Lecture 4 : Micronutrients

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Definition: Vitamin B6 is a water-soluble vitamin that plays a crucial role in over 100 enzymatic reactions involved in amino acid metabolism, neurotransmitter synthesis, and red blood cell formation. It exists in several forms, including pyridoxine, pyridoxal, pyridoxamine, and their phosphorylated derivatives.

Basic: Pyridoxine is involved in the conversion of amino acids, such as tryptophan, into neurotransmitters like serotonin and norepinephrine, which regulate mood, sleep, and stress response. It also participates in the synthesis of hemoglobin and other heme-containing compounds critical for oxygen transport and energy production.

Intermediate: Vitamin B6 deficiency can lead to symptoms such as anemia, impaired immune function, dermatitis, depression, confusion, and neurological abnormalities, including peripheral neuropathy. Certain populations at risk of deficiency include pregnant women, individuals with malabsorption disorders, alcoholics, and users of certain medications that interfere with vitamin B6 metabolism.

Advanced: Dietary sources of vitamin B6 include poultry, fish, lean meats, eggs, dairy products, nuts, seeds, legumes, and fortified cereals. While vitamin B6 toxicity is rare from dietary sources, high-dose supplementation can cause adverse effects such as sensory neuropathy, numbness, and nerve damage. However, vitamin B6 supplementation may be beneficial for individuals with specific health conditions, such as premenstrual syndrome (PMS), carpal tunnel syndrome, or certain types of anemia.

Definition: Vitamin B7, also known as biotin or vitamin H, is a water-soluble vitamin that serves as a cofactor for enzymes involved in carbohydrate, fat, and protein metabolism. It plays a critical role in the synthesis of fatty acids, glucose, and certain amino acids.

Basic: Biotin is essential for the metabolism of macronutrients, facilitating the conversion of carbohydrates into energy and the synthesis of fatty acids and cholesterol. It also supports the production of glucose from non-carbohydrate sources (gluconeogenesis) and helps maintain stable blood sugar levels.

Intermediate: Biotin deficiency is rare but can occur in individuals with conditions such as malabsorption disorders, prolonged antibiotic use, or excessive consumption of raw egg whites, which contain avidin, a protein that binds to biotin and inhibits its absorption. Symptoms of deficiency may include thinning hair, brittle nails, dermatitis, muscle pain, fatigue, and neurological abnormalities.

Advanced: Dietary sources of biotin include egg yolks, liver, nuts, seeds, legumes, whole grains, and certain fruits and vegetables. Biotin supplementation is generally safe and well-tolerated, even at high doses, as excess biotin is excreted in urine. Biotin supplementation is sometimes used therapeutically to support hair, skin, and nail health, although scientific evidence supporting its efficacy for these purposes is limited.

Definition: Vitamin B9 encompasses naturally occurring folates found in food and synthetic folic acid, the form used in supplements and fortified foods. Folate is a water-soluble B vitamin essential for DNA synthesis, cell division, and red blood cell formation. It is particularly important during periods of rapid growth and development, such as pregnancy and infancy.

Basic: Folate plays a crucial role in the synthesis of DNA and RNA, the body's genetic material, as well as in the methylation of homocysteine to form methionine, an essential amino acid. Adequate folate intake is critical for preventing neural tube defects (such as spina bifida) in early pregnancy and supporting normal fetal growth and development.

Intermediate: Folate deficiency can lead to megaloblastic anemia, a condition characterized by large, immature red blood cells (megaloblasts) and symptoms such as fatigue, weakness, shortness of breath, and pale skin. It is also associated with an increased risk of neural tube defects, cardiovascular disease, and certain cancers.

Advanced: Dietary sources of folate include leafy green vegetables, legumes, citrus fruits, fortified cereals, and liver. Folic acid supplementation is recommended for women of childbearing age to prevent neural tube defects, with a daily intake of 400 to 800 micrograms recommended before conception and during early pregnancy. Folic acid fortification of grain products has been successful in reducing the prevalence of neural tube defects in many countries.

Definition: Vitamin B12 is a water-soluble vitamin essential for DNA synthesis, red blood cell formation, neurological function, and metabolism. It is unique among the B vitamins in that it contains cobalt in its molecular structure, hence its name cobalamin.

Basic: Vitamin B12 plays a critical role in the metabolism of folate, helping to convert folate into its active form (methylfolate) and facilitating the remethylation of homocysteine to methionine. It is also necessary for the maintenance of myelin, a fatty substance that insulates nerve fibers and facilitates nerve impulse conduction.

Intermediate: Vitamin B12 deficiency can lead to megaloblastic anemia, neurological symptoms such as tingling or numbness in the hands and feet (paresthesia), difficulty walking, memory loss, and cognitive impairment. Pernicious anemia, an autoimmune condition characterized by the destruction of gastric parietal cells that produce intrinsic factor, is a common cause of vitamin B12 deficiency.

Advanced: Dietary sources of vitamin B12 include animal-derived foods such as meat, poultry, fish, eggs, dairy products, and fortified plant-based foods such as fortified cereals, plant-based milks, and nutritional yeast. Individuals at risk of vitamin B12 deficiency include vegetarians, vegans, older adults, individuals with gastrointestinal disorders, and those with reduced gastric acid secretion. Vitamin B12 supplementation or fortified foods may be necessary to ensure adequate intake and prevent deficiency in these populations.

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