Unit 8 - The B Vitamins

Question 0

Bioavailability

Answer 0

The rate at and the extent to which a nutrient is absorbed and used.

Question 1

Vitamins

Answer 1

Organic, essential nutrients required in small amounts by the body.

Question 2

What are the functions of Thiamin in the body?

Answer 2

The main coenzyme of thiamin (thiamin pyrophosphate) is used to remove one carbon from pyruvate to form acetyl CoA, a oxidative decarboxylation reaction.

Question 3

What are the symptoms of deficiency and toxicity of thiamin?

Answer 3

Deficiency - loss of appetite, weakness and numbness of legs, indigestion, constipation, increased pulse rate (uncommon in North America but often seen in Asia where it is known as beriberi)

Toxicity - generally non-toxic

Question 4

What are some major food sources of thiamin?

Answer 4

Present in small amounts in almost all foods. Whole grain is a major source, thiamin is found in the hull.

Question 5

Discuss the chemical stability of Thiamin.

Answer 5

Easily lost in food preparation. Dry heating at high temperatures (ie. toasting bread) can result in losses. If water used to cook is thrown out thiamin losses are substantial.

Question 6

What are the functions of Niacin in the body.

Answer 6

• Two coenzymes (NAD and NADP)
• function as hydrogen carriers
• Important role in the electron transport chain
• support synthesis of triglycerides, non-essential amino acids, and glycogen

Question 7

What are the symptoms of Niacin deficiency and toxicity?

Answer 7

Deficiency (Pellagra)
- Four Ds (dermatitis, diarrhea, dementia… death)

Toxicity

• “flush” - dilated capillaries and tingling sensation
• nausea and vomiting
• liver damage

Question 8

What are some major food sources of Niacin?

Answer 8

Meat, fish, and poultry

Question 9

Discuss the chemical stability of Niacin?

Answer 9

Most stable of the B vitamins, loss occurs due to leaching

Question 10

What are the functions of vitamin B-6 in the body?

Answer 10

• involved in every step of protein and amino acid metabolism
• absorption and transport of amino acids across intestinal membrane
• production of niacin from tryptophan

Question 11

What are the symptoms of vitamin B-6 deficiency and toxicity?

Answer 11

Deficiency - rare due to wide distribution of food sources

• muscle weakness
• irritability
• insomnia
• weight loss

Toxicity
- neurological damage

Question 12

What are some major food sources of vitamin B-6?

Answer 12

• Legumes
• Meats
• Certain fruits (bananas, watermelon, fig, canteloupe)
• Certain vegetables (potato, spinach, broccoli)
• Whole grain breads and flour

Question 13

Discuss the chemical stability of vitamin B-6

Answer 13

• Sensitive to light and alkaline conditions

- Freezing of vegetables can lead to 20% loss

Question 14

What are the functions of folate in the body?

Answer 14

Primary coenzyme tetrahydrofolate (THF)

• carries methyl groups from one substance to another.
• required for synthesis of nucleic acids (DNA and RNA)
• essential for the formation of red and white blood cells.

Question 15

What are the symptoms of folate deficiency and toxicity?

Answer 15

Deficiency - common

• megaloblastic amenia - large red blood cells that are immature and have a nucleus
• changes in the epithelial cell of the GI tract, tongue, stomach, vagina and cervix
• behavioural changes: fatigue, mild depression, disorientation, poor memory
• decreased and abnormal white blood cells

Toxicity
- no danger but may mask a vitamin B-12 deficiency

Question 16

What are some major food sources of folate?

Answer 16

• Dark green leafy vegetable (spinach, asparagus, broccoli)

- Legumes (Beans and lentils)

Question 17

Discuss the chemical stability of folate.

Answer 17

• storing leafy vegetables at room temperature can result in significant losses - action of oxygen and UV light
• leaching in water used to cook
• milling grain

Question 18

What are the main functions of vitamin B-12 in the body?

Answer 18

• carrier of single carbon methyl groups
• carrier of hydrogen atoms
• works cooperatively with folate in the synthesis of DNA and RNA
• required for the synthesis of the myelin sheath of nerve fibres

Question 19

What are the symptoms of B-12 deficiency and toxicity?

Answer 19

Deficiency - may take a long time to become apparent because large amounts are stored in the liver

• often results in the elderly due to gastric atrophy = condition that damages the stomach, impairing absorption of B-12 = pernicious anemia
• megaloblastic anemia (same condition as folate deficiency)
• neurologic damage
• oral and gastrointestinal effects

Toxicity
- no reported symptoms

Question 20

What are some major food sources of vitamin B-12?

Answer 20

Foods of animal origin: meat, milk, and eggs

Microbial in origin - produced by bacteria in the rumen of some animals

Question 21

Discuss the chemical stability of vitamin B-12.

Answer 21

• relatively stable to heat

- water-soluble but food sources are generally not cooked in water.

Question 22

What are the functions of Riboflavin in the body?

Answer 22

• The two coenzymes (FAD and FMN) function as hydrogen carriers - carry hydrogen and electrons to the electron transport chain.
• Essential for other B-vitamin activities.
• Essential for growth.

Question 23

What are the symptoms of Riboflavin deficiency and toxicity?

Answer 23

Deficiency - tissue inflammation and breakdown

Toxicity - Rare, excess excreted by the kidneys. May cause urine to become fluorescent yellow.

Question 24

What are some major food sources of Riboflavin?

Answer 24

• Milk and milk products

- Whole grain and enriched breads

Question 25

Discuss the chemical stability of Riboflavin.

Answer 25

Exposure to ultraviolet or visible light causes losses - milk should be stored in a cool, dark place.