What is Vitamin B?

The B-vitamins comprise a group of eight water soluble vitamins that perform essential, closely inter-related roles in cellular functioning, acting as co-enzymes in a vast array of enzymatic reactions. Their collective effects are particularly prevalent to numerous aspects of brain function, including energy production, DNA/RNA synthesis/repair and the synthesis of neurochemical molecules. B-vitamins are involved in homocysteine metabolism.

Adequate levels of all members of this group of micronutrients are essential for optimal physiological and neurological functioning.

Understanding the role of the B group of vitamins namely, thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin (B6), folate (B9) and vitamin (B12) in health and brain function is limited.

Below are the detrimental effects of B vitamin deficiency:  

Vitamin Good Dietary Sources Principal Bioactive Coenzymes Symptoms of Deficiency Specific risk factors for deficiency   
Vitamin B1 (Thiamin) Cereals (esp. whole grain), brown rice, green vegetables, potatoes, pasta, liver, pork, eggs Thiamine pyrophosphate (Generation of leaving group potential) Mild deficiency: general fatigue/weakness gastro-intestinal symptoms. Alcohol abuse, obesity  
Deficiency: “Beri-beri”— Peripheral nerve damage and cardiovascular dysfunction leading to: pain, impaired sensory perception; swelling, weakness and pain in the limbs; shortness of breath, irregular heart rate, heart failure
Vitamin B2 (Riboflavin) Dairy products, leafy vegetables, legumes, liver, kidneys, yeast, mushrooms Flavoproteins: flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN) (redox reactions) Weakness, oral pain/tenderness, burning/itching of the eyes, dermatitis, anaemia inherited riboflavin malabsorption/ utilization (10%–15% prevalence)  
Vitamin B3 (Niacin) Meat, fish, whole grain cereal, legumes, mushroom, nuts Nicotinamide adenine dinucleotide (NAD) and its phosphate (NADP) (redox reactions) Pellagra: dermatitis/photo dermatitis, alopecia, muscle weakness, twitching/burning in the extremities, altered gait, diarrhoea Alcohol abuse  
Vitamin B5 (Pantothenic acid) Meat, whole grain cereals, broccoli Co-enzyme A (CoA) (acyl activation and transfer) Numbness/burning sensations in extremities, dermatitis, diarrhoea -  
Vitamin B6 (Pyridoxine) Meat, fish, legumes, nuts, bananas, potatoes pyridoxal-5′-phosphate (PLP) and pyridoxamine-5′-phosphate (PMP) (Generation of leaving group potential) Anaemia Alcohol abuse, age-related malabsorption, contraceptive medications  
Vitamin B7 (Biotin) Eggs, liver, pork, leafy vegetables biotin (carboxylation reactions) Seborrheic eczematous rash, tingling/burning of the extremities Type II diabetes, poor gluco-regulation  
Vitamin B9 (Folic acid) Leafy vegetables, legumes, citrus fruits tetrahydrofolates inc. methyltetrahydrofolate (One carbon transfer) megaloblastic anaemia, peripheral neuropathy 3, spinal cord lesions, metabolic abnormalities Common genetic polymorphisms (inc. MTHFR C667T) Low Riboflavin and B12  
Vitamin B12 (Cobalamin) Meat, fish and other animal products Methylcobalamin, adenosylcobalamin (vicinal rearrangements) age-related malabsorption, vegetarians, vegans  
Genetic polymorphisms