ER

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.