lots of milk, which poses potential health concerns related to fat intake. Raw nuts and seeds, whole grains, and leafy greens can provide adequate amounts of calcium. If we orient ourselves to the healthiest of diets -- eating a variety of wholesome foods, we will assure ourselves the basics of good mineral nutrition.