Unit 9: Antioxidant Vitamins

Question 1

For Vitamin A: Identify its naturally occurring and biologically active forms.

Answer 1

Retinol
Retinal
Retinoic acid
Beta‑carotene.

Question 2

For Vitamin A: Identify its functions in the body.

Answer 2

Vision; maintenance of cornea, epithelial cells, mucous membranes, skin; bone and tooth growth; reproduction; immunity

Question 3

For Vitamin A: Describe the symptoms of deficiency and the prevalence of deficiency in the Canadian population.

Answer 3

Night blindness, corneal drying (xerosis), triangular gray spots on eye (Bitot’s spots), softening of the cornea (keratomalacia), and corneal degeneration and blindness (xerophthalmia); impaired immunity (infectious diseases); plugging of hair follicles with keratin, forming white lumps (hyperkeratosis)
While actual deficiency may be quite rare, a low intake of vitamin A is found in a sizable fraction of the population of Canada

Question 4

For Vitamin A: Discuss its therapeutic uses.

Answer 4

Vitamin A toxicity is possible through an excessive intake of preformed vitamin A from animal sources (e.g., cod liver oil) or from supplements. Children are especially susceptible. Adolescents and adults should also be cautioned against self‑treatment of skin conditions, such as acne, with the use of over‑the‑counter oral vitamin A. Accutane as an example of a synthetic analog of retinoic acid (called isotretinoin). Although effective, it is highly toxic when taken orally.

Beta‑carotene is non‑toxic; the only effect of prolonged excessive intake is hypercarotenemia. The symptom is yellowish staining of the skin, which is reversible and harmless; infants and young children are especially susceptible.
Preformed vitamin A appears to be of very limited effectiveness in preventing cancer, and toxicity symptoms have been reported with long‑term doses
Epidemiological and animal studies have shown an association between high intakes of beta‑carotene and a decreased risk of some cancers. Because beta‑carotene functions as an antioxidant, researchers hypothesized that beta‑carotene could ward off cancer through its antioxidant effect. (However, trials have shown no effect)l

Question 5

For Vitamin A: List the symptoms of toxicity.

Answer 5

Chronic Toxicity:
Increased activity of osteoclasts causing reduced bone density; liver abnormalities; birth defects
Acute Toxicity:
Blurred vision, nausea, vomiting, vertigo; increase of pressure inside skull, mimicking brain tumour; headaches; muscle incoordination

Question 6

For Vitamin A: List some of its major food sources.

Answer 6

Retinol: fortified milk, cheese, cream, butter, fortified margarine, eggs, liver
Beta-carotene: spinach and other dark leafy greens; broccoli, deep orange fruits (apricots, cantaloupe) and vegetables (squash, carrots, sweet potatoes, pumpkin)

Question 7

For Vitamin A: Discuss its chemical stability in relation to food preparation practices and other factors.

Answer 7

Little vitamin A is lost in normal food preparation. The only method of food processing that significantly affects vitamin A content is the removal of fat from such foods as milk. However, such foods are fortified with vitamin A, making the low‑fat products equivalent to the full‑fat ones in vitamin A content.

Vitamin A is sensitive to oxidation by air in the presence of light. Oxidation of fats and oils that contain fortified vitamin A can destroy fat‑soluble vitamins, including vitamin A. vitamin E, an antioxidant, can protect vitamin A.

Question 8

For Vitamin E: Identify its function in the body as an antioxidant.

Answer 8

Fat soluble antioxidant (stabilization of cell membranes, regulation of oxidation reactions, protection of unsaturated fatty acids and vitamin A)
Prevents the formation of free radicals (unstable molecules containing unpaired electrons) and the cell damage they can cause.

Question 9

For Vitamin E: Describe its deficiency symptoms.

Answer 9

Red blood cell breakage, and nerve damage
Primary vitamin E deficiency is rarely seen in human adults because body stores are extensive and the vitamin is widely available. However, secondary vitamin E deficiency may develop as a result of serious fat malabsorption syndromes resulting from liver, pancreatic, or gallbladder disease in infants, children, or adults.

Question 10

For Vitamin E: Discuss the claims of benefits for the use of supplements and possible toxicity symptoms.

Answer 10

Intervention studies have provided weak evidence (at best) that high‑dose supplements of vitamin E are of preventive value against heart disease or cancer. Research has also discredited claims that vitamin E improves physical or sexual performance, and delays the aging process. However, many people still take vitamin E supplements for all kinds of reasons—often in large doses.
Toxicity Symptoms: Augments the effects of anti-clotting medication
Vitamin E is considered the least toxic of the fat‑soluble vitamins because absorption decreases rapidly with increased intake. However, although toxicity is rare, some signs of toxicity are now suspected. The tolerable upper intake level is 1000 milligrams. What is almost certainly a much more serious problem than actual toxicity is an increased risk of mortality.

Question 11

For Vitamin E: List some of its major food sources.

Answer 11

Polyunsaturated plant oils, margarine, salad dressings, leafy green vegetables (spinach, turnip greens, collard greens, broccoli), wheat germ, whole grains, liver, egg yolks, nuts, seeds

Question 12

For Vitamin E: Discuss its chemical stability to food preparation practices and other factors.

Answer 12

Vitamin E is easily destroyed by intense heating and by exposure to oxygen; thus, deep fat frying will significantly reduce the vitamin E content of both the oil used for frying and the fried food itself. Oxidation of vitamin E in foods can occur through improper storage and handling. For example, food frozen for a long time at an insufficiently low temperature may lose some of its vitamin E. The major loss of vitamin E occurs through the milling of grains.

Question 13

For Vitamin C: Identify its functions in the body.

Answer 13

Collagen synthesis (strengthens blood vessel walls, forms scar tissue, provides matrix for bone growth), antioxidant, thyroxin synthesis, amino acid metabolism, strengthens resistance to infection, helps in absorption of iron

Question 14

For Vitamin C: Describe its deficiency and toxicity symptoms.

Answer 14

Deficiency Symptoms:
Although uncommon, vitamin C deficiency is likely to occur in people who consume little or no fruit and vegetables. Susceptible groups are the elderly, alcoholics, infants consuming cow’s milk exclusively, and the severely ill. As tissue saturation drops to about 20%, specific clinical symptoms of scurvy start to appear.
Anemia (small-cell type),a atherosclerotic plaques, pinpoint hemorrhages; bone fragility, joint pain; poor wound healing, frequent infections; bleeding gums, loosened teeth; muscle degeneration, pain; hysteria, depression; rough skin, blotchy bruises
Toxicity Symptoms:
nausea, abdominal cramps, and diarrhea. Ascorbic acid in the large intestine has an osmotic effect.
interference with the testing of urinary glucose. The chemical resemblance between ascorbic acid and glucose is close. Thus, people consuming high doses of ascorbic acid can test positive for urine glucose.
blood cell breakage, especially in certain racial groups.
rebound scurvy. When high intakes of vitamin C are suddenly stopped, a deficiency may occur—probably caused by the body’s adaptation to a high rate of vitamin C intake.
Anemia (small-cell type),a atherosclerotic plaques, pinpoint hemorrhages; bone fragility, joint pain; poor wound healing, frequent infections; bleeding gums, loosened teeth; muscle degeneration, pain; hysteria, depression; rough skin, blotchy bruisesd

Question 15

For Vitamin C: Describe factors that may influence requirements.

Answer 15

Several conditions increase an individual’s requirement for vitamin C:

-Smoking. Cigarette smokers show reduced plasma and leucocyte levels of vitamin C. Thirty‑five mg over the RDA is recommended for smokers.
-Severe physical trauma, such as burns or surgery. A moderate increase in vitamin C intake may enhance the healing process because of the vitamin’s role in collagen formation.
-Infections may also increase vitamin C requirements.
severe emotional or environmental (temperature) stress. As we have seen, vitamin C functions in the synthesis of the stress hormones, epinephrine and norepinephrine, in the adrenal glands.
drug intake.
Use of oral contraceptives, aspirin, barbiturates, sulphonamides, and tetracycline seems to increase excretion of vitamin C.
***Should be in the diet not taken as a supplement

Question 16

For Vitamin C: List some of its major food sources.

Answer 16

Citrus fruits, cabbage-type vegetables (such as Brussels sprouts and cauliflower), dark green vegetables (such as bell peppers and broccoli), cantaloupe, strawberries, lettuce, tomatoes, potatoes, papayas, mangoes

Question 17

For Vitamin C: Discuss its chemical stability with respect to food preparation practices and other factors.

Answer 17

Vitamin C is one of the vitamins most vulnerable to destruction. As does any water‑soluble vitamin, it dissolves readily in water during cooking. It is easily oxidized, especially in the presence of alkali, copper, or iron; copper and iron cookware therefore cause loss of vitamin C. It is also sensitive to heat.

Question 18

For Vitamin C: Discuss the controversies associated with its use.

Answer 18

The prophylactic (disease preventing) and therapeutic uses of vitamin C in cardiovascular disease, the common cold, flu, and cancer are highly controversial.

Question 19

Vitamin A and Vision

Answer 19

Retinal is required in the retina to combine with the protein opsin to form iodopsin (the visual pigment of the cone cells) and rhodopsin (the visual pigment of the rod cells). The cone cells are responsible for colour vision, while the rod cells are responsible for vision in dim light, and address only black and white vision. Although retinal can be regenerated to its original cis form and can recombine with opsin, repeated small losses occur—especially with rhodopsin—because sudden bright light in the dark destroys more retinal than does daylight. Consequently, night blindness (poor visual adaptation to darkness) is an early symptom of vitamin A deficiency

Question 20

Vitamin A and Immunity

Answer 20

Vitamin A functions in fighting against bacterial, viral, and parasitic infections by maintaining the integrity of mucous membranes. Vitamin A also seems to be involved in the growth of the lymph glands, where antibodies are produced.

Question 21

Vitamin A and Growth and Bone development

Answer 21

Retinoic acid is required for the differentiation of bone cells. Bone growth occurs through a balanced activity of two types of bone cells: osteoblasts (bone‑synthesizing cells) and osteoclasts (bone‑resorbing cells). Osteoblasts and osteoclasts enlarge bone through a process of simultaneous bone deposition and bone removal, a process often called bone remodelling. Faulty cell differentiation caused by a vitamin A deficiency can produce insufficient osteoclasts—bone cells with impaired enzyme function that fail to resorb the parts not needed for bone growth. As a result, stunted bone growth and thickened, abnormal bone tissue occur.

Question 22

Vitamin A and Tooth Development

Answer 22

Through its involvement in the development of enamel‑forming epithelial cells, vitamin A also plays a role in the growth of teeth. Vitamin A deficiency may result in teeth that have a thin layer of enamel, making them susceptible to cracking, chipping, breaking, and decay.

Question 23

Explain Vitamin E

Answer 23

Tocopherol, the name of the family of vitamin E compounds, comes from the Greek word tokos, meaning offspring. The name was given because vitamin E was first recognized as an antisterility vitamin in both male and female rats.

Although vitamin E is identified as essential, its role in human nutrition is not yet fully understood. Despite the relative lack of knowledge, vitamin E is very popular as a supplement for a variety of ailments.

Question 24

Define Hemolytic Anemia

Answer 24

hemolytic anemia, a condition in which red blood cells rupture easily and spill their contents into the plasma.
Without vitamin E, the red blood cells break open and spill their contents, probably due to oxidation of the polyunsaturated fatty acids in their membranes. This classic sign of vitamin E deficiency, known as erythrocyte hemolysis

Question 25

Explain Vitamin C

Answer 25

Vitamin C is also known as ascorbic acid. Ascorbic means “without scurvy.” Foods containing vitamin C were discovered to be essential in preventing and curing scurvy. Today, vitamin C is probably the best known and most controversial of all the vitamins. Linus Pauling’s 1970 book, Vitamin C and the Common Cold, popularized the use of megadoses of vitamins to cure or prevent diseases. Since then, vitamin C has been the most commonly taken single vitamin supplement, based on claims that it cures or prevents flu, colds, cold sores, cancer, atherosclerosis, arthritis, and allergies.

Question 26

Explain Vitamin C

Answer 26

Vitamin C is also known as ascorbic acid. Ascorbic means “without scurvy.” Foods containing vitamin C were discovered to be essential in preventing and curing scurvy. Today, vitamin C is probably the best known and most controversial of all the vitamins. Linus Pauling’s 1970 book, Vitamin C and the Common Cold, popularized the use of megadoses of vitamins to cure or prevent diseases. Since then, vitamin C has been the most commonly taken single vitamin supplement, based on claims that it cures or prevents flu, colds, cold sores, cancer, atherosclerosis, arthritis, and allergies.

Question 27

Vitamin C and the Common Cold and Flu

Answer 27

Study concluded that there is no justification for the general community to routinely use large doses of vitamin C to treat the common cold.

Question 28

Vitamin C and Cardiovascular Disease

Answer 28

Collagen synthesis, vital in maintaining the integrity of the vascular walls, is dependent on vitamin C. Any injury to the intima (innermost layer) of the arterial walls can allow cholesterol and other lipids to be deposited, causing atherosclerotic plaque. However, there is no good evidence that supplements of vitamin C are effective for prevention or therapy.

Question 29

Vitamin C and Cancer

Answer 29

It has been speculated that vitamin C is protective against cancer, partly because of the function of vitamin C in inhibiting the formation of carcinogenic nitrosamines from nitrites in foods. Nitrates are naturally present in many fruits and vegetables, including carrots and beets. Nitrites are found in drinking water and human saliva. Even if we eat no foods preserved with nitrite, a significant amount is still present in our body, generated from nitrates. Vitamin C prevents this process.

Question 30

Define Retinol

Answer 30

Retinol is in the vitamin A family. It or other forms of vitamin A are needed for eyesight, maintenance of the skin, and human development. It is converted in the body to retinal and retinoic acid through which it acts. Dietary sources include fish, dairy products, and meat. Found in green and yellow vegetables, egg yolk, and fish-liver oil. It is essential for growth and for vision in dim light.

Question 31

Define Beta-Carotene

Answer 31

The human body converts beta carotene into vitamin A (retinol) - beta carotene is a precursor of vitamin A. We need vitamin A for healthy skin and mucus membranes, our immune system, and good eye health and vision. … The advantage of dietary beta carotene is that the body only converts as much as it needs.

Question 32

Define Scurvy

Answer 32

A disease caused by a deficiency of vitamin C, characterized by swollen bleeding gums and the opening of previously healed wounds, which particularly affected poorly nourished sailors until the end of the 18th century.