MN16 - Water Soluble Vitamins

What are vitamins?

Chemically unrelated organic substances required for normal metabolic functions.

What are key characteristics of vitamins?

Required in small amounts, non-caloric, and cannot be adequately synthesized in the body.

What are exceptions to vitamin synthesis?

Vitamin A (from beta-carotene), niacin B3 (from tryptophan), and vitamin D (from UV light in skin).

What are the two main classifications of vitamins?

Water-soluble and fat-soluble vitamins.

What vitamins are fat-soluble?

Vitamins A, D, E, and K.

What vitamins are water-soluble?

B-complex vitamins and vitamin C.

What is included in the non-B water-soluble group?

Vitamin C (ascorbic acid).

What are the energy-releasing B vitamins?

Thiamin (B1), riboflavin (B2), niacin (B3), biotin (B7), and pantothenic acid (B5).

What are hematopoietic B vitamins?

Folate (B9) and cobalamin (B12).

What are other B vitamins?

Pyridoxine (B6), pyridoxal, and pyridoxamine.

How are water-soluble vitamins absorbed?

Absorbed into bloodstream via active or passive transport in the portal system.

How are fat-soluble vitamins absorbed?

Carried in micelles to brush border and transported via chylomicrons through lymph to bloodstream and liver.

What happens to excess water-soluble vitamins?

Filtered by kidneys and excreted in urine.

Where are vitamins released from food?

Digestion in stomach and small intestine releases vitamins.

What factors influence vitamin status?

Food content, physiological status, food preparation/cooking, and natural compounds affecting availability.

How does physiological status affect vitamin needs?

Increased needs during illness, stress, and when body stores are low (absorption increases).

How do raw egg whites affect vitamins?

Contain avidin, which binds biotin and prevents absorption.

How does raw fish affect vitamins?

Contains enzymes that destroy thiamin.

Why is niacin in corn less available?

It must be liberated by alkaline processing (e.g., tortillas).

How do lipid-soluble and water-soluble vitamins differ in storage?

Lipid-soluble stored in larger amounts; water-soluble stored in small amounts.

How do lipid vs water-soluble vitamins differ in cooking vulnerability?

Lipid-soluble less vulnerable; water-soluble very vulnerable.

What is enrichment?

Replacing nutrients lost during food processing.

What is fortification?

Adding nutrients to foods that do not naturally contain them.

Which vitamins are more likely to cause toxicity?

Fat-soluble vitamins.

Why are megadoses of vitamins not recommended?

Doses >10x DRI may be harmful and unnecessary.

Who is at risk for vitamin deficiency?

People with poor diets, alcoholism, liver disease, elderly, and those with absorption disorders.

What are key characteristics of water-soluble vitamins?

Dissolved in water, not stored, must be replenished regularly, easily destroyed by heat/light, and can leach into cooking water.

How should fruits and vegetables be stored to preserve vitamins?

Keep cool, refrigerate, and store in airtight/moisture-proof conditions.

Why minimize cutting fruits and vegetables?

Exposure to oxygen increases vitamin breakdown.

What cooking methods preserve vitamins best?

Microwave, steam, or stir-fry with minimal cooking time.

Why avoid prolonged cooking?

Reduces vitamin content.

Why avoid adding baking soda to vegetables?

Alkalinity destroys vitamins like thiamin.

What are the main functions of vitamin C?

Antioxidant, stabilizes vitamin E, and involved in collagen synthesis.

What are the main functions of B vitamins?

Act as coenzymes in energy metabolism; B12, B6, and folate also support amino acid, nucleic acid, and RBC synthesis.

What is the coenzyme form of thiamin (B1)?

Thiamin pyrophosphate (TPP).

What reactions require TPP?

Decarboxylation of branched-chain alpha-keto acids, pyruvate and alpha-ketoglutarate dehydrogenase, and transketolase.

What neurotransmitter synthesis involves thiamin?

Acetylcholine synthesis.

Where is thiamin absorbed?

Jejunum via active transport.

Where is thiamin stored?

Mainly in muscles, also liver and other organs.

How is thiamin excreted?

In urine.

What is thiamin half-life?

9-18 days.

What are thiamin food sources?

Pork, legumes, nuts, seeds, fish, seafood, enriched grains.

What destroys thiamin?

Cooking, soaking, and alkaline conditions (baking soda).

What is thiamin deficiency called?

Beriberi.

What are types of beriberi?

Dry (neuropathy) and wet (cardiac failure).

What are oral signs of thiamin deficiency?

Taste loss, burning tongue, sensitive oral mucosa.

What conditions are linked to alcoholism and thiamin deficiency?

Wernicke encephalopathy (acute) and Korsakoff syndrome (chronic).

What are symptoms of Wernicke-Korsakoff?

Visual changes, ataxia, memory impairment, confabulation.

What is riboflavin (B2)?

A yellow-green fluorescent pigment (flavin).

What destroys riboflavin?

Alkali, UV light, and light exposure.

What is riboflavin's function?

Component of FMN and FAD for redox reactions in energy metabolism.

How is riboflavin absorbed?

Active transport.

How is riboflavin excreted?

In urine as bright yellow color.

What are riboflavin food sources?

Milk, enriched grains, eggs.

What are symptoms of riboflavin deficiency?

Growth failure, eye irritation, light sensitivity, greasy skin, bloodshot cornea.

What are the two forms of niacin?

Nicotinamide and nicotinic acid.

What are niacin's coenzymes?

NAD and NADP.

What is niacin's function?

Redox reactions in metabolism, steroid formation, RBC formation, and drug metabolism.

How is niacin obtained?

From diet and synthesized from tryptophan (60 mg tryptophan = 1 mg niacin).

What vitamins are needed to convert tryptophan to niacin?

B1, B2, and B6.

What are niacin food sources?

Meat, fish, nuts (high-quality protein sources).

What is niacin deficiency called?

Pellagra.

What are the 4 Ds of pellagra?

Dermatitis, diarrhea, dementia, death.

What are oral signs of niacin deficiency?

Angular cheilosis, red swollen tongue, infections.

What are effects of high-dose niacin supplements?

Lower cholesterol but can cause flushing and liver damage.

What are forms of vitamin B6?

Pyridoxine, pyridoxal, and pyridoxamine.

What coenzyme is derived from B6?

Pyridoxal phosphate (PLP).

What are functions of B6?

Amino acid metabolism, hemoglobin synthesis, glycogenolysis, phospholipid synthesis.

How is vitamin B6 absorbed?

Passive transport.

Where is B6 used?

Liver and muscles.

How is B6 excreted?

Urine.

What are food sources of B6?

Animal foods, fish, legumes, potatoes, bananas, sunflower seeds.

What are symptoms of B6 deficiency?

Irritability, depression, anemia, dermatitis, neuropathy, seizures, high homocysteine.

What is a unique feature of B6 toxicity?

Neurotoxicity and photosensitivity at high doses (>1 g/day).

What is folate?

Vitamin B9 involved in one-carbon metabolism.

What is the difference between folate and folic acid?

Folate is natural; folic acid is synthetic and more bioavailable.

What are functions of folate?

Amino acid metabolism, DNA synthesis, enzyme regeneration.

How is folate absorbed?

Both active and passive transport.

Where is folate stored?

Liver.

What are folate food sources?

Fortified grains, leafy greens, orange juice, legumes, sunflower seeds.

What are effects of folate deficiency?

Megaloblastic anemia, neural tube defects (spina bifida), high homocysteine.

What is a risk of excess folate?

Masks vitamin B12 deficiency.

What is vitamin B12?

Cobalamin, complex vitamin containing cobalt.

What is the synthetic form of B12?

Cyanocobalamin.

Where is B12 found?

Only in animal foods.

What are functions of B12?

DNA synthesis, RBC maturation, homocysteine metabolism, and myelin maintenance.

How is B12 absorbed?

Requires intrinsic factor in the small intestine.

Where is B12 stored?

Liver (up to 10 years supply).

What are food sources of B12?

Clams, oysters, liver, milk, eggs, fish, meat, fortified foods.

What causes B12 deficiency?

Lack of intrinsic factor, malabsorption, alcoholism, or strict vegan diet.

What are symptoms of B12 deficiency?

Neurological impairment, confusion, gait issues, reduced RBC production.

What is pernicious anemia?

Autoimmune destruction of intrinsic factor causing B12 deficiency and megaloblastic anemia.