How we absorb Vitamin D
Vitamin D is actually more like a hormone, synthesised in the skin by ultraviolet B radiation by the action of the 7-dehydrocholesterol reductase. Once absorbed through the skin it is hydroxylated in the body in both the liver (storage form) and then the kidney when it becomes the active from of vitamin D – cholecalciferol. The vitamin can also be absorbed into the body from foods such as fatty fish, however the best absorbed form is that of the skin’s reaction to the sun.
Barriers to absorption and function
The major barriers to absorption are: wintertime; lack of sun exposure; darker coloured skin (a high melanin content); sunscreen blockers; pollution; issues with the converting pathways within the body (e.g. polymorphisms on the genes); and the amount of vitamin D receptors in the target tissues.
A brief Overview of the Various Functions of Vitamin D in the body
1. Cell organisation
Vitamin D plays an active role in the cell cycle, function and differentiation. Differentiation broadly means that the cells are organised into their various tissues within the body – hence they know where to go and what to do in terms of cell renewal. The active form of vitamin D exerts its function in various areas of the body via the vitamin D receptor (VDR). The extent of importance vitamin D has in the human body is still largely unknown, however the sheer abundance of VDRs signals its importance.
2. Thyroid function
It’s not exactly clear the function of vitamin D with the thyroid gland. What is know is that there is a direct relationship between low levels of vitamin D and thyroid disease. Furthermore, auto-immune thyroiditis also correlates with low levels of vitamin D.
3. Immune System
The complex immune system utilises vitamin D in both the innate and adaptive immune systems.
4. Blood Sugar Metabolism
Studies have showed a beneficial role of vitamin D in diabetes with improved fasting blood sugar and insulin levels and a decrease of insulin resistance.
5. Skin diseases
Vitamin D has been shown to assist with the improvement of inflammation and skin barrier function. There is a direct inverse relationship between vitamin D levels and skin conditions such as psoriasis, vitiligo and atopic dermatitis.
6. Bone Health
Vitamin D is well known to be involved in the maintenance of bones and teeth with a focus on the balance of calcium and phosphorus and management of these minerals.
7. Chronic disease prevention
Vitamin D is thought to have a protective effect in the from cancer, cardiovascular disease, hypertension, diabetes and autoimmune diseases. It has been shown to exert a beneficial effect on cancer by inhibiting the proliferation and spread of cancer cells. With cardiovascular disease its show to help regulate thrombosis (blood clots), atherosclerosis (hardening of the arteries) and endothelial function (ensuring smooth flow within the arteries). There is a relationship between low levels of vitamin D and autoimmunity, however the exact mechanism warrants further research. It is thought to largely assist with the control of inflammation.
There is growing evidence to support the relationship with vitamin D levels and mood disorders such as depression and anxiety.
Naturopathic view on Vitamin D
From a naturopathic viewpoint, the range shown on the blood test reports are low. Obtaining a higher level than what is stated on your blood test is often a strong consideration for optimal health. Vitamin D is cheap and best absorbed sublingually. If supplementation is recommended, it may take 3-6 months to obtain the desired level. Signs and symptoms of vitamin D deficiency or insufficiency may be overlapping numerous other potential causes. Naturopathy is an individualised whole systems approach to health and wellness, and the status of vitamin D is always considered in the context of your health concern.