Vitamin D – Benefits, Sources and Precautions
Most of us have been made aware of the need for Vitamin D from an increased media campaign over the last couple of years. What we call Vitamin D isnt a pure vitamin as such like for example Vitamin C because our bodies do make it. It crosses into the territory of a hormone too, that our body produces through a series of processes which happen naturally from receiving UVB sunlight through the skin. Molecules from our cholesterol convert this received light to cholecalciferol, also known as D3. It is really our own form of a type of photosynthesis. Cholecalciferol travels to the liver where it is converted to 25-hydroxyvitamin D (25OHD). The kidney then converts 25OHD to 1,25-hydroxyvitamin D (1,25OHD), also known as calcitriol, which possesses hormonal properties and regulates calcium and phosphate balance.
Sadly most of us lack enough sunlight caused by a cloudy climate, being indoors too much and not exposing enough skin to it without suncream for long enough. So most of us do become deficient.
Vitamin D is really essential for maintaining your health, and we can easily underestimate how important it is. We dont know all of its functions for sure but here are some correlations to deficiency:
Some small deficiency symptoms are; poor energy, insomnia, compromised immune system, and mood imbalance.
Some higher deficiencies are being linked to; Autism,Breast cancer,MS,Brittle Bones,Heart and Brain problems for example Dementia, Type 2 Diabetes, Auto-immune diseases, Skin and Colon cancer. New research is also looking at the relationship between IBS and vitamin D deficiency. There is rarely one isolated cause for any illness or symptom, it is usually a multi-layered one so please bare that in mind.
It is doubly important in pregnancy to have enough for you and your child as the child is totally dependent on the mother at this stage for this. Teeth are formed in the womb for example and I believe alot more is determind there as a kind of blue print than we are aware of. There are studies that even link a lack of vitamin D in the womb to poor verbal skills in childhood.
Getting enough naturally from diet alone can be tricky as there aren’t many foods that contain the nutrient in the first place and second the quality of these foods as they are presented to us today is questionable. The best sources for D3 are eggs, oily fish,whole organic milk,butter and cheese and ergocalciferol or plant D2 from mushrooms but it is not loads. Here it is also worth being aware that farm fed salmon for example are not able to make enough and mushrooms need UV sunlight to make it too so again it depends on the cultivation as to how rich they are in it. Also pasteurisation of dairy makes calcium and proteins and vitamin D less absorbable so raw milk is totally preferable to receive any benefit – this is a good link to read on this matter –
The above is a point to bare in mind with all stated availability of nutrients in foods. The best supplements to take are D3 or Cholecalciferol made from Lichen, some also extract it from lanolin. The D3 from Cytoplan is good quality and from Lichen so fine for vegans and vegetarians too. Remember vitamin D is fat soluable, This means that if you take a supplement you must have it with foods containing healthy fats or your body is unable to absorb and use it so well.
In the US the recommended daily intake is higher than in the UK for some reason, even though we tend to get less sunshine hours here. The average daily base recommendation in the UK is 400iu (10mcg) by the government for the whole population, adults and children, but this is an average baseline. In the US it is 600iu
What needs to be considered is age and more importantly if there is already a deficiency. The above doses are recommended to maintain an optimum level. If you were already deficient you would need to take much more. Please refer to this article here and seek advice from myself or another qualified nutritionist or doctor if you believe you are very deficient; http://www.vitamind3uk.com/VitaminD_Dose_How_Much_Needed.html
The optimum way for maintenance would be 15-30 minutes a day of sun-cream free skin exposure to midday sun ! Everything we have been told to avoid over the last decades. And a varied and healthy diet. Vegans are definately advised to supplement.
Word of awareness D3 – cholecalciferol v D2 – ergocalciferol – Many sites state that fortified cereals and milks are a good source. I do not recommend these as they usually contain D2 which although original from yeast or fungus often goes through alot of processing and is a form that your body does not use so well and can be calcifying in an unhelpful way especially if a person tends to be over acid. You will see articles for and against D2 but from my research I would definately prefer the foodstate D3. It is more effective at increasing levels of 25OHD which convert to calcitriol, responsible for calcium regulation. Research has also shown that higher serum levels of D2 are associated with lower levels of D3 and therefore a high intake of D2 may reduce availability of D3 and potentially calcitriol. Further studies conclude that D3 is more appropriate to sustain adequate 25OHD levels than D2, therefore it is recommended to obtain vitamin D in the form of D3. A couple of examples of research opinions are;
- A study looking at improvement in myelination and recovery from nerve injury concluded that cholecalciferol (D3) is more efficient than ergocalciferol (D2). When delivered at a high dose (500 IU/kg/day), cholecalciferol induced a significant locomotor and electrophysiological recovery. The study also demonstrated that cholecalciferol increases i) the number of preserved or newly formed axons in the proximal end, ii) the mean axon diameter in the distal end, and iii) neurite myelination in both distal and proximal ends.
- One report suggests that vitamin D2 should no longer be considered equivalent to vitamin D3 based on differences in their efficacy at raising serum 25-hydroxyvitamin D, diminished binding of vitamin D2 metabolites to vitamin D binding protein in plasma, and a non-physiologic metabolism and shorter shelf life of vitamin D2. Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.In a recently published study in the Journal of Clinical Endocrinology & Metabolism, vitamin D3 was shown to be 87% more effective in raising vitamin D levels in the blood over vitamin D2. According to the lead researcher Dr. Robert Heaney (Creigton University School of Medicine in Omaha, Nebraska),
“Given its greater potency, D3 should be the preferred treatment option when correcting vitamin D deficiency.”
Their research showed that vitamin D3 produced significantly greater bioavailability and reserve storage than vitamin D2.
Over dosing on Vitamin D supplementation would cause death, for this reason the processed version is the main ingredient in rat poison and all animals are vulnerable to this. But this is not a danger for humans unless exceeding doses of over 40,000IU over a couple of months. The majority of the population are not obtaining adequate levels of vitamin D, however it is possible to have excessive and therefore toxic levels of vitamin D with the main consequence of this a too high level of calcium within the blood (hypercalcaemia) causing calcification and kidney stones etc. I suggest that if you are taking more than 5000 IU per day for more than 3 months, then vitamin D blood levels should be checked regularly, especially during the summer months.
An adequate blood level is considered to be above 50 nmol/litre; the scientific literature suggests that a higher level of between 100 to 150 nmol/litre is optimal; levels above 250 nmol/litre are not advised and in this case measures should be taken to lower levels. Please note some laboratories use different units i.e ng/ml rather than nmol/litre quoted here. In this case the optimal range is 40 to 60 ng/ml.
Vitamin D Benefits in more detail:
Calcitriol (the active form of vitamin D) plays an essential role in maintaining and supporting adequate bone density and it has been shown that vitamin D deficiency is related to an increased risk of osteoporosis and osteomalacia as well as specifically leading to rickets, particularly in children. This is because the primary effect of vitamin D is enhanced calcium absorption in the small intestine.
When there are low levels of blood calcium, PTH (parathyroid hormone) secretion is increased which stimulates production of 1,25OH2D (calcitriol) in the kidney. Calcitriol interacts with the vitamin D receptor (VDR) in intestinal cells and signals to increase the expression of calcium transporters and calcibindin D and increase ATP dependent Ca2+ pumps, all of which increases calcium absorption. Vitamin D also stimulates the reuptake of calcium from the kidneys, therefore reducing the excretion of calcium.
So vitamin D is responsible for maintaining adequate serum levels of calcium and in doing so it helps to maintain bone density. Serum calcium needs to be regulated within a tight physiological range and if levels fall, then the other action of PTH is to cause the release of calcium and phosphate from bone (i.e. in order to maintain adequate serum calcium and phosphate levels). Thus, vitamin D protects bone from calcium and phosphate loss.
Low serum vitamin D levels have been associated with an increased risk of hypertension, atherosclerosis, dyslipidaemia, metabolic syndrome and cardiovascular disease. The precise mechanisms for how vitamin D protects the cardiovascular system remain unclear, however potential hypotheses include:
- Downregulation of the renin-angiotensin-aldosterone system – this system is involved in increasing blood volume and therefore blood pressure. Therefore, it is suggested that vitamin D reduces hypertension via this downregulation
- Direct effects on the heart and vasculature
- Improvement of glycaemic control
- Downregulation of inflammatory pathways
Again, as with many other conditions, the role of vitamin D in cognitive health is not yet completely understood. A large 2014 study published in Neurology showed people with extremely low blood levels of vitamin D were more than twice as likely to develop Alzheimer’s disease or other types of dementia as those with normal vitamin D levels.
Studies have found that vitamin D has pro-cognitive and neuroprotective functions, including the reduction of hallmarks of Alzheimer’s disease such as amyloid beta and phosphorylated tau. In rats, decline in learning and memory was ameliorated by vitamin D3 supplementation, whereas no improvement was observed in controls.
Mechanisms of action by which vitamin D may be supportive of cognitive health include:
- Inducing nerve growth factors and neurite outgrowth (observed in embryonic rat hippocampal neurons), i.e. supporting nerve growth
- Increasing activity of choline acetyltransferase, an enzyme involved in the synthesis of the acetylcholine neurotransmitter (a brain chemical important for in memory)
- Increasing the clearance of amyloid plaques (this has been observed in vitro)
- Reducing pro-inflammatory cytokine IL-1β, and increasing the anti-inflammatory cytokine, IL-10
Epidemiological evidence has shown increased prevalence of several autoimmune diseases, including inflammatory bowel disease, MS, type I diabetes and rheumatoid arthritis at Northern latitudes where sun exposure is reduced; therefore, it has been suggested that vitamin D is protective against autoimmune conditions.
This is likely to be due to anti-inflammatory and immune modulating effects that vitamin D has demonstrated, such as regulating the production of inflammatory cytokines and inhibiting the proliferation of pro-inflammatory cells, both of which are crucial for the development of inflammatory and autoimmune diseases.
- In a recent study, both forms of vitamin D – 1,25(OH)2D3 and 25(OH)D3 exhibited anti-inflammatory actions by dose-dependently inhibiting lipopolysaccharide induced production of IL-6, and TNFα (pro-inflammatory cytokines) by human monocytes (immune cells).
- T helper 1 (Th1) is essential for part of the innate immune system, particularly in response to infection. However, the balance of T Helper 1 cells with T Helper 2 cells needs to be tightly regulated. Excess Th1 compared with Th2 for prolonged periods of time, in the absence of acute infection, is known as Th1 dominance and is associated with tissue specific autoimmune disease such as multiple sclerosis or rheumatoid arthritis. Research has shown that D3 can reduce Th1 (T helper 1) dominance.
Additional evidence has strongly suggested that vitamin D plays an important role in modifying the risk of type 2 diabetes, an effect which is likely mediated by an effect of vitamin D on beta cell function, insulin sensitivity and systemic inflammation. Vitamin D has both direct and indirect effects, the latter via regulation of calcium effects on various mechanisms related to the pathophysiology of type 2 diabetes, including pancreatic beta cell dysfunction, impaired insulin action and systemic inflammation.