The Wonder Vitamin and the Sun

Vitamin D has been latterly rediscovered as a wonder substance, an element -- a neuroregulatory hormone -- about whose full potential there is still much to be known, but which helps us to be healthy human specimens. People who live in the northern hemisphere have been shown to have insufficient amounts of that vital vitamin in their systems, since exposure to the sun is critical to to ability of all living creatures to produce vitamin D.

It is the healing vitamin. There is not yet complete consensus on its absolute, complete potential to make us healthy, but it has demonstrated an almost miraculous capacity to ease depression, increase healthy bones structure, improve brain function, enhance the health of hearts, and even possibly to prevent cancer.

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)₂D], also known as calcitriol [1].
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts [1,2]. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults [1]. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

 

When the sun withdraws seasonally many people experience wild mood swings, depression and no small extent of irritability. It's called 'seasonal affective disorder', affecting mood-susceptible people during the winter months. The health benefits attributed by science to vitamin D are unparalleled by any other vitamin. Its health and healing properties were known in ancient times, when exposure to the sun was known to treat epilepsy, paralysis, asthma, jaundice, bladder and colon diseases and obesity.

Sun exposure was indicated in the treatment and relief of scurvy and rickets in the 1700s, when sailors in particular onboard vessels for prolonged periods of time suffered from the lack of food known to aid in the production of vitamin D. It's how the British acquired the sobriquet 'Limey' because of the penchant for the British Navy to stow limes aboard, known to fend off scurvy onset. Sailors, infamously, began to experience brittle bones, their teeth would fall out and they would become ill from lack of vitamin D.

Without our exposure to the sun all living things would expire. In the late 1920s sun therapy was set aside when penicillin was discovered, followed by science discovering antibiotics used in the treatment of so many ailments that previously increased sun exposure was prescribed for. A wide variety of illnesses, from bacterial infection such as anthrax, cholera and dysentery, to tuberculosis. The influence of Florence Nightingale was responsible for hospitals at the turn of the century increasing window space to maximize sunlight exposure.

Direct exposure to sunlight for 15 to 30 minutes in midday is required for the absorption and storage of vitamin D, leading to good health. That exposure should be increased the further north one lives. It is not absorbed through glass, but only through direct rays of the sun in the out-of-doors. During World War I, sun therapy was used to treat wounds and prevent tetanus and gangrene from setting in. Sun therapy was used in the treatment of skin diseases, the nervous system, circulatory system, and ear, nose and throat ailments.

Fear of prolonged exposure to the sun at peak sunlight  hours during the day has led people to be warned they must use sun block. Sunscreen is fine once the required daily exposure to the sun has been achieved. Too prolonged exposure without sun block on t he other hand can have a determinedly deleterious effect on the skin, from burning to premature ageing and some forms of cancers.

A diet high in produce helps build up an internal sunscreen as it were, lowering sunburn opportunities. Alternatives to the use of sun block such as light, white body-covering cotton clothing and hats to cover the skin at peak sunlight hours works as well. An antioxidant-rich diet is another invaluable assist.

Recommended Dietary Allowances (RDAs) for Vitamin D [1]

Age	Male	Female	Pregnancy	Lactation
0–12 months*	400 IU (10 mcg)	400 IU (10 mcg)
1–13 years	600 IU (15 mcg)	600 IU (15 mcg)
14–18 years	600 IU (15 mcg)	600 IU (15 mcg)	600 IU (15 mcg)	600 IU (15 mcg)
19–50 years	600 IU (15 mcg)	600 IU (15 mcg)	600 IU (15 mcg)	600 IU (15 mcg)
51–70 years	600 IU (15 mcg)	600 IU (15 mcg)
>70 years	800 IU (20 mcg)	800 IU (20 mcg)

* Adequate Intake (AI)

Sources of Vitamin D

Food
Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources [1,11]. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Vitamin D in these foods is primarily in the form of vitamin D₃ and its metabolite 25(OH)D₃ [12]. Some mushrooms provide vitamin D₂ in variable amounts [13,14]. Mushrooms with enhanced levels of vitamin D₂ from being exposed to ultraviolet light under controlled conditions are also available.