It is part of my job to compare health policy in Scotland to what is happening on the ground, for there is inevitably a gap.

The NHS, after all, employs 157,000 people and deals with almost 5.3 million patients. The way people are looked after will sometimes stray from the guidance produced by the Scottish Government - though I can talk at some length about the need for more honesty about that.

Today I am going to mention how I fell into the crack between the cliffs of policy and practice.Before leaving work for my second maternity leave I had written about new advice saying pregnant women should take a supplement containing that sunshine nutrient vitamin D.

My midwife, however, seemed to know nothing about it. She suggested I buy one of those pregnancy multivitamin products from Boots as she was sure that would cover it.

Some months later, attending a breastfeeding support group at my GP surgery with my newborn twins, I again asked if I should be swallowing vitamin D. The nursing assistant present said she would try to find out. A week later I returned to the same group holding a leaflet I had found in the waiting room about vitamin D that listed breastfeeding women among those at risk of deficiency.

I was told those leaflets were meant for staff and should not really have been on display. In terms of my question about whether I should take the supplement, I only found out when I returned to work in 2012 and discovered then Chief Medical Officer Sir Harry Burns had issued a reminder to the NHS.

It said: "All pregnant and breastfeeding women should take a daily supplement containing 10 micrograms of vitamin D, to ensure the mother's requirements for vitamin D are met and to build adequate foetal stores for early infancy."

I can't turn back time, so I have not investigated what difference that supplement would have made at a time when I was feeding two babies myself and surviving on four-and-a-half hours sleep. I make sure my children get their vitamin D "sweeties" and I started taking a pill myself a couple of weeks ago. Blood tests ordered by my GP had shown my vitamin D levels were insufficient. My lovely doctor did remark she had never seen a lab report that found adequate vitamin D, but then those who were feeling tiptop did not get their blood tested.

I mention this because a study involving researchers at Edinburgh University was published last week looking at how sunshine benefitted mice. The researchers shone UV rays on over-fed rodents and found it slowed weight gain and the development of diabetes. This bonus was not, however, attributed to higher vitamin D levels.

In fact, researcher Professor Richard Weller suggested it may be possible that, while sunshine increases vitamin D levels, it is not the vitamin D itself that is beneficial. Its presence simply flags up the extra exposure to the sun that has health benefits. Just typical, isn't it? As soon as I catch up with health advice, the received wisdom is called into question. No wonder the NHS struggles to align policy and practice.