Vitamin D is a fat-soluble vitamin in a family of compounds, including Vitamins D-1, D-2, and D-3, which are obtained from sun exposure, foods, and supplements. Unfortunately, it is only naturally present in very few foods, but can be found added to certain foods and drinks, or as a supplement. It is produced when ultraviolet B rays from sunlight come into contact with the skin and trigger Vitamin D synthesis. Scientifically, ultraviolet rays with a wavelength of 290 – 320 nanometres penetrate the uncovered skin and convert cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes Vitamin D3. UV radiation does not penetrate glass so sunshine through a window will not produce Vitamin D. This is the same with sunscreen and clothing.
This vitamin is biologically inert and requires two hydroxylation’s in the body for activation. The liver converts the Vitamin D into 25-hydroxyvitamin D (also known as calcidiol), then the kidneys help to form 1,25-dihydroxy vitamin D (also known as calcitriol).
Vitamin D affects as many as 2,000 genes and has many roles in the body, some of which include bone health, calcium absorption, modulation of cell growth, neuromuscular and immune function, and reduction of inflammation.
The recommended daily allowance (RDA’s) for Vitamin D is as follows:
| Male and female 0 – 12 months | 10mcg |
| Male and female 1 – 13 years | 15mcg |
| Male and female 14 – 18 years | 15mcg |
| Male and female 19 – 50 years | 15mcg |
| Male and female 51 – 70 years | 15mcg |
| Male and female 70+ years | 20mcg |
| Pregnant females | 15mcg |
| Lactating females | 15mcg |
Most people only get approximately 10% of their required daily intake of Vitamin C from their diet.
It is estimated that sun exposure on bare skin for 5 – 10 minutes 2 – 3 times a week allows most people to produce sufficient amounts of Vitamin D. it must also be noted that Vitamin D breaks down quite quickly, which means stores can run low, particularly in winter.
Deficiency of Vitamin D may cause no symptoms at all.
Levels of Vitamin D are expressed in nanomoles/litre (nmol/L). Levels under 30 nmol/L is considered deficient.
Deficiency can also cause obesity, multiple sclerosis, cancer, type 1 and 2 diabetes, hypertension, heart disease, mental health conditions, cognitive decline, Alzheimer’s, and certain autoimmune diseases.
Doctors can diagnose Vitamin D deficiency by performing a simple blood test. If found to be deficient in this Vitamin, the doctor may then order X-rays to check the strength of the patient’s bones.
The upper-level limit recommended for Vitamin D IS 4000 IU per day, though it has been suggested that Vitamin D toxicity is unlikely at levels lower than 10,000 IU per day.
Known as hypervitaminosis D, excessive consumption of this Vitamin can cause the over-calcification of the bones and the hardening of blood vessels.
The most common symptoms of Vitamin D toxicity are nausea, vomiting, headaches, loss of appetite, dry mouth, constipation, and diarrhea. Other severe side effects of Vitamin D toxicity include kidney stones, kidney damage, muscle weakness, and excessive bleeding. It may also cause allergic skin reactions in select people, facial swelling, and breathing difficulties, and can affect blood sugar levels which can be dangerous for people with diabetes.
Excessive amounts of Vitamin D can cause a condition known as hypercalcaemia which is characterized by elevated blood calcium levels. Symptoms of this include vomiting, nausea, stomach pain, dizziness, fatigue, confusion, excessive thirst, and frequent urination.
Too much of this vitamin may actually be detrimental to your bone health. This is due to the fact that excessive levels of Vitamin D may lead to low levels of Vitamin K2 in the blood. One of the main functions of Vitamin K2 is to keep calcium in the bones and out of the blood.
This vitamin can also interact with certain medications or other supplements so always consult with a doctor before taking this supplement.
Also, it should be noted that excessive sun exposure can cause skin cancers and skin damage.
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