Vitamins and Vitamin A Flashcards
What are Vitamins?
- Essential for bodily function
- Do not provide our body with energy (or kcalories)
- Organic compounds
- Obtained from foods, fortification (the addition of nutrients to foods) or supplements
Small but mighty
Bioavailability
the rate and extent to which a nutrient is absorbed and used
- Extent: iron + vitamin C
Precursors
compounds that can be converted into other compounds
- AKA pre-vitamins
- Examples: Beta-carotene + vitamin A
Minimizing Nutrient Losses
- Prevent Enzymatic Destruction
- Protect from Light and Air
- Prevent Heat Destruction or Losses in Water
Types of Vitamins: Fat Soluble
- A, D, E, K
- Absorbed with fat into the lymph before entering the blood
- Stored in the liver and fatty tissues
- Rarely leave the body and thus builds up in tissues
- Can be taken periodically
Types of Vitamins: Water Soluble
- B complex, C
- absorbed directly into the blood
- most not stored in the body
- Leave the body in urine
- Needed frequently
B Vitamins
- Thiamin
- Riboflavin
- Niacin
- Pantothenic acid
- Biotin
- Vitamin B6
- Folate
- Vitamin B 12
Vitamins: Primary Deficiency
vitamin not consumed in sufficient amounts to meet physiological needs (ex. scurvy d/t only fast food intake)
Vitamins: Secondary deficiency
- impaired absorption or excess excretion (inadequate intrinsic factor = vitamin B12 deficiency)
Vitamins: Toxicities
- Rarely occurs from food consumption
- Supplements may be toxic
Nutrition in Practice: Phytochemicals
compounds in plants that confer colour, taste, and other characteristics; some phytochemicals are bioactive food components in functional foods
Functional Foods
whole, fortified, enriched, or enhanced foods that have a potentially beneficial effect on health when consumed as part of a varied diet on a regular basis at effective levels.
Vitamin A: and beta-carotene
- beta-carotene is the plant-derived precursor to vitamin A
- vitamin A has role in gene expression, vision, cell differentiation (helps maintain health of body linings and skin), immunity, and reproduction and growth
- three different forms active in the body:
1. retinol
2. retinal
3. retinoic acid
Retinol
supports reproduction and is the major transport and storage form of the vitamin; the cells convert retinol to either retinal or retinoic acid as needed
Retinal
active in vision
Retinoic acid
a hormal, regulating cell differentiation, growth, and embryonic development
Vitamin A’s role in gene expression
- Retinoic acid helps activate or deactivate genes
- genes direct the synthesis of proteins, inclduing enzymes, and enzymes perform the metabolic work of the tissues.
Vitamin A’s role in vision
- maintains cornea
- rhodopsin (opsin (protein portion of the visual pigment molecule) + retinal) participates in light detection in retina
- early deficiency causes night blindness
Vitamin A’s role in protein synthesis and cell differentiation
- Differentiation: development of specific functions during cell maturation
Example: epithelial cells with the help of Vit. A helps to maintain the integrity of epithelial cells
Vitamin A’s role in immunity
- Immune defenses
- regulation of related genes (without suffiecient supply of vit A, the genetic interactions produce an altered response to infection that weakens the body’s defenses)
Vitamin A’s role in reproduction, growth, and development
- Sperm development
- Fetal growth and development (essential for development of the nervous system, lungs, heart, kidneys, skeleton, eyes and ears)
Beta-Carotene’s Role as an Antioxidant
- Antioxidant: a compound that protects other compounds from oxygen by itself reacting with oxygen; Oxidation is a potentially damaging effect of normal cell chemistry involving oxygen.
- oxygen triggers the formation of free radicals that can start chain reactions in cell membranes. if left uncontrolled this can damage cell structure and impair cell function
- can instigate early stages of cancer and heart disease. Alzheimers disease, arthritis, cataracts, diabetes, kidney disease
Vitamin A Deficiency
- All epithelial surfaces: cells harden (produce keratin) and flatten
- Major cause of preventable blindness (xerophthalmia - progressive blindness caused by inadequate mucus production due to severe vitamin A deficiency) via damage to cornea
Xerosis (dryness in the cornea) –> keratomalacia (softening of the cornea) - increased susceptibility to infection
Vitamin A toxicity
- caused by excessive performed vitamin A (vitamin A in its active form)
- Teratogenic risk (birth defects)
- Weakens bones
- Children are most vulnerable to Vitamin A toxicity
- exhibit symptoms in same body systems as deficiency
Beta-carotene conversion and toxicity
- Retinol activity equivalents (REA): a measure of vitamin A activity; the amount of retinol that the body will derive from a food containing performed retinol or its precursor beta-carotene
- high intake from foods not hazardous
- high intake from supplements may be
Vitamin A and Beta-Carotene in foods and RDA
- Performed vitamin A: liver, fish oil, milk, cheese, fortified milk
- Beta-carotene in foods: bright orange produce: carrots, sweet potatoes, pumpkins, cantaloupe, apricots. Dark green vegetables: spinach, other greens, broccoli
RDA: 700mcg for women and 900mcg for men
