Beginning of the twentieth century marked the rising problem of rickets among infants in the polluted cities of Europe and the Northeastern part of America. One of the main reasons for this condition was due to inadequate absorption of calcium into the bones. It was in the year 1920 when people started relating this less absorption of calcium with the exposure of Sun[2]. With deficiency in Vitamin D, our bodies cannot extract calcium from the we eat, so our body then take the essential calcium from the bones making the bones deprived of calcium. Soon, Vitamin D deficiency became a big problem to solve among all the northern countries as Sun’s exposure in these countries is believed to lack the essentials required for the production of Vitamin D.
Vitamin D isn’t readily available in the plants as well as in the human or animal body. Precursors like ergosterol and 7-dehydrocholesterol are converted into vitamin D by exposure of UV radiation. Sun produces a large number of UV rays and hence acts as an important source of UV radiation, essential for the conversion. To be more specific UV-B radiation (280-315 nm) coming from the sun acts as a catalyst for converting sterols into Vitamin D. Vitamin D can be of different types- Vitamin D1, Vitamin D2, Vitamin D3 or Vitamin D4. Above all D2 and D3 are the major ones. The basic difference in all these Vitamins is the starting precursor. [3]
- Vitamin D is A fat-soluble compound.
- Plays a significant role in the regulation of calcium and maintenance of phosphorus levels in the blood.
Vitamin D3
The vitamin D3 precursor – 7-dehydrocholestrol present in the skin is photocatalysed into pre-vitamin D3 knowns as- chlorocaciferol upon the exposure to a narrow band of solar ultraviolent-B photons (290-315 nm).
These are then bonded with proteins and travel from skin to the liver where it is further hydroxylated in the liver to 25-hydroxyvitamin D3 and in the kidney to 1,2,5-dihydroxyvitamin D3, the active form of vitamin D3. 1,2,5-dihydroxyvitamin D3 is the active form of Vitamin D and this form is responsible for absorption of calcium from the food. [5]
Vitamin D2
People realised food to be a potent source of vitamin D much later. Ergosterol in the plant gets converted to ergocalciferol which is again another pre-vitamin of Vitamin D. Vitamin D from the diet is absorbed in the small intestine and transported to the liver via DBP (Vitamin D binding protein). Once it reaches the liver, it is converted into the active form similar to the cholecalciferol.[6]
Deficiency and treatment:
Many factors contribute to the deficiency of vitamin D. Alone decreased sun exposure cannot be blamed. Malabsorption, inadequate vitamin D rich diet, wrinkled skin, dark skin and age are other few important factors.[7] As a person ages, his/her skin has a less tendency to photo-catalyse the 7-dehrocholesterol into chlorocalciferol. Malabsorption is again a big problem as in this condition, even if you intake an adequate amount of vitamin D due to poor absorption the whole of vitamin D will not be able to convert in its active form. Dark-skinned persons have the problem of lower absorption of UV radiation because of the pigment (melanin).
The usual dosage recommended by WHO is 2200 – 3000 IU/day.
*1 IU of vitamin D equals to 0.025 mcg of cholecalciferol and ergocalciferol.
| Daily Dose/ Dietary Supplement | Treatment | |
| Breast Feeding Babies. | 400 IU/day and sensible heat exposure. | 1000 IU/day + Calcium supplement. 2,00,000IU/3 months |
| 1-18 year (less sun sxposure or having dark skin) | 400 – 1000 IU/day. | 50,000 IU /week for 8 weeks. |
| Adult | 800-100 IU/day or 50,000 IU/month | 50,000 IU /week for 8 weeks. |
| Pregnant or lacting | 1000-2000 IU/day compulsory or 50,000 IU/2 weeks. | 50,000 IU /week for 8 weeks. |
| Malabsortion Symtoms | 50,000 IU every other day. | UV-B radiation. |
Available Treatment:
Chemical.
Photo-light therapy.
Fortification.
- Chemical treatment.
Around 258 formulations are available in the market. The chemicals used mostly are Alfacalcidol, Calcitriol and cholecalciferol. All the three mentioned above are vitamin D3 formulations. Of 258, only 3-4 formulations are comprised of ergocalciferol which is a vitamin D2 supplement. Usually, these supplements cost around 20 rs/tablet of 1000IU. - Photo-light therapy
Recently, Sperti lamps have gained a robust demand in western countries. For converting the 7-dehydrocholesterol to the chlorocalciferol (pre-vitamin D) UV radiation is important so when we have very less Sun exposure, one can think of these lamps. These lamps artificially produce the required emissions for the conversion. Tanning beds, PUVA, Turban PUVA are some other photo light therapies available. In PUVA therapy, the patient is made to consume light-sensitive drugs, (psoralen) which absorb the UV radiation and made to stand either under the sun or a UV chamber.[8] - Fortification.
Western countries have already employed this technique of fortifying food products with the micronutrients to combat vitamin deficiency that is increasing.
References:
- https://qsun.co/vitamin-d-getting-the-sunshine-vitamin-without-the-sunshine/
- Rajakumar et al.,American Journal of Public Health,October 2007, Vol 97, No. 10.
- Gui-Dong Zhu and William H. Okamura,Chem. Rev, 1995, 95, 1877-1 952.
- Smriti Murali Krishna , Int. J. Mol. Sci.2019, 20(19), 4907 .
- Ola Engelsen,Nutrients 2010, 2, 482-495.
- Pelc and E. Kodicek ,J. Chem. SOC. (C).
- Hanns Moshammer , Stana Simic and Daniela Haluza,Int. J. Environ. Res. Public Health 2016, 13, 1041.
- US 8,647,373 B1
