chapt 10 pt 1
NTR 306: Fundamentals of Nutrition
Chapters 10 & 11: Micronutrients: Vitamins
Vitamins – An Overview
Definition and Importance of Vitamins:
Vitamins are a category of micronutrients that are organic, essential nutrients required in small amounts in the diet for normal growth and health.
They are essential for life and health, important for energy pathway processes (e.g., TCA cycle, Electron Transport).
Vitamins have established Dietary Reference Intakes (DRIs) such as Estimated Average Requirements (EARs), Recommended Dietary Allowances (RDAs), and Adequate Intakes (AIs).
Similarities to Macronutrients:
Just as essential for life and health.
Important parts of energy pathway processes.
Subject to EARs, RDAs, and AIs, similar to macronutrients (carbohydrates, proteins, fats).
Differences from Macronutrients:
Structural Differences: Vitamins exist as individual units, unlike macronutrients, which are linked (proteins = amino acids; carbohydrates = glucose).
Functional Differences: Vitamins are not oxidized and do not yield energy directly; they support metabolic processes instead.
Quantity: Required in small amounts (micrograms or milligrams rather than grams).
Tolerable Upper Intake Levels (ULs) also correspond to vitamin intake (as mentioned in Chapter 2).
Vitamins – Intake and Requirements
Intake Ranges to Consider:
Meeting DRI requirements (notably, EAR).
Not Meeting DRI Requirements:
Inadequacy: Consumption below EAR that does not cause significant health issues; often asymptomatic.
Deficiency: Intake significantly below EAR, leading to negative health outcomes.
Vitamins – Categorization
Based on Solubility:
Water-Soluble Vitamins: Include B-Vitamins and Vitamin C.
Absorption: Directly absorbed into the bloodstream.
Transport: Free and independent in circulation.
Storage: Not stored significantly in the body; circulate in water-based areas.
Excretion: Kidneys remove excess vitamins; potential for toxicity is less common but possible with supplements.
Requirements: Need to be consumed frequently (1-3 days).
Fat-Soluble Vitamins: Include Vitamins A, D, E, and K.
Absorption: Absorbed into lymphatic system before entering blood.
Transport: Requires protein for transport in the bloodstream.
Storage: Stored in fat cells and tissues.
Excretion: Less frequent removal from the body; can build up to toxic levels.
Requirements: Can be consumed periodically (weeks to months).
Vitamins – Factors Affecting Requirements
Bioavailability:
The rate and extent to which a nutrient is absorbed and utilized by the body.
Influenced by:
Source of Nutrient:
Supplements: Synthetically made and isolated vitamins.
Fortified Foods: Added vitamins to foods without them naturally.
Enriched Foods: Added back vitamins to processed foods that lost nutrients.
Natural Foods: Vitamins that occur naturally in foods.
Preparation Methods: Cooking methods can destroy vitamins (e.g., heat, light, oxygen exposure, or leaching into water).
Gastrointestinal & Nutritional Status: Individual digestion and absorption capabilities.
Concurrent Food Intake: Some vitamins may lose their effectiveness based on what other vitamins are consumed with them (e.g., Vitamin C and B12).
Vitamins – Toxicity Considerations
Toxicity:
More does not equal better; excessive intakes can cause harm.
Thus, proper establishing of Upper Levels (ULs) is crucial; while some vitamins may have no UL, exceeding recommended levels can be harmful.
The B Vitamins - Overview
B Vitamins do not act directly to provide energy.
Serve primarily as coenzymes, facilitating various metabolic pathways.
B-Complex Vitamins include eight essential vitamins:
B1: Thiamin
B2: Riboflavin
B3: Niacin
B5: Pantothenic Acid
B6: Pyridoxine
B7: Biotin
B9: Folic Acid
B12: Cobalamin
Biological Roles of Vitamin Bs
Involved in key functions such as:
Energy metabolism.
Supporting functions of the brain, nerve, and muscles.
Cell growth and proper function.
Eye and skin health.
Interaction with other B vitamins for effective functioning.
Assisting in hormone and neurotransmitter production.
Interactions Among the Bs
Each B vitamin contributes to energy metabolism through:
Facilitating energy-releasing reactions.
Building new cells needed for oxygen and nutrient transport in energy reactions.
Deficiencies:
Isolated deficiencies of single B vitamins are rare; often occur due to malnutrition, poor diet choices, or conditions such as alcoholism, which impairs the metabolism and increases excretion of B vitamins.
Energy Metabolism – Summary of B Vitamins
Metabolism Contributions:
Each B vitamin (with respective coenzymes) plays a critical role in carbohydrate (CHO), fat, and protein (PRO) metabolism.
This includes processes like glycolysis, the TCA cycle, and the electron transport chain.
Unique Biological Roles of Vitamin Bs
Each B vitamin has specific roles beyond energy metabolism:
Thiamine (B1): Protects against neurological issues.
Riboflavin (B2): Essential for converting other nutrients.
Niacin (B3): Aids HDL cholesterol production and triglyceride reduction.
Pantothenic Acid (B5): Vital for synthesis of red blood cells and hormones.
Pyridoxine (B6): Affects brain and spinal cord health.
Folate (B9) and Cobalamin (B12): Interdependent activation mechanisms for DNA synthesis.
B Vitamin Deficiencies
Riboflavin (B2): Symptoms include inflammation of membranes (mouth, skin, eyes, and GI tract).
Thiamine (B1): Deficiency leads to Beriberi, which can manifest as wet (cardiovascular forms) or dry (neural muscular forms), with symptoms including edema, muscle weakness, and fatigue.
Niacin (B3): Deficiency results in Pellagra, characterized by the 4 D’s: Diarrhea, Dermatitis, Dementia, and possible Death.
Pantothenic Acid (B5): Deficiency is rare but can lead to neurological disturbances and overall fatigue.
Pyridoxine (B6): Short-term deficiencies can result in depression and confusion; long-term deficiency can cause convulsions.
Biotin (B7): Rare deficiencies can reveal skin rash, hair loss, and neurological impairments.
Folate (B9): Critical in preventing neural tube defects and other birth anomalies; discovered through fortification of grain products.
Cobalamin (B12): Symptoms include anemia and a range of others; common in older adults and vegans; excessive folate can obscure B12 deficiency signs.
B Vitamins: DRIs & Habitual Intake
Definitive Values for B vitamins depend on age and sex with specified RDAs and ULs:
Examples:
Thiamine (B1): RDA for men 1.2 mg/d (N/A UL), habitual intake around 1.95 mg/d.
Riboflavin (B2): RDA for men 1.3 mg/d (N/A UL), habitual intake approximately 2.5 mg/d.
Niacin (B3): RDA for men 16 mg/d, UL 35 mg/d (set to align with niacin flush effects), habitual intake ~31 mg/d.
Comprehensive chart detailing gender-based RDA, UL, and habitual intake for each B vitamin.
Food Sources and Vulnerabilities of B Vitamins
Numerous food sources listed for each B vitamin, detailing:
Specific mg per serving and % Daily Value (DV).
Cooking Vulnerabilities: Heat sensitivity, water-solubility, and leaching risks in preparation methods.
Notably, refining leads to nutrient loss (i.e., grains) and ongoing legislation ensures enrichment of food products.
Final Wrap-Up and Reminders
Next topics include Water-soluble and Fat-soluble Vitamins impacting bodily functions and health.
Critical assignments and reports due by specified dates (DAP - Part 2, due 11/10).
Questions and Interactive Discussions
Throughout the session, prompts for questions and participation (instapoll) were included, highlighting the importance of student engagement.