It is good to see how many people are finding out the benefits of vitamin D . Your own health is dependent upon your body's level.
VitD3 becomes a hormone , unlike other vitamins. It becomes a hormone that is substrate limited . That means your body cannot make more of it ( if required) unless you have enough precursor , available to all your cells. VitaminD3( from supplement or UVB,sun exposure) , is the precursor, 25D3 is the intermediate step, that is measured in your blood by doctors tests, finally 1,25D3 is the Vitamin D hormone form. Your body orchestrates the conversions in a fairly complicated interaction with other signalling compounds. ( one of which is parathyroid hormone)
As the hormone form, the final conversion to a compound called 1,25 D3, enables your cells to read genes and thus produce the products of, or change the behaviour of those cells as is required. If that process is hindered , by low VitD3, at any step, then illness of various types can result. Both short latency ( rickets in children, etc ) or long latency such as osteoporosis, osteopenia , osteomalacia , autoimmune problems, MS, cancers etc in adults. At least 2000 genes are affected, that is about 10% of your entire genome. Myriad bodily processes are affected.
Throughout human evolution , our blood levels of 25D3 were in the region of 120 -140 , it is only when we caused the production of VitD3 , to be curtailed by changing our environment, less sun, migrating North where sunlight is weaker, covering up our skin , etc etc that we have now engineered a situation that results in many /most of us being low in a vital hormone. Taking a long view, Europeans moved into Northern climes about 10,000 years ago , at this juncture , we had a white skin mutation in our genes which allowed us to make more VitD3 from the very limited sunlight, this allowed us to somewhat better survive where other primates cannot. All other primates live below 33 degrees latitude where UVB in sunlight is stronger.. Our physiology developed at low latitudes and if changes in our environment causes our blood levels of a vital hormone to reduce, you can of course expect consequences. Persons that live outside a lot, in that kind of ancient sunny environment achieve those levels. As Westerners ,we generally do not. That is why doctors very often say , "we are all low"...or something like that. If you put a Westerner into that kind of ancient environment his blood levels rises , exactly as expected, to those ancient levels..
It is the realisation of the above situation , by some, that has allowed us to understand how and what levels of vitamin d are required , how sunlight or supplements or artificial sunlight can be used to replicate the healthy levels that we need. It is a mistake to think that just because most people have a similar low level, that level is all that is required. Currently, in the UK , we expect to see blood levels of 25D3 of about 30 -70 , depending upon time of year. Many people are even below that. They have an increased risk of many diseases. Diet , in general, cannot supply all that we need.
One of the most convincing arguments for the above explanation for Vit D deficiencies is the conundrum of human milk. Throughout evolution , until relatively recently , human milk contained every nutrient required for baby. If it did not, then we would not be here.
But now, in modern times, human milk is deficient in Vitamin D generally down to about 25 IU per litre. ( UK ) People living in that ancient environment nowadays have levels around 400 IU per litre. This level is exactly what we recognise to be the optimum.( Incidentally - This figure of 400 IU is duplicated by formula milk.) . We should be asking ourselves the Question - Howcome .. ? The answer is that modern mothers do not have sufficient VitD3 in their milk , because their intake is insufficient. The problem has become worse in the last few hundred years , and in the last 50 years much worse than even that. Indoor living, sunscreen, overzealous avoidance of sun , consumption of vegetable oil rather than animal fat containing VitD etc etc.
It is important to grasp the whole picture , do not suddenly bask in intense sunlight on a foreign holiday , if you are white skinned. Burning is not beneficial , but is harmful. Try to ensure you get a modest dose of VitD3 daily , that is what your body needs, whether breastfeeding or not , you require enough VitD3 to enable your body ( cells) to maintain normal functioning. Levels of 120 – 140 of 25D3 in the blood will do that …!
Here I am trying to explain what is happening , and why many people with a western lifestyle are low in Vitamin D . I hope this is helpful.
BTBH