Updated: Feb 19
Vitamin D - also known as the "sunshine vitamin" - is produced naturally in your skin through "direct" exposure to sunlight, and then converted into bio usable form in your liver and the kidneys. The amount of vitamin D3 that your skin produces depends on the time of day and season. Both factors change how much UV light hits your skin. Yet, many other factors affect the amount of vitamin D your skin can produce, including your skin color (pigmentation), age, clothing, use of high factor sunscreens, and where you live. In the winter months, it is surely advisable to take vitamin D supplements.
A word of caution though – too much sun exposure can be damaging due to the risk of developing skin cancer. Spend only a small amount of time in the sun without sunscreen, either early in the morning or late in the afternoon, and the rest of the time be sure to cover up and avoid sunburn. Between April and September, 10-15 minutes daily sunlight exposure for lighter skin types and 25-35 minutes daily sunlight exposure for darker skin types provides sufficient year-round vitamin D.
How Is Vitamin D Produced In The Skin?
Ultraviolet radiation of the sun rays penetrate into the epidermis (the outermost of the three layers that make up the skin, the inner layers are the dermis and hypodermis) and photolyzes provitaminD3 to previtaminD3. PrevitaminD3 can either isomerize to vitamin D3 or be photolyzed to lymisterol and tachysterol.
ProvitaminD3 (7-Dehydrocholesterol) is a side product from the cholesterol and found in abundant quantities in the epidermis. ProvitaminD3 has a skin barrier function, increases skin resistance against environmental aggressors and supports the skin's natural recovery.
Why do you need to take vitamin D3 supplements regularly at advanced age?
Because as you age, your epidermis gets thinner (holds less cholesterol). Consequently, your skin has less ProvitaminD3 which is required for conversion into Vitamin D3. Furthermore, elderly people are less likely to access the outdoors and may be more at risk of deficiency. Studies suggest that some forms of Vitamin D supplements are more easily absorbed by the body.
Certain groups are considered to be at higher risk for developing Vitamin D deficiencies.
People who aren't often outdoors, such as those who are frail or housebound
People who have darker skin, such as those of south Asian, African or African-Caribbean backgrounds
People who stay out of the sun or cover up when outside
Why Do You Need Vitamin D?
Vitamin D is a fat-soluble compound that includes the family of vitamins D-1, D-2, and D-3. It is extremely important for strong bones and teeth, as it helps us absorb the calcium you eat and it also controls the amount of calcium in your blood. At low vitamin D levels your body won’t absorb the calcium you eat. If your levels are severely low, you may be at risk of developing weaker bones (osteomalacia). Furthermore, the excessive amounts of un-absorbed calcium floating in your blood may with time cause calcification at your joints and development of kidney and gal stones. Severe deficiency in children may result in their legs becoming curved (rickets).
Unfortunately, there aren't any visual signs of vitamin D deficiency. Low levels of vitamin D are common in the US. It is advisable that you get a blood test through your health service provider.
Blodd test vitamin D levels classification:
Under 25 nmol/L – Deficient
25 - 50 nmol/L – Insufficient
50-75 nmol/L – Sufficient
Over 75 nmol/L – Optimal
Vitamin D And The Immune System
The immune system defends the body from foreign, invading organisms, promoting protective immunity while maintaining tolerance to self. The implications of vitamin D deficiency on the immune system have become clearer in recent years. As the vitamin D receptor is expressed on immune cells (B cells, T cells and antigen presenting cells) and these immunologic cells are all are capable of synthesizing the active vitamin D metabolite, vitamin D has the capability of acting in an autocrine manner in a local immunologic milieu. Immune cells (B cells, T cells, monocytes, DCs) from multiple autoimmune diseases appear to respond to the immunomodulatory effects of vitamin D. Read more.
Foods That Contain Vitamin D
Foods that naturally contain vitamin D include oily fish such as mackerel, sardines, and salmon. There are smaller amounts found in eggs and some red meats.
Natural vitamin D content of some foods:
Mackerel (grilled, 5 oz) – 11.9µg vitamin D
Salmon (grilled, 5 oz) – 19µg vitamin D
Sardines (grilled, 5 oz) – 7µg vitamin D
Eggs (poached, 2) – 2.9µg vitamin D