The total weight of all vitamins in the human body is approximately 1/4 ounce. This is based on the fact that the body contains very small quantities of vitamins - fat-soluble vitamins (A, D, E, K) are stored in minimal amounts, and water-soluble vitamins (B complex, C) are present in even smaller quantities since excess is excreted. 1/4 ounce is roughly 7 grams, which aligns with physiological estimates.