Micronutrients Overview, Food Sources and Functions

MICRONUTRIENTS: VITAMINS( WITH OVERVIEW ON FAT-SOLUBLE VITAMINS AND WATER SOLUBLES), CALCIUM, IRON, IODINE AND MINERAL ELEMENTS

VITAMINS

Vitamins are organic compounds found in small amounts in many foods. They are very essential in nutrition since the body cannot synthesize them in most cases. They can be prepared artificially.  Letters of the alphabets – A, B, C, D, E, K, were used to designate these vitamins. With time, the chemistry of the vitamins became clear, leading to specific names being given to the various vitamins. We now know that vitamin C is ascorbic acid.

The quantities of vitamins needed by people are small and these quantities can be sufficiently found in foods. Vitamins are distributed among several types of food.  This brings in the idea of the importance of variety and combinations in meal planning. The content of vitamins in foods varies considerably. For example, the freshness of fruits and vegetables, the variety and the climatic conditions of growth determine its vitamin content (Fox & Cameron, 1993). One should consume sufficient quantities of vitamins and it must be realized that the B-Complex vitamins form part of the co-enzyme molecule necessary for the maintenance of good health.

Several food processing methods result in the loss of vitamins and even mineral salts. There are laws that require that such nutrient losses must be replaced. We call this process enrichment or fortification. In some cases, the vitamin content is low and so extra vitamins are added. When we eat margarine, we get vitamins A and D. These are added to margarine since theses two vitamins are lost during processing any time you buy a tin of milk check the labels. You will observe that there is an inscription “With vitamins A and D added”.

An Overview of Fat-Soluble Vitamins

Vitamins, which are important for our health. They are protective nutrients. We shall start with the fat-soluble vitamins. Pay attention to the facts because they are good for our lives. As you have seen already, vitamins are either fat-soluble or water-soluble. We are going to examine the fat-soluble vitamins at this point.  These are A, D, E, and K.  They are fat-soluble and so they found or carried in the fats and oils that we consume. This means that when we use fat or oil to cook, we shall have these vitamins in our bodies but the quantities will depend on the amounts of fats and oils we consume and the method we used in cooking. Find out the names of these vitamins and write them in your jotters

Functions, Deficiency-Diseases and Main Sources of Fat-Soluble Vitamins

The fat- soluble vitamins have several functions and are considered individually. The functions, deficiency diseases and source have all been presented in the tables.

 

Excessive Intake of the Fat-Soluble Vitamins

Fat-soluble vitamins need the help of proteins to transport them in the blood plasma.  The water-soluble vitamins, on the other hand, are soluble in water so the excess can be excreted through the kidneys.  They are easily destroyed.  The fat-soluble vitamins need the fat in the diet to stimulate the flow of bile.  Excess fat-soluble vitamins are stored in the liver and fatty tissues.

Vitamin A: Due to the fact that vitamin A is not soluble in water, excess becomes a drug.  It can also not be broken down to a form that can be stored.  Excessive amount leads to a loss of vitamins appetite, a dry itching skin, coarse hair and painful swellings on the long bones of the arms and legs.  According to Pyke (1986) it has been known to cause poisoning. Hypervitaminosis A is the name given to too much intake of vitamin A.  The symptoms include drowsiness, headache, vomiting, itching and peeling of the skin.

Various Factors Influencing Food Habits

Vitamin D (Cholecalciferol): We have to know that vitamin D is also insoluble in water.  What then do you think can happen to its excretion?  The same reason why vitamin A cannot be excreted through the kidney applies to vitamin D.  Increased accumulation of plasma calcium damages the kidneys and cardiovascular vessels. The excess may force the body to absorb calcium form its own bones.

Symptoms of vitamin D toxicity are intense thirst, vomiting, weight loss, diarrhoea, irritability, loss of appetite, high blood calcium, and deposition of calcium in the muscles and even blood vessels. This condition cannot be reversed. It may lead to death. The good news is that our bodies can protect us from excess vitamin D in most cases.

The RDA for vitamin D is 5 micrograms for healthy adult men and women aged from 25 to 50 years.  Younger adults, pregnant or lactating women need double that amount.

Vitamin E (Tocopherol): Vitamin E is relatively non-toxic. However, studies have shown that intakes exceeding 500 mg/day can impair the functioning of the immune system.  In addition, excessive amounts can interfere with vitamin K’s role in its lood clotting mechanism.

Usually before you take vitamin E, you must know your body size.  The RDA is 8mg for women and 10mg for men.  It is recommended that the advice of a doctor should be sought before taking in the vitamin as a supplement.

Vitamin K : Adverse side effects have not been reported in situations when there is an excess intake of vitamin K.  The only known effect is that it can interfere with anticoagulant medications.

An Overview of Water-Soluble Vitamins

Before we take a detailed look at the B vitamins, we want you to have an idea on the general properties of the water-soluble vitamins.  Generally, while the water-soluble are important as co-enzymes, the fat-soluble vitamins regulate activities.  You have seen several people who visit the medicine stores or pharmacies  to buy say B Complex without doctor’s recommendation or proper prescription.  Have you done this before?  Why did you buy it? Study the table and give an answer.

Functions, Deficiency-Diseases and Main Sources of Water-Soluble Vitamins

It will interest you to know that there do not seem to be any reported cases of serious side effects from excessive intake of most of the water-soluble vitamins. The reason can be attributed to the fact that the excess vitamins can be excreted from the body since they can dissolve in the body fluids.

Thiamine (B₁):  There is no evidence of benefit or toxicity from an excess intake of vitamin B₁. If you are a woman between 19 and 50 years you need 1.1 mg of thiamine a day.  If you are a man of the same age, you need 1.5mg thiamine daily. This works out to 0.5mg of thiamine daily for every 1000 Calories consumed. The highest requirements are for very active people, adolescents, pregnant and lactating mothers.

As you consume more carbohydrates your bodies need for thiamine increases why do you think this happens? It is logical that more thiamine will be needed to act on a bigger quantity of carbohydrates.

Riboflavin (B₂): No side effect of excess intake of B2 has been reported. Males require 16mg, while females require 1.2mg.

Niacin/Nicotinic acid (B₃).  Excessive intake of the nicotinic acid causes a number of diseases that include nerve damage, irregular heartbeat, facial flushing and also decrease lipids.  Chronic doses can worsen peptic ulcers and damage the liver. Vomiting, nausea, loss of appetite can also happen.

RDA for men and women currently is 19mg and 15mg of niacin equivalent per day respectively.   I Niacin Equivalent = 1mg niacin or 60mg tryptophan.

Pyridoxine (B₆)_. Excess intake is not common because it is soluble in water and so it is excreted easily through the kidneys. However, excessive doses can cause damage to individual sensory neurons in long term use.  These are the nerve cells.  The need for B₆ increases when protein intake increases.

Adults aged 25 – 50 years need 1.6mg, if you are a woman.  If you are a man, you need 2.0 mg. i.e. 0.016mg. per gm of protein (Wardlaw & Insel, 1996).  If we did not have B₆ every amino acid will have to be eaten.

Folic acid: No toxicity has been detected although excess intake must be avoided.  The RDA for folic acid for healthy adults is 200ug (micrograms) for men and 180ug for women.

Cobalamine (B₁₂): No effect of excessive intake reported. The RDA for B₁₂ is 2micrograms per day for healthy men and women. Pregnant women need extra 0.2micrograms and lactating mothers need extra 0.6micrograms daily.

Panthothenic acid: Effects of excess intake is unknown. The RDA of Panthothenic acid for adults of both genders is 4.7mg per day.

Biotin: Excess biotin is not toxic at any level of consumption.  The bacteria in the large intestines can produce some small quantities of biotin. No RDA has definitely been established but some recommendations are that adults of both sexes need 30 – 100ug of biotin per day.

Ascorbic acid:  Vitamin C intake is different for different people.  Some of us may get on with as little as 10mg per day.  Other people may take up to 1000mg a day without any ill effects.  Despite these, excessive intake of the vitamin can irritate the stomach and cause diarrhoea.  Some of the excessive intake from supplements can interfere with diabetic and colon cancer tests.

Extra Information on Vitamin B₃ and VitaminC

Vitamin B₃

When the human body lacks vitamin B₃, results in the incidence of a disease called pellagra.  Pellagra has been denoted as the “Three D’s” (DuPuy & Mermel, 1995)

The symptoms of pellagra are.

• Dermatitis – a flaky skin that turns black on expose to sunlight
• Diarrhoea.
•  Inflammation of the mucous membranes
• Dementia – loss of intellectual function in severe cases
• These lead finally to death – a fourth ‘D’

Importance of Vitamin C

It is important to emphasize that vitamin C requires particular attention as far as nutrition is concerned.  The reason why you need to pay attention to vitamin C is that several factors make the vitamin more often lacking than perhaps the other vitamins.  The factors outlined by Pyke (1986) include:

1. It is present in restricted range of foods. The significant amounts can be found in fresh fruits and vegetables.
2. It is very soluble in water and can be readily washed out the food cooking water.
3. It is very unstable. The least amount of heat may destroy it.
4. When vegetables are stored or when they become stale and wilted, the vitamin can decompose.
5. Different amounts of vitamin C exist in even the same fruits and vegetables, depending on the source.
6. It is often lost during processing.
7. The body does not store it to any appreciable extent. Thus, it has to be adequately and steadily supplied in our diets.
8. The type of cooking method used has effect on the amount of losses. When potatoes are boiled, loss of vitamin C can be as high as 50 percent, while fried potatoes have about 30 percent loss.

Food, Nutrition, Food Sources And Functions

Generally, symptoms of vitamins and excesses are seen in such tissues as the eyes and blood. Scientists believe that fat-soluble vitamins are more toxic than the water-soluble ones. The reason is that our bodies cannot excrete the fat-soluble ones.

A diet rich in vitamin D and exposure to sunlight can correct rickets if it is noticed in the very early stages.

Vitamin E be prescribed for any of you if you made report to the hospital about spontaneous abortions. This is because the vitamin has long been associated with reproduction in experimental animals. Vitamin A was also prescribed to people against aging. All these functions have not been found in human to warrant a strong support for this function.  Another name for vitamin E is tocopherol.

The scientist who dealt with it found out that birds that were bleeding stopped bleeding when they were given doses of the vitamin E. It is a combination of compounds from fish and plant oils called quinines. Excessive intakes of these vitamins can be injurious to health. The sources are common in Ghana so try and include them in you meals.

Vitamins are very important because without them a lot of the body’s biochemical processes cannot go on. Study the tables well and they will be quite clear.

MINERAL ELEMENTS

Another important component of food, also a group of nutrients, called the mineral elements.  It is believed that there are about 25 of the mineral elements found in food but only 16 are important in Nutrition.

General Overview of the Mineral Elements

A number of mineral elements are important in our bodies.  They contribute to good nutrition and health. In your study of Elementary School Science, you might have learnt that plants absorb mineral salts dissolved in water through their roots.  The minerals then become part of the plant tissues and fluids.  As we humans consume the plants or other animals that have eaten the plants, we get the mineral elements in our bodies.  This is called the food chain.

You will recall that all the nutrients we studied were combinations of carbon, hydrogen and oxygen.  In the case of proteins, there was nitrogen.  The mineral elements are unique elements from the group of metals.

Mineral elements are found in a variety of ways in the body.  Some are components of the skeleton; some are present in the cell fluids (intra cellular) while some are found outside the cell fluids (extra cellular).  Some are needed in amounts that are higher than others.  For example, the amount of calcium needed is more than iron.  In this group of mineral elements calcium is a major element while iron is a trace element that is iron is needed in traces.

A brief examination of some other elements important in nutrition.

–   Phosphorus is found with bones in smaller quantities than calcium.  It works together with calcium for strong bones.

–   Sodium, found in table salt, plays an important role in our diet with potassium. The two mineral elements play important roles in controlling the movement of water in our bodies.  Too much sodium leads to high blood pressure and the swelling of our hands and feet.

–   Potassium regulates muscle contractions and the transmission of nerve signals in addition to the role it plays with sodium

–   Magnesium helps the body to use proteins and carbohydrates.  It also helps to regulate the nervous system.

–   Cobalt is required for the formation of red blood cells.  It is also a part of the Intrinsic factor for vitamin B₁₂ absorption.

–   Fluorine is important for bone and tooth formation.

–   Zinc is an essential component of a large number of enzymes in the body.  It is also needed for protein synthesis.

Deficiency Diseases of the Mineral Elements

Deficiency diseases are not seen in people who eat normal balanced food. However, if the diet is not balanced i.e. if it contains too little or a large amount of one food then the food is not balanced.  Again, when there is an excess growth or lactation or if there is an extra stress on the body due to injury, pregnancy, rapid degeneration of cells without the body meeting the necessary requirements then the chances of deficiency might occur.  Fruits and vegetables can give us these mineral elements.

Calcium

Calcium is the most abundant mineral element found in within our bodies.  Of all the calcium in our bodies, 99% are found in the bones and teeth.  The remaining one percent is responsible for the other functions of calcium in the body.

Functions of Calcium

• Gives the framework of the body. It strengthens the bones and teeth. The bones act as stores for calcium.
• As a component of blood. It assists in metabolic processes in the blood.iii. Blood Clotting .The blood clots help to keep the red blood cells and other salts from being lost during injury.

• Muscle contraction. Calcium helps the contraction of muscles which helps the body to move.
• Transmission of nerve impulses. Calcium aids in the transmission of nerve impulses so that the body can perform its activities.
• Activation of enzymes. Calcium helps to activate some enzymes for digestion. For example, trypsin.

Deficiency Diseases and Excess Intake of Calcium

Lack of or inadequate calcium in our bodies results in rickets in children.  In adults, osteomalacia/osteoporosis occurs.  Osteoporosis refers to weak bones.  The blood may also fail to clot in injury leading to death.

Lack of calcium may be as a result of interference with the absorption or lack of vitamin D.  You may recall that if vitamin D is lacking, absorption of calcium is a problem.

Excess intake of calcium may interfere with the absorption of other mineral elements such as iron, since and some other essential minerals. Constipation, urinary stones and important kidney function can also result from excessive calcium intake.

Sources of Calcium

In general, milk and dairy products bones and limestone (clay) are good sources of calcium.  Leafy green vegetables have good concentrations but they contain substances that make the calcium not easy to be absorbed by the body.  Drinking a lot of alcohol reduces calcium intake.

The RDA is 1200 mg per day for people aged 11 -24 years and pregnant and lactating mothers.  For males and females above 24 years, 800 mg a day is recommended.

Iron

Have you ever been told by the doctor to go to the laboratory for blood test?  Were you asked to take HB test?  If yes, this test was to taken to find out your blood haemoglobin concentration.  This gives and index of the amount of Iron in your body.  Iron is very important for health for several reasons.

The functions of Iron in the human body.

1. Iron is a component of haemoglobin found in the red blood cells. Haemoglobin enables the blood to carry oxygen as oxyhaemoglobin.
2. Iron is found in the red muscles called myoglobin. It transports oxygen to the muscle cells.
3. Iron is found in cytochromes. These are concerned with respiration.

Deficiency Diseases and Excess Intake of Iron

When you have a low haemoglobin percentage your blood will not be able to carry the required oxygen.  This is a condition that is a source of worry for people with sickle-cells.  At the initial stages of iron deficiency, there is a low level of plasma, followed by a decrease in red blood cells, then the full-blown anaemia leading to death.  The symptoms of anaemia include: apathy, short attention span, general body weakness. Iron-deficiency anaemia can result from injury, internal bleeding, blood loss, worm infestations and strict vegetarianism.

Excess iron is very serious.  The body stores iron and so excessive intake leads to the failure of many organs.  It can lead to death if not stopped.

Sources of Iron

Meat, fish and poultry are primary sources of Iron that the body easily absorbs.  Eggs, legumes, whole and enriched grains, nuts are also sources but they iron content is not absorbed as easily as the iron in meat, fish and poultry.

The RDA for adult men is 10 mg; for females of reproductive age, it is 15 mgs.  Pregnant women require 30 mg. per day.

Iodine

The main function of iodine is that it is a component of thyroxine which regulates the basal metabolic rate.  Basal metabolic rate is in the next Unit.

A dietary deficiency of iodine reduces the production of thyroxine by the thyroid gland.  The body’s response is to increase the size of the thyroid gland.  This gland is found in front of the neck.  The enlarged thyroid gland results in what we called goitre, a swelling in the neck.  The affected person feels tired, cold, with brittle hair and nails.  Some of them gain weight.  In children, the condition called cretinism results.  Cretins have dwarfish appearance with severe mental and physical retardation.

Excess iodine can result in toxicity of iodine.  Iodine is found highly in sea foods, sea weeds and animals that feed on iodine-rich soils.  In Ghana, the regions in the North are in the area where iodine-deficiency is prevalent because of the distance from the sea.  Now with iodated salt, the problem can be contained if people are educated well on its consumption.

Summarily, Plants absorb the mineral elements from the soil and then they become part of the plants’ body tissues and fluids. When we humans and other animals consume the plants we get the mineral elements.These mineral elements form parts of our skeleton or are found in the cell fluids or outside the cells.

Some of these elements, such as calcium, are needed in larger quantities than some others, such as iron and iodine. Calcium is the major element in the bone. It is absorbed better when vitamin d is present.

Iron is a component of haemoglobin found in the red blood cells. Low haemoglobin content of the blood can lead to anaemia. Iodine is needed to aid in the proper functioning of thyroxine which regulates the basal metabolic rate. Deficiency of iodine results in goitre, a swelling found in the neck region.

Effect of Heat on Cooking

When foods are heated they undergo certain changes which may be external changes or internal or both as presented in figure 5:1 below. Let us see some of the external changes that can occur and how you can recognise them.

External Changes : Colour, Flavour/Odour,  Texture

Change in colour: This change is visual and you can see it. Generally you will notice that

vegetables become darker in colour when heat is applied. But when they are overcooked the colour changes for example, green vegetables change to a darker brown colour, carrots cooked in milk imparts pink colour to milk, similarly red meat turns brownish red.

Change in flavour: You can smell this change. Sometimes it is all over the house. Strong smell of fish and other non-vegetarian foods decrease on cooking. Clove acquires a special smell on roasting.

Change in texture: This change is best known when eaten but you can also feel it on touching the food or even visually. Cereals and pulses, root vegetables become soft on boiling. Similarly meats become soft and tender and egg coagulates on cooking to give a soft solid.

Internal Changes: Food undergoes some internal changes as well and these changes are in termsof the nutrients.

Carbohydrates absorb water and swell up in the presence of moist heat. Over cooking results in the bursting of carbohydrate molecules and makes the food pasty and sticky.

Proteins coagulate on heating and become tender with prolonged cooking resulting in their shrivelling and hardening.

Fats do not changeat optimum cooking temperature, however, on extensive heating, they start to disintegrate into fatty acids and glycerol.

Minerals normally do not change. However, if excessive water is used for cooking and then discarded, a lot of minerals leach into the cooking water and go wasted.

Vitamins need special mention specially water soluble ones like the B-complex and vitamins C. Vitamin C in the presence of light and on heating easily oxidizes and is lost. It is better that fruits and vegetables, which contain vitamin C, are consumed in raw form. Vitamin B complex are lost even during washing of foods. It is also lost due to leaching. Discarding the cooking water and addition of soda bicarbonate also leads to further losses.

Cooking and food preparation skills are important in preparing nutritious foods and keeping a healthier body. These skills include:

Knowledge about food, nutrition, label reading, food safety and ingredient substitution

Planning (organizing meals, food preparation on a budget, teaching food skills to

children)

Conceptualizing food (creative use of leftovers and adjusting recipes)

Mechanical techniques (preparing meals, chopping/mixing, cooking and following recipes)

Food Perception (using your senses-texture, taste, when foods are cooked)”.

Heat affects food in different ways especially when in excess it tends to destroy important food nutrients which are needed by the body. Heat changes color, taste and texture of food easily and thus how these changes affect quality of food is important to know.

In developing new healthy recipes, it is important to consider using low fat dairy products, lean meat, less dense carbohydrates among others for preparing food. Different methods of food preparation also affect the nutritional status of food. It is also important to use raw spices rather than