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 its 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 (see below) supply vitamin D. Varying factors such as the latitude you live at, the time of day and length of time 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 for some people 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
- 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 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.
What happens if I don’t get enough Vitamin D?
The well-known most serious 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. Prior to this stage, smaller deficiency symptoms include sore muscles, low energy, fatigue, reduced immunity, high blood pressure, depression, memory loss, mood fluctuations and erratic sleep patterns can present in the body.
What do we know about Vitamin D levels in relation to health conditions?
Vitamin D deficiency is also 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 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 normal healthy cholesterol levels, inflammatory markers, blood sugar, immune responses, weight and cognitive function. 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 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, 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 needs to be balanced 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 the Dr 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.
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.
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