Unit 8 - The B Vitamins Flashcards
Bioavailability
The rate at and the extent to which a nutrient is absorbed and used.
Vitamins
Organic, essential nutrients required in small amounts by the body.
What are the functions of Thiamin in the body?
The main coenzyme of thiamin (thiamin pyrophosphate) is used to remove one carbon from pyruvate to form acetyl CoA, a oxidative decarboxylation reaction.
What are the symptoms of deficiency and toxicity of thiamin?
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
What are some major food sources of thiamin?
Present in small amounts in almost all foods. Whole grain is a major source, thiamin is found in the hull.
Discuss the chemical stability of Thiamin.
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.
What are the functions of Niacin in the body.
- 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
What are the symptoms of Niacin deficiency and toxicity?
Deficiency (Pellagra)
- Four Ds (dermatitis, diarrhea, dementia… death)
Toxicity
- “flush” - dilated capillaries and tingling sensation
- nausea and vomiting
- liver damage
What are some major food sources of Niacin?
Meat, fish, and poultry
Discuss the chemical stability of Niacin?
Most stable of the B vitamins, loss occurs due to leaching
What are the functions of vitamin B-6 in the body?
- involved in every step of protein and amino acid metabolism
- absorption and transport of amino acids across intestinal membrane
- production of niacin from tryptophan
What are the symptoms of vitamin B-6 deficiency and toxicity?
Deficiency - rare due to wide distribution of food sources
- muscle weakness
- irritability
- insomnia
- weight loss
Toxicity
- neurological damage
What are some major food sources of vitamin B-6?
- Legumes
- Meats
- Certain fruits (bananas, watermelon, fig, canteloupe)
- Certain vegetables (potato, spinach, broccoli)
- Whole grain breads and flour
Discuss the chemical stability of vitamin B-6
- Sensitive to light and alkaline conditions
- Freezing of vegetables can lead to 20% loss
What are the functions of folate in the body?
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.
What are the symptoms of folate deficiency and toxicity?
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
What are some major food sources of folate?
- Dark green leafy vegetable (spinach, asparagus, broccoli)
- Legumes (Beans and lentils)
Discuss the chemical stability of folate.
- 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
What are the main functions of vitamin B-12 in the body?
- 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
What are the symptoms of B-12 deficiency and toxicity?
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
What are some major food sources of vitamin B-12?
Foods of animal origin: meat, milk, and eggs
Microbial in origin - produced by bacteria in the rumen of some animals
Discuss the chemical stability of vitamin B-12.
- relatively stable to heat
- water-soluble but food sources are generally not cooked in water.
What are the functions of Riboflavin in the body?
- 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.
What are the symptoms of Riboflavin deficiency and toxicity?
Deficiency - tissue inflammation and breakdown
Toxicity - Rare, excess excreted by the kidneys. May cause urine to become fluorescent yellow.
What are some major food sources of Riboflavin?
- Milk and milk products
- Whole grain and enriched breads
Discuss the chemical stability of Riboflavin.
Exposure to ultraviolet or visible light causes losses - milk should be stored in a cool, dark place.
