What is Vitamin D?
Vitamins are required from our diet because our body cannot actually make them. Vitamin D is a fat-soluble vitamin, requiring the presence of fat to dissolve. If using supplementations, excess amounts can be toxic as fat-soluble vitamins store within the body until they’re used (Higdon, 2000; Blahd, 2015). There are two types of Vitamin D characterised by their source: Vitamin D3 and Vitamin D2.
Vitamin D3, known as cholecalciferol, is obtained through ultraviolet-B (UVB) radiation (or sunlight) exposure to the uncovered skin. To gain a sufficient amount, it is recommended to spend a minimum of 10-15 minutes 2-3 times a week, between 10am-3pm in the sun without sunscreen applied (Blahd, 2015; Holick, 2012). After exposure to sunlight the Vitamin D3 is metabolised by the liver and kidneys to produce its metabolically active form (Higdon, 2000). However, the amount that the body actually produces is determined by several factors including, the time of day, geographic location, skin tone, health conditions and, age (Gani & How, 2015; Blahd, 2015).
Vitamin D2, known as ergocalciferol, is obtained through various whole foods and fortified foods. Whole food sources are limited and include some butters, egg yolk produced by hens that have been fed vitamin d, various fish types such as, salmon, tuna, mackerel, sardines and, fish liver oils. Alternatively, vitamin D is occasionally added to fortified foods such as, low-fat milk, orange juice, cereal and, bread (Blahd, 2015; Higdon, 2000). Vitamin D2 is produced into its active form the same way as D3 through metabolisation in the liver and kidneys.
How Vitamin D benefits our health
We’re finding out that Vitamin D is much more important than we’ve ever thought before but, there is still a lot to learn about how it functions and benefits us. What we do know is, that its metabolically active form regulates calcium and phosphorus homeostasis and therefore, is vital for bone health including, the mineralisation, development and, maintenance of our skeletal system (Higdon, 2000; Blahd, 2015). Essentially, vitamin D supports the absorption of minerals, resulting in increased bone density which is important for children, pregnant and postmenopausal women and, the elderly (Blahd, 2015). A lack of vitamin D for the elderly can lead to osteomalacia, falls and fractures; likewise in the early stages of child development, a lack can lead to rickets especially for children fed exclusively on breast milk (Gani & How, 2015; Higdon, 2000; Blahd, 2015).
What we’re beginning to find is that there are also non-skeletal benefits and effects on the immune, endocrine, muscular and, cardiovascular system (Gani & How, 2015). The metabolically active form of Vitamin D actually binds to the Vitamin D receptor (VDR) found in most body cells to assist in cell differentiation and growth regulating the expression of genes and many biological functions (Higdon, 2000).
Several studies have found that vitamin D deficiency is linked to an increased risk of cancers, type 2 diabetes mellitus, autoimmune diseases, elevated blood pressure, high blood glucose levels and, the metabolic syndrome (Blahd, 2015; Holick, 2012; Battault, et al. 2013; Higdon, 2000). For example, adequate levels of the metabolically active form of vitamin D suppresses the proliferation and stimulating differentiation of cancer cells, it also increases the immune system by enhancing antimicrobial properties of white blood cells (monocytes and macrophages) and, antibacterial proteins (peptides) that are capable of destroying virus and microbe cell membranes.
Upon exposure to vitamin D, the VDR cells in the pancreas stimulate insulin production and secretion, playing a role in the correlation with disorders such as, diabetes mellitus (Holick, 2012). Vitamin D can decrease parathyroid hormone levels which lowers blood pressure and results in the prevention of hypertension and cardiovascular disease (Holick, 2012; Battault, et al. 2013; Gani & How, 2015). Lastly, the balancing of hyperparathyroidism enhances muscular physiology whilst, calcium intake benefits the muscular system by supporting functions such as, relaxation and contraction (Battault, et al. 2013). However, further research and more evidence is required to confirm these findings and determine whether it is a causal factor or resulting factor of ill health (Onham & Lamberg-Allardt, 2014).
Influences on vitamin D status
Unfortunately, deficiency is a common problem in the modern world. Sun exposure is decreased through an increased amount of time working indoors, sunscreen protection, darker skin tones, clothing, air pollution and, clouds (Holick, 2012; Blahd, 2015; Weishaar & Vergili, 2013). Many common health conditions such as, lactose intolerance, chronic kidney disease, malabsorption syndromes, obesity and, certain pharmaceutical drugs have a negative effect on the status of vitamin D (Gani & How, 2015; Higdon, 2000).
Overall, Vitamin D may be a pivotal nutrient in our health status. Fortunately, it is possible to maintain adequate levels of vitamin D naturally, by setting aside a little bit of time each day to get some sun, safely, in combination with maintaining a healthy, balanced diet and exercise regime. If you’re unsure, the best way to find out where your vitamin D levels sit is to get a blood test with your GP today.