Water-Soluble Vitamins Flashcards
Vitamin B12 deficiency is common with…
Low meat intake and old age
Symptoms of vitamin B12 deficiency include?
- tingling
- numbness
- memory problems
- other NS symptoms
- diarrhea
What are vitamins?
- organic compounds required to maintain health, by allowing for growth and reproduction
- regulate body processes
- many are coenzymes
- often sensitive to light and heat
- obtained in the diet through consumption of natural and fortified foods and supplements
How does a low-fat diet affect bioavailability of vitamins?
- may inhibit absorption of fat-soluble vitamins because they require fat in diet to pass into bloodstream
- packaged into chylomicrons
How else is bioavailability of vitamins impacted?
- some water-soluble vitamins may need a carrier protein
- provitamins forms may be absorbed requiring conversion to active form
- interaction with other dietary components may also affect absorption
Grain products contain…
- thiamin
- riboflavin
- niacin
- pantothenic acid
- vitamin B6
- folate
Fruits and vegetables contain…
- riboflavin
- niacin
- vitamin B6
- folate
- vitamin C
- vitamin A
- vitamin E
- vitamin K
Plant oils contain…
- vitamin E
Milk and alternatives contain…
- riboflavin
- vitamin A
- vitamin D
- vitamin B12
Meat & alternatives contain…
- thiamin
- riboflavin
- niacin
- biotin
- pantothenic acid
- folate
- vitamin B12
- vitamin A
- vitamin D
- vitamin K
Why do smokers have a high prevalence of inadequate vitamin C intake?
- vitamin C protects against free radicals, which are increased with smoking
Fortification vs enrichment?
- fortified foods have nutrients added that are NOT normally found in that food (ex. calcium fortified orange juice)
- enriched foods have nutrients added BACK that have been removed in processing (ex. enriched white flour)
What are supplements?
- source of vitamins in the diet
- contain some combination of vitamins, minerals, herbs, amino acids, botanicals, extracts
- cannot replace healthy foods
- take caution as regulation is not as stringent as for drugs
Approximately ____% of vitamins are absorbed in small intestine.
40-90%
Which type of vitamins are less likely to be present at toxic levels?
- water-soluble
- excreted when ingested in excess
What are other characteristics of water-soluble vitamins?
- tend to be less stable
- tissue depletion can occur more readily
- most converted to coenzymes that aid in energy generation and hematopoiesis
- deficiencies first appear in rapidly growing tissues (skin, tongue, nervous tissue)
Dietary composition often affects…
How much of a vitamin is available
What is the function of thiamin?
- converted to thiamin pyrophosphate (TPP), required for glucose metabolism
What are the symptoms of thiamin deficiency?
- Beriberi; characterized by lack of energy, weakness and neurological symptoms (acetylcholine synthesis also uses TPP)
- can advance to neurological condition called Wiernicke-Korsakoff syndrome
What is a common cause of thiamin deficiency?
- alcohol abuse
- chronic alcoholism inhibits absorption
- liver creates TPP, but alcoholism damages liver
- people w AA also less likely to eat healthy foods w this vitamin
What foods is thiamin found in?
- pork, lentils, grain products
What two molecules is riboflavin converted into?
- flavin adenine dinucleotide (FAD)
- flavin mononucleotide (FMN)
- help w energy production and cellular respiration
What is the function of riboflavin?
- energy production and cellular respiration
- iron mobilization
- conversion of vitamins (folate, niacin, vitamin B6, vitamin K) into active forms
Where is riboflavin deficiency most commonly seen?
- chronic alcoholics with deficiency of other B vitamins
What are the symptoms of riboflavin deficiency?
- poor wound healing
- inflammation of the eyes, lips, mouth, tongue
- confusion
Where is riboflavin found in the diet?
- milk, pork, trout, grains, lentils
Condition resulting from niacin deficiency?
- pellagra
Symptoms of pellagra?
- dermatitis, dementia and diarrhea (3 D’s)
What is niacin made from in the body?
- made from tryptophan (essential amino acid) if adequate in diet
Niacin-derived enzymes important in components of cellular respiration reactions?
- oxidation-reduction coenzymes: nicotinamide adenine dinucleotide (NAD) and NADP
What foods contain high levels of niacin?
- peanuts, lentils, meat, rice
What is biotin a component of?
- pyruvate carboxylase, acetyl-CoA carboxylase and other carboxylases
When can biotin deficiencies occur?
- people who eat raw egg whites
What do raw eggs contain?
- avidin (binds tightly to biotin)
What are symptoms of biotin deficiency?
- thinning hair, depression, lethargy, loss of hair colour, nausea and hallucinations
When/ where does deficiency occurs?
- deficiency is are
- occurs due to B-vitamin deficiency
What is the function of pantothenic acid?
- part of coenzyme A (CoA), the acetyl CoA intermediate in carbohydrate, fatty acid and amino acid metabolism
- involved in fatty acid and cholesterol synthesis
What foods contain high levels of pantothenic acid?
- found in most foods
- sunflower seeds, meat, dairy, fruit and veg, grains
What is vitamin B6 also known as?
- pyridoxal phosphate (active coenzyme of B6)
Where is B6 needed?
- necessary in amino acid metabolism, transamination, deamination and decarboxylation
- involved in production of myelin sheath
- hemoglobin synthesis
- converts homocysteine to cysteine
- white blood cell formation
Where is vitamin B6 found in foods?
- animal products
- lentils
- rice
Symptoms of vitamin B6 deficiency?
- neurological symptoms (due to its function as neurotransmitter synthesis or myelin formation)
- headaches, depression, confusion, numbness in extremities, and seizures
- anemia occurs due to role in synthesis of hemoglobin
Vitamin B6 absorption can be affected by…
- some drugs, such as alcohol and contraceptives
What is homocysteine?
- an intermediate in cysteine biosynthesis
- elevated levels linked to CV disease
How are B vitamins implicated in CV disease?
- some B vitamins required to convert homocysteine
- folate and vitamin B12 convert homocysteine to methionine
- vitamin B12 converts homocysteine to cysteine
Where does vitamin B12 come from?
- present only in animal products, made by bacteria, fungi, algae
Where do vegetarians get B12 from?
- fortified foods or supplements, or nutritional yeast
What process must occur in order for vitamin B12 to be absorbed?
- B12 comes into body bound to protein
- pepsin in stomach releases B12 from proteins
- cells in stomach lining release intrinsic factor
- IF in upper intestine binds B12, allowing it to bind to receptors for absorption in lower
intestine - need sufficient stomach acid to allow cleavage
- small amount can be absorbed passively
In the colon, B12 is synthesized by…
Microorganisms but cannot be absorbed
What is pernicious anemia?
- anemia resulting from lack of IF; autoimmune attack on the cells that create it
What proportion of the population is vitamin B12 deficient?
- 1/3
- especially vegetarians and the elderly
What foods contain vitamin B12?
- all animal products - meat and dairy
- not found in any plants
What are the functions of vitamin B12?
- B6 and B12 both necessary for formation of myelin sheath
- coenzymes formed from B12 needed for breakdown of fatty acids and homocysteine to methionine conversion reaction
- conversion reaction also allows regeneration of folate necessary for DNA synthesis
What occurs in vitamin B12 deficiency?
- increased blood levels of homocysteine
- megaloblastic anemia (also seen in folate deficiency)
- deficiency develops slowly because little is lost from body - reabsorbed from bile
What hastens vitamin B12 deficiency?
- atrophic gastritis
- pernicious anemia
- both result in impaired absorption and reabsorption
What are the functions of folate?
- makes coenzymes necessary for DNA synthesis (dividing cells) and metabolism of some amino acids
- folate from diet must be converted to active form before absorption by vitamin B12
What occurs in folate deficiency?
- megaloblastic (macrocytic) anemia
- neural tube defects if inadequate intake during pregnancy
- also linked with heart disease because conversion of homocysteine to methionine does not occur
What is megaloblastic anemia?
- larger and fewer RBCs resulting from a problem with cell division
Higher folate levels in blood correlate with…
Lower risk for breast and colorectal cancer
What foods is folate found in?
- lentils a good source
- nuts and seeds
- vegetables and fruits
- many foods now fortified to prevent neural tube defects in infants
What can result from excess folate?
- can mask early symptoms of B12 deficiency
- very high folate allows conversion of methyl folate to folate without need for B12
- anemia due to B12 is prevented but low B12 interferes with myelin sheath synthesis - permanent damage can occur because treatable symptom of megaloblastic anemia does not appear
What is the function of vitamin C?
- coenzyme involved in reactions to form hydroxyproline and hydroxylysine – necessary for collagen stability and cross-linking (and prevention of scurvy)
- coenzyme for the synthesis of bile acids, neurotransmitters, hormones and in fatty acid metabolism
- important antioxidant, neutralizing damaging free radicals
What foods is vitamin C found in?
- fruits and veg
- oranges, kiwis, strawberries, broccoli, cantaloupe
What are oxygen free radicals?
- derived from oxygen
- enter our bodies from foods and environmental toxins
- also routinely generated by metabolic processes (ex. ETC)
How do free radicals cause cell damage?
- can damage cell membranes, DNA, proteins, and mitochondria
- implicated in aging and diseases such as cancer and CVD
- neutralization of free radicals minimizes possible damage
How does vitamin C work as an antioxidant?
- donates electron to free radical so stabilize it and neutralize it
- regenerated by body (ex. dehydroascorbic to ascorbic acid)
How is cancer risk and lifestyle related?
- estimated that about 35% of cancers are preventable
- exercise, eating well, maintenance of healthy body weight and moderation in alcohol consumption are ways to reduce risk
- research is consistent with consumption of higher fibre foods, and those that contain more ω-3 fatty acids and antioxidants
What two optical conditions can be prevented with higher antioxidant intake?
- age-related macular degeneration
- cataracts
What are the benefits of quitting smoking before age 40?
Avoids 90% of the excess mortality caused by smoking
