بسم الله الرحمن الرحيم MicronutrientsVitamins and Minerals Dr. Mahmoud Sirdah
Classes of Nutrients Macronutrients • Carbohydrate • Protein • Lipids • Water Micronutrients • Vitamins • Minerals
Vitamins and minerals are called micronutrients because we only need them in very small amounts. • That doesn’t mean they aren’t important; in fact we can’t live without vitamins and minerals. • we measured protein, carbohydrate and fat needs in grams. However, Vitamins and minerals are measured in milligrams (mg), micrograms (mcg) and international units (IU).
Vitamins • A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. • Vitamins serve crucial functions in almost all bodily processes (immune, hormonal and nervous systems) and must be obtained from food or supplements as our bodies are unable to make vitamins. • A compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. • Thus, the term is conditional both on the circumstances and the particular organism. • For example, ascorbic acid functions as vitamin C for some animals but not others, and vitamins D and K are required in the human diet only in certain circumstances.
Vitamins are classified in two categories: • Water-soluble • Fat-soluble • Classification is based on whether or not the vitamins can dissolve in water. • Water-soluble vitamins include the B complex of vitamins and vitamin C. • The fat-soluble vitamins include vitamins A, D, E and K
The fat-soluble vitamins • Because they are soluble in fat (lipids), these vitamins tend to because stored in the body's fat tissues, fat deposits, and liver. • This storage capability makes the fat-soluble vitamins potentially toxins. • Care should be exercised when taking the fat-soluble vitamins. The fat-soluble vitamins, especially vitamin A, should be consumed with care because of their storage capabilities. • They have the potential of building up to harmful levels. Even though very few cases of vitamin toxicity have been reported, concern has grown during recent years as the practice of taking mega doses has become popular.
Water-soluble vitamins • In contrast to the fat-soluble vitamins, the water-soluble vitamins are not easily stored by the body. They are often lost from foods during cooking or are eliminated from the body. • We don’t store water-soluble vitamins in your body very well so they need to be replaced constantly through your diet. That is one of the reasons we need to eat good foods every day, not just once in a while. • With exception of vitamin B6 and B12, they are readily excreted in urine without appreciable storage, so frequent consumption becomes necessary. • They are generally nontoxic when present in excess of needs, although symptoms may be reported in people taking mega doses of niacin, vitamin C, or pyridoxine (vitamin B6). • All the B vitamins function as coenzymes or cofactors, assisting in the activity of important enzymes and allowing energy-producing reactions to proceed normally. As a result, any lack of water-soluble vitamins mostly affects growing or rapidly metabolizing tissues such as skin, blood, the digestive tract, and the nervous system.
Water-soluble vitamins • The water-soluble vitamins include vitamins B1, B2, B3, B6, B12 and vitamin Cas well as Folic acid and Biotin. • Vitamin C has been in the spotlight for many years and is best known for its ability to combat colds and its function as an antioxidant. • The B vitamins basically act as coenzymes and are involved in the metabolism of fat, protein, and carbohydrates. • The water-soluble vitamins are not normally stored in the body in any significant amounts. Therefore, they must be consumed in constant daily amounts to avoid depletion and interference with normal metabolic functioning.
Coenzymes and Cofactors • Coenzymes and cofactors are any non-protein molecules (usually organic molecules or metal ions) that are required by an enzyme for its activity. • Enzymes may or may not have a nonprotein molecule attached to them. Some enzymes contain covalently bound carbohydrate groups, which do not affect the catalytic activity, but may influence enzyme stability or solubility. • Many enzymes have metal ions, while some others possess low weight organic molecules; these are called cofactors /coenzymes, and are essential for enzyme activity.An organic cofactor is commonly known as coenzyme. Cofactors and coenzymes may be covalently or noncovalently attached to the protein molecule, called apoenzyme. • Cofactors are often classified as inorganic substances that are required for, or increase the rate of, catalysis. • coenzymes are organic molecules that are required by certain enzymes to carry out catalysis.
Coenzymes and Cofactors • cofactors /coenzymes bind to the active site of the enzyme and participate in catalysis but are not considered substrates of the reaction. • An apoenzyme lacks catalytic activity in the absence of its specific cofactor /coenzyme. • When a cofactor is so tightly bound to the apoenzyme that it is difficult to remove it without damaging the enzyme, the cofactor is often called a prosthetic group. Both coenzymes and cofactors generally contribute to enzyme activity as well as stability. The complex of an apoenzyme and the cofactor is known as holoenzyme. • Coenzyme molecules are often Vitamins or are made from vitamins
Inactive enzyme Enzyme Vitamin coenzyme cofactor Substrate Active enzyme
Vitamins Overview • What is a vitamin? • What are the two types of vitamins? • Where do I get my vitamins? • How much do I need? • Why are the vitamins important? • Associated diseases.
Vitamins Overview • The term vitamin is derived from the words: vital and amine because vitamins are required for life and were originally thought to be amines. • Although not all vitamins are amines, they are organic compounds required by humans in small amounts from the diet. • An organic compound is considered a vitamin if a lack of that compound in the diet results in overt symptoms of deficiency.
Vitamins Overview • Vitamins are grouped by their biological and chemical activity, not their structure. • Thus, each "vitamin" may refer to several vitamer compounds that all show the biological activity associated with a particular vitamin. • Vitamers are often inter-converted in the body. • Such a set of chemicals are grouped under an alphabetized vitamin "generic descriptor" title, such as "vitamin A," which includes the retinoid compounds (retinal, retinol , retinoic acid and many carotenoids
Vitamins Bioavailability Vitamins Bioavailability = amount available + amount absorbed • Vitamins Bioavailability affected by • Efficiency of digestion • Nutrition status • Other foods consumed at the same time • Method of food preparation • Source of nutrient • synthetic, naturally occurring, fortified
Reference Value Definitions • Estimated Average Requirement (EAR) • a daily nutrient intake value that is estimated to meet the requirements of half the healthy individuals in a group • intake at which the risk of inadequacy is 0.5 (50 percent) to an individual • Recommended Daily Allowance (RDA) • the average daily intake level that is sufficient to meet the nutrient requirement of nearly all (97-98%) healthy individuals in a particular life stage and gender group • the intake at which the risk of inadequacy is very small—only 0.02 to 0.03 (2 to 3 percent) • Tolerable Upper Limit (UL) • highest level of a daily nutrient that is likely to pose no risk of adverse health effects to almost all individuals
Water Soluble • Vitamin C • B Vitamins • Thiamin • Riboflavin • Niacin • Pantothenic Acid • Biotin • Vitamin B6 • Folic Acid • Vitamin B12 Fat Soluble • Vitamin A • Vitamin D • Vitamin E • Vitamin K Two Classifications of Vitamins
Fat Soluble Vitamin Functions • Vitamin A • Vitamin D • Vitamin E • Vitamin K
Vitamin A Retinol • Vitamin A is a generic term for a large number of related compounds. • Retinol (an alcohol) and retinal (an aldehyde) are often referred to as preformed vitamin A. • Retinal can be converted by the body to retinoic acid, the form of vitamin A known to affect gene transcription. • Retinol, retinal, retinoic acid, and related compounds are known as retinoids (Vitamer). • Beta-carotene and other carotenoids that can be converted by the body into retinol are referred to as provitamin A carotenoids.
Vitamin A • Vital – promote growth and reproduction and maintain health • organic • do not supply calories • required in the diet in small amounts (micrograms or milligrams per day) for the maintenance of normal health and metabolic integrity
Vitamin A • Vitamin A was the first fat-soluble vitamin identified (in 1913). • Vitamin A comprises the preformed retinoids (Retinol, retinal, retinoic acid), plus the precursor forms, the provitamin A carotenoids. • Preformed retinoids is a collective term for retinol, retinal, and retinoic acid, all of which are biologically active. • The provitamin A carotenoids include mainly beta-carotene, which is converted to retinoids with varying degrees of efficiency. • Retinoids are sensitive to heat, light, and oxidation by air. while Beta-carotene is relatively more stable. • There is some loss of vitamin A with cooking, but only after boiling for a comparatively long period.
Vitamin A • Retinoids are converted to retinol in the intestines and transported with dietary fat to the liver, where it is stored. • A special transport protein, retinolbinding protein (RBP), transports vitamin A from the liver to other tissues. • Carotenoids are absorbed intact at a much lower absorption rate than retinol. Of all the carotenoids, beta-carotene has the highest potential vitamin-A activity.
Vitamin A functions • The active forms of vitamin A have three basic functions: • vision, • growth and development of tissues, • immunity. • Vision. Vitamin A combines with a protein called opsin to form rhodopsin in the rod cells of the retina. When vitamin A is inadequate, the lack of rhodopsin makes it difficult to see in dim light.
Vision Retinalis the key molecule involved in vision and responsible for converting the energy in light photons into electrical impulses in the retina • The precursor of 11-cis-retinal is the alcohol all-trans-retinol (Vitamin A). These molecules (11-cis-retinal or vitamin A) cannot be synthesized by mammals and has to be acquired through the diet. • Precursors to Vitamin A are carotenes, which are found in many vegetables including carrots. Perhaps this leads credence to the old superstition that carrots help you see better in the dark - indeed, it is known that a deficiency of Vitamin A leads to night blindness and eventually damage to the retinal cells involved in vision.
Vision • All-trans-retinol is converted to 11-cis-retinal. • The photosensitive molecule involved in vision is called rhodopsin, (also known as visual purple) which consists of a large protein (having a molecular weight of around 38,000) called opsin, joined to 11-cis-retinal. • Opsin does not absorb visible light, but when it is bonded with 11-cis-retinal to form rhodopsin, the new molecule has a very broad absorption band in the visible region of the spectrum. rhodopsin
Vitamin A functions, continue • Growth and development of tissues. Vitamin A is involved in normal cell differentiation specially for epithelial tissue cells of Cornea, skin, respiratory lining, GI tract lining • Vitamin A supports male and female reproductive processes and bone growth. • Immunity. Vitamin A is essential for immune function and vitamin-A deficiency is associated with decreased resistance to infections. • Respiratory infections and diarrhea 2-3X more likely in kids with low Vitamin A. • Bacteria and viruses more likely to invade unhealthy epithelial tissue • The severity of some infections, such as measles and diarrhea, is reduced by vitamin-A supplementation among those who suffer from vitamin-A deficiency.
Vitamin A functions, continue • It has been suggested that beta-carotene and other carotenoids (also called phytochemicals) may function as antioxidants by neutralizing free radicals. • Free radicals are unstable, highly reactive molecules that damage DNA, cause cell injury, and increase the risk of chronic disease. • Beta-carotene has also been associated with reducing the risk of lung cancer. • Lutein and zeaxanthin, yellow carotenoid pigments in corn and dark green leafy vegetables, may reduce the risk of macular degeneration of cornea or retina (تبقع القرنية او الشبكية ) and age-related cataracts (الماء الازرق). • Lycopene, a red carotenoid pigment in tomatoes, may help reduce the risk of prostrate cancer, cardiovascular disease, and skin damage from sunlight. • Repairs skin and promotes the growth of elastin e.g Retain A
which foods are rich in vitamin A sources (preformed and provitamin A precursors)? • Provitamin A Carotenoids • Dark greens • Yellow-orange • Carrots, • kale (اللفت), • spinach, • squash, • sweet potatoes, • cantaloupe, • peaches, • broccoli, • apricots • PreformedRetinoids • Liver • Fish • Fish oils • Fortified milk • Egg
which foods are rich in vitamin A? Essential Nutrient
Vit A deficiency • Dietary deficiency of vitamin A is rare in North America and western Europe. • it is the leading cause of blindness in children worldwide. • Newborn and premature infants, the urban poor, older adults, people with alcoholism or liver disease, and those with fat malabsorption syndrome are all at increased risk. • One of the earliest symptoms of vitamin-A deficiency is night blindness. It is a temporary condition, but if left untreated it can cause permanent blindness. This degeneration is called xerophthalmia جفاف الملتحمة)), and it usually occurs in children after they are weaned. • Symptoms of xerophthalmia include dryness of the cornea and eye membranes due to lack of mucus production, which leaves the eye vulnerable to surface dirt and bacterial infections.
Vit A deficiency • Vitamin-A deficiency can cause follicular hyperkeratosis (ضخامة و تقرن جريبات شعر الجلد), a condition in which hair follicles become plugged with keratin, giving a bumpy appearance and a rough, dry texture to skin. • In developing countries, the severity of infectious diseases such as measles is often correlated to the degree of vitamin-A deficiency. • Providing large doses of vitamin A reduces the risk of dying from these infections. • The age range of the target population for vitamin-A intervention programs is usually from birth to seven years. • Administration of high-potency doses in the range of 15,000 to 60,000 micrograms (μg) are distributed to young children in targeted areas of the world to build up liver stores for up to six months. However, consumption of adequate food sources is the most important long-term solution to vitamin-A deficiency.
Vit A Toxicity None of the forms of vitamin are easily excreted, so toxicity is a risk for those with kidney disease or as people age. • Vitamin-A toxicity, called hypervitaminosis A, • It can result from long-term supplementation of two to four times the Recommended Daily Allowance (RDA) for preformed vitamin A. • Excess intake of preformed vitamin A is a teratogen, meaning it can cause birth defects. • Birth defects associated with vitamin-A toxicity include: • cleft palate (انشقاق الحنك) • heart abnormalities • brain malfunction. • Acute excess intake during pregnancy can also cause spontaneous abortions. • Pregnant women should avoid prenatal supplements containing retinal, as well as medications made from retinoids, such as Accutane and Retin-A. • Prolonged and excessive consumption of carotene-rich foods can lead to hypercarotenemia (فرط جزرنة الدم), a clinical condition characterized by deep orange discoloration of the skin and increased carotene levels in the blood. This condition is usually harmless.
Vitamin D (Calciferol) • Common Names: Vitamin D; Calciferol, Cholecalciferol, Ergocalciferol • Forms: Calciferol, cholecalciferol, ergocalciferol, irradiated ergosterol • Vitamin D plays a critical role in the body’s use of calcium and phosphorous. It increases the amount of calcium absorbed from the small intestine and helps form and maintain bones. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth. • Vitamin D is Called a “conditional” vitamin. • For most people in sunny regions , sun provides 80-100% of their needs of Vitamin D Vitamin D2 (ergocalciferol) is obtained from plants. • Vitamin D3 is cholecalciferol derived from animal products Vitamin D
Structures of Vitamin D • There are different forms of vitamin D • Vitamin D2 (ergocalciferol) • vitamin D3 (cholecalciferol) • provitamins • Vitamin D is a generic term and indicates a molecule of the general structure that contains the 4 fused rings of steroid with differing side chain structures. • Technically vitamin D is classified as a seco-steroid. • Seco-steroids are those in which one of the rings has been broken. • in vitamin D, the 9,10 carbon-carbon bond of ring B is broken, and it is indicated by the inclusion of "9,10-seco" in the official nomenclature
Vitamins D3 & D2 • Vitamin D2 (ergocalciferol) is obtained from plants. • Vitamin D3 is cholecalciferol derived from animal products • Vitamin D3 (cholecalciferol) can be produced photochemically by the action of sunlight or ultraviolet light from the precursor sterol 7-dehydrocholesterol which is present in the epidermis or skin of most higher animals. • Thus, it is important to appreciate that vitamin D3 can be endogenously produced and that as long as the animal (or human) has access on a regular basis to sunlight there is no dietary requirement for this vitamin. • Vitamin D2 = ergocalciferol (which is equivalently potent to vitamin D3 in humans and many mammals) is produced commercially by the irradiation of the plant sterol ergosterol with ultraviolet light.
Absorption of Vitamin D • Vitamin D from foods is absorbed from the upper part of the small intestine, along with dietary fat, and transported to the liver. • In the skin, ultraviolet (UV) radiation from the sun converts a cholesterol derivative 7-dehydrocholesterol to cholecalciferol, which enters the blood stream and is transported to the liver. • In the liver, vitamin D is converted to calcidiol, an inactive form that circulates in blood. Kidneys take up calcidiol and convert it to an active hormone form of vitamin D called calcitriol. • People with chronic kidney failure have very low levels of calcitriol and must be routinely treated with this form of the vitamin.
Vitamin D – Cholecalciferol Cholesterol derivative Skin blood blood Calcidiol (inactive) Calcitriol (Active hormone form of vitamin D) 5-15 min Sunlight/week
Functions of Vitamin D • The group known as the D vitamins are required for growth, especially bone growth or "calcification". • The best-known function of active vitamin D is to help regulate blood levels of calcium and phosphorous. Vitamin D increases absorption of these minerals from the gastrointestinal (GI) tract. In combination with parathyroid hormone, it enhances their reabsorption from the kidneys and their mobilization from bones into the blood. • Vitamin D can be considered both a vitamin and a hormone. • Vitamin D plays an important role in maintaining adequate blood levels of insulin and may assist the metabolism of sugar. • 1,25 dihydroxycholecalciferol (DHCC), the most active form of vitamin D, functions to:» Increase the absorption of calcium from the intestines by stimulating the synthesis of calcium-binding protein. This occurs in the brush border of the intestinal mucosa.» Increase the resorption (ارتشاف) of calcium from bone.» Increase serum calcium levels. Once this occurs calcium can then be stored in the bones. Thus, even though it initially causes bone resorption, the net effect is to increase calcium deposition in the bone • Vitamin D helps maintain calcium levels even if dietary intakes are not optimal. Calcitriol controls growth of normal cells and some cancer cells. Adequate vitamin-D status has been linked to a reduced risk of developing breast, colon, and prostrate cancers
Primary sources of vitamin D • The primary food sources of vitamin D are milk and other dairy products fortified with vitamin D. • Egg yolk • Vitamin D is also found in oily fish as well as in cod liver oil. • Vegetables are usually low in vitamin D. Leafy dark green vegetables and mushrooms are significant sources of vitamin D from non-animal sources. • In addition to the vitamin D provided by food, we obtain vitamin D through our skin which makes vitamin D in response to sunlight.
Although about 10 substances have fat soluble vitamin D activity, vitamins D2 (or ergocalciferol) and D3 (or cholecalciferol) are the two most significant to humans. • Vitamin D3 is found in our diet, while vitamin D2 occurs in yeasts and fungi. Both can be formed from their respective provitamins by ultraviolet irradiation; in man the provitamin (7-dehydrocholesterol), which is found in skin, can be converted by sunlight to vitamin D3 and thus is an important source of the vitamin. Human beings can utilize both vitamins D2 and D3.