nutrients

Did you know that organisms need nutrients to survive? Different organisms use different means to acquire these nutrients. For example, most plants acquire nutrients from the soil through the roots. People and animals get most of their nutrients from food. Let's find out more.

LEARNING OBJECTIVES

By the end of this lesson, you should be able to:

• Describe nutrient
• Explain sources of nutrients
• Explain the classification of nutrients
• Describe essential nutrients
• Explain different food sources of nutrients

The term nutrient refers to a substance that is used by an organism for its survival, growth and reproduction. Dietary nutrient intake requirements apply to plants, animals, protists and fungi. Nutrients may be incorporated into cells for purposes of metabolism or they can be excreted from cells and create non-cellular structures like hair, feathers, exoskeletons or scales. Some nutrients can be converted metabolically to smaller molecules in the energy-releasing processes, such as for lipids, proteins, carbohydrates, and fermentation products (vinegar or ethanol), leading to water and carbon dioxide as the end products. All organisms need water. Essential nutrients for animals are those that provide energy, some amino acids that combine to create proteins, vitamins, a subset of fatty acids and some minerals. Plants need more diverse minerals. Plants absorb their nutrients through the roots, plus oxygen and carbon dioxide through the leaves. Fungi live by feeding on living or dead organic matter thus meeting nutrient needs.

Different organisms have different essential nutrients. Vitamin C (ascorbic acid) is essential. This means that it must be consumed in enough amounts, to humans as well as some other animal species but not to plants and not to all animals. Plants are able to synthesize it.

Nutrients can be organic or inorganic. Organic nutrients are mainly made up of compounds that contain carbon. All the other chemicals are inorganic. Inorganic nutrients include nutrients like zinc, iron and selenium. Organic nutrients on the other hand include vitamins and energy-providing compounds among others.

CLASSIFICATION OF NUTRIENTS

A classification that is primarily used to describe the nutrient needs of animals classifies nutrients into micronutrients and macronutrients.

• Macronutrients are consumed in large amounts. They include carbohydrates, proteins, fats and water. They are used primarily for energy generation or they are incorporated into tissues for repair and growth. Water is a macronutrient in the sense that the body needs it in large amounts, but it does not contain carbon or yield energy.
• Micronutrients are required in smaller amounts (micrograms or milligrams). They have subtle physiological and biochemical roles in cellular processes such as nerve conduction and vascular functions.

Lack of enough essential nutrients or diseases interfering with absorption lead to a state of deficiency. This state compromises survival, growth and reproduction. Excessive amounts of nutrients can also have harmful effects. Water must be consumed in large quantities.

Macronutrients that provide energy include;

• Carbohydrates. These are compounds that are made up of types of sugar. Carbohydrates are classified based on the number of sugar units. They can be classified into monosaccharides, disaccharides, oligosaccharides and polysaccharides.
• Proteins. These are organic compounds that are made up of amino acids joined by peptide bonds. As the body cannot manufacture some essential amino acids, they must be supplied in the diet. Proteins are broken down back into free amino acids by proteases through digestion.
• Fats. They consist of 3 fatty acids and a molecule of glycerin attached. The food energy content of fat is 38 kilojoules per gram (9 kilocalories per gram). Carbohydrates and proteins have (17 KJ/g (4 Kcal/g).

Micronutrients

Micronutrients are often referred to as vitamins and minerals. They are responsible for disease prevention, healthy development, and the general well-being of the body. All micronutrients apart from Vitamin D are not produced in the body. Therefore, they must be gotten from our diets.

Only small amounts of micronutrients are required by the body but consuming them in enough amounts is important. There are 6 essential micronutrients;

• Iron. Iron is important for cognitive and motor development. Pregnant women and children are most vulnerable to iron deficiency. Anemia (a condition of low hemoglobin concentration) is mainly caused by iron deficiency. Fortifying flour with folic acid and iron, and taking iron supplements help improve the iron condition.
• Vitamin A. It is important for our immune system and promotes healthy eyesight. Vitamin A deficiency can cause blindness or death in children.
• Vitamin D. It helps build strong bones and helps in the absorption of calcium. The deficiency of Vitamin D causes bone problems like rickets in children and osteoporosis in adults. Vitamin D is made by our bodies from sunlight.
• Iodine. It is mainly required during infancy and pregnancy for the healthy growth of the infant and cognitive development. Fortifying salts with iodine helps improve iodine levels.
• Folate (Vitamin B9). It is most important during the early days of fetal development to help develop the brain and spine. Folic acid supplements and fortIfying foods with folic acid helps maintain healthy folate levels.
• Zinc. It is important for promoting immune functions.

ESSENTIAL NUTRIENTS

Essential nutrients are nutrients required by the body for normal physiological functions. These nutrients are not synthesized by the body, either at all or in enough amounts. They are obtained from dietary sources.

Amino acids. Essential amino acids are those required by the body but cannot be synthesized in the body. These amino acids are supplemented through diet. The number of standard protein-producing amino acids is 20. Nine of these, cannot be synthesized in the body. They are; valine, phenylalanine, tryptophan, threonine, methionine, lysine, leucine, histidine, and isoleucine.

Two fatty acids are essential to humans. They are alpha-linolenic (omega-3 fatty acid), and (an omega-6 fatty acid) called linoleic acid.

Vitamins are neither fatty acids nor amino acids. They are organic molecules essential for organisms. They mainly function as metabolic regulators, enzymatic cofactors, or antioxidants.

SOURCES OF NUTRIENTS

Below are some food sources of nutrients:

Nutrient	Food sources
Vitamin A	Milk, eggs, sweet potatoes, cantaloupe, and carrots.
Vitamin E	Nuts, seeds, avocados, spinach, whole-grain foods, and dark leafy greens
Vitamin C	Tomatoes, strawberries, oranges, peppers, and broccoli
Magnesium	Almonds, peas, black beans, and spinach
Fiber	Whole-grain foods, carrots, apples, strawberries, raspberries, and legumes (dried beans and peas)
Potassium	Bananas, cantaloupe, nuts, spinach, and fish
Calcium	Low-fat dairy, broccoli, dark leafy greens, sardines, and dairy substitutes
Iron	Red meat, seafood, beans, spinach, and peas
Zinc	Seafood, almonds, pumpkin, cashew, and peas

Foods rich in carbohydrates include corn, maize, sweet potatoes, yams, turnip, pumpkin, rice, and wheat.

Foods rich in proteins include eggs, milk, meat, peas, and beans.

Foods rich in vitamins include oranges, mangoes, tomatoes, and vegetables like spinach.

We have learned about;

• The meaning of nutrients.
• Types of nutrients.
• Deficiencies and toxicity of nutrients.
• Essential nutrients.
• Sources of nutrients.