Overview
- European guidance highlights upper intake thresholds, with EFSA judging 100 µg/day supplemental B12 as safe while Germany’s BfR advises a 25 µg/day cap for supplements.
- Recent reporting cites studies associating long-term, high-dose vitamin B12 and some antioxidants with increased lung cancer risk, including higher risk in men taking more than 55 µg/day B12 for a decade.
- Overdosing is chiefly tied to supplements, as fat‑soluble vitamins A, D, E and K can accumulate, while water‑soluble vitamins are usually excreted but high B6 or niacin can still cause neuropathy or liver effects.
- Vitamin D status is assessed via 25‑hydroxyvitamin D, with the RKI calling 30–50 ng/ml optimal and the DGE recommending 800 IU daily when sunlight is insufficient.
- Most people meet needs through varied diets, but pregnant women, infants, vegans and those with malabsorption may require supplements and should confirm needs with blood tests before high doses.