Information

Vitamin D

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 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. 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 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 may not be enough to generate adequate vitamin D and consequently studies show at least 40% of us have insufficient levels of this important vitamin, while 3- 4% are clinically deficient.

Factors that increase Vitamin D deficiency risk

People in residential care facilities are particularly at risk. Also those taking statin drugs prescribed to lower cholesterol levels can experience vitamin D deficiency, as 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.

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.

A New Zealand programme funded by ACC, DHBs and PHOs 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.

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. Vitamin D deficiency may also be a factor in kidney problems, heart attacks, strokes, irritable bowel syndrome, cancer and many autoimmune diseases including multiple sclerosis. Research published in January 2010 found vitamin D deficiency is a contributing factor in Crohn’s disease.

What are the known health benefits of Vitamin D?

Vitamin D is well known to improve bone strength and reduce the risk of fractures. Recent research is showing many other benefits of maintaining optimum vitamin D levels.

A study published in January 2010 shows colorectal cancer risk increases with low vitamin D concentrations. Vitamin D deficiency is also shown to be associated with three other common cancers: breast, prostate and skin. Prevention and treatment of diabetes, depression, fibromyalgia, heart disease and flu as well as improving weight loss in overweight people and promoting fertility are all well researched benefits of increasing vitamin D intake to optimum levels.

Vitamin D supplementation is 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 the only way to adequately determine your vitamin D status. Serum levels are measured as nanomoles per litre (nmol/L) and the current recommended normal range is 75–250nmol/L. Below 75nmol/L is considered insufficient and below 50nmol/L is considered deficient. 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 this year (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 140nmol/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.

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.

Learn more about the range of quality Vitamin D supplements available at discount prices from healthpost.co.nz.

Carolyn Simon
ND, DipMedHerb