How our Bodies use Vitamin D
Wednesday, 18 November 2015 | Stuart
The vitamin D3 (cholecalciferol) that we make from sunshine or ingest from foods and certain supplements is sent first to the liver to be converted into calcidiol, or (OH)D, with the help of certain enzymes. This is the blood serum form that is now largely measured in trials and studies to determine the correlation between vitamin D levels and a whole host of illnesses and conditions, as well as to assess deficiency.
The calcidiol is then sent to the kidneys first, and then any excess to the rest of the tissues in the body. Both in the kidneys and in the tissues, it is converted to (OH)2D3 or calcitriol. This is the form that is now recognised as the hormone that triggers very fast gene expression by attaching to receptors on the actual DNA in the cell nucleus. Proteins are then produced that play a role in cellular growth, cellular death, immune system regulation, detoxification, the regulation of blood calcium levels and the release of neurotransmitters such as serotonin. I would consider these functions to be among the fundamental basics for life and good health.
Vitamin D2 is converted to very similar forms, but many argue that there is a slight alteration in the chemical make-up which means that it doesn’t bind so readily to the enzymes in the liver that convert it to the hormonal form, and also that it doesn’t attach so easily to the vitamin D receptors in each of our cells. In addition, D2 may therefore carry a higher risk for toxicity, as there will be greater levels of the unconverted form floating around in the body. There are, however, many conflicting studies surrounding vitamin D metabolism which makes it difficult to state all of this conclusively.
So the form you choose may depend on your reason for supplementation, your interpretation of the evidence so far and your degree of comfort with using a sheep’s wool based product. Many choose vitamin D3 to stay as true as possible to the form we naturally obtain from sunshine and food sources.
We have a number of articles about different aspects of Vitamin D and the vital roll it plays. Click of any link below to look at that subject or, below the links, click to bring up a printable PDF document covering all of the subjects by the excellent Nutrigold company, which also incorporates references.