Parents, please be up to date with the current guidelines. The UK is unusual in Europe in having a poorly communicated Vitamin D policy and in not having a monitoring programme to enforce best practice.
So it’s down to parents to be well informed.
I recommend you listen to this podcast from the BBC.
For new mums who are interested in making sure their babies are getting enough, this article by nutri.co.uk might be helpful. Discuss with your GP before supplementing small babies.
Low levels of magnesium, something that’s common in the affluent western world, make it harder for the body to use Vitamin D.
For those who want to dig a bit more, this recent lecture by the geneticist Steve Jones should be interesting.