DR. S.M. ALAM
Jan 17 - 23, 2011
Vitamins and minerals make our bodies work properly. Vitamins fall into two categories: fat soluble and water soluble. The fat-soluble vitamins — A, D, E, and K - dissolve in fat and can be stored in our body. The water-soluble vitamins - C and the B-complex vitamins (such as vitamins B6, B12, niacin, riboflavin, and folate) - need to be dissolved in water before our body can absorb them. Vitamins are organic substances (made by plants or animals) and minerals are inorganic elements that come from the soil and water and are absorbed by plants or eaten by animals. Our body needs larger amounts of some minerals, such as calcium to grow and stay healthy. Other minerals like iron, manganese, boron, copper, iodine, iron, selenium, and zinc are called trace minerals because you only need very small amounts of them each day.
Vitamins and minerals boost the immune system, support normal growth and development, and help cells and organs do their jobs. Carrots are full of substances called carotenoids that our body converts into vitamin A, which helps prevent eye problems. Another vitamin K helps blood to clot (so cuts and scrapes stop bleeding quickly). We will find vitamin K in green leafy vegetables, broccoli, and soybeans.
Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous. People, who are exposed to normal quantities of sunlight, do not need vitamin D supplements because sunlight promotes sufficient vitamin D synthesis in the skin. Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamins D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D for humans is obtained from sun exposure, food, and supplements. It is biologically inert and has to undergo two hydroxylation reactions to become active in the body. The active form of vitamin D in the body is called calcitriol (1,25-Dihydroxycholecalciferol).
Calcitriol promotes the absorption of calcium and phosphorus from food in the gut and re-absorption of calcium in the kidneys - this increases the flow of calcium in the bloodstream. This is essential for the normal mineralization of bone and preventing hypocalcemic tetany. Hypocalcemic tetany is a low calcium condition in which the patient has overactive neurological reflexes, spasms of the hands and feet, cramps and spasms of the voice box (larynx). Calcitriol also plays a key role in the maintenance of many organ systems. Various forms of vitamin D: We know about 5 forms of vitamin D, of which vitamins D2 and D3 are the major forms as far as humans are concerned. They are known collectively as calciferol.
Vitamin D1, molecular compound of ergocalciferol with lumisterol. Vitamin D2, ergocalciferol (made from ergosterol).
It is produced by invertebrates (animals without a spine, vertebral column), fungus and plants in response to sunlight (UV irradiation). Humans and other vertebrates do not produce vitamin D2. We do not know much about what vitamin D2 does in invertebrates. We know that ergosterol is a good absorber of ultraviolet radiation, which can damage DNA, RNA and protein; consequently many scientists believe it may serve as a sunscreen that protects organisms from sunlight damage. Vitamin D3, cholecalciferol (made from 7-dehydrocholesterol).
Vitamin D3 is made in the skin when 7-dehydrocholesterol reacts with ultraviolet light at 270-300 nm wavelengths - peak vitamin D3 production occurs between 295-297 nm. A human requires ten to fifteen minutes of sun exposure at least twice a week on the face, arms, hands, or back without sunscreen with a greater than 3 UV index for adequate amounts of vitamin D3. Vitamin D4, 22-dihydroergocalciferol. Vitamin D5, sitocalciferol (made from 7-dehydrositosterol). Both vitamins D2 and D3 are used in human nutritional supplements. Pharmaceutical forms include calcitriol (1alpha, 25-dihydroxycholecalciferol), doxercalciferol and calcipotriene. The majority of scientists state that D2 and D3 are equally effective in our blood stream. However, some say that D3 is more effective. Animal experiments, specifically on rats, indicate that D2 is more effective than D3.
It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones. Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79. Vitamin D is probably linked to maintaining a healthy body weight. It has been shown to reduce the risk of developing rheumatoid arthritis in women. A form of vitamin D could be one of our body's main protections against damage from low levels of radiation.
Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status. Experts say that people with a high risk of vitamin D deficiency should consume 25 ?g (1000 IU) of vitamin D each day so that there is a good level of 25-hydroxyvitamin D in the bloodstream. Elderly people, as well as people with dark skin should consume extra vitamin D for good health.
Not that many foods contain vitamin D. Some fish, such as salmon, tuna and mackerel, as well as fish liver oils are considered to be the best sources. Some vitamin D is also present in beef liver, cheese, and egg yolks. Most of these are Vitamin D3. Some mushrooms provide variable amounts of vitamin D2. Most of the food sourced vitamin D in the western diet comes from fortified foods - where vitamin D is artificially added. Most US milk is fortified with 100 IU/cup of vitamin D.
Vitamin D, also called calciferol, is a vitamin that dissolves in the body's fat. Vitamin D is found in food, but also can be made in your body after exposure to ultraviolet rays from the sun. There are several different forms of vitamin D. Each form has a different activity. The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Calcium is a mineral in your body that makes up your bones and keeps them strong. Phosphorus is a mineral that helps maintain good teeth and bones and keep muscles and nerves working properly. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. Without vitamin D, bones can become thin, brittle, and soft. Vitamin D prevents rickets in children and osteomalacia in adults. Rickets cause skeletal deformities.
Osteomalacia causes muscular weakness and weak bones. The major sources of vitamin D are food and exposure to sunlight. Exposure to sunlight is an important source of vitamin D. The Sun is a main sequence 'Star' being one of the some 1011 stars that constitute our galaxy.
Mean distance from the earth is approximately 149.6106 kilometers. The Sun is composed of about 90 per cent hydrogen and 8 per cent helium and 2 per cent other elements. The Sun rays coming to the earth at a speed of 186,000 miles per second and reaching to the earth in about eight minutes. The ultraviolet (UV) rays from sunlight trigger vitamin D synthesis in the skin. If a person is deficient in vitamin D, diseases such as rickets and osteomalacia may develop. A deficiency of vitamin D can occur when dietary intake of vitamin D is inadequate, when there is limited exposure to sunlight, when the kidney cannot convert vitamin D to its active form, or when someone cannot adequately absorb vitamin D from the gastrointestinal tract.
The classic vitamin D deficiency diseases are rickets and osteomalacia. In children, vitamin D deficiency causes rickets. In adults, vitamin D deficiency can lead to osteomalacia. Americans over the age of 50 may be at risk of vitamin D deficiency. This occurs because the ability of skin to convert vitamin D into its active form decreases as we grow older. Also, the kidneys, which help, convert vitamin D to its active form, sometimes does not work as well in older people. Individuals who have reduced ability to absorb dietary fat (fat mal-absorption) may need extra vitamin D because it is a fat soluble vitamin.