CONTENTS 1.0 Introduction 2.0 Objectives 3.0 Main content
3.1 What are micronutrients?
3.2 Types of micronutrients 3.3 Functions of micronutrients 3.4 Micronutrient deficiencies 4.0 Conclusion
5.0 Tutor-Marked Assignments (TMAs) 6.0 Summary
7.0 References/Further Readings
1.0 INTRODUCTION
In this Unit two, we will be discussing micronutrients. Micronutrients are another essential class of nutrients. We are going to be looking at nutrients that make up of micronutrients, their physical and chemical properties, sources and functions.
2.0 OBJECTIVES
36
At the end of this unit, you should be able to:
i. Understand and explain what micronutrients are ii. Describe the nutrients that are called micronutrients iii. List and discuss classes of micronutrients
iv. List and explain the functions of micronutrients v. Discuss micronutrient deficiencies in details
3.0 MAIN CONTENT
3.1 VITAMINS AND MINERALS
Vitamins are a group of organic compounds needed in minute quantities for normal function, growth and maintenance of body tissues. Majority of the vitamins are not synthesized in the body and have to be provided through dietary intake. Examples include vitamins A, B, C, D, E and K. Only folic acid and vitamin D are partially synthesized in the body. Minerals are inorganic elements that occur in the form of their salts. They make up about four percent of the body weight. Examples are phosphorus, calcium, potassium, sodium, iodine, iron, copper, sulphur, chlorine, manganese, magnesium and molybdenum.
Like vitamins, minerals are also needed in minute quantities. They are excreted from the body through the kidney, skin and the bowel so they need to be supplied daily through the diet. Minerals can also be in the body in the form of organic (carbon containing) compounds, inorganic compounds and free ions. Examples of organic compounds are phospholipids, phosphor-proteins, haemoglobin and thyroxine while examples of inorganic compounds are sodium chloride and calcium phosphate.
37
3.2 CLASSIFICATION OF VITAMINS Vitamins are classified into two:
i. Fat soluble vitamins: They dissolve in organic solvents. Examples are vitamins A, D, E and K.
ii. Water soluble vitamins: They dissolve in water. Examples are vitamins B-complex and C. Vitamins B-B-complex includes vitamins B1 (Thiamine), B2 (Riboflavin), B3 (Pantothenic acid), B6 (Pyridoxine) and B12 (Cyanacobalamin).
3.3 CLASSIFICATION OF MINERALS Minerals are classified into three:
i. Major minerals or macro-minerals: They are required in large amounts in the body. Their recommended daily allowance (RDA) is approximately 100 mg/day. Examples are phosphorus, calcium, chlorine, sodium and potassium.
ii. Minor minerals: They are required in small amounts in the body. Examples are iron, magnesium and sulphur.
iii. Trace elements: They are needed in few micrograms. Examples are iodine, zinc, fluorine and molybdenum
3.4 Chemical characteristics of vitamins a. Fat-soluble vitamins
i. They are not easily destroyed by cooking methods. However ever, vitamin A is unstable and easily destroyed by heat, light, pH, moisture, etc.
ii. They are not easily eliminated and so are stored in the body. Their excess consumption could lead to toxicity.
iii. They are destroyed by rancidity.
38
b. Water-soluble vitamins
i. Unlike fat-soluble vitamins, they are unstable to heat, light oxidation and radiation.
ii. They are affected by cooking practices. Since they leach into the water, if the water is decanted, they are wasted.
iii. Excess intake does not result in toxicity since they are excreted in the urine.
3.5 FUNCTIONS OF MINERALS i. They regulate cellular oxidation.
ii. Minerals act as enzyme activators.
iii. They are part of hormone and enzyme molecules.
iv. Minerals help to maintain acid-base balance of body fluids.
v. They control the water balance in the body through osmotic pressure and by regulation of the permeability of cell membranes.
39
3.6 SOURCES OF VITAMINS AND MINERALS
The major sources of vitamins and minerals are shown in tables 6 and 7.
Table 6: Good sources of vitamins
Vitamin Good sources
Vitamin A -Retinol
-Precursor -carotene
Green and yellow fruits and vegetables, ripe tomatoes, liver, whole milk, egg-yolk, butter, fortified margarine and fish liver oil Vitamin B1
-Thiamine
Meat especially pork, liver, nuts and peanut butter, grain and enriched cereals, milk and milk products, eggs, brewer‟s yeast and wheat germ, legumes especially soybeans
Vitamin B2 -Riboflavin
Milk and milk products, liver, legumes, eggs, brewer‟s yeast, green leafy vegetables, enriched and whole grain cereals.
Niacin
-Tryptophan precursor
Meat especially liver, poultry, fish, enriched and whole grain cereals, brewer‟s yeast, nuts and peanuts
Vitamin C Fresh fruits especially citrus such as oranges, lemon, strawberries, canned fruit juices, tomatoes, raw vegetables especially green cabbage, pepper and potatoes
Vitamin D -Calciferol
Milk, butter (small amounts), egg-yolk, liver, fish oil and organ meat, nuts, legumes
Vitamin E Green leafy vegetables, vegetable oil, margarine, egg-yolk, milk fat, wheat germ oil
Vitamin K Green leafy vegetables, liver, cabbage and cauliflower
40
The major sources of minerals are as shown in Table 7.
Table 7: Good sources of minerals MINERALS GOOD SOURCES
Calcium Green leafy vegetables, milk, cheese, bones Chlorine Table salt
Copper Whole grain cereals, organ meat, shell-fish, nuts and legumes Fluorine Tea, sea-foods
Iodine Iodine fortified table salt, salt water fish, shell fish, seaweed
Iron Green leafy vegetables, liver, lean meat, fish and poultry, legumes, dry fruits, whole grain cereals
Magnesium Fresh green vegetables, dairy products, meat nuts, legumes and sea foods
Potassium Meat, fish, poultry, milk and curds
Phosphorus Milk, meat, fish, legumes, whole grain cereals and flour
Sodium Table salt, milk, egg-white, meat, fish, poultry and vegetables such as spinach (Fruits, vegetables, cereals, legumes and drinking water contain small quantities of sodium).
Sulphur Meat, milk, egg, meat, fish, poultry, cheese and nuts. All proteins containing methionine, cysteine and cysteine are excellent sources of sulphur.
Zinc Human colostrum, beef, liver, oyster, spices and wheat bran, popcorn, pork, crab, peanuts, peanut butter, cheddar cheese
3.7 MICRONUTRIENT DEFICIENCIES
Micronutrient deficiencies arise as a result of a prolonged low dietary intake of micronutrients such as vitamin A, iodine, folic, zinc and iron. These nutrients have their daily recommended quantities needed by the body every day for normal function of cells, tissues and organs. If these standard quantities are not being consumed in food for a long time, micronutrient deficiencies will arise.
41
The major challenge is that some of these micronutrients are taken in small quantities and are not produced by the body. So prolonged dietary intake of foods that lack these nutrients will result in micronutrient deficiencies (Uchendu and Atinmo, 2011). Long term strategies that have been taken to eradicate micronutrient deficiencies include food supplementation, micronutrient food fortification, biofortification, dietary diversification and nutrition education (Uchendu and Atinmo, 2011)
3.7. 1 Types of Micronutrient deficiencies
Global micronutrient deficiencies that have been declared public health problems are vitamin A deficiency (VAD), iodine deficiency disorders (IDD), Iron deficiency Anemia (IDA), zinc deficiency and folic deficiency. It is important to note that these micronutrient deficiencies coexist and interrelate with one another (Uchendu and Atinmo, 2011). The at-risk groups for micronutrient deficiencies are young children especially the Under-5, pregnant mothers and lactating mothers. Table 8 shows the micronutrient deficiencies and the nutrients involved.
Table 8: Micronutrient deficiencies and the nutrients involved S/N Micronutrient deficiencies Nutrients involved
1. Vitamin A deficiency Vitamin A 2. Iodine deficiency disorders Iodine 3. Iron deficiency Anemia Iron
Zinc deficiency Zinc
Folic deficiency Foliate
42
4.0 TUTOR- MARKED ASSIGNMENTS (TMAs)
1). Explain with relevant examples the nutrients that make up micronutrients.
2). Discuss micronutrient deficiencies.
3). Describe the at-risk groups of micronutrient deficiencies.
5.0 CONLUSION
In Module 1 Unit 2, we have learnt about micronutrients which are made up of vitamins and mineral. We also looked at the good sources of these nutrients especially fruits and vegetables. Their physical and chemical properties were explained as well as their functions. Global micronutrient deficiencies and the long-term strategies that have been adopted to eradicate these deficiencies were also considered. I hope you enjoyed it.
6.0 SUMMARY
Module 1, Unit 2 discussed the micronutrients, their sources, functions, physical and chemical properties and deficiencies. Adequate knowledge of nutrients is very important because it will be applied in subsequent modules.
7.0 REFERENCES/FURTHER READINGS
43
Byrd-Bredbenner C., Moe G., Beshgetoor D., and Berning J. (2007). Wardlaw‟s Perspectives in Nutrition. 8th ed. McGraw Hill International Student ed. Pp. 152 – 534.
Joshi S. A. (2003). Nutrition and Dietetics. 2nd ed. Tata McGraw Hill Publishers New Delhi. Pp. 54 – 124.
Bhutta Z. A., Hurrell R. F. and Rosenberg, I. H. (2012). Meeting Micronutrient Requirements for Health and Development. Nestle Nutrition Institute Workshop Series Vol. 70: 1 - 194. Karger Publishers.
The American Heritage Stedman‟s Medical dictionary. Houghton Mifflin Company, Boston, New York. Pp. 225-569.
Uchendu F. N. and Atinmo T. (2011). The Silent and Neglected Crisis of Malnutrition:
Scientific Evidence for taking Decisive Action. Global Journal of Health Science, Canada. Vol. 3, No. 1: 193-202.
Uchendu F. N. (2011). Micronutrient Malnutrition, a Tragedy to Childhood Growth and Education. Global Journal of Medical Research USA. Vol. 11 Issue 1 Ver. 1.0 April/May 2011.
Uchendu F. N. (2013). The role of biofortification in the reduction of micronutrient food insecurity in developing countries. African Journal of Biotechnology Vol.
12(37):5559-5566.
Uchendu F. N. and Atinmo T. (2016). Vitamin A stability in Nigerian wheat flour and fortification compliance level. African Journal of Food Science Vol.10 (3): 33-40, USA, March 2016. DOI: 10.5897/AJFS2015.1385.
Uchendu F. N. and Oyewole E. O. (2016). Stability of Vitamin A in Nigerian Retailed Biscuits. Journal of Food Research, Vol.5, No.5: 23-31.
DOI: 10.5539/jfr:v5n5p23 Canada
44
MODULE 1 NUTRIENTS, THEIR FUNCTIONS AND METABOLISM