It's important to get exposure to sun around midday to get sufficient vitamin D. I know this goes against the skin cancer advice, but I think the recommendation is half-an-hour without suncream around midday for vitamin D. It'll be on the internet somewhere!
However that's probably not much help for you at this time of year I'm afraid.
DD3 blood tests often show lack of vitamin D. She also has supplemant drinks and very high fat/dairy diet. (she has CF)
Her dietician (at childrens hospital in Bristol) prescribes a huge dose of Abidec vitamin drops which sometimes does the trick and others not. It's a pain. She is outside every day, her diet should do the trick but she sometimes she is ok and sometimes not. It's a mystery. It doesn't seem to do her any harm as far as we can tell.
It was in the news a little while ago, during the autumn and winter and possibly even spring, children in most parts of the UK do not get enough sun light to produce enough vitamin D hence the call to give them vitamin supplements. I will see if I can find the link to the BBC website.
Like D said, the sun in the uk is not strong enough for any of us to produce Vit D in the winter, and Vit D cannot be stored in the body for long so what we make in the summer doesn't last us for winter. Vit D supplement and a SAD light could help?
It could be something to do with absorption, dairy is usually high in calcium but not necessarily in vit D. ALso, D3 seems to be a flavour of the day, rather than standard D. I know some people on Adcal which was recommended to my ds too, but I just give him occasional fish oil capsule. Actually, I am surprised that your dd on keto is D deficient, as fats are more likely to have fat-soluble vits in them, does she have non-dairy fats in her diet? I personally prefer single vits rather than multivits, as they can be targeted more at the deficiency.
I like scream Do you use goats butter? Don't know for def but I would like to hope that the goats see more of natural daylight than dairy cows, which might make it a little more natural. Goats dairy is certainly easier to digest, my ds has goats butter.
Apparently D is/works as a more natural steroid, prob part of the hype.
I'd also try fish oil, after all fish live in a fairly natural environment.
I would mash fish with butter and potato for my kids. It works very well with cod, and also fresh salmon. Also the mackerel can be mashed in with something, if the flavour is too strong. Have you tried milk fortified with omega3? It is quite dear though.
I don't think they have ever fortified butter with vit D - they fortified margarines (by law) to the vit D level of "summer butter" (i.e. that which comes from milk the cows produce in the summer - higher in vit D) but I don't think butter was fortified (coudl have misremembered that though). I don't think the fortification applies to low fat spreads either, although that isn't relevant to Riven.
oooh, looks like you will be headed on a vitamin d in butter research expedition to the shops!
I have a block of Flora Soft. It is not butter, but margarine, but the full fat, not light variety, and it says the nutritional content, and apparently 100g is 160% of daily recommended intake. So quite a lot. Maybe I am leading you astray, maybe all butter carry the same high vit d content?