49-46 Recording

Vitamin Classification

• Fat Soluble Vitamins: These vitamins require dietary fat for optimal absorption and utilization within the body. The fat-soluble vitamins include A, D, E, and K, all of which play pivotal roles in physiological processes, including vision, bone health, antioxidant defense, and blood coagulation.

• Water Soluble Vitamins: In contrast, water soluble vitamins dissolve readily in water and are typically absorbed directly into the bloodstream, leading to easier uptake by the body, resulting in less storage and therefore a more consistent need for daily intake. This group includes the B vitamins and vitamin C.

Vitamin A

• Three active forms exist:

  • Retinol: The alcohol form, which is essential for vision and cellular functions; it can be converted to retinal.

  • Retinal: Important for vision; it plays a critical role in forming visual pigments in the retina and is interconvertible to retinol, allowing for regeneration of visual cycle components.

  • Retinoic Acid: The oxidized form essential for growth and development, particularly affecting gene expression and cellular differentiation; this form cannot revert back to retinal.

• Characteristics: Retinal's hydrophobic tail fosters its fat-soluble nature, enabling it to be integrated into cell membranes, which are primarily lipid-based.

• Functions: Vitamin A regulates gene expression in target cells, influencing various processes such as cell division, growth, and differentiation, which include immune functions, epithelial integrity, and reproductive health.

Role in Vision

• Rhodopsin: A crucial photopigment in the rod cells of the retina, composed of opsin and cis retinal, vital for low-light vision.

• Light Reaction: The exposure of rhodopsin to light triggers a conformational change that separates opsin from cis retinal, initiating an electrical signal that travels to the brain. The process is cyclical, where cis retinal converts to trans retinal and then reconverts back, essential for continued vision functionality.

• Night Blindness: A deficiency in Vitamin A can lead to difficulty seeing in low light conditions, known as night blindness; severe deficiency may result in xerophthalmia, a serious vision impairment which is reversible with proper dietary correction.

Sources and Recommendations

• Sources: Dietary sources rich in Vitamin A include:

  • Animal Sources: Beef liver, dairy products, egg yolk, and certain fish which are high in preformed Vitamin A (retinol).

  • Plant Sources: Fruits and vegetables like carrots, spinach, and sweet potatoes, where beta carotene acts as a precursor that the body can convert to active Vitamin A.

Vitamin D

• Two forms:

  • D2 (Ergocalciferol): Sourced from plants and fungi, and typically ingested through fortified foods.

  • D3 (Cholecalciferol): Derived from animal sources and synthesized in the skin upon exposure to UV radiation from sunlight, making it a critical nutrient that is often deficient in places with limited sunlight.

• Activation Process: The synthesis of Vitamin D begins when UV light converts cholesterol in the skin to pre-vitamin D3, which is then activated through hydroxylation processes in the liver (25 hydroxylase) and kidneys (1 alpha hydroxylase) leading to the production of calcitriol, the biologically active form.

• Functions: Vitamin D plays a pivotal role in regulating calcium metabolism essential for maintaining bone health and homeostasis by enhancing calcium uptake in the gut and facilitating calcium resorption from bones if dietary intake is insufficient.

Recommendations

• Supplementation Advice: Given common deficiencies observed in populations, especially in Canada where sunlight exposure is limited, higher doses around 5000 IU may be advisable, particularly during winter months. Taking vitamin D with dietary fat enhances absorption significantly, ensuring maximum efficacy.

Vitamin E

• Forms: Vitamin E comprises various forms, including alpha tocopherol and alpha tocotrienol, each with unique physiological benefits.

• Functions: Key functions include acting as an antioxidant, protecting cellular membranes from oxidative damage caused by free radicals, and stabilizing polyunsaturated fats to minimize cell damage and associated pathological processes.

Recommendations and Sources

• Sources: Good dietary sources include nuts, seeds, and vegetable oils, all of which provide high levels of tocopherols and tocotrienols vital for health maintenance.

Conclusion

• Emphasizes the importance of consuming a balanced diet rich in both fat-soluble and water-soluble vitamins to ensure adequate nutrient intake essential for optimal health.

• Ongoing monitoring for deficiencies, especially of Vitamin D in regions with reduced sunlight exposure like Canada, is crucial to prevent long-term health implications.

• Recommendations highlight that supplementation should be approached judiciously, ideally with professional guidance to tailor to individual health needs and dietary considerations.