Vitamin D3 and why vitamin D3 requirement cannot be met through sunlight exposure

Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and to prevent hypocalcaemia tetany (involuntary contraction of muscles, leading to cramps and spasms). It is also needed for bone growth and bone remodelling by osteoblasts and osteoclasts. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteocalcin in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in the body, including reduction of inflammation as well as modulation of such processes as cell growth, neuromuscular and immune function, and glucose metabolism. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D.
Most of the studies reporting a prevalence of 80%–90% in India. Our Indian diet generally fails to satisfy the daily requirement of Vitamin D for a normal adult.
Sunlight is not a reliable method to get adequate amounts of vitamin D. Sun induced vitamin D synthesis is greatly influenced by season, time of day, latitude, altitude, air pollution, skin pigmentation, sunscreen use, passing through glass and plastic, and aging. People with darker skin tone have higher melanin content which prevents absorption of sunlight by the skin and affects vitamin D3 production. The only reliable way to complete the requirement of vitamin D3 is through supplementation. The dosage and frequency of vitamin D supplements will depend on the levels of vitamin D in the blood.
You can assess vitamin D levels in the blood using a blood test.


Aparna P, Muthathal S, Nongkynrih B, Gupta SK. Vitamin D deficiency in India. J Family Med Prim Care. 2018 Mar-Apr;7(2):324-330. doi: 10.4103/jfmpc.jfmpc_78_18. PMID: 30090772; PMCID: PMC6060930.