Playing a crucial role in the human body’s metabolism, vitamins can be defined as organic chemicals that must be obtained from dietary sources. According to this definition, vitamin D is technically not a vitamin as very little is obtained from dietary sources, as it is mostly produced in the skin when exposed to sunlight. Simply put, the ultraviolet B rays in sunlight converts cholesterol – that is present in the cells of the skin – into vitamin D. Tiny amounts of vitamin D are found in food such as egg yolks and oily fish, but not in sufficient quantities for the body’s needs.
Modern lifestyles however leads to little exposure to sunlight, while the use of sunblock further inhibits the conversion to vitamin D. A simple blood test will reveal if you, like many other people worldwide, have insufficient levels of vitamin D in your blood, which is known as a vitamin D deficiency. You may need daily supplements to maintain healthy levels of vitamin D.
Why is vitamin D important?
Its most well-known function is to maintain normal blood levels of calcium. It acts as facilitator for the absorption of calcium from the gut, which is essential to form and maintain strong bones. Vitamin D deficiency can lead to thin, brittle or misshapen bones or even osteoporosis (“thin bone” disease) in older adults. Vitamin D deficiency in children can result in a painful condition called rickets (softening or weakening of the bones).
Vitamin D also plays other roles in the body, such as:
- Vitamin D is vital for optimal functioning of the Immune System. Sufficient levels of vitamin D are required to trigger T-cells (the protective “killer” cells of the immune system) into action, otherwise these cells remain dormant and inactive
- Vitamin D acts as a steroid hormone in cells, where it binds to a receptor in the cell nucleus and in this way influences the functioning of about 10% of our genes.
- Vitamin D switches on the gene that induces synthesis of a calcium binding protein that is responsible for the absorption of calcium from food in the gut of humans.
- Normal neuromuscular function requires adequate levels of vitamin D.
- Vitamin D helps to lower insulin resistance, which plays a major part in heart disease.
- Vitamin D influences the working of the thyroid gland, which secretes a hormone that regulates the blood calcium levels, which in turn helps to regulate blood pressure.
Sources:
Vitamin D. Fact sheet for health professionals. Updated 11 February 2016. National Institute of Health. U S Department of Health and Human Services. (www.nih.gov)
Vitamin D and your health: breaking old rules, raising new hopes. Published February 2007. Harvard Health Publications, Harvard Medical School. www.health.harvard.edu)
Vitamin D. Updated 1 November 2013. Mayo Clinic. (www.mayoclinic.org)
Insights into vitamin D. Article by Health Insight, published in June 2010 edition of CEO Magazine.
Prevalence of vitamin D deficiency. Article by Health Insight, published in July 2010 edition of CEO Magazine.
HEALTH INSIGHT
MARCH 2017