Micronutrients: Biotin, Pantothenic Acid, Pyridoxine, and Choline

This discussion covers the physiological roles, risk factors for deficiency and toxicity, signs and symptoms of deficiency and toxicity, minimum and maximum intake recommendations, and food sources for biotin, pantothenic acid, pyridoxine, and choline.

Biotin

Classification: Water-soluble vitamin.
- Water-soluble vitamins function as co-enzymes or co-factors, assisting various bodily reactions.
Physiological Roles:
- Facilitates metabolic steps crucial for yielding potential energy from fatty acids, glucose, and amino acids.
- Supports cell signaling and gene regulation.
Intake Recommendations (Adequate Intake - AI):
- AI levels are established when insufficient scientific literature exists to set a Recommended Dietary Allowance (RDA).
- Adults: 30 \mu g/day.
- Breastfeeding women: 35 \mu g/day (due to high biotin dependence during this process).
- Units: Biotin intake is measured in micrograms (\mu g).
  - 1000 \mu g = 1 mg.
Food Sources:
- Found in a wide variety of foods including certain meats, vegetables, seeds, grains, and dairy products.
- Excellent sources: Eggs, sweet potatoes.
Deficiency:
- Rarity: Relatively rare.
- Risk Factors:
  - Certain genetic disorders.
  - Raw egg consumption: Egg whites contain avidin, a protein that binds to biotin and prevents its absorption. Cooking denatures avidin, rendering it unable to inhibit biotin absorption.
Toxicity:
- Tolerable Upper Intake Level (UL): Not established due to insufficient scientific literature regarding the health effects of excessive intake.

Pantothenic Acid

Classification: Water-soluble vitamin.
Physiological Roles:
- Part of the chemical structure of coenzyme A (CoA), a vital compound in several metabolic pathways.
- Helps to build fatty acids, which play key physiological roles.
Intake Recommendations (Adequate Intake - AI):
- Much like biotin, an AI level is set instead of an RDA.
- Adults: 5 mg/day.
Food Sources:
- Exists in a wide variety of foods, including certain meats, vegetables, seeds, grains, and dairy products.
- Excellent sources: Shiitake mushrooms, sunflower seeds.
Deficiency:
- Rarity: Extremely rare due to its ubiquitous nature in food.
- Symptoms (when deficiency occurs): Numbness and burning of the hands and feet, headache, fatigue, irritability, restlessness, disturbed sleep, gastrointestinal disturbances (with appetite loss).
Toxicity:
- Tolerable Upper Intake Level (UL): Not established due to insufficient scientific literature regarding the health effects of excessive intake.

Pyridoxine (Vitamin B6)

Classification: Water-soluble vitamin, also known as Vitamin B6.
Nomenclature: Pyridoxine or Vitamin B6 are umbrella terms for six different compounds:
- Pyridoxine, pyridoxal, pyridoxamine, and their respective 5' -phosphate esters (chemically similar, phosphorus-containing counterparts).
- Active Coenzyme Forms: Pyridoxal 5' -phosphate (PLP) and Pyridoxamine 5' -phosphate (PMP).
Physiological Roles (facilitate over 100 enzyme reactions):
- Protein Metabolism: Assists in the formation of non-essential amino acids (amino acids the body can synthesize).
- Gluconeogenesis: The creation of glucose from a non-glucose substrate (occurs more frequently in low blood glucose).
- Glycogenolysis: The breakdown of glycogen stores, which yields glucose (occurs more frequently in low blood glucose).
- Immune function.
- Hemoglobin formation (a key component of red blood cells).
- Neurotransmitter synthesis (chemical messengers of the nervous system).
- PLP-specific role: Also involved in carbohydrate and fat metabolism.
Intake Recommendations (Recommended Dietary Allowance - RDA):
- An RDA is established for pyridoxine, indicating a relatively large body of scientific literature.
- Adults: Approximately 1-2 mg/day.
- This intake is generally met with a balanced diet, unless specific behaviors or disease processes inhibit absorption.
Food Sources:
- Excellent sources: Chickpeas, yellowfin tuna.
Deficiency:
- Individuals at Increased Risk: Individuals with alcohol use disorder, autoimmune disorders, impaired kidney function, or those taking isoniazid (a tuberculosis medication).
- Symptoms:
  - Reduced red blood cell production (anemia) and the production of smaller red blood cells (microcytosis), collectively termed microcytic anemia, due to pyridoxine's role in hemoglobin formation.
  - Neurologic symptoms: Changes to brain wave patterns, depression, confusion.
  - Skin changes: Cheilosis (scaling of the lips) and cracks at the corners of the mouth, glossitis (a swollen tongue).
  - Weakened immune function.
- Application in Pregnancy: Approximately 50\% of pregnant individuals experience nausea and vomiting, and 75\% experience nausea. Severe cases can lead to weight loss, dehydration, and hospitalization.
  - Pyridoxine, when given in prescribed doses (10-25 mg, 3-4 times per day), has been found to be an effective and safe treatment for pregnancy-related nausea and vomiting.
  - This treatment is endorsed by the American College of Obstetrics and Gynecology.
Toxicity:
- Possibility: Pyridoxine toxicity is possible, though challenging to achieve with food alone.
- Tolerable Upper Intake Level (UL): Established for this micronutrient.
  - Adults: 100 mg/day (significantly higher than the RDA).
- Primary Symptom: Neuropathy (nerve damage).

Choline

Classification: Essential micronutrient without an official micronutrient category; often discussed alongside water-soluble vitamins.
Physiological Roles:
- Precursor for the neurotransmitter acetylcholine, which participates in physiological processes such as memory, mood, and muscle control.
- Necessary for the synthesis of the phospholipid portion of cell membranes, vital for maintaining cell integrity.
Intake Recommendations (Adequate Intake - AI):
- An AI level is established for choline, similar to biotin and pantothenic acid.
- Adults: Ranges from 425-550 mg/day.
Food Sources:
- Excellent sources: Eggs, kidney beans, cruciferous vegetables (e.g., Brussels sprouts), and meat (e.g., ground beef).
Deficiency:
- Rarity: Uncommon.
- Symptoms (if deficiency occurs): Liver and muscle damage.
Toxicity:
- Possibility: Toxicity is possible.
- Tolerable Upper Intake Level (UL): Established for choline.
- Symptoms: Fishy body odor, vomiting, excessive sweating and salivation, hypotension (low blood pressure), and liver toxicity.

Conclusion

Biotin, pantothenic acid, pyridoxine, and choline are all micronutrients essential for facilitating various physiological processes, many of which are necessary for macronutrient metabolism.
Biotin, pantothenic acid, and pyridoxine are classified as water-soluble vitamins.
AI values have been established for biotin, pantothenic acid, and choline.
An RDA has been established for pyridoxine.
A UL has been established for pyridoxine and choline, but not for biotin and pantothenic acid.