Vitamin D – not enough, too much or just right?

The calcium pills I am now prescribed contain Vitamin D.  If you don’t have Vitamin D you don’t absorb the calcium.  If you are lucky and live in a sunny place and can actually get out in the sunshine with some bare skin you can make your own- the closest we come to being like plants, making their food from sunshine.

Living in the UK there just isn’t enough sunshine for much of the year, and in the winter sunny days are too cold to run around naked for a couple of hours at lunchtime.  I used a calculator made available by the Norwegian Institute of Air Research to see how much exposure I’d need outside today (gloomy weather, and guessing a few factor like the ozone level) and got this result:

Processing … (this may take a minute)Done
minimum recommended exposure time (hours:minutes)
24: 0

So I’d need to be outside from dawn to sunset everyday to get anywhere close to the exposure levels- and that is giving myself a day length of twelve hours, which is longer than we have at the moment.  At least that doesn’t say naked, just exposing hands and arms and face.  It didn’t have a box for ‘how much clothing are you going to wear’.

Rickets, which you get from a deficiency of Vit D, used to be very common – with an estimate of 90% of northern European children having rickets in the early 20th C. With less Vit D you absorb less calcium, and the body takes what it needs for other functions from the bones.  Softening of the bones leads to leg bowing in kids.  The harder bones of adults don’t show this bending of the bones, but you can get general bone aches and fatigue as a sign. (the chapter by M Holick I took this from is very interesting if you want to read more about the many aspects of Vit D).

I was surprised to see that the NHS says infants (unless formula-fed) and children up to age 5 should have Vit D supplements everyday, and also pregnant, breastfeeding, housebound and over 65’s should supplement their diet. The MS UK website says older people make less Vit D as their skin is thinner.  Osteoporosis Canada recommends routine vitamin D supplementation for all Canadian adults year round due to their northern climate.

The relationship of Vit D with calcium is a complex one.  Understanding how they interact seems like an important aspect of managing bone health for people like me with osteoporosis. The NHS website states:


So, if you take too little you can get rickets, which gives you bone pain and deformities.  If you take too much you can wreck your kidneys and give yourself weak bones.  Some studies suggest that Vit K can help keep the calcium in the bones and out of the arteries when used in higher doses than we would normally get through food.

So how much is enough and how do you tell if that is what you are getting? The NHS website says not to take more than 25 micrograms a day.  My prescription pills give me 20 micrograms a day.  I’ve had a blood test to check that this is ok (and heard nothing so presume it is ok) and assume that I’ll get this tested every now and then to be sure I’m not ruining my kidneys.

There seems to be some disagreement on the appropriate levels, with the levels described here being considered much to low by some practitioners. RDAs are based on the levels people need not to be ill, rather than optimal health, so vitamin proponents often say RDAs are too low for people trying to address associated issues.

Vitamin D is fat soluble, and can be stored in the body.  So, if you miss a pill one day you can top up by taking two the next.  I wondered if that meant I should take my pills with a fatty meal, but research on absorption tested by blood plasma levels shows it isn’t important you absorb a bit more with a low fat meal versus either fasting or a high fat meal, but there isn’t a difference in the blood plasma levels in the longer term.  Some types of calcium should be taken with a meal (calcium carbonate), the others can be taken any time.

You can get your Vit D from fortified dairy products( which as a person with lactose intolerance I don’t eat), fatty fish (Yuk!) or, interestingly, mushrooms which are grown under ultraviolet light.  I bought some of those the other week as I spotted them in the supermarket; I had wondered how they came to have more Vit D.  I’m not too sure about eating mushrooms, I sometimes feel a bit glutened after eating them, and they can be grown on grain which leads to a low level of contamination.  The pills seem safer.

It does seem that Vit D might also help with depression– so being in sunshine might cheer you up for that reason too.  It is certainly a lot easier to take a Vit D supplement than hae sunny holidays throughout the winter, however attractive that might be as a proposition.

So what about Vit K?  You get it by eating your dark leafy greens and eggs. Its role in treating osteoporosis is, apparently,  controversial. Some studies suggest that higher Vit K levels reduce osteoporosis, others don’t.  One interesting new bit of information for me is that our gut bacteria manufacture Vit K.  Vit K looks like a complex enough issue that it will need its own investigation.  However, if you have a poorly performing gut (like in Chrones or coeliac disease) you are less likely to absorb Vit K, and when I still ate gluten I got bacterial gut and respiratory tract infections a lot, so took antibiotics these antibiotics would have killed off my VIt K producing bacteria as well as the harmful ones.  It seems likely I would have been Vit K deficient for quite some time and that wouldn’t have helped my bone health.  The Coeliac Society says “the malabsorption that occurs in untreated coeliac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with coeliac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, folic acid and zinc.”

The National Osteoporosis Society has these recommendations about VIt D (abbreviated)

“Key recommendations

  • Serum 25OHD measurement is recommended for:

* patients with bone diseases that may be improved with vitamin D treatment
* patients with bone diseases, prior to specific treatment where correcting vitamin D deficiency is appropriate

* patients with musculoskeletal symptoms that could be attributed to vitamin D deficiency.


O serum 25OHD < 30 nmol/L is deficient
O serum 25OHD of 30–50 nmol/L may be inadequate in some people
O serum 25OHD > 50 nmol/L is sufficient for almost the whole population.




So, this is all more complicated than I expected.  It’s going to take me quite a while to unpack all the research on Vit D and its relationship with calcium absorption and use in the body, and any role Vit K has in this equation.