Written by: Dr. Lohi Pratti
Vitamin D, also called the ‘sunshine’ vitamin has been a major concern for years, especially since a large portion of the world's population is lacking in it.
Sources – Sunlight, Diet, and Supplements.
50 to 90% of Vitamin D source is from sunlight. Vitamin D is maximally synthesized in the skin following exposure to sunlight at a wavelength of 255-350nm (UVB range) (Mostafa and Hegazy, 2015). 7-dehydrocholesterol in the epidermis is converted by UVB to pre-vitamin D. Heat isomerization transforms this pre-vitamin D into vitamin D, which then undergoes metabolism in liver and kidney to form active vitamin D. Melanin in skin absorbs UVB and prevents Vitamin D production. So, individuals with more pigmented skin need more sun exposure. A minimum of 15 – 20 min of sun exposure at around 11 am to 2 pm daily with over 40% skin exposed is needed for optimal production of active Vitamin D (up to 250mcg) (Harinarayan et al., 2013).
This particular timing is essential because, in the morning and night, sun rays reach the earth in more oblique way and maximum UVB rays are absorbed by ozone layer. This is the same reason why there is reduced Vitamin D production in winter months. (Chauhan et al., 2022)
Cod liver oil, cheese, egg yolks, mackerel, salmon, tuna, and beef liver are the only natural vitamin D sources. Many nations fortify orange juice, milk, yogurt, and cereal with vitamin D since many people cannot get enough vitamin D from natural sources.
Functions – The major function is to maintain calcium levels in the blood and to form bone. Apart from this, it also has many anti-inflammatory, antimicrobial, anti-aging and anti-cancer properties. Topically, it is very effective in treatment of psoriasis, which is an inflammatory skin disease with redness and scaling. (Mostafa and Hegazy, 2015) Screening the deficiency of Vitamin D and supplementation can reduce the hair loss and also improve atopic dermatitis.
Deficiency – Deficiency can occur due to reduced sun exposure, malabsorption syndromes, lower dietary intake, chronic liver disease, and antiepileptic medications, which can increase the breakdown of active Vitamin D. These are more commonly seen in elderly and obese individuals, as Vitamin D being a fat soluble vitamin is stored mainly in fat tissue and less available for biological actions. (Sizar et al., 2022)
Most of the patients have no symptoms. Long term severe deficiency can present with bone pains, muscle or joint pains, and weakness. Children can present with developmental delay and fractures. (Sizar et al., 2022)
Calcium is required for secretion of insulin. So, vitamin D deficiency can lead to increased risk of developing hyperglycaemia in diabetes mellitus. (Matyjaszek-Matuszek et al., 2015)
Vitamin D deficiency is classified depending on the serum 25-hydroxyvitamin D levels. The preferred range is 40-60 ng/mL. To maintain this level, daily intake of 600 IU is recommended. This can be from the diet/ supplements and sun exposure. Deficiency is seen when the levels are <30 ng/mL and insufficiency is when the levels are 20-30 ng/mL. (Chauhan et al., 2022).
Vitamin D and Sunscreens - UVB is necessary for vitamin D production but causes sunburn and skin cancer. Although sunscreens can drastically reduce vitamin D synthesis under highly stringent circumstances, their normal use does not often result in vitamin D deficiency. Sunscreens can be either UVA or UVB protective or broad spectrum (both UVA and UVB protective).
Proper Sunscreen Use - Sunscreen should be applied in a thick, even layer, and it should be put on 15 minutes before going out in the sun. The right amount to put on is 2 mg/cm2, which is equal to 30 mL/body. Reapplying sunscreen every two hours and after sweating or swimming is important.(Latha et al., 2013; Young et al., 2019)
“Teaspoon rule” is an easy way to apply the recommended amount of sunscreen.
3 mL (slightly more than half a teaspoon) - for each arm, for the face and neck.
6 mL (slightly more than a teaspoon) - for each leg, for the chest, for the back.
Protection from UVB is graded using SPF (sun protection factor) and UVA is measured by PA factor (photoprotection factor of UVA).
Preferred use of sunscreen is with SPF of 30 to 50 and with a PA factor of +++.
Sunscreens with SPF >60 do not have significant beneficial effects than the ones with SPF <50 and the former can even cause irritant reactions and make skin more dry. (Latha et al., 2013).
Although SPF 50 sunscreens can reduce Vitamin D production, there is no significant reduction in the active vitamin D levels even with prolonged use. (Libon et al., 2017)
Better vitamin D synthesis is possible with an SPF 30 formulation with strong UVA protection than with one with poor UVA protection. More UVB can transmit when the former is used. (Young et al., 2019)
References:
Chauhan, K., Shahrokhi, M., Huecker, M.R., 2022. Vitamin D, StatPearls [Internet]. StatPearls
Publishing.
Harinarayan, C.V., Holick, M.F., Prasad, U.V., Vani, P.S., Himabindu, G., 2013. Vitamin D
status and sun exposure in India. Dermatoendocrinol. 5, 130–141.
Latha, M.S., Martis, J., Shobha, V., Sham Shinde, R., Bangera, S., Krishnankutty, B., Bellary, S.,
Varughese, S., Rao, P., Naveen Kumar, B.R., 2013. Sunscreening Agents. J. Clin.
Aesthetic Dermatol. 6, 16–26.
Libon, F., Courtois, J., Le Goff, C., Lukas, P., Fabregat-Cabello, N., Seidel, L., Cavalier, E.,
Nikkels, A.F., 2017. Sunscreens block cutaneous vitamin D production with only a
minimal effect on circulating 25-hydroxyvitamin D. Arch. Osteoporos. 12, 66.
Matyjaszek-Matuszek, B., Lenart-Lipińska, M., Woźniakowska, E., 2015. Clinical implications
of vitamin D deficiency. Przegla̜d Menopauzalny Menopause Rev. 14, 75–81.
Mostafa, W.Z., Hegazy, R.A., 2015. Vitamin D and the skin: Focus on a complex relationship:
A review. J. Adv. Res. 6, 793–804. https://doi.org/10.1016/j.jare.2014.01.011
Sizar, O., Khare, S., Goyal, A., Givler, A., 2022. Vitamin D Deficiency, StatPearls [Internet].
StatPearls Publishing.
Young, A.R., Narbutt, J., Harrison, G.I., Lawrence, K.P., Bell, M., O’Connor, C., Olsen, P., Grys,
K., Baczynska, K.A., Rogowski‐Tylman, M., Wulf, H.C., Lesiak, A., Philipsen, P.A., 2019.
Optimal sunscreen use, during a sun holiday with a very high ultraviolet index, allows
vitamin D synthesis without sunburn. Br. J. Dermatol. 181, 1052–1062.
Disclaimer: This organization's content is not intended to provide diagnosis, treatment, or medical advice. Content provided on this website is for informational and educational purposes only. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. Information on this website should not be considered as a substitute for advice from a healthcare professional.
コメント