What is Vitamin D?
Vitamin D is one of the fat soluble vitamins and is a precursor to an important steroid hormone called calcitriol, the active form of vitamin D required by our bodies to regulate a number of important functions. The two forms of vitamin D available to us are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is the form produced by plants, while vitamin D3 is produced naturally by our bodies when our skin is exposed to the sun’s ultraviolet rays.
Both D2 and D3 are converted to a storage form (25-hydroxyvitamin D) by our liver and released as needed to the kidneys for conversion to the bioactive form calcitriol (also referred to as 1,25 D).
The bioactive 1,25 D form of vitamin D has a short lifespan and needs continual replenishment from the storage form. Ongoing production of 1,25 D is critical for the healthy function of our bodies. It is an essential factor in calcium absorption, maintaining normal blood levels of calcium and phosphorus, bone formation and strength, muscle integrity and immune function.
There is strong research showing Vitamin D improves bone strength and reduces the risk of fractures. There are many other health benefits of maintaining optimum vitamin D levels. It has a significant role in reducing inflammation. Most importantly, 1,25 D controls the development of many serious diseases by it’s proven role in inhibiting the conversion of healthy tissue to diseased tissue.
Are you getting enough Vitamin D?
Most of us are aware that we produce vitamin D through exposure to sunlight. It’s difficult to get enough just from your diet, as only a few foods (e.g. wild caught deep sea fish) supply vitamin D. Varying factors such as the latitude you live at, the time of day you spend in sunlight, changing seasons, your age, culture and your type of skin pigmentation all have a major influence on how much vitamin D you produce through the skin. During winter even the strong New Zealand sunlight isn’t enough to generate adequate vitamin D and latest studies show at least 27% of us have insufficient levels of this important vitamin, while 5% are clinically deficient. In many parts of the South Island deficiency levels rise to 18% from August to October.
Factors that increase Vitamin D deficiency risk
- Patients on statin drugs prescribed to lower cholesterol levels can experience vitamin D deficiency – we need adequate cholesterol to naturally synthesise vitamin D in the body
- Excessive use of high SPF sunscreens blocks natural synthesis of vitamin D in the skin, leading to deficiency
- In cultures where women are required to completely cover themselves from head to toe in public vitamin D deficiency is common
- Similarly populations in colder climates who have minimal midday sun exposure during winter months are likely to be deficient in the sunshine vitamin.
- People with very dark skin are more at risk due to absorbing less UV light
- Those who completely avoid sun exposure (due to skin damage or skin cancer history, or taking photosensitive medication)
- People with kidney or liver disease who take medical drugs that affect vitamin D levels
- Breastfed infants with mothers who have high risk of vitamin D deficiency
- Consuming both too much animal protein and too much calcium decreases vitamin D’s important metabolic conversion to 1,25 D in the kidneys. As cow’s milk is high in both, research shows high consumption of dairy products is a risk factor in low vitamin D status.
- People in residential care facilities are particularly at risk
A New Zealand programme funded by government agency PHARMAC provides vitamin D supplements for people in residential care facilities who are unlikely to have sufficient exposure to natural sunlight to meet their vitamin D needs. The supplements are only available by prescription from their GP, and the standard script is 1 x 1.25mg (50,000 IU) tablet per month.
What happens if I don’t get enough Vitamin D?
The well known effects of deficiency are rickets, causing bowed legs and knocked knees in children, and osteomalacia in adults where bones become soft and weak, increasing the risk of fractures. Other deficiency symptoms include sore muscles, low energy, fatigue, reduced immunity, high blood pressure, depression, memory loss, mood fluctuations and erratic sleep patterns.
What do we know about Vitamin D levels in relation to health conditions?
Vitamin D deficiency is also a cofactor in kidney problems, heart attacks, strokes, irritable bowel syndrome, Crohn’s disease and many autoimmune diseases including multiple sclerosis. Vitamin D decreases are associated with three common cancers: breast, prostate and skin. Depression, fibromyalgia, and flu as well as reduced weight loss outcomes in overweight people and low fertility all correlate with vitamin D deficiencies according to research studies.
A 2013 research review on non-skeletal disorders and vitamin D has produced unexpected results. The International Prevention Research Institute in Lyons, France did a meta-analysis of data from 290 observational studies and 172 clinical trials. First indications were that high levels of circulating vitamin D correlate with improvements in cholesterol levels, inflammatory markers, glucose metabolism disorders, infections, weight gain and cognitive function. A lower risk of cardiovascular diseases, diabetes, colorectal cancer and other serious health conditions was also related to high vitamin d levels.
On reviewing the clinical trials however, there was no reduction in risk for non-bone health outcomes. The researchers concluded that rather than a cause of ill health, low vitamin D is a consequence of ill health in these cases. These findings suggest that decreasing vitamin D levels are a significant marker of deteriorating health.
This latest research review highlights the need to keep vitamin D production (from sunshine) or intake (from supplementation) at optimum levels. Whether the cause of decreasing levels is lack of sun exposure or an active disease process, Vitamin D is an essential nutrient among many for maintaining healthy functioning. These findings suggest that supplementing vitamin D may be indicated whenever a serious disease process is diagnosed.
Vitamin D supplementation is also recommended for pregnant women to improve their children’s bone density and health throughout life.
How do I get it and how much do I need?
Food sources of vitamin D include oily fish (salmon, tuna, sardines, eel and warehou are good examples), eggs and liver. However the small amounts derived from these foods is generally not enough to restore deficient levels of vitamin D to an optimal level for good health. Another concern is the toxic levels of contaminants such as mercury contained in some fish, so this factor needs to be balanced against the positive value of fish as a nutrient source.
The recommended sources of vitamin D to maintain adequate levels are safe exposure to sunlight and dietary supplements. Current NZ Ministry of Health guidelines for daily vitamin D intake assume little or no exposure to sunlight. Recommendations for those aged from birth to 50 years is 5 micrograms (200 IU) per day. This increases to 10 micrograms (400 IU) per day for adults aged 51 to 70 years, and 15 micrograms (600 IU) per day for the over 70s. Recent research suggests these guidelines may be far too low.
Measuring Vitamin D levels in the body
A blood test (measuring the blood serum level of 25-hydroxyvitamin D) is used by doctors to determine your vitamin D status. Serum levels are measured as nanomoles per litre (nmol/L) and the current officially recommended normal range is 75–250nmol/L. Below 75nmol/L is considered insufficient and below 50nmol/L is considered deficient. Internationally guidelines vary, and many studies show the lower end of this broad accepted range is still inadequate, indicating 150nmol/L is the minimum normal requirement, while for optimal health 200-250nmol/L is recommended.
Getting safe and adequate Vitamin D supplementation
Vitamin D synthesised in the body through exposure to sunlight is self regulating and non-toxic. Toxicity is only possible from supplemented vitamin D, and there are no published reports of toxicity in amounts under 40,000IU per day. When treating deficiency symptoms an initial blood test to check serum levels is a good idea, and another after a few months of supplementation to monitor progress towards optimum levels and adjust dosage accordingly.
A study of pregnant women published in 2010 followed three treatment groups taking respectively 400, 2000 and 4000 IU per day. The most beneficial results regarding pregnancy, labour and birth outcomes were found in the group taking the highest dosage of 4000 IU per day. This finding indicates that the higher daily supplementation level of vitamin D is both safe and therapeutic.
To get just 140 nmol/L blood serum vitamin D requires about 10,000IU in supplements per day in the absence of exposure to sunlight. While this is a safe dose, to achieve optimum vitamin D levels, supplementation of 3000 to 5000 IU per day in conjunction with exposure to sunlight is the recommended approach. The Ministry of Health recommended daily upper limit for vitamin D intake for children and young people is 80 µg (3200IU).
Most vitamin D supplements currently available have only 1000IU per capsule.
There are two forms of vitamin D supplement: D2 and D3. Vitamin D3 (Cholecalciferol) is the safest and most effective form of supplementation to take.
http://www.awhinahealthcampus.co.nz/Portals/0/Images/Research/WHEA2011//210.pdf latest NZ vitamin D survey results
http://www.bpac.org.nz/BPJ/2011/june/vitamin-d.aspx The Best Practice Advocacy Centre New Zealand (bpacnz) Journal June 2011
http://www.health.govt.nz/system/files/documents/publications/vitamind-sun-exposure.pdf MoH 2012 Consensus Statement on vitamin D & sun exposure in NZ
http://www.health.govt.nz/system/files/documents/publications/food-and-nutrition-guidelines-for-healthy-children-and-young-people-p4.pdf govt guidelines
http://circ.ahajournals.org/cgi/content/short/117/4/503 (cardiovascular disease)
http://www.medicalnewstoday.com/articles/153669.php (weight loss)
http://www.medicalnewstoday.com/articles/51913.php (flu prevention)
http://www.sciencedaily.com/releases/2010/05/100501013417.htm (vit D in pregnancy)
Sigma Life Science http://www.sigmaaldrich.com/etc/medialib/life-science/biofiles/issue4-6/pdfs/vitamin-d-and-prevention.Par.0001.File.dat/vitamin%20d%20and%20prevention%20of%20human%20disease.pdf role in disease prevention
Meta analysis study http://www.nutraingredients.com/Health-condition-categories/Cardiovascular-health/Review-questions-vitamin-D-for-reducing-chronic-disease-risk/?utm_source=Newsletter_Product&utm_medium=email&utm_campaign=Newsletter%2BProduct&c=LCzvjyakHzAZO8kJpmWfRvGHTAxKUZSm
TheChinaStudy. T. Colin Campbell, 2006. Benbella Books,DallasTexas
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