What is a Vitamin...

Beta-Carotene/carotenoids and Vitamin A

The entire family of carotenes is found naturally in many vegetables and fruits. Specifically, beta-carotene is found in dark orange or green vegetables and fruits. The difference between a dark orange carrot and a pale on is its carotene content. Unfortunately, due to food choices, many diets are lacking in these important nutrients.

Beta and alpha carotene are precursors to vitamin A and act as antioxidant nutrients. They are the only carotenoids converted to appreciable amounts of vitamin A as required. Beta and alpha carotene are important to the health of the immune system, which provides resistance to infection. They are also necessary for the development and maintenance of healthy epithelial tissue and mucous membranes, such as the lining of the lungs, bronchi and other respiratory tissue. Epithelial tissue forms a barrier against bacteria and other foreign substances and aids directly in the prevention of infection and disease. Recently, much attention has been devoted to the entire family of carotenoids, including: alpha carotene, lutein, lycopene, zeaxanthin and capsanthin. Research has demonstrated that some of these carotenoids have significant antioxidant and protective benefits greater than beta-carotene alone.

Vitamin A

Vitamin A is a fat-soluble vitamin that has many different functions. First, it is related to the maintenance of normal vision in dim light and the prevention of night blindness. It also helps in the growth and formation of body cells, making it essential for body growth. It is especially needed for bone growth. If the intake is not sufficient, bones will stop growing before the soft tissues are fully mature. Vitamin A is also needed for normal tooth development, because the enamel-forming cells are affected by a lack of vitamin A. Like the carotenoids, vitamin A is also important for the maintenance of healthy epithelial cells. There are two kinds of epithelial tissue: those that cover the outer surfaces of the body - the resistant, protective skin (epidermis) and those that line all the mucus membranes. Without vitamin A, the epithelial cells become dry and flat and gradually harden to form scales that shed. Vitamin A is also important to the health of the membranes lining the stomach, intestinal wall, bladder and urinary tract and for the health of the sex glands and uterus. Lastly, vitamin A works better where there are sufficient levels of zinc and adequate protein intake in the diet.

Although vitamin A can be manufactured in the body from carotenoids, there are some foods that provide this nutrient in its active form. These include kidney, liver, butter and whole milk.

The B Vitamins

The B vitamins consist of a large number of substances that are involved in the metabolism of all living cells. Acting as coenzymes, they work together with the proteins in the various enzyme systems of our body.

The functions of the B vitamins are closely synergistic, and because of these inter-relationships, a deficient intake of one or more of them can cause deficiencies in the others by hampering their utilisation. B vitamins are water-soluble and are not stored in the body. They must be replaced daily, and any excess is excreted. Although the B vitamins do work together, some of their individual functions are as follows.

Vitamin B1 (Thiamin)

Vitamin B1 acts as a coenzyme necessary for the conversion of carbohydrates into glucose, which is burned in the body or energy. It is essential for the functioning of the nervous system, and severe deficiency can cause Beriberi, a disease marked by weakness, paralysis and oedema. Possible signs of marginal B1 deficiency include fatigue, mental impairment, depression and numbness or tingling in the extremities. Food sources of thiamin include brewer's yeast, whole grains, nuts and beans.

Vitamin B2 (Riboflavin)

Vitamin B2 acts as a coenzyme that activates the breakdown and utilisation of carbohydrates, fats and proteins. It is essential for cellular oxidation the maintenance of eye health. A deficiency of vitamin B2 can cause tissue inflammation and oversensitivity to bright lights. Intakes in excess of the body's requirements are excreted via the kidneys and may cause a harmless change in the colour of one's urine to fluorescent green/yellow. Food sources of riboflavin include liver, whole grains, mushrooms and almonds.

Vitamin B3 (niacin)

Vitamin B3 is a coenzyme that assists in the breakdown of carbohydrates, fats and proteins. Niacin is essential for the health of the skin, tongue and digestive system and is involved with the regulation of cholesterol, blood pressure and blood sugar levels. In supplemental form, niacin is also available as Niacinamide. A sign associated with a B3 deficiency include rough, dry skin, mouth ulcers, headaches and fatigue. A severe deficiency results in a disease called pellagra, which is characterised by dermatitis, diarrhoea and dementia. Food sources of riboflavin include liver, whole grains, seeds, fish, beef and leafy green vegetables.

Vitamin B5 (Pantothenic Acid)

Vitamin B5 is found in a wide variety of food sources and exerts influences in a number of functions in the body. It is necessary for the normal functioning of the adrenal glands and is involved in the formation of certain hormones and nerve regulating substances. It is also essential for the formation of fatty acids, and as a coenzyme it participates in the utilisation of riboflavin and in the release of energy from carbohydrates. Possible symptoms associated with deficiency include low tolerance to stress, fatigue and adrenal exhaustion. Food sources of Pantothenic acid include liver, nuts, soybeans, fish, milk, poultry and whole grains.

Vitamin B6 (pyridoxine)

Vitamin B6 plays a role as a coenzyme in the breakdown and utilisation of carbohydrates, fats and proteins. It facilitates the release of glycogen for energy from the liver and muscles. It also participates in the utilisation of energy in brain and nervous tissues and is essential for the regulation of the central nervous system. Vitamin B6 is needed to maintain hormone balance- in particular those of the female reproductive system. Possible signs associated with B6 deficiency include nervous tension and irritability, depression, pregnancy-related sickness and cracks in the tongue and lips. Food sources of pyridoxine include wheat germ, sunflower seeds, beans, poultry and brown rice.

Vitamin B12 (Cobalamin)

Vitamin B12 is the only vitamin that contains cobalt, a trace mineral. It is essential for the normal functioning of all body cells, especially those of bone marrow, gastrointestinal tract and nervous system. B12 is necessary for the formation of red blood cells and haemoglobin. Without adequate B12 the red blood cells enlarge and do not mature properly, leading to a potentially dangerous condition known as pernicious anaemia. Mild B12 deficiency is common with symptoms including lethargy, forgetfulness, tinnitus and fatigue. Vitamin B12 is found in foods of animal origin and those consuming a vegan diet are at increased risk of deficiency.

Folic Acid

Folic Acid, also known as folacin or vitamin B9, functions along with vitamin B12 and vitamin C in the utilisation of proteins. It has an essential role in he formation of heme, the iron-containing protein in haemoglobin and therefore is important in the formation of red blood cells. Folic acid (along with vitamin B6 and B12) is needed to regulate homocysteine in the blood, high levels of which are associated with cardiovascular disease and impaired mental function. Folic acid is essential during pregnancy as it is integral in the formation of the spinal chord in the developing foetus. Food sources of folic acid include beans and legumes, citrus foods and juices, wheat bran and other whole grains, poultry and dark green leafy vegetables.

Biotin

Biotin (sometimes called vitamin H) is an essential coenzyme that assists in the making of fatty acids and in the burning of carbohydrates and fats for body heat and energy. It also aids in the utilisation of amino acids, folic acid, Pantothenic acid and vitamin B12. Biotin is a potent stimulant to the growth of healthy cells. Because biotin is synthesized by intestinal bacteria, deficiencies are not generally a concern, however antibiotics and avidin (a protein found in raw egg white) can inhibit biotin absorption. Foods rich in biotin include nuts, cheese, brewer's yeast and cauliflower.

Choline

Choline is usually considered to be part of the B complex. It is a constituent of lecithin, which facilitates the movement of fat from the liver and into the cells. It must be present before vitamin A can be stored. It is manufactured in the body, but most tissue choline is derived from dietary phospholipids (found in lecithin). Some other food sources include liver, eggs, whole grains, soy and cauliflower.

Inositol

Inositol is usually considered part of the vitamin B complex. Along with choline, inositol is necessary for the formation of lecithin within the body. It is a primary component of cell membranes, and although not an essential nutrient, exerts many beneficial effects. Food sources of inositol include citrus fruits, whole grains, nuts, seeds, legumes and animal produce.

PABA

PABA (Para-aminobenzoic acid) is sometimes classified as a member of the B complex. It influences intestinal bacteria, enabling them to produce folic acid, which in turn helps in the production of pantothenic acid. PABA plays a role in the formation of red blood cells and in the break down and utilisation of proteins. Since PABA is not considered an essential nutrient, no RDA has been set, neither have deficiency states been reported. Grains and animal products are good sources of PABA, however it is synthesised naturally from friendly bacteria in the intestines.

Vitamin C

Vitamin C is an antioxidant vitamin essential to the body's health and is especially important for maintaining healthy skin. Also known as ascorbic acid, vitamin C is a water-soluble vitamin.

Unlike other animals, humans cannot make their own vitamin C. Because of the many roles that vitamin C plays in the human body, good health depends on upon its daily replenishment. Its primary function is to maintain collagen, a protein necessary for the formation of skin, ligaments, bones and teeth and for the strength of blood vessel walls.

In addition vitamin C plays an important part in the absorption of iron - a mineral necessary for the formation of red blood cells. It also plays a role in the utilisation of folic acid in the body.

It is well documented that vitamin C is destroyed by food preparation more than any other nutrient. It is also well known that the body does not store vitamin C, but excretes any excessive intake.

Most people consider citrus fruits to be the best source of vitamin C, however some vegetables contain even higher concentrations. The vegetables richest in this vitamin include red sweet peppers, broccoli, kale, parsley, cabbage and brussel sprouts. Berries and most other fruits are also rich sources.

Vitamin D

Vitamin D is a fat-soluble nutrient required the absorption and utilisation of calcium and phosphorus. Two forms are available from foods - ergocalciferol (D2) and cholecalciferol (D3). Vitamin D is necessary for growth, development and maintenance of bones and teeth in children and adults. In its most active form, vitamin D works with calcium to control bone formation. Vitamin D can be obtained from two sources - the spontaneous formation in the skin by the sun via a phytochemical reaction in the epidermis, and the eating of a food containing vitamin D. A severe deficiency of vitamin D results in rickets in children and osteomalacia in adults, which are both skeletal diseases that weaken the bones. Good food sources of vitamin D include cold-water fish, butter, egg yolks, fortified milk and cod liver oil.

Vitamin E

Vitamin E is a fat-soluble antioxidant nutrient. The term 'vitamin E' refers to a family of eight related compounds, the tocopherols and the tocotrienols. The four major forms of vitamin E are designated alpha, beta, delta and gamma on the basis of chemical structure. The tocotrienols are less widely distributed in nature than the tocopherols, although they are present in palm oil. Alpha-tocopherol, commonly known as vitamin E, is the form found most in nature and the most biologically active.

As an antioxidant, vitamin E protects against damage to the cell membranes. It prevents saturated fatty acids and vitamin A from breaking down and combining with other substances that may become harmful to the body. Not surprisingly, fats and oils that contain vitamin E are less susceptible to rancidity than those not containing this nutrient. Vitamin E also has the ability to unite with oxygen and prevent it from being converted into toxic peroxides. This leaves the red blood cells fully supplied with the pure oxygen that the blood carries to the heart and other organs.

Vitamin E plays an essential role in cellular respiration of all muscles, especially cardiac and skeletal. Vitamin E makes it possible for these muscles and their nerves to function with less oxygen, thereby increasing their endurance and stamina. It also causes dilation of the blood vessels, permitting a fuller flow of blood to the heart. Vitamin E also aids in bringing nourishment to the cells and strengthening the capillary walls.

Although severe vitamin deficiency is quite rare, low levels are typically seen in patients with malabsorption syndromes (such as coeliac disease) and in premature infants. Symptoms of deficiency include nerve damage and poor coordination.

The best food sources of vitamin E are polyunsaturated vegetable oils, nuts, seeds, wheat germ and whole grains.

Vitamin K

Vitamin K is a fat-soluble vitamin that exists in three major forms - vitamin K1 (phylloquinone) the natural vitamin K found in plant foods; vitamin K2 (menaquinone) produced by intestinal bacteria; and vitamin K3 (menadione) a synthetic compound.

Vitamin K is important for proper blood clotting or coagulation. It is essential for the synthesis by the liver of four blood clotting proteins. Without vitamin K, the level of blood clotting proteins in the blood is reduced and clotting time is prolonged. Vitamin K has also been recognised for its role in the maintenance and health of the bone. Since natural vitamin K is fat-soluble, it requires bile and pancreatic juice in the intestines for maximum absorption. By contrast, some of the synthetic vitamin K compounds (K3) are water-soluble and more easily absorbed and are subsequently used by people who may not tolerate natural vitamin K well, such as those with decreased bile secretion. Absorption of vitamin K takes place mainly in the upper part of the small intestine and then carried to the liver for the synthesis of prothrombin, a key blood-clotting factor.

Vitamin K is found in both plant and animal sources in nature, Good amounts are found in dark green leafy vegetables, most green plants, alfalfa and kelp. In animal-source foods, vitamin K is found in liver, milk, yogurt and egg yolks. A major source of vitamin K for humans is that made by the intestinal bacteria.