For how we live.
SOLARIS, a publicly funded phase 3 trial, tested vitamin D3 added to chemotherapy after a promising phase 2 signal. Progression-free survival was 11.8 versus 10.3 months — not a significant difference.
A varied diet covers most of the 13 essential vitamins. The evidence-based exceptions are specific: vitamin D is hard to get from food, older adults and vegans need B12, and folic acid is advised before pregnancy.
Real deficiency shows as bone pain, muscle weakness or, in children, rickets. But US surveys suggest most people meet their needs, and both a 2011 and a 2024 review advise against routine testing in healthy adults.
VITAL, with 25,871 adults, and D-Health, with 21,315, both tested vitamin D against placebo. Neither cut cancer incidence or cancer death — and one saw a signal pointing the wrong way.
The DO-HEALTH sub-study is the first randomised evidence that a supplement can nudge DNA-methylation ageing clocks. The effect was tiny, and the parent trial found no benefit on health outcomes that matter.
Its 2024 guideline also advises against routine blood testing for vitamin D, on the grounds that no trial evidence supports it. The largest randomised trial found no effect on cancer, heart disease or fractures.
An 876-participant double-blind trial across 24 Chinese fertility centres nearly doubled serum 25-OHD in women with PCOS. Live births were 52.0% against 50.2% on placebo.