THE HEALTH AND FITNESS BLOG
June 05, 2022 – By Dr. Haider Khalid
Vitamin D is soluble in fat, meaning that our body can store it in fat for longer durations. However, it is entirely different from other vitamins. One of the reasons behind its variability is that our body can also synthesize this vitamin.
Our skin contains a steroid that gets converted into vitamin D once exposed to sunlight. Therefore, you would have heard the name ‘sunshine vitamin.’
The supply of vitamin D through the skin is not enough to fulfill your daily dietary requirements. In addition, in colder places where people do not experience much sunlight, its deficiency is prevalent. For example, about half of the US population has some degree of vitamin D deficiency in their body (1).
Therefore, consuming foods or supplements containing vitamin D would help you prevent vitamin D deficiency. But don’t worry, as this article will guide you through everything you need to understand about it.
How does Vitamin D Get Activated in the Body?
Vitamin D needs two conversions to get activated. The first reaction occurs in the liver. So first, vitamin D is converted into calcidiol in the liver, the storage form (2). Then, when the body needs this vitamin, calcidiol travels to the kidneys, where it gets converted into the active form, calcitriol (3).
Kidneys are essential for the activation of this vitamin. Therefore, chronic kidney disease patients present with vitamin D deficiency regardless of sufficient dietary intake.
After activation, vitamin D binds to its receptors present on several cells in the body. On attachment, it provides signals to the cells that perform appropriate functions (4). Some of the roles that vitamin D plays in our body include,
- Absorb calcium and phosphorus from the gut
- Deposits calcium on the bone to make it stronger
- Prevent excretion of calcium in urine
Recent studies also show that vitamin D plays a significant role in boosting immunity. In addition, it has also been reported as an anti-cancer substance (5).
How Effective is Sunlight for Vitamin D Production?
As I have already mentioned, ultraviolet rays in sunlight convert a steroid substance to vitamin D in the skin (6). Therefore, if you live in sunny areas, you probably can get enough vitamin D through exposure to the sun.
But you need to know that only exposed hands and feet and not enough to get enough vitamins. You would need to sunbathe a few times a week to get the amount that your body demands.
Moreover, UV rays of sunlight can damage the skin of sensitive people. A longer duration of exposure also increases your risk of skin aging and skin cancer. Therefore, you should expose your body to the sun only for 10-30 minutes to prevent any damage.
What are the Sources of Vitamin D?
Suppose you live in a colder environment and do not get appropriate exposure to sunlight. In that case, you may be deficient in vitamin D.
You need to know some of the essential sources you can use to fulfill your daily requirements for this vitamin.
- Mushrooms: It is a plant source that contains a significant amount of vitamin D
- Fortified food materials: You can get enough vitamin D from several foods fortified with vitamin D. Some important ones are fortified cereals, soy milk, almond juice, and almond milk.
- Supplements: Several supplements are present in the market that can help you achieve the required amount of vitamin D.
What are the Symptoms of Vitamin D Deficiency?
Vitamin D gets stored in body fat for a longer duration. Therefore, your body has reserves even if you are not consuming enough amounts. The deficiency of the vitamin, thus, does not develop immediately. Initially, it remains subtle. It takes several months of poor diet to show some symptoms.
One of the most common presentations of vitamin D deficiency is rickets in children. Children who don’t get enough vitamins tend to have bowed legs and deformed pelvis. These signs are the classical presentation of rickets. In western countries, rickets has been eliminated by introducing fortified food products (7).
As evident from the function of vitamin D, its deficiency causes the bones to become porous, a disease known as osteoporosis. Osteoporosis is the classical presentation of vitamin D deficiency in older adults. However, it is prevalent in females after menopause.
Porous bones are weak and tend to break with external stress. Therefore, patients with osteoporosis are prone to bone fractures from falls (8).
We have discussed the symptoms of vitamin D that are related to bones only. But, surprisingly, people with vitamin D deficiency are more likely to develop diabetes, cancer, dementia, and several other chronic diseases (9). Moreover, the life expectancy of such patients is also lower than those who have sufficient vitamin D in their bodies.
What are the Health Benefits of Vitamin D?
Here I have compiled the health benefits of vitamin D for developing your understanding of its health effects.
- Better bone strength with reduced risk of fractures
- Prevention of cancer
- Increased life expectancy
- Increased body immune response
- Improved brain function
- Reduced risk of chronic diseases
How Much You Need Daily?
The recommended dietary intake of vitamin D is
- Infants (0-12 months) need 400 IU daily
- Children and Adults (1-70 years) need 600 IU daily
- Older Adults (>70 years) need 800 IU daily
- Pregnant or breastfeeding women need an additional 600 IU.
Everyone should have an idea about these recommended values as you would need to keep a record of your consumption. Moreover, you should not start any supplements without prior blood testing to confirm the vitamin D deficiency.
You need to visit your doctor if you notice any symptoms of vitamin deficiency. He will advise you on a test to check the vitamin D levels in your blood. If you have below 12ng/ml of the vitamin, you would need supplements. Otherwise, you should focus more on your diet to get all the benefits of this vitamin.
- Forrest KYZ, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutrition Research [Internet]. 2011 Jan [cited 2022 Jun 5];31(1):48–54. Available from: https://pubmed.ncbi.nlm.nih.gov/21310306/
- Norman AW. From vitamin D to hormone D: fundamentals of the vitamin D endocrine system essential for good health. The American Journal of Clinical Nutrition [Internet]. 2008 Aug 1 [cited 2022 Jun 5];88(2):491S499S. Available from: https://pubmed.ncbi.nlm.nih.gov/18689389/
- Christakos S, Ajibade DV, Dhawan P, Fechner AJ, Mady LJ. Vitamin D: Metabolism. Endocrinology and Metabolism Clinics of North America [Internet]. 2010 Jun [cited 2022 Jun 5];39(2):243–53. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2879391/
- Dirks-Naylor AJ, Lennon-Edwards S. The effects of vitamin D on skeletal muscle function and cellular signaling. The Journal of Steroid Biochemistry and Molecular Biology [Internet]. 2011 Jul [cited 2022 Jun 5];125(3-5):159–68. Available from: https://pubmed.ncbi.nlm.nih.gov/21397021/
- Lappe JM. The Role of Vitamin D in Human Health: A Paradigm Shift. Journal of Evidence-Based Complementary & Alternative Medicine [Internet]. 2011 Jan [cited 2022 Jun 5];16(1):58–72. Available from: https://journals.sagepub.com/doi/abs/10.1177/1533210110392952
- Bogh MKB, Schmedes AV, Philipsen PA, Thieden E, Wulf HC. Vitamin D production depends on ultraviolet-B dose but not on dose rate: A randomized controlled trial. Experimental Dermatology [Internet]. 2010 Dec 16 [cited 2022 Jun 5];20(1):14–8. Available from: https://pubmed.ncbi.nlm.nih.gov/21158934/
- Holick MF. Resurrection of vitamin D deficiency and rickets. J Clin Invest. 2006 Aug;116(8):2062-72. doi: 10.1172/JCI29449. PMID: 16886050; PMCID: PMC1523417.
- Dobnig H. A review of the health consequences of the vitamin D deficiency pandemic. Journal of the Neurological Sciences [Internet]. 2011 Dec [cited 2022 Jun 5];311(1-2):15–8. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0022510X11005430
- Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. The American Journal of Clinical Nutrition [Internet]. 2008 Apr 1 [cited 2022 Jun 5];87(4):1080S1086S. Available from: https://pubmed.ncbi.nlm.nih.gov/18400738/
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