The principally pharmacological aspects of vitamins are described here.The nutritional aspects, physiological function, sources, daily requirements and deficiency syndromes (primary and secondary) are to be found in any textbook of medicine. • • • • Vitamin A: retinol Vitamin B: complex Vitamin C: ascorbic acid Vitamin D, calcium, parathyroid hormone, calcitonin, bisphosphonates, bone • Treatment of calcium and bone disorders • Vitamin E:tocopherol
that subclinical vitamin deficiencies are a cause of much chronic ill-health and liability to infections.
This book is for anyone who wants an understanding of the fascinating role vitamins
and minerals play in nutrition. It can be used as a supplementary textbook for
nutrition classes, as a self-learning guide, and as a refresher for health professionals.
This book broadens and explains the vitamin and mineral information found in
standard nutrition courses.
Throughout the text are many figures, graphs, and tables that visually display
information and relationships. If you have not taken a class in biochemistry, then
this will be an interesting and relevant way to be introduced to it....
The safe upper limit for vitamin B6 has been set at 100 mg/d, although no adverse effects have been associated with high intakes of vitamin B 6 from food sources only. When toxicity occurs, it causes a severe sensory neuropathy, leaving patients unable to walk. Some cases of photosensitivity and dermatitis have also been reported.
Folate, Vitamin B12 See Chap. 90.
Vitamin C Both ascorbic acid and its oxidized product dehydroascorbic acid are biologically active.
Vitamin E Deficiency: Treatment
Symptomatic vitamin E deficiency should be treated with 800–1200 mg of αtocopherol per day. Patients with abetalipoproteinemia may need as much as 5000–7000 mg/d. Children with symptomatic vitamin E deficiency should be treated with 400 mg/d orally of water-miscible esters; alternatively, 2 mg/kg per d may be administered intramuscularly. Vitamin E in high doses may protect against oxygen-induced retrolental fibroplasia and bronchopulmonary dysplasia, as well as intraventricular hemorrhage of prematurity.
Treatment of pellagra consists of oral supplementation of 100–200 mg of nicotinamide or nicotinic acid three times daily for 5 days. High doses of nicotinic acid (2 g/d in a time-release form) are used for the treatment of elevated cholesterol and triglyceride levels and/or low high-density lipoprotein (HDL) cholesterol level (Chap. 350).
Toxicity Prostaglandin-mediated flushing due to binding of the vitamin to a G protein–coupled receptor has been observed at daily doses as low as 50 mg of niacin when taken as a supplement or as therapy for dyslipidemia.
The retinol activity equivalent (RAE) is used to express the vitamin A value of food. One RAE is defined as 1 µg of retinol (0.003491 mmol), 12 µg of βcarotene, and 24 µg of other provitamin A carotenoids. In older literature, vitamin A was often expressed in international units (IU), with 1 RAE being equal to 3.33 IU of retinol and 20 IU of β-carotene, but these units are no longer in current scientific use.
Liver, fish, and eggs are excellent food sources for preformed vitamin A; vegetable sources of provitamin A carotenoids include dark green and deeply colored...
Harrison's Internal Medicine Chapter 71. Vitamin and Trace Mineral Deficiency and Excess
Vitamin and Trace Mineral Deficiency and Excess: Introduction
Vitamins and trace minerals are required constituents of the human diet since they are either inadequately synthesized or not synthesized in the human body. Only small amounts of these substances are needed for carrying out essential biochemical reactions (e.g., acting as coenzymes or prosthetic groups).
Thiamine (Vitamin B1) Thiamine was the first B vitamin to be identified and is therefore also referred to as vitamin B1. Thiamine functions in the decarboxylation of αketoacids, such as pyruvate α-ketoglutarate, and branched-chain amino acids and thus is a source of energy generation. In addition, thiamine pyrophosphate acts as a coenzyme for a transketolase reaction that mediates the conversion of hexose and pentose phosphates.
Biotin is a water-soluble vitamin that plays a role in gene expression, gluconeogenesis, and fatty acid synthesis and serves as a CO 2 carrier on the surface of both cytosolic and mitochondrial carboxylase enzymes. The vitamin also functions in the catabolism of specific amino acids (e.g., leucine). Excellent food sources of biotin include organ meat such as liver or kidney, soy, beans, yeast, and egg yolks; however, egg white contains the protein avidin, which strongly binds the vitamin and reduces its bioavailability.
Acute toxicity of vitamin A was first noted in Arctic explorers who ate polar bear liver and has also been seen after administration of 150 mg in adults or 100 mg in children. Acute toxicity is manifested by increased intracranial pressure, vertigo, diplopia, bulging fontanels in children, seizures, and exfoliative dermatitis; it may result in death. In children being treated for vitamin A deficiency according to the protocols outlined above, transient bulging of fontanels occurs in 2% of infants, and transient nausea, vomiting, and headache occur in 5% of preschoolers.
Thiamine Deficiency: Treatment
In acute thiamine deficiency with either cardiovascular or neurologic signs, 100 mg/d of thiamine should be given parenterally for 7 days, followed by 10 mg/d orally until there is complete recovery. Cardiovascular improvement occurs within 24 h, and ophthalmoplegic improvement occurs within 24 h. Other manifestations gradually clear, although psychosis in Wernicke-Korsakoff syndrome may be permanent or persist for several months.
The vitamins are a chemically disparate group of compounds whose only common
feature is that they are dietary essentials that are required in small amounts for the
normal functioning of the body and maintenance of metabolic integrity.Metabolically,
they have diverse functions, such as coenzymes, hormones, antioxidants,
mediators of cell signaling, and regulators of cell and tissue growth and differentiation.
It has been recognized for many years that states of nutrient deficiency are associated
with an impaired immune response and with increased susceptibility to infectious
disease. In turn, infection can affect the status of several nutrients, thus setting
up a vicious circle of under nutrition, compromised immune function and infection.
The Encyclopedia of Diseases and Disorders provides
authoritative information on a wide variety of diseases
and health disorders. Although the focus in planning
this collection of articles was on subjects of interest to
young readers, the information provided here is
valuable to users of any age. More than two hundred
articles are categorized in three major areas of interest:
infections, noninfectious diseases, and mental
Introduction Micronutrient deficiencies affect the majority of the population in Asia. Though somewhat lower than in other countries in the region, micronutrient deficiencies remain p r eva len t in Vie tna m. The prevalence of xerophthalmia, or clinical vitamin A deficiency (VAD), is now lower than the cut-off point established by the World Health Organization (WHO) to indicate a significant public health problem. However, the prevalence of sub-clinical VAD as measured by low serum retinol exceeds 10% for children under five and pregnant women.
From John Glenn s mission to orbit Earth to the
International Space Station program, space food
research has met the challenge of providing food
that tastes good and travels well in space. To better understand
this process, we can look back through history.
Explorers have always had to face the problem of how to
carry enough food for their journeys. Whether those
explorers are onboard a sailing ship or on the Space
Shuttle, adequate storage space has been a problem.
Vitamins and trace minerals are required constituents of the human diet since they are either inadequately synthesized or not synthesized in the human body. Only small amounts of these substances are needed for carrying out essential biochemical reactions (e.g., acting as coenzymes or prosthetic groups). Overt vitamin or trace mineral deficiencies are rare in Western countries due to a plentiful, varied, and inexpensive food supply; however, multiple nutrient deficiencies may appear together in persons who are chronically ill or alcoholic.
Flavonoids constitute a large family of polyphenols that contribute to the aroma, taste, and color of fruits and vegetables. Major groups of dietary flavonoids include anthocyanidins in berries; catechins in green tea and chocolate; flavonols (e.g., quercitin) in broccoli, kale, leeks, onion, and the skins of grapes and apples; and isoflavones (e.g., genistein) in legumes. Isoflavones have a low bioavailability and are partially metabolized by the intestinal flora.