Intro to Nutrition - Water-Soluble Vitamins

Intro to Nutrition - Water-Soluble Vitamins (Chapter 8)

• Vitamins are essential for growth and health.
• Water-soluble and fat-soluble vitamins exist.
• B vitamins are a group of distinct compounds that act as co-factors/coenzymes.
• B-complex vitamins include B1, B2, B12.
• The word "vitamin" comes from the Latin "vita" (life) and "amine."
• Vitamins are commonly found in grains, vegetables, and fruits.

Vitamins Objectives

• Describe the role of vitamins in normal physiological function/metabolism.
• Identify dietary sources of each vitamin.
• Outline the Dietary Reference Intakes (DRI) for each vitamin in adults.
• Discuss symptoms and pathologies associated with vitamin deficiencies.

Vitamins in the Digestive Tract

• Digestive enzymes release vitamins from food.
• 40-90% of vitamins from food are absorbed in the small intestine.
• Fat-soluble vitamins are packaged as chylomicrons.
• Some vitamins are absorbed in precursor forms.
• The absorbed vitamins are transported to the blood or lymph.

Vitamins function as coenzymes and cofactors

• Vitamins combine with a chemical group to create a functional coenzyme (active vitamin).
• The functional coenzyme combines with an incomplete enzyme to create an active enzyme.
• The active enzyme binds to one or more molecules to accelerate the chemical reaction
• The new molecules are released, and the enzyme and vitamin can be reused.

B Vitamins: Co-enzymes for energy metabolism

• B vitamins are coenzymes in energy metabolism.
• They are involved in glycolysis and other metabolic processes.

Thiamin (B1)

• Coenzyme in pentose (ribose for RNA) and acetylcholine (ACh) production.
• Widely available in enriched grains and whole grains.
• Deficiency symptoms include neurological symptoms like lethargy, fatigue, and foot drop, more common in people in poorer countries (e.g. white rice). Can also cause congestive heart failure and weakness/irritability throughout the body.

Riboflavin (B2)

• Coenzyme in energy metabolism.
• Crucial for the Krebs cycle.
• Easily destroyed by heat and light.
• Deficiency symptoms include inflammation of the eyes, lips, mouth, tongue and skin eruptions, cracked lips.
• This is rarely seen alone and is commonly associated with other B vitamin deficiencies.
• Sources include the same as thiamin (grains, vegetables, etc.)

Niacin (B3)

• Nicotinic acid, nicotinamide, are important metabolic coenzymes.
• Can be synthesized from tryptophan.
• Important role in energy metabolism, NAD/NADH, NADP.
• Involved in serotonin production and CNS functioning.
• Deficiency can lead to dermatitis (3D's: dermatitis, diarrhea, and dementia), cracked skin, and also fatigue, reduced appetite, and indigestion.

Vitamin B6

• Also called pyridoxal, pyridoxine, or pyridoxamine.
• Converted to pyridoxal phosphate, is crucial for >100 enzyme reactions.
• Coenzyme in amino acid synthesis and helps convert tryptophan to niacin.
• Is involved in immune response, steroid hormone action, neurotransmitter and myelin synthesis, glycogen metabolism, and hemoglobin synthesis.
• Mandatory in meal replacements/simulated egg products and can be added to cereals.
• Deficiency can lead to neurological symptoms like impaired hemoglobin synthesis, depression, headaches, confusion, numbness, and tingling.

Biotin (B7)

• Found in liver, egg yolks, yogurt, and nuts.
• Coenzyme involved in adding a COOH group to other molecules (e.g. citric acid cycle, glucose synthesis).
• Deficiency might result in hair loss, dermatitis, nausea, and neuromuscular dysfunction.
• Recommended intake for adults is 30 µg/day.

Folate/Folic Acid (B9)

• Found in various foods, and can be fortified.
• Crucial for DNA replication, synthesis and expression, metabolism of amino acids (especially during pregnancy), homocysteine breakdown.
• Essential for supporting growth and development of tissues, especially pregnancy during early pregnancy.
• Deficiency can produce megaloblastic/macrocytic anemia and neural tube defects.
• DFE (Dietary Folate Equivalent) conversions exist between folate and folic acid.
• High levels of folate intake during pregnancy may reduce the risk of neural deficiencies.

Vitamin B12

• Primarily found in animal products, like nutritional yeast and certain algae/seaweed.
• Necessary for myelin production, single-carbon metabolism.
• Important for some dietary modifications.
• Pernicious anemia (inability to absorb B12 in the gut), megaloblastic/macrocytic anemia, unrelated to iron are common deficiencies.
• Can be provided via injection, gel, and mega-dosage.
• Excessive folic acid intake can mask B12 deficiencies.

Vitamin C

• Also known as ascorbic acid.
• Plays many crucial roles like support, production processes (especially involving iron), scavenging.
• Sensible to heat/light/oxygen and can be destroyed during food preparation.
• Important in collagen synthesis, strengthening connective tissues.
• Deficiency in vitamin C can lead to abnormal/weak connective tissue.

This quiz covers Chapter 8 of Introduction to Nutrition, focusing on water-soluble vitamins. It explores the functions, dietary sources, and deficiencies of B-complex vitamins, and the role they play in metabolism and health. Test your knowledge about the essential vitamins that sustain life.