Vitamins are nutrients that are vital to the human body yet cannot be synthesized by it. In this post, we’re going to introduce you to the basics of vitamin D so that you can find the future posts addressing its relationship with cancer enjoyable and easier to read.
What is vitamin D?
Vitamin D is one of the fat-soluble vitamins and can only be obtained by either getting exposed to sunlight, eating certain foods, or taking supplements. Generally speaking, vitamin D exists in two forms inside the human body: the storage form (25OHD) and the active form (1,25OHD). Physicians usually order lab tests that measure the level of these forms in order to identify vitamin D abnormalities (Mahan & Raymond, 2017); (Holick, et al., 2011).
What does it do?
Vitamin D plays various roles inside the human body: It helps strengthening the bones, regulating blood calcium, and has been under investigations for years for possible cancer and diabetes risk reducing effects (Holick, et al., 2011). It also has hormonal-like functions at the level of nucleus and genes (i.e. affecting cell growth, muscle strength and size gains, & reducing inflammation) (Mahan & Raymond, 2017); (Dorfman, 2017).
How much is enough/too much?
It’s not surprising that vitamin D’s requirements (i.e. recommended daily allowances (RDA)) vary according to age, sex and stages like pregnancy and lactation. Interestingly, vitamin D can also cause toxicity if taken in huge amounts so a level called tolerable upper limit (TUL) has been set in order to help prevent that. For more information please check the following table. (Mahan & Raymond, 2017)
Tips & tricks:
– Sun exposure is the best source for vitamin D. It can supply people with a huge amount that can last them for an extended period of time (i.e. those adequately exposed in summer get enough stores that can last them through the winter). (Mahan & Raymond, 2017).
– For the best results, ditch the sunscreens and expose at least your arms and legs to sunlight directly (i.e. not through glass) for the duration that results in your skin turning slightly pink after 24 hours (Dark-skinned individuals need 3-5 times the duration needed by fair-skinned ones). Vitamin D synthesis is maximum between 11:00am and 3:00pm in the summer and people generally need 2-3 days of exposure per week. (Mahan & Raymond, 2017); (Holick, et al., 2011).
– Some apps can help time the exposure correctly (i.e. Vitamin D calculator, D-minder, & Vitamin D pro). (Mahan & Raymond, 2017).
– For vitamin D content of various sources please check the following table:
References and attributions:
Dorfman, L., 2017. Nutrition in Exercise and Sports Performance. In: L. K. Mahan & J. L. Raymond, eds. Krause’s Food and the Nutrition Care Process. 14th ed. St. Louis: Elsevier.
Holick, M. F. et al., 2011. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 96(7), p. 1911–1930.
Holick, M. F. et al., 2011. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 96(7), pp. 1915 & 1917, TABLES 1 & 3.
Mahan, L. K. & Raymond, J. L., 2017. APPENDIX 45: Nutritional Facts on Vitamin D. In: L. K. Mahan & J. L. Raymond, eds. Krause’s Food and the Nutrition Care Process. 14th ed. St. Louis: Elsevier.
OpenStax, 2014. “Figure 1. Sunlight is one source of vitamin D” licensed by Rice University under a Creative Commons Attribution License (by 3.0). It got slightly edited and is used by our post as its featured image. It can be found here: http://cnx.org/contents/FPtK1zmh@6.27:g-vsB2Y2@4/Exercise-Nutrition-Hormones-an.
More readings and links:
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