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 many 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, by the liver, into a storage form (25-hydroxyvitamin D) and released as needed to the kidneys for conversion into the bioactive form calcitriol (also referred to as 1,25 D).

The bioactive form, 1,25 D has a short lifespan and needs continual replenishment from the storage form.  Ongoing production of 1,25 D is essential to support 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.

Research suggests that Vitamin D may provide support for optimal bone health, muscle strength, joint mobility and immunity.

Are you getting enough Vitamin D?        

Most of us are aware that we produce vitamin D through exposure to sunlight. Varying factors such as the latitude you live at, time of day and length of time you spend in the sunlight, changing seasons, your age, culture and your type of skin pigmentation all have an influence on how much vitamin D you produce through the skin.  During winter, even the strong New Zealand sunlight isn’t enough for some people to generate adequate vitamin D.  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. It is also difficult to get optimum levels of Vitamin D just from our diets, as only a few foods (see below), supply Vitamin D.

Factors that increase Vitamin D deficiency risk:

  • Excessive use of high SPF sunscreens may block the natural synthesis of vitamin D in the skin, leading to deficiency.
  • In cultures where women are required to completely cover themselves in public, vitamin D deficiency is common.
  • Similarly, populations in colder climates who have minimal sun exposure during winter months are likely to be deficient in this sunshine vitamin.
  • People with very dark skin may be 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 prescription medicine that may affect Vitamin D levels.
  • Breastfed infants with mothers who have a high risk of Vitamin D deficiency. Consuming both too much animal protein and too much calcium may decrease the important metabolic conversion of Vitamin D to 1,25 D in the kidneys.

What happens if I don’t get enough Vitamin D?

The two most common and advanced forms of Vitamin D 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.  Prior to this stage, deficiency symptoms may include, sore muscles, 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 other health conditions?

Vitamin D deficiency may also be a factor in many disorders involving the kidneys, heart, digestive system, and immune system.  Vitamin D has been shown to help support the mood as well.  A 2013 research review on non-skeletal disorders and vitamin D 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 normal healthy cholesterol levels, inflammatory markers, blood sugar, immune responses, weight and cognitive function.   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 may be a significant marker of deteriorating health.

This research review highlights the need to keep vitamin D production (from sunshine) or intake (from food and 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.

How do I get it and how much do I need?

Food sources of vitamin D include fatty fish, (tuna, mackerel, eel, salmon), beef liver, and egg yolks.  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 may need to be considered against the positive value of fish as a nutrient source.

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 at very high doses. When treating deficiency symptoms, an initial blood test through a qualified professional to check serum levels is recommended, and another blood test a few months after supplementation has begun to monitor progress towards optimum levels and adjust dosage accordingly.

Vitamin D supplements currently available in NZ have 1000IU per capsule.

There are two forms of vitamin D supplement:  D2 and D3.  Vitamin D3 (Cholecalciferol) is the most effective form of supplementation to take.

By The HealthPost Naturopaths

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