Comment by nradov

Vitamin D deficiency is common in high latitudes. Most people don't get enough from their diets so supplements are recommended for them.

https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-...

Vitamin B (thiamine) deficiency is also common among alcoholics. Lots of heavy drinkers out there. While obviously drinking less is the preferred solution, if they aren't willing to do that then supplements can reduce the harm.

https://adf.org.au/insights/alcohol-related-thiamine-deficie...