alt Hacker NewsVitamin D supplements don’t work consistently across different populations. Very few (~10%) of people can absorb dietary vitamin D. If you aren’t some form of Northern European, you probably need to take at least 10 times the daily recommended dose of vitamin D to influence your levels significantly.
Most people need sun!
Don't most people who take supplements just take 10X the RDA? It is still a tiny amount of supplement that is safer and costs a fraction of the indoor tanning or traveling often to somewhere with adequate Sun.