B Vitamin Notes

B Vitamins - Individual Breakdown

Introduction

• B vitamins are active in the body and form coenzymes that assist enzymes in releasing energy.
• Recommendations are expressed as RDIs, AIs, and upper levels of intake.
  • RDI: Recommended Dietary Intake.
  • AI: Adequate Intake (set when RDI information is insufficient).
• Each B vitamin has unique deficiencies, toxicities, and food sources that are likely to be assessed.

Thiamine (Vitamin B1)

• Absorption:
  • Absorbed in the duodenum and jejunum of the small intestine via active transport using a carrier.
  • Alcohol inhibits absorption, leading to deficiency in alcoholics. This is often compounded by poor dietary intake.
• Utilization:
  • Tissues take up thiamine and phosphorylate it into thiamine pyrophosphate (TPP).
  • Excess is excreted in urine and may be lost in sweat.
  • Limited storage in the body; deficiency can occur within days.
• Importance:
  • Needed for aerobic metabolism.
  • TPP is involved in the conversion of pyruvate to acetyl CoA in the TCA cycle.
  • Without thiamine, pyruvate builds up in the mitochondria, and lactate builds up in the cytosol.
• Deficiency Symptoms:
  • Enlarged heart or cardiac failure.
  • Muscular weakness.
  • Apathy, short-term memory loss, confusion, and irritability.
  • Anorexia and weight loss.
• Beriberi:
  • Wet Beriberi: Presents with edema. High carbohydrate intake with TPP deficiency causes excess pyruvate buildup, leading to fluid movement into interstitial tissues.
  • Dry Beriberi: Presents with muscle wasting. Associated with low energy and low carbohydrate intake.
• Wernicke-Korsakoff Syndrome:
  • Severe deficiency in chronic alcohol consumption.
  • Can lead to brain damage, confusion, and hallucinations.
• Requirements:
  • RDI for men: 1.2 mg/day.
  • RDI for women: 1.1 mg/day.
  • No toxicities reported.
• Food Sources:
  • Whole grains, breakfast cereals, and meats.
• Other Considerations:
  • Easily destroyed by heat; bread makers add it during fortification to compensate for losses.
  • Leaches into water during boiling or blanching.

Riboflavin (Vitamin B2)

• Absorption:
  • Absorbed in the upper small intestine.
  • Milk and eggs contain free riboflavin; most in foods is present as flavin coenzymes.
• Flavin Coenzymes:
  • Flavin adenosine dinucleotide (FAD) is produced in the TCA cycle.
• Storage and Excretion:
  • No significant storage; surplus is rapidly excreted in urine, causing fluorescence.
• Function:
  • Part of the FADH complex and attached to diphosphate, ribose, and adenine.
  • Needed for energy metabolism.
• Coenzyme Forms:
  • Flavin mononucleotide.
  • Flavin adenine dinucleotide.
• Requirements:
  • RDI for men: 1.3 mg/day.
  • RDI for women: 1.1 mg/day.
  • Body efficient in recycling riboflavin.
• Deficiency Symptoms:
  • Tissues with rapid turnover are first affected.
  • Inflamed eyelids, sensitivity to light, sore throat, painful smooth, purplish-red tongue.
  • No reported toxicities.
• Ariboflavinosis:
  • Inflammation of membranes of the mouth, skin, eyes, and GI tract.
  • Ulcerated corners of the mouth with redness.
• Food Sources:
  • Widely distributed in foods like liver.
• Other Considerations:
  • Stable to heat but destroyed by UV light.

Niacin (Vitamin B3)

• Nature of Niacin:
  • Not strictly a vitamin; body can manufacture it from tryptophan.
  • 1 mg of niacin requires 60 mg of dietary tryptophan.
  • Expressed as niacin equivalents.
• Niacin Equivalent Calculation:
  • A food containing 1 mg of niacin and 60 mg of tryptophan provides the equivalent of 2 mg of niacin equivalents.
• Function:
  • Part of nicotinamide adenine dinucleotide (NAD).
  • Involved in over 200 metabolic reactions.
  • NAD+ and NADH are involved in energy production via the electron transport chain.
  • Absorbed from the small intestine.
• Requirements:
  • RDI for men: 16 mg/day.
  • RDI for women: 14 mg/day.
  • Upper level of intake: 35 mg/day for adults.
• Toxicity Symptoms:
  • Excess supplemental niacin can cause flushing (capillary dilation, tingling, redness).
  • Hives or rashes.
  • Excessive sweating, blurred vision, liver damage, and impaired glucose tolerance.
  • Large doses may raise good cholesterol.
• Deficiency (Pellagra):
  • In the 1900s, caused many deaths in the US due to corn-based diets lacking protein and tryptophan.
  • The four D's: diarrhea, dermatitis, dementia, and death.
• Other names:
  • Nicotinic acid or nicotinamide.
• Food Sources:
  • Animal products.
  • Foods that contain tryptophan.
  • Chicken breast, mincemeat, liver and tuna
• Stability:
  • Fairly heat resistant but leaches into cooking water.

Pantothenic Acid (Vitamin B5)

• Function:
  • Part of coenzyme A (CoA), which forms acetyl CoA.
  • Plays a role in energy production.
  • Involved in over 100 steps in the synthesis of lipids, neurotransmitters, hormones, and hemoglobin.
• Absorption and Transport:
  • Absorbed in the jejunum by active transport and passive diffusion.
  • Blood cells carry vitamin B5 to tissues.
  • Converted to acetyl CoA within cells.
• Requirements:
  • No RDI; has an Adequate Intake (AI).
  • AI for men: 6 mg/day.
  • AI for women: 4 mg/day.
• Deficiency and Toxicity:
  • Rare because it's widespread in foods as CoA.
• Food Sources:
  • Organ meats, mushrooms, avocados, broccoli, and whole-grain foods.