The importance of Vitamin D

1st February 2013

The topic of vitamin D is very much in vogue, with evidence suggesting that the majority of the world’s population has inadequate vitamin D status. While historically vitamin D has been known as critical for bone health, it is now known that deficiency constitutes a key factor in many of today’s most prevalent chronic diseases and has important health consequences for us all.

What does vitamin D do

Aside from preventing rickets, vitamin D is involved in the expression of more than 1000 genes. This means that it acts on cells in every organ of the body and so has far reaching effects on human health. Some of its key roles are:

• Regulation of calcium homeostasis for bone health, nerve transmission and to prevent calcium deposition in soft tissue. Its effect on calcium metabolism means deficiency in vitamin D is a known risk factor for heart disease and osteoporosis.
• Control of cell proliferation, differentiation and apoptosis; meaning vitamin D may affect all stages of cancer from initiation, to progression to metastasis.
• Regulation of the action of renin, which is important in controlling blood pressure.
• Regulation of the immune system, enabling the immune system to be more “tolerant”, thereby reducing the risk of autoimmune diseases such as rheumatoid arthritis, psoriasis, type 1 diabetes, Chrohn’s disease, multiple sclerosis and auto-immune hypothyroidism.
• Control of microbes by producing antibiotic substances that improve resistance to bacterial infection, including periodontal disease, pneumonia and respiratory tract infections.
• Foetal and adult brain development and function. Recent studies have found vitamin D deficiency to have play a role in Alzheimer’s disease and seasonal affective disorder, as well as other mood disorders.

Vitamin D headlines to note

• Multiple adverse health outcomes for mothers, neonates and children: a recent survey finds high prevalence of vitamin D deficiency in pregnant women.
• Cancer risk halved by increasing vitamin D: a large scale, randomised, placebo controlled study concludes that you can decrease your risk of getting cancer by more than half by increasing vitamin D levels.
• Low levels of vitamin D associated with an 81% higher risk of death from heart disease: a study of more than 10,000 subjects found low levels of vitamin D, when compared to optimal levels, are linked to a 40% higher risk of ischemic heart disease, 64% higher risk of heart attack, 57% higher risk of early death and an 81% higher risk of death from heart disease.
• Chief Medical Officers urge health professionals to take action: Professor Dame Sally Davies writes of the urgent need to address vitamin D deficiency to prevent adverse health consequences in the population at large.

Sources of vitamin D

The action of sunlight on our skin allows our bodies to synthesise vitamin D. Some foods, such as oily fish, naturally contain vitamin D and others, like breakfast cereals, are fortified with vitamin D but dietary sources are insufficient to satisfy our vitamin D requirements. For example, you would need 2-4 servings of wild salmon per day to maintain daily vitamin D requirements!

The sun is our most important source of vitamin D and the reason for widespread vitamin D deficiency is simply lack of sunlight exposure.

Deficiency

Sunlight’s ability to help us produce vitamin D is hampered by sunscreen (blocking out the sun’s action), season (winter sun simply isn’t strong enough), latitude (far northern or southern latitudes), time of day (needs to be between 11am and 3pm), cloud cover (reducing vitamin D synthesis by 50%), pollution (city living) and skin melanin content (the darker your skin, the less vitamin D you will get from the sun).

In summer, when vitamin D is most available, it is estimated that 45% of the English population have vitamin D levels of less than 40nmol/L (deficient) and 75% fail to reach the “optimal” level of 75nmol/L. It’s worse in Scotland, where people are twice as likely as the southern English to have low serum levels. Even in countries with very high amounts of sunlight vitamin D deficiency prevalence is still high.

Given that many of us were deficient before the winter even began, the majority of us will be now that it is February. The situation is of such concern that some experts are calling for vitamin D deficiency to be classified as a major “lifestyle” risk, like smoking, obesity, alcohol and lack of exercise.

People at high risk

While the majority of the general population have insufficient vitamin D levels, certain groups are at a particularly high risk of insufficiency. Major risk factors for deficiency include:

• pregnancy and childbearing;
• increasing age;
• higher body fat mass; and
• darker skin pigmentation.

So should you supplement vitamin D? And if so, how much?

Recent publicity about the nation’s poor vitamin D status has highlighted the need to take a regular vitamin D supplement. Further, new medical research indicates that vitamin D daily requirements may be up to ten times more than current recommendations.

The level of supplementation should be varied according to baseline serum levels (if known), skin type, age, size and lifestyle. As a guide, a recent study suggests people of European ancestry with high sun exposure need 1300iu of vitamin D during winter months. That said, other researchers consider average daily maintenance doses of over three times this amount to be more realistic to promote optimal vitamin D levels.

Vitamin D toxicity is extremely rare; reviews have found 10,000iu/day to be safe. The UK’s Expert Group on Vitamins and Minerals acknowledges that supplementing as much as 4000iu/day is unlikely to have any effect on blood calcium levels.

D2 or D3?

Vitamin D supplements come in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). D3 is the natural form and so considered to be more bioavailable than D2.

If you would like the references for anything mentioned in this article then please contact Nutritional Therapy Works.

Categories: Nutritional News