Vitamin D3 (also called Cholecalciferol) is one of five different forms of Vitamin D. Vitamin D3 and D2 are considered essential for human health. We need Vitamin D because it helps us to absorb calcium, magnesium, phosphate, iron and zinc from our foods. However, unlike other vitamins (which cannot be synthesised by the body and must therefore be ingested), Vitamin D can be synthesised by the body, when the skin is exposed to sunlight.
There are two ways of getting Vitamin D3 into the body - through exposure to sunlight or by ingestion.
Exposure to sunlight is our greatest source of Vitamin D3. The UVB radiation in sunlight enables a reaction in the epidermal layer of our skin to convert a compound, 7-Dehydrocholesterol, into Cholecalciferol (Vitamin D3).
Vitamin D3 can also be obtained through diet, but there are only a small number of foods that naturally contain it: alfalfa, lichen, fish liver oils, ‘fatty’ fish species (salmon, mackerel, tuna, sardines), and eggs and beef and liver contain small amounts.
However, cholecalciferol is also produced industrially for use as a supplement and many ‘fortified’ but processed foods, such as breakfast cereals, contain it.
A lack of Vitamin D results in impaired bone mineralization and bone damage which leads to bone-softening diseases such as Osteomalacia, also known as Ricketts when it affects children. This condition can cause bending of the spine, bowing of the legs, muscle weakness, increased bone fragility and a higher risk of fractures. Pregnant and breastfeeding women, children under the age of 5 years, older people over the age of 65 years, people who have low or no exposure to sunlight (for example, the housebound) and people who have darker skin tones are more at risk of Vitamin D deficiency. In the UK, pregnant and breastfeeding women are recommended to take Vitamin D supplements (0.01mg) daily.
Aside from the obvious benefits of avoiding the health problems caused by Vitamin D deficiency there has, in recent years, been an increased interest in the other potential health benefits of Vitamin D3. There is evidence that Vitamin D could play a role in preventing/relieving a wide range of severe conditions:
As it is a relatively new area of research, there is still much to learn about any potential benefits of Vitamin D3, and many more studies are needed before the health benefits of supplementing with Vitamin D3 can be confirmed. However, the early indicators are very positive, and there is hope that, with further understanding of the effects of Vitamin D3 on the human body, we will potentially help to prevent deadly diseases and provide relief to millions of people suffering debilitating conditions such as Alzheimer’s and Multiple Sclerosis .
It is impossible to overdose on Vitamin D by over-exposure to sunlight (which should always be avoided for other health reasons) as your body naturally stops producing and absorbing Vitamin D once it has reached equilibrium. However, though rare, people with existing medical conditions (such as hyperparathyroidism) can overdose on Vitamin D by ingesting large amounts of supplemental Vitamin D, causing a condition known as hypercalcaemia - where the body absorbs more calcium than can be excreted.
There is a delicate balance between too much and too little calcium in your blood, and therefore supplementation should remain conservative and within acceptable limits at present despite many doctors recommending a very high daily dosage.
Hypercalcemia can cause renal failure and irreversible kidney damage, as well as damaging bone tissue.
Before taking any additional supplements or making any changes to your diet it is always best to discuss it with your doctor first.
A daily vitamin D intake of anywhere between 400 IU and 4000 IU, or 25-100 micrograms with 4000 IU considered a safe upper limit. Anyone with special requirements such as MS who wants to take more should consult with their doctor. Vitamin D intake is recommended at 400-800 IU/day. In certain instances, studies a higher daily intake of 1000-4000 IU (25-100 micrograms) may be appropriate to maintain optimal blood levels.