Vitamins and Vitamin A

Question 1

What are Vitamins?

Answer 1

• 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

Question 2

Bioavailability

Answer 2

the rate and extent to which a nutrient is absorbed and used
- Extent: iron + vitamin C

Question 3

Precursors

Answer 3

compounds that can be converted into other compounds
- AKA pre-vitamins
- Examples: Beta-carotene + vitamin A

Question 4

Minimizing Nutrient Losses

Answer 4

• Prevent Enzymatic Destruction
• Protect from Light and Air
• Prevent Heat Destruction or Losses in Water

Question 5

Types of Vitamins: Fat Soluble

Answer 5

• 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

Question 6

Types of Vitamins: Water Soluble

Answer 6

• B complex, C
• absorbed directly into the blood
• most not stored in the body
• Leave the body in urine
• Needed frequently

Question 7

B Vitamins

Answer 7

• Thiamin
• Riboflavin
• Niacin
• Pantothenic acid
• Biotin
• Vitamin B6
• Folate
• Vitamin B 12

Question 8

Vitamins: Primary Deficiency

Answer 8

vitamin not consumed in sufficient amounts to meet physiological needs (ex. scurvy d/t only fast food intake)

Question 9

Vitamins: Secondary deficiency

Answer 9

• impaired absorption or excess excretion (inadequate intrinsic factor = vitamin B12 deficiency)

Question 10

Vitamins: Toxicities

Answer 10

• Rarely occurs from food consumption
• Supplements may be toxic

Question 11

Nutrition in Practice: Phytochemicals

Answer 11

compounds in plants that confer colour, taste, and other characteristics; some phytochemicals are bioactive food components in functional foods

Question 12

Functional Foods

Answer 12

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.

Question 13

Vitamin A: and beta-carotene

Answer 13

• 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

Question 14

Retinol

Answer 14

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

Question 15

Retinal

Answer 15

active in vision

Question 16

Retinoic acid

Answer 16

a hormal, regulating cell differentiation, growth, and embryonic development

Question 17

Vitamin A’s role in gene expression

Answer 17

• Retinoic acid helps activate or deactivate genes
• genes direct the synthesis of proteins, inclduing enzymes, and enzymes perform the metabolic work of the tissues.

Question 18

Vitamin A’s role in vision

Answer 18

• maintains cornea
• rhodopsin (opsin (protein portion of the visual pigment molecule) + retinal) participates in light detection in retina
• early deficiency causes night blindness

Question 19

Vitamin A’s role in protein synthesis and cell differentiation

Answer 19

• 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

Question 20

Vitamin A’s role in immunity

Answer 20

• 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)

Question 21

Vitamin A’s role in reproduction, growth, and development

Answer 21

• Sperm development
• Fetal growth and development (essential for development of the nervous system, lungs, heart, kidneys, skeleton, eyes and ears)

Question 22

Beta-Carotene’s Role as an Antioxidant

Answer 22

• 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

Question 23

Vitamin A Deficiency

Answer 23

• 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

Question 24

Vitamin A toxicity

Answer 24

• 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

Question 25

Beta-carotene conversion and toxicity

Answer 25

• 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

Question 26

Vitamin A and Beta-Carotene in foods and RDA

Answer 26

• 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