B-complex is not a single vitamin but a family of eight: B1 (thiamine), B2 (riboflavin), B3 (niacin/niacinamide), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate/5-MTHF), and B12 (cobalamin). Each is a co-enzyme piece of the metabolic jigsaw, turning carbs, fats, and proteins into ATP and driving synthesis of DNA, myelin, and key neurotransmitters. The brain, which burns 20% of the body’s energy, concentrates B vitamins via active transport across the blood–brain barrier. Intake falls when diets are low in whole grains, legumes, green veg, and animal foods, when absorption is blocked by drugs (e.g., metformin, PPIs), or when requirements spike during stress or illness. Because tissue stores are tiny and water-soluble excess is lost in urine, steady supply—food first, supplements when required—is vital.
Effectiveness4/5
Evidence5/5
Safety3/5
