Дефицит витаминов: причины, симптомы и профилактика

Vitamin deficiency is the condition of a long term lack of a vitamin. When caused by not enough vitamin intake it is classified as a primary deficiency, whereas when due to an underlying disorder such as malabsorption it is called a secondary deficiency. An underlying disorder can have 2 main causes:
Metabolic causes: Genetic defects in enzymes (e. g. kynureninase) involved in the kynurenine pathway of synthesis of niacin from tryptophan can lead to pellagra (niacin deficiency). Lifestyle choices: Lifestyle choices and habits that increase vitamin needs, such as smoking or drinking alcohol. Government guidelines on vitamin deficiencies advise certain intakes for healthy people, with specific values for women, men, babies, children, the elderly, and during pregnancy or breastfeeding. Many countries have mandated vitamin food fortification programs to prevent commonly occurring vitamin deficiencies. Updated in 2016, the US Food and Drug Administration published a set of tables that define Estimated Average Requirements (EARs) and (RDAs). RDAs are higher to cover people with higher than average needs. Together, these are part of Dietary Reference Intakes. For a few vitamins, there is not sufficient information to set EARs and RDAs. For these, an Adequate Intake is shown, based on an assumption that what healthy people consume is sufficient. India sets its recommendation at 40 mg/day.

Vitamin Symptoms & Diagnosis InformationThiamine (Vitamin B1) deficiency Weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart beat. Deficiency is assessed by red blood cell status and urinary output. Especially common in countries that do not require fortification of wheat and maize flour and rice to replace the naturally occurring thiamine content lost to milling, bleaching and other processing. Riboflavin (Vitamin B2) deficiency Deficiency causes painful red tongue with sore throat, chapped and cracked lips, and inflammation at the corners of the mouth (angular cheilitis). Eyes can be itchy, watery, bloodshot and sensitive to light. Riboflavin deficiency also causes anemia with red blood cells that are normal in size and hemoglobin content, but reduced in number. This is distinct from anemia caused by deficiency of folic acid or vitamin B12. Especially common in countries that do not require fortification of wheat and maize flour and rice to replace the naturally occurring riboflavin lost during processing. Chronic alcoholism is a contributing risk factor. Pantothenic acid (Vitamin B5) deficiency Irritability, fatigue, and apathy. Extremely rare. Vitamin B6 deficiency Microcytic anemia, electroencephalographic abnormalities, dermatitis, seborrhoeic dermatitis like eruption, atrophic glossitis with ulceration, angular cheilitis, conjunctivitis, and intertrigo. Neurologic symptoms of depression, somnolence, confusion, and neuropathy (due to impaired sphingosine synthesis) and microcytic anemia Uncommon, although it may be observed in certain conditions, such as end stage kidney diseases or malabsorption syndromes, such as celiac disease, Crohn disease or ulcerative colitis. Biotin (Vitamin B7) deficiency Rashes including red, patchy ones near the mouth and fine, brittle hair. Hallucinations, Lethargy, Mild depression, which may progress to profound fatigue and, eventually, to somnolence, Generalized muscular pains (myalgia) and Paresthesias. Decreased urinary excretion of biotin and increased urinary excretion of 3 hydroxyisovaleric acid are better indicators of biotin deficiency than concentration in the blood. Rare, although biotin status can be compromised in alcoholics and during pregnancy and breastfeeding. Deficiency affects hair growth and skin health. Folate (Vitamin B9) deficiency Symptoms may include feeling tired, heart palpitations, shortness of breath, feeling faint, open sores on the tongue, loss of appetite, changes in the color of the skin or hair, irritability, and behavioral changes. In adults, anemia (macrocytic, megaloblastic anemia) can be a sign of advanced folate deficiency. Common, and associated with numerous health problems, but primarily with neural tube defects (NTDs) in infants when the mother's plasma concentrations were low during the first third of pregnancies. Government mandated fortification of foods with folic acid has reduced the incidence of NTDs by 25% to 50% in more than 60 countries using such fortification. Cerebral folate deficiency is a rare condition in which concentrations of folate are low in the brain despite being normal in the blood. Vitamin B12 deficiency Anemia, neurological and digestive disorders. This may result in feeling tired, shortness of breath, lightheadedness, headaches, mouth ulcers, pale skin, rapid heartbeat, loss of appetite, hair loss, low blood pressure, decreased ability to think, joint pain, numbness and tingling to the fingers and toes, and tinnitus. Damage to nerves may result in depression, confusion, memory loss, difficulty walking, sense loss, mania, and psychosis. Lead to megaloblastic anemia, subacute combined degeneration of spinal cord, and methylmalonic acidemia, among other conditions. Supplementation with folate can mask vitamin B12 deficiency. Consuming a vegan diet increases the risk, since Vitamin B12 is mostly found in food and drinks made from animal products, including eggs and dairy products. Vitamin C deficiency Deficiency leads to weakness, weight loss and general aches and pains. Longer term depletion affects connective tissues, severe gum disease, and bleeding from the skin. Rare, consequently, no countries fortify foods as a means of preventing this deficiency. It is the leading cause of preventable childhood blindness, afflicting 250,000 to 500,000 malnourished children in the developing world each year, about half of whom die within a year of becoming blind, as vitamin A deficiency also weakens the immune system. Vitamin D deficiency Usually asymptomatic, causes reduce bone density (osteomalacia), rickets, myopathy, and is associated with the development of schizophrenia. It is typically diagnosed by measuring the concentration of the 25 hydroxyvitamin D (25(OH)D) in plasma, which is the most accurate measure of stores of vitamin D in the body. Deficiency is defined as less than 10 ng/mL, and insufficiency in the range of 10–30 ng/mL. Serum 25(OH)D concentrations above 30 ng/mL are "not consistently associated with increased benefit." Serum concentrations above 50 ng/mL may be cause for concern. Common, most foods do not contain vitamin D, indicating that a deficiency will occur unless people get sunlight exposure or eat manufactured foods purposely fortified with vitamin D. Vitamin D deficiency is a known cause of rickets, and has been linked to numerous other health problems. Vitamin E deficiency Causes poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function. The US Institute of Medicine defines deficiency as a blood concentration of less than 12 μmol/L. Rare, occurring as a consequence of abnormalities in dietary fat absorption or metabolism, such as a defect in the alpha tocopherol transport protein, rather than from a diet low in vitamin E. Vitamin K deficiency Signs and symptoms can include sensitivity to bruising, bleeding gums, nosebleeds, and heavy menstrual bleeding in women. Rare as consequence of low dietary intake. A deficient state can be a result of fat malabsorption diseases. Newborn infants are a special case. Plasma vitamin K is low at birth, even if the mother is supplemented during pregnancy, because the vitamin is not transported across the placenta. Vitamin K deficiency bleeding (VKDB) due to physiologically low vitamin K plasma concentrations is a serious risk for premature and term newborn and young infants. Untreated, consequences can cause brain damage or death. The prevalence of VKDB is reported at 0.25 to 1.7%, with higher risk in Asian populations. The recommended prevention treatment is an intramuscular injection of 1 mg of vitamin K at birth (called the Vitamin K shot.). There are protocols for oral administration, but intramuscular injection is preferred.

Food fortification is the process of adding micronutrients (essential trace elements and vitamins) to food as a public health policy which aims to reduce the number of people with dietary deficiencies within a population. Staple foods of a region can lack particular nutrients due to the soil of the region or from inherent inadequacy of a normal diet. Addition of micronutrients to staples and condiments can prevent large scale deficiency diseases in these cases. As defined by the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), fortification refers to "the practice of deliberately increasing the content of an essential micronutrient, i. e., vitamins and minerals in a food irrespective of whether the nutrients were originally in the food before processing or not, so as to improve the nutritional quality of the food supply and to provide a public health benefit with minimal risk to health", whereas enrichment is defined as "synonymous with fortification and refers to the addition of micronutrients to a food which are lost during processing". The Food Fortification Initiative lists all countries in the world that conduct fortification programs, and within each country, what nutrients are added to which foods. Vitamin fortification programs exist in one or more countries for folate, niacin, riboflavin, thiamin, vitamin A, vitamin B6, vitamin B12, vitamin D and vitamin E. As of 21 December 2018, 81 countries required food fortification with one or more vitamins.

Starting in 2000, rice was experimentally genetically engineered to produce higher than normal beta carotene content, giving it a yellow/orange color. The product is referred to as golden rice (Oryza sativa). Biofortified sweet potato, maize, and cassava were other crops introduced to enhance the content of beta carotene and certain minerals. When eaten, beta carotene is a provitamin, converted to retinol (vitamin A). The concept is that in areas of the world where vitamin A deficiency is common, growing and eating this rice would reduce the rates of vitamin A deficiency, particularly its effect on childhood vision problems. and were being assessed for taste and education about their health benefits to improve acceptance and adoption by consumers in impoverished countries. and hypervitaminosis D are the most common examples. Vitamin D toxicity does not result from sun exposure or consuming foods rich in vitamin D, but rather from excessive intake of vitamin D supplements, possibly leading to hypercalcemia, nausea, weakness, and kidney stones. The United States, European Union and Japan, among other countries, have established "tolerable upper intake levels" for those vitamins which have documented toxicity.