Energy and nutrient need of human body

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Energy and nutrient

An adequate, healthy diet must satisfy human needs for energy and all essential nutrients. Furthermore, dietary energy needs and recommendations cannot be considered in isolation of other nutrients in the diet, as the lack of one will influence the others. Thus, the following definitions are based on the assumption that requirements for energy will be fulfilled through the consumption of a diet that satisfies all nutrient needs.

Energy requirement is the amount of food energy needed to balance energy expenditure in order to maintain body size, body composition and a level of necessary and desirable physical activity consistent with long-term good health. This includes the energy needed for the optimal growth and development of children, for the deposition of tissues during pregnancy, and for the secretion of milk during lactation consistent with the good health of mother and child.

The recommended level of dietary energy intake for a population group is the mean energy requirement of the healthy, well-nourished individuals who constitute that group.

energy requirements is the prescription of dietary energy intakes that are compatible with long-term good health. Therefore, the levels of energy intake recommended by this expert consultation are based on estimates of the requirements of healthy, well-nourishedindividuals. It is recognized that some populations have particular public health characteristics that are part of their usual, “normal” life. Foremost among these are population groups in many developing countries where there are numerous infants and children who suffer from mild to moderate degrees of malnutrition and who experience frequent episodes of infectious diseases, mostly diarrhoeal and respiratory infections. Special considerations are made in this report for such sub-populations.

Carbohydrates

Two of the three carbohydrates — sugars and starches — serve as the body’s preferred source of energy. During digestion, they’re broken down into glucose, which is quickly converted into energy that can be used by every cell. Some glucose is stored in the liver and muscles so that you have energy ready whenever it’s needed. Excess glucose is converted into fatty acids and stored as fat. One significant difference between the two is that sugar provides energy without nutrients, but starches, or complex carbohydrates, deliver energy plus vitamins, minerals and fiber. Fiber is the third type of carbohydrate, but it is not digested. Insoluble fiber adds bulk that keeps food moving through the digestive system, and soluble fiber helps lower cholesterol and keeps blood sugar balanced.

Proteins

Proteins consist of long chains of amino acids. When you eat proteins, they’re digested into the individual amino acids, which your body then uses to build the specific proteins it needs. Amino acids aren’t stored in the body, which means that it’s essential to get a regular supply from your daily diet. Every part of your body needs protein because it’s responsible for the structure, growth, repair and function of cells, tissues and organs. Just one example: you can’t maintain lean muscle mass without protein. Hemoglobin, antibodies, enzymes and some hormones are all made from proteins.

Fats

In spite of their bad reputation, fats are an essential part of your diet because they ensure normal growth and development. Fats form the structure that supports cell walls, cushion your organs and help produce hormones. Vitamins A, E, D and K can’t be properly absorbed unless fats are present. Saturated fats and cholesterol are “bad” fats because they contribute to heart disease. Trans fats, which are identified as hydrogenated vegetable oils, should also be avoided because they raise cholesterol. The best way to add fats to your diet is by consuming healthy unsaturated fats — monounsaturated and polyunsaturated — which actually lower cholesterol and help prevent inflammation.

Requirements

Men and women need 130 grams of carbohydrates daily, preferably from complex carbohydrates, such as whole grains, seeds, nuts, fruits, vegetables and beans. Men should include 56 grams of protein in their daily diet, while women need 46 grams. Some of the highest sources of protein also have saturated fat and cholesterol, so the healthiest choices include poultry, fish, beans, lean meat and low-fat dairy products. Your total daily fat consumption should not exceed 20 to 35 percent of your daily calories. Saturated fat should be limited to less than 7 percent of total daily calories and cholesterol shouldn’t exceed 300 milligrams. Healthy fats come from vegetable oils, nuts, seeds and fish.

Vitamins and Minerals

Vitamins and minerals are needed in very small amounts, hence they are sometimes called micronutrients, but are essential for good health. They control many functions and processes in the body, and in the case of minerals also help build body tissue such as bones (calcium) and blood (iron). 

The important vitamins are: vitamin A; the B vitamins including thiamine, niacin and folate; vitamin C and vitamin D. Vitamin A helps to prevent infections, is essential to keeping the eyes healthy and helps children grow properly. Food rich in vitamin A include: orange and yellow fruit and vegetables including mangoes, carrots, sweet potatoes and pumpkins; dark green vegetables for example spinach; liver and eggs. B Vitamins including Thiamine, Niacin and folate help the body burn nutrients to release energy and for building and repairing the body’s tissues. Sources of B vitamins include: dark green vegetable; meat, poultry and fish; liver; milk and eggs.

Vitamin C helps the body to absorb iron and to use nutrients to build bones and blood vessels. Most fruit, especially citrus fruit and many vegetables including potatoes are good sources of vitamin C. Vitamin D helps the body absorb and use calcium to build healthy bones and teeth. Vitamin D is found in fish oils, eggs, milk, cheese and liver and is also produced by the body when the skin is exposed to sunlight. The important minerals include iron, calcium, iodine and zinc.

Iron is needed to make red blood cells, which are essential for getting oxygen from
the lungs to all the other parts of the body and also helps all of the body’s cells
working properly. The best sources of iron are meat, fish, liver and other organ meats and dark green leafy vegetables. Calcium is needed for healthy bones and teeth. Milk and other dairy products are the best source of calcium.

Iodine is needed for proper growth and development of the brain and nervous
system. Iodine comes from the soil, so the amount of iodine in food depends on how much iodine there is in the soil. Soils low in iodine are found mainly in upland, mountainous areas and in places where there are frequent floods. Fish and other foods from the sea (eg. sea salt) are usually rich in iodine, because they get iodine from the seawater.


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