Overview

Sunlight exposure causes the skin to produce vitamin D. The difficulty is that most people do not get enough sunshine for cutaneous vitamin D synthesis because of where they reside, they do not spend enough time outside at midday, or they apply sunscreen when they are outside.

Vitamin D is necessary for bone health because the body can only absorb calcium when it has an adequate supply of vitamin D. Vitamin D is also involved in the regulation of many other cellular functions in the body.

Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are the two most common types. Without a subscript, vitamin D refers to either D2 or D3, or both, and is referred to collectively as calciferol.

Key Benefits

• Controls the amounts of calcium and phosphate in the blood serum.
• Stimulates bone calcification
• Calcium absorption from the intestines is increased.
• Calcium excretion from the kidneys is reduced.
• T-cell production and the immune system are aided.
• It has been demonstrated to lower the risk of certain types of cancer, MS, diabetes, and cardiovascular disease.
• It aids in the management of blood pressure.

History of Usage

Since the 1970s, vitamin D has been recognized as a powerful antioxidant that plays a vital role in health maintenance. It was discovered while scientists were looking for a means to cure rickets and discovered that sunlight exposure was fully successful. In the 1920s, irradiating certain meals became the normal practice for preventing rickets, and vitamin D was discovered in the 1930s when researchers analyzed the molecular structures of members of the cholesterol family.

Today, pharmaceutical companies generate vast quantities of vitamin D3, commonly known as cholecalciferol or vitamin D3. In general, they extract cholesterol from animal products (such as lanolin from sheep wool) and use it as a starting material for the purification of the precursor 7-dehydrocholesterol, which is subsequently irradiated to produce vitamin D3. This manufactured vitamin D3 is found in a variety of foods, most notably milk products. It is also an important component of multivitamin supplements.

Vitamin D is currently suggested in doses of 600 IU for children, pregnant and breastfeeding teens and women, and adults aged 19 to 70. The revised RDA for persons aged 71 and up is 800 IU. This is the first formal vitamin D advice from the government since 1997.

According to recent research, women and men who consume more than 400 IU of vitamin D each day reduce their chance of acquiring multiple sclerosis by around 40%.

Furthermore, scientists believe that one of the reasons influenza occurs in the winter is because we do not produce enough vitamin D. The consequent vitamin D deficit may increase our susceptibility to flu viruses, including Novel Coronavirus 19.

Biochemistry

Vitamin D is made up of two physiologically inactive precursors: D3 (cholecalciferol) and D2 (ergocalciferol). When exposed to UVB radiation (290 to 320 nm), the skin produces vitamin D3, which is more bioactive than D2.

Sun exposure converts the precursor 7-dehydrocholesterol present in the skin to vitamin D3, which is then processed in the liver and kidneys to the bioactive forms of the molecule. These metabolites are released by the kidneys and accumulate in target organs such as the intestine, where they help to control calcium and phosphorus absorption. A lack of these vitamin D metabolites in the body causes a failure to manage calcium homeostasis, resulting in osteoporosis, osteomalacia, and rickets. Vitamin D has a receptor in every cell, which is why it is so important for overall health.

Vitamin D is best recognized for assisting the digestive system in the absorption of calcium and phosphorus. As a result, it aids the body in the formation and maintenance of healthy bones. Adequate vitamin D is thought to help promote cardiovascular and bone health, as well as a healthy immune system and cognitive function.

Vitamin D is obtained in supplemental form or from these foods: fortified dairy products, fortified cereals, and some brands of orange juice, fatty fish (trout, salmon, tuna, and mackerel), and fish oils, eggs, and beef liver. 

Recent Trends

Vitamin D remains the most important mineral for general health. It aids in immunity, emotional well-being, bone and skin health, and the prevention of chronic disease.

The study of vitamin D functions has surged in the last ten years. Obesity, diabetes, thyroid illness, coronary heart disease, ischemic stroke, respiratory tract disease, Alzheimer’s disease, digestive system disease, and skin disorders have all been linked to vitamin D insufficiency, according to a growing body of research.

In 2020-21, studies linked low levels of vitamin D to an increased risk of COVIDS-19 symptoms. Notably, the vitamin D market is predicted to grow by 7.2% by 2025.

To lower the risk of infection, patients at risk of influenza and/or COVID-19 should consider taking 10,000 IU/d of vitamin D3 for a few weeks to quickly elevate 25(OH)D concentrations, followed by 5000 IU/d. The goal should be to increase 25(OH)D concentrations to greater than 40-60 ng/mL (100-150 nmol/L). Higher vitamin D3 doses may be beneficial in the treatment of persons who become infected with COVID-19. To evaluate these proposals, randomized controlled trials and large population studies should be done.

Vitamin D supplements come in a variety of forms, including softgels, chewable tablets, gummies, and drops.

Precautions

When taken in the authorized amount, vitamin D supplementation is safe.
Too much supplemental vitamin D, or doses exceeding 4,000 IU, can cause nausea, poor appetite, constipation, kidney stones, and heart rhythm disorders. Because some medicines are contraindicated when used with vitamin D, people should contact their doctor.

References

1. Holick MF. Vitamin D. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease, 10th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.
2. Stechschulte SA, Kirsner RS, Federman DG. Vitamin D: bone and beyond, rationale and recommendations for supplementation. Am J Med. 2009 Sep;122(9):793-802.
3. A dose of vitamin D history. Nat Struct Mol Biol 9, 77 (2002). https://doi.org/10.1038/nsb0202-77
4. Garland, CF; Garland, FC; Gorham, ED; Lipkin, M; Newmark, H; Mohr, SB; Holick, MF (2006). “The role of vitamin D in cancer prevention,” American Journal of Public Health 96 (2): 252–61. doi:10.2105/AJPH.2004.045260. PMID 16380576
5. Munger KL, Zhang SM, O’Reilly E, Hernan MA, Olek MJ, Willett WC, Ascherio A.  Vitamin D intake and incidence of multiple sclerosis.  Neurology 2004; 62(1):60-5.
6. Penckofer S, Kouba J, Wallis DE, Emanuele MA. Vitamin D and diabetes: let the sunshine in. Diabetes Educ. 2008 Nov-Dec;34(6):939-40, 942, 944 passim.
7. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, Benjamin EJ, D’Agostino RB, Wolf M, Vasan RS. Vitamin D deficiency and risk of cardiovascular disease. Circulation. 2008 Jan 29;117(4):503-11. Epub 2008 Jan 7.
8. Cannell, J.J., Vieth, R., Umhau J.C., et.al. Epidemic influenza and vitamin D. Epidemiology and Infection (2006), 134:6:1129-1140 Cambridge University Press Hall LM, Kimlin MG, Aronov PA, Hammock BD, Slusser JR, Woodhouse LR, Stephensen CB. Vitamin D intake needed to maintain target serum 25-hydroxyvitamin D concentrations in participants with low sun exposure and dark skin pigmentation is substantially higher than current recommendations. J Nutr. 2010 Mar;140(3):542-50. Epub 2010 Jan 6. http://www.ncbi.nlm.nih.gov/pubmed/20053937
9. Aolin Yang, Qingqing Lv, Feng Chen, Difei Wang, Ying Liu, Wanying Shi. Identification of Recent Trends in Research on Vitamin D: A Quantitative and Co-Word Analysis Med Sci Monit 2019; 25:643-655

DOI: 10.12659/MSM.913026

10. Grant WB, Lahore H, McDonnell SL, Baggerly CA, French CB, Aliano JL, Bhattoa HP. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020 Apr 2;12(4):988. doi: 10.3390/nu12040988. PMID: 32252338; PMCID: PMC7231123.
11. Meltzer DO, Best TJ, Zhang H, Vokes T, Arora V, Solway J. Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results. JAMA Netw Open. 2020 Sep 1;3(9):e2019722. doi: 10.1001/jamanetworkopen.2020.19722. PMID: 32880651; PMCID: PMC7489852.
12. DeLuccia R, Clegg D, Sukumar D. The implications of vitamin D deficiency on COVID-19 for at-risk populations. Nutr Rev. 2021 Jan 9;79(2):227-234. doi: 10.1093/nutrit/nuaa092. PMID: 32974671; PMCID: PMC7543577.