Water Soluble Vitamins

Water Soluble Vitamins

Learning Objectives

• Understand the different B-Vitamins and Vitamin C

• Study and apply knowledge from Smolin, Grosvenor, and Gurfinkel’s Nutrition Science & Applications, 3rd Canadian Edition

What are Vitamins?

• Organic chemicals necessary for normal growth and health

• Needed for human survival; each vitamin is critical for at least one bodily process

• Found abundantly in food, especially fruits and vegetables

• Each vitamin has an optimal intake range for functionality

Vitamin Bioavailability

• Definition: The extent to which a nutrient is absorbed and utilized by the body

• Most vitamin absorption occurs in the small intestine (jejunum and ileum)

• Primarily achieved through passive diffusion

• Some vitamins may need conversion from inactive provitamin or precursor forms to active forms

• Water-soluble vitamins are often lost during food storage and preparation

Vitamins as Coenzymes

• Coenzymes: Small organic compounds that bind to enzymes, essential for their function

B Vitamin Functions

Energy Metabolism

• B vitamins (Thiamin, Riboflavin, Niacin, Pantothenic Acid, Biotin) act as coenzymes essential for glucose, fatty acids, and amino acid oxidation

Specific B Vitamins

Thiamin (Vitamin B1)

• Functions:

  • Energy production (conversion of pyruvate to Acetyl-CoA)

  • Nervous system support (acetylcholine production)

• Deficiency Signs: Headaches, confusion, muscle pain, weakness; severe cases lead to Beriberi

• Sources: Enriched grains, whole grains, legumes, nuts, seeds

• History: Increased incidence of Beriberi in East Asia during the 1800s discovered by Christian Eijkman

Riboflavin (Vitamin B2)

• Function: Electron transport in energy production

• Sources: Dairy products

• Stability: Easily destroyed by heat and light, leading to bright yellow urine as a characteristic sign

Niacin (Vitamin B3)

• Functions:

  • Electron transport in both aerobic and anaerobic environments

  • Potential supplementation benefits to athletic performance (blocks FFA release)

• Deficiency/Toxicity:

  • Deficiency can lead to Pellagra (3 D's: dermatitis, diarrhea, dementia)

  • Toxicity symptoms: skin rashes, elevated blood pressure, nausea, vomiting, liver impairment at >35mg/day synthetic niacin

• Sources: Can be synthesized from tryptophan; historical dietary impact with corn

Biotin

• Functions:

  • Coenzyme in amino acid metabolism and gluconeogenesis

• Sources: Produced by gut bacteria

Pantothenic Acid

• Functions: Part of coenzyme A; vital for aerobic energy production from carbohydrates, fats, and proteins

Interaction of B Vitamins in Metabolism

• B6, Folate, and B12 work together in single-carbon metabolism regulation

• High homocysteine levels can lead to vascular damage

Vitamin B6 (Pyridoxine)

• Functions:

  • Transamination (synthesis of non-essential amino acids)

  • Glycogen metabolism

  • White blood cell production (immune function)

  • Hemoglobin synthesis

• Deficiency: Leads to anemia due to impaired hemoglobin production

• Toxicity: Can cause nerve impairment at doses of 2-6g/day (UL = 100 mg/day)

Folate and Folic Acid

• Functions:

  • DNA synthesis and RBC maturation

  • Gene regulation through DNA methylation

• Deficiency:

  • Megaloblastic anemia

  • Neural tube defects (NTDs)

  • Increased cardiovascular disease risk related to homocysteine

• Requirements: 600ug dietary folate equivalents during pregnancy, UL set at 1000ug to prevent masking of B12 deficiency

Folate and Neural Tube Defects

• Folate reduces NTDs, mechanism likely involves DNA methylation

• NTDs have decreased with folate fortification; ~58% of Canadian women take folic acid supplements pre-conception

Vitamin B12

• Functions:

  • RBC synthesis

  • Myelin formation (requires methionine derivative, reliant on B12)

  • Cardiovascular health

• Deficiency:

  • Associated anemia and neurological symptoms

• Sources:

  • Primarily found in animal products; synthesized by gut bacteria

  • Can be stored in the liver for up to one year

  • Vegans should supplement with bioavailable forms

Vitamin C

• Functions:

  • Antioxidant in the body

  • Essential for collagen production

  • Enhances iron absorption (keeps iron in Fe2+ state)

• Deficiency: Can lead to Scurvy (symptoms including swollen gums, fatigue)

• Toxicity: Generally non-toxic, but excessive intake (>2000 mg) may cause kidney stones, nausea, diarrhea