Lecture 5 : Micronutrients

Definition: Vitamin C is a water-soluble vitamin and powerful antioxidant that plays essential roles in collagen synthesis, immune function, wound healing, and iron absorption. It is necessary for the growth and repair of tissues throughout the body.

Basic: Vitamin C is best known for its role in supporting the immune system, where it enhances the function of white blood cells and acts as an antioxidant, neutralizing harmful free radicals. It also aids in collagen formation, which is vital for maintaining skin, cartilage, bones, and blood vessels.

Intermediate: Vitamin C deficiency can lead to scurvy, a condition characterized by fatigue, weakness, swollen gums, joint pain, and easy bruising or bleeding. While scurvy is rare in developed countries due to the availability of vitamin C-rich foods, certain populations, such as smokers, individuals with limited fruit and vegetable intake, and those with malabsorption disorders, may be at higher risk.

Advanced: Dietary sources of vitamin C include citrus fruits (such as oranges, lemons, and grapefruits), strawberries, kiwi, bell peppers, broccoli, Brussels sprouts, and tomatoes. While vitamin C supplementation is generally safe and well-tolerated, high doses may cause gastrointestinal discomfort and diarrhea in some individuals. Vitamin C supplementation is sometimes used therapeutically to support immune function, reduce the duration and severity of colds, and enhance wound healing.

Definition: Vitamin D is a fat-soluble vitamin and hormone precursor essential for calcium absorption, bone health, immune function, and regulation of gene expression. It is primarily synthesized in the skin upon exposure to sunlight but can also be obtained from dietary sources and supplements.

Basic: Vitamin D plays a crucial role in maintaining optimal bone health by enhancing calcium and phosphorus absorption in the intestines and promoting their deposition in bones. It also regulates immune function, modulating the activity of immune cells and reducing inflammation.

Intermediate: Vitamin D deficiency can lead to rickets in children and osteomalacia in adults, conditions characterized by weakened, soft bones and an increased risk of fractures. Additionally, inadequate vitamin D status has been associated with an increased risk of various chronic diseases, including autoimmune disorders, cardiovascular disease, and certain cancers.

Advanced: Dietary sources of vitamin D include fatty fish (such as salmon, mackerel, and tuna), egg yolks, fortified dairy and plant-based milk, and fortified cereals. Sunlight exposure is the primary source of vitamin D for most people, as ultraviolet B (UVB) radiation converts a precursor molecule in the skin into vitamin D. However, factors such as geographic location, season, time of day, skin pigmentation, sunscreen use, and aging can affect vitamin D synthesis. Supplementation may be necessary for individuals at risk of deficiency, including those with limited sun exposure, dark skin, malabsorption disorders, or obesity.

Definition: Vitamin E is a fat-soluble antioxidant that protects cells from oxidative damage by scavenging free radicals and inhibiting lipid peroxidation. It exists in several forms, with alpha-tocopherol being the most biologically active form in humans.

Basic: Vitamin E plays a critical role in maintaining cellular integrity and protecting cell membranes from oxidative stress, particularly in tissues with high oxygen consumption, such as the brain, heart, and lungs. It also supports immune function and may have anti-inflammatory properties.

Intermediate: Vitamin E deficiency is rare but can occur in individuals with conditions that impair fat absorption, such as cystic fibrosis, cholestatic liver disease, or pancreatic insufficiency. Symptoms of deficiency may include muscle weakness, nerve damage, impaired coordination, and an increased susceptibility to infections.

Advanced: Dietary sources of vitamin E include nuts, seeds, vegetable oils (such as wheat germ, sunflower, safflower, and olive oil), avocado, and leafy green vegetables. While vitamin E supplementation is generally safe, high doses may interfere with blood clotting and increase the risk of hemorrhagic stroke. The role of vitamin E supplementation in preventing chronic diseases such as cardiovascular disease, cancer, and cognitive decline remains controversial, with mixed evidence from clinical trials.

Definition: Vitamin K is a fat-soluble vitamin essential for blood clotting, bone metabolism, and cardiovascular health. It exists in two primary forms: vitamin K1 (phylloquinone), found in green leafy vegetables, and vitamin K2 (menaquinone), synthesized by bacteria in the gut and found in fermented foods and animal products.

Basic: Vitamin K plays a crucial role in the activation of clotting factors in the blood coagulation cascade, facilitating the formation of blood clots to prevent excessive bleeding. It also regulates calcium metabolism, directing calcium to bones and teeth for mineralization and preventing its deposition in soft tissues, such as blood vessels.

Intermediate: Vitamin K deficiency can lead to bleeding disorders, osteoporosis, and an increased risk of fractures. Newborns are particularly vulnerable to vitamin K deficiency bleeding (VKDB) due to low vitamin K stores at birth and limited transfer across the placenta.

Advanced: Dietary sources of vitamin K1 include green leafy vegetables (such as kale, spinach, collard greens, and broccoli), while vitamin K2 is found in fermented foods (such as natto, cheese, and sauerkraut) and animal products (such as liver, egg yolks, and meat). Supplementation with vitamin K may be necessary for individuals at risk of deficiency, such as those with malabsorption disorders, liver disease, or long-term antibiotic use. Additionally, vitamin K supplementation has been studied for its potential role in cardiovascular health, bone health, and cancer prevention, although more research is needed to establish its efficacy and safety for these indications.

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