Vitamin D from a Nutritionist’s point of view!
International Unit of vitamin D
World Health Organization has defined the International Unit (IU) of vitamin D to standardize the reporting of vitamin D potency. 1.0 IU of this vitamin is the activity of 0.025 micrograms of the international standard preparation of crystalline vitamin D3. Through the advent of the metabolism of vitamin D3 to other active seco-steroids, mainly 1α,25-(OH)2D3, it was advised that 1.0 unit of 1α,25-(OH)2D3 be set equivalent in molar terms to that of the parent vitamin D3. Therefore, 1.0 unit of 1α,25-(OH)2D3 has been effectively defined to be equivalent to 65 picomoles.
Vitamin D3 is more effective than vitamin D2
Since 1930, after the discovery of the chemical structures of vitamin D3 and vitamin D2 it has been presumed that both vitamins had equivalent biological activity in humans. R. Heaney and co-workers in the year 2010 claimed that vitamin D3 is approximately 87% more potent in raising and maintaining serum 25(OH)D levels than was vitamin D2. Again, vitamin D3 produced a 2- to 3-fold greater storage of vitamin D than does equimolar amount of D2. Hence, it appears that vitamin D3 should be the preferred choice for correcting the deficiency of this vitamin in humans due to its greater effectiveness and obviously lower cost.
Symptoms of vitamin D deficiency
Symptoms of vitamin D deficiency may include fatigue, painful bones and back, depressed mood, impaired wound healing, hair loss and muscle pain. If the deficiency persists for a prolonged time period then problems like obesity, diabetes, hypertension, depression, fibromyalgia, chronic fatigue syndrome, osteoporosis, neurodegenerative diseases, such as Alzheimer’s disease can result.
You may need regular dietary supply of vitamin D
No one can precisely define the requirement of this vitamin for a healthy adult. When adequate sunlight is available human does not need this vitamin from outside. However, vitamin D becomes an important nutritional factor in the absence of sunlight. Often due to geographical and seasonal factors, ultraviolet light from the sun may also be blocked by air pollution. Again, usage of sunscreens, living in cities where tall buildings block adequate sunlight, tendency to wear too many clothes etc., need regular dietary supply of vitamin D3.
Many people all round the world use sunscreen lotions to look better. I don’t know whether you will believe me or not that a sunscreen with sun protection factor (SPF) 30 can reduce the body’s ability to synthesize the vitamin by 95 percent!
Dietary sources of vitamin D
Salt water fishes and fish liver oils are good sources of vitamin D3. Herring, salmon, sardines are the examples. Eggs, veal, beef, butter and vegetable oils also contain small quantities of the vitamin. However, plants, fruits and nuts are extremely poor sources of this vitamin. In many countries artificial fortification of foods such as, milk, margarine and butter, cereals and chocolate mixes help in meeting the Recommended Dietary Allowance (RDA).
