Vitamin D

Vitamin D is a fat-soluble steroid hormone responsible for the intestinal absorption of calcium, iron, magnesium, phosphate and zinc. In humans, dietary Vitamin D is negligible; most comes from exposure of skin to sunlight or from supplementation.

Function
Vitamin D is fat-soluble, regulates calcium levels, helps modulate the immune system, and is vital to good bone health.

Vitamin D2
Vitamin D2, known as ergocalciferol, is a vitamin D found in plants, mushrooms, and yeasts, and sometimes in foods fortified with vitamin D.

Vitamin D3
Vitamin D3, known as cholecalciferol, is synthesized in the human skin from the UVB radiation in sunlight. D3 can also be obtained from supplements.

VDR gene
The VDR gene, also known as nuclear receptor subfamily 1 group I member 1, provides instructions for making vitamin D receptor, which controls the body's response to vitamin D. Vitamin D-dependent rickets, alopecia areata (an autoimmune disease), intervertebral disc disease, kidney stones and leprosy have all been linked to the VDR gene.

Immune function
Vitamin D improves regulatory T cell function in healthy adults and in patients with relapsing remitting multiple sclerosis, suggesting that it may play a role in both preventing and ameliorating autoimmune disease. Experimental studies have shown that vitamin D helps protect against a proliferation of CD4+ T cells, and reduces the number of Th1 and IL-17 cytokines.

Infectious disease
Vitamin D deficiency increases the risk of viral infections.

Epstein-Barr virus
An Epstein-Barr virus protein EBNA-3 has an affinity for the Vitamin D receptor and may actually block the activation of VDR-dependent genes by Vitamin D.

Deficiency
Vitamin D deficiency can cause complex medical problems, and because vitamin D cannot be absorbed from sunlight shining through windows, people who are mostly or totally housebound are particularly at risk of Vitamin D deficiency.

Recommended level
The recommended blood level of Vitamin D varies considerably by government body and health society.

The US Institute of Medicine suggests levels between 20 ng/ml and 50ng/ml.

The Vitamin D Council suggests a level of 50 ng/ml or 125 nmol/l as ideal.

In the United States, 41.6% have serum levels below 20 ng/ml, the threshold for deficiency or 82.1% of African-Americans and 69.2% of Hispanics.

Toxicity
Taking very high Vitamin D levels long term can cause hypercalcemia, which causes serious health problems, although more serious effects like kidney stones are relatively rare. Taking very high amounts of calcium (1,000mg daily) combined with moderate levels of vitamin D can also be harmful. The NHS and the US Office of Dietary Supplements both recommend a maximum daily limit of 100mcg (4,000IU).

ME/CFS
A retrospective study found patients with CFS have lower levels of Vitamin D than the general population. However, it was uncertain whether this is correlated with the amount of time CFS patients spend indoors or with some other factor.

Raising Vitamin D levels has reportedly resulted in remission for some CFS patients.

Recent research has found no toxicity at 10,000 IU per day and levels as high as 15,000 IU/day are probably tolerated. At this dosage it will take 75-90 before symptom improvement is expected to be seen. Some people have seen some symptoms improved within days, but those are likely a small minority.

In 2015, Witham et al. found that high-dose oral vitamin D3 did not improve markers of vascular health or fatigue in patients with chronic fatigue syndrome. The study consisted of patients meeting the the Fukuda criteria (1994) for CFS and the Canadian (2003) ME/CFS criteria who were either given 100,000 units oral vitamin D3 or a matching placebo every 2 months for 6 months.

In 2017, a study by Earl et al. concluded that low serum concentrations of total 25(OH)D do not appear to be a contributing factor to the level of fatigue of CFS/ME.

Fibromyalgia
A cohort of Saudi women with fibromyalgia was found to be Vitamin D deficient. Vitamin D status was inversely correlated with pain. High dose Vitamin D supplementation resulted in improvement or resolution of symptoms. A second study also found improvement of symptoms with Vitamin D supplementation.

Autoimmune disease
Low vitamin D is a possible or known risk factor for systemic lupus erythematosus, multiple sclerosis, rheumatoid arthritis, type 1 diabetes, inflammatory bowel disease, alopecia areata (an autoimmune disease causing hair to fall out), and the autoimmune thyroid disease Hashimoto's thyroiditis (hypothyroidism). Active Crohn's disease has also been found to be associated with lower Vitamin D levels.

Multiple sclerosis
Among people with early stage multiple sclerosis (MS), those with higher vitamin D levels had better outcomes five years after follow up.

It is theorized that there may be a link between low Vitamin D, Epstein-Barr virus and MS.

There are high levels of both vitamin D deficiency among Scotland's 15,000 MS sufferers; Scotland has the highest prevalence of MS anywhere in the world at over 200 per 100,000 of the population, with over 400 per 100,000 in Orkney, and Scottish ancestry is a recognized risk factor.

Notable studies

 * 2014, Association between vitamin D status and markers of vascular health in patients with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME)
 * 2015, Effect of intermittent vitamin D3 on vascular function and symptoms in chronic fatigue syndrome – A randomised controlled trial
 * 2017, Vitamin D status in chronic fatigue syndrome/myalgic encephalomyelitis: a cohort study from the North-West of England (Full Text)
 * 2018, Exogenous VD3 alleviates chronic fatigue syndrome by activating MEKs/ERKs-SIRT1 signaling pathway in skeletal muscle (Abstract)

Learn more

 * Linus Pauling Institute Micronutrient Information Center - Vitamin D
 * Vitamin D - drugs.com
 * Vitamin D - MedlinePlus Encyclopedia