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Facts about Nutrients

Posted on: 13-09-2007

Facts about Nutrients

Facts about Nutrients


Nutrients are chemicals in foods that are used by the body for growth, maintenance, and energy.

Macronutrients are nutrients required in large amounts

Micronutrients are nutrients needed in small or even minute amounts


I- Macronutrients

-         They constitute the bulk of diet

-         They supply energy and many essential nutrients (such as vitamins, minerals, etc…)


Macronutrients are:

A- Carbohydrates

      B- Proteins

C- Fats

D- Macrominerals

E- Water


Carbohydrates, fat, and proteins are sources of energy. Carbohydrates and proteins yield 4 kcal/g and fats yield 9 kcal/g.


  1. Carbohydrates:

Dietary carbohydrates are broken down into glucose and other monosaccharide. They increase blood glucose levels supplying energy.


- Simple carbohydrates are composed of small molecules. They are rapidly absorbed, such as glucose and sucrose.

- Complex carbohydrates are composed of larger molecules. They increase blood glucose levels more slowly and for a longer time, such as starch and fibers. 


  1. Proteins:

Proteins are required for tissue maintenance, replacement, function and growth. They can also be used as a source of energy especially if the body is not getting enough calories from other sources (like fat). During situations like starvation, infections, or burns, more protein may be used by the body. The protein requirement decreases from infancy to childhood and to adulthood (because it correlates with growth rate.) Adults who try to increase muscle mass need very little extra protein.


  1. Fats:

Fats are required for tissue growth and hormone production. Saturated fatty acids that are commonly found in animal fats tend to be solid at warm temperature (example: butter).

Unsaturated fatty acids usually derived from plants tend to be liquid at warm temperatures (example: canola oil, except for palm and coconut oils.)


  1. Macrominerals:


Examples of macrominerals are Sodium (NA), Potassium (K), Chloride (Cl), Calcium (Ca), Phosphorus (P) and Magnesium (Mg). They are required in relatively large amounts. The principal sources are:


Ca :  milk, milk products, meat, fish, cereals, beans


K :  bananas, prunes, raisins, meat


Mg : Green leaves, nuts, cereal, grains, seafood


P : Milk, cheese, meat, poultry, fish


Na: beef, pork, sardines, cheese, green olives, urn bread



  1. Water


Water is required in large amounts, almost 2500 ml. The need of water changes according to fever, warm and cold climates, high or low humidity.


II- Micronutrients


Micronutrients are vitamins and minerals required in minute amounts.


Other Dietary Substances


The daily human diet typically contains as many as 100, 000 chemicals. Of these chemicals, only 300 are nutrients, only some of which are essential. However, many nutrients in foods are useful.


Example: Food additives (such as emulsifiers, preservatives, etc.)


Only certain amounts of additives shown to be safe by lab tests are permitted in commercially prepared foods.

Example: Trace Components (spices, flavors, aromas) which  are added to improve appearance and taste


However, weighing the benefits of additives against the risk is often complex.


Contaminants: they are substances that sometimes can not be eliminated completely without damaging foods, so limited amounts are permitted (ex: heavy metals, pesticides, hormones, animal hairs, etc…)


Nutritional Requirements:


Proper nutrition aims at achieving and maintaining a desirable body composition and high potential for physical and mental work. Pregnant women and infants have special nutritional needs. Balancing energy intake with energy expenditure is necessary for a desirable body weight. Energy expenditure depends on:


-         age

-         sex

-         weight

-         metabolic activity

-         physical activity


If energy intake exceeds expenditure, weight is gained. If energy intake is less than expenditure, weight is lost.


The table below lists the amount of food per serving for each food group, while the food pyramid (please refer to Top) illustrates the nutritional needs for an average adult.


Food Group

Serving Sizes

Bread, cereal, rice, pasta

1 slice of bread

1 oz (30 cc) ready-to-eat cereal

½ a cup cooked cereal, rice or pasta


¾ cup of fruit juice

1 medium apple, banana or orange       

½ cup chopped, cooked, or canned fruit

Meat, Poultry, fish, eggs,

Dry beans, and nuts

½ cup cooked dry beans

2-3 oz cooked lean meat, poultry or fish

1 egg or two tablespoons peanut butter

Counts as 1 oz of lean meat

Milk, yogurt, cheese

1 cup of milk or yogurt

1 ½ oz natural cheese

2 oz processed cheese


¾ cup vegetable juice

1 cup raw leafy vegetables

½ cup other vegetables, cooked or chopped Raw


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