They found D2 often reduced D3 levels, sometimes below those in people taking no supplement, suggesting the two forms are not interchangeable and D3 may benefit most people more.
The findings could affect supplementation and fortification guidance, especially in winter, while researchers also highlighted growing availability of plant-based D3 for vegetarians and vegans.
If D3 is far superior, why are our foods and medicines still using D2?
Could your 'healthy' vitamin D supplement actually be making you more deficient?
With genetics defining vitamin D needs, is personalized dosing the only real answer?