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Vitamin D | Deficiency Symptoms, Benefits & Dosage

Vitamin D | Deficiency Symptoms, Benefits & Dosage

Most people would tell you that it is good to spend a little time each day outside in the sun.  One of the benefits of this is that sunlight plays a key role in our bodies formation of vitamin D.  What exactly is vitamin D and what roles does it play in our bodies?  Should you be taking a supplement, or do you get enough of it from your diet and activity outside?  In this article, I hope to answer these questions and more about vitamin D.

What is It?

Vitamin D, along with vitamins A, E, and K, is a fat soluble vitamin that is not found in a lot of different foods (3).  For most people, the most common natural source of vitamin D is from the sun, but it is present in fish and eggs.  Our bodies create vitamin D from cholesterol when it is exposed to UV light, like the sun (1).  On the supplement market, vitamin D comes in two form, D2 and D3, the latter of which is similar to what is produced by our bodies when it comes in contact with the sun (4).  The main role of vitamin D is to help maintain our bodies calcium and phosphorus levels by helping our bodies absorb them better (3).  Vitamin D also helps in bone growth, so without enough vitamin D, bones will not form properly, which could lead to rickets in children and osteoporosis in adults (4).

Vitamin D Deficiency

vitamin dIf you are active outside, get a good amount of sunlight, and eat a well-balanced diet, you are probably not going to be deficient in vitamin D.  Due to the lack of naturally occurring vitamin D in foods, some countries, like the United States, fortify foods like milk and breakfast cereal with vitamin D (3).  For most people, eating fortified foods and being exposed to sunlight will provide adequate amounts of vitamin D, but others might require some supplementation.

The main groups of people at risk for vitamin D deficiency are breast-fed infants, older people, people with limited exposure to the sun, people with darker skin, and obese people.  As previously mentioned, the main symptoms of vitamin D deficiency are rickets in children and osteomalacia.  Some other symptoms may include bone pain and muscle weakness.  Vitamin D deficiency could be cause when “usual intake is lower than recommended levels over time, exposure to sunlight is limited, …, or absorption of vitamin D from the digestive tract is inadequate.”  (2).   However, even though you are not deficient, you might still not have optimal level of vitamin D in your body (1).

Vitamin D supplementation

So, how much vitamin D should one take if they want to maintain optimal levels?  Well, that is where there is not one, clear recommendation.  In 2010, the Institute of Medicine raised the daily recommended dosage of vitamin D to 600 IU (International Units), but that still might not be enough (4).  For supplementation purposes, a good dosage should fall somewhere between 1,000 IU and 2000 IU per day (1).  These dosages have been shown to be safe, as the upper limit for vitamin D has been set a 4,000 IU (4), but studies note that the actual upper limit might be closer to 10,000 IU (1).  Usually, supplemental vitamin D comes in the form of D3 because this form is better used by our bodies.  It is also recommended to take vitamin D with a meal of with some fat source, like fish oils (1).


Besides helping to keep our bones strong, studies suggest that vitamin D supplementation has many other health benefits.  Researchers found that taking a moderate dose of vitamin D, 700 IU to 1,000 IU, may help increase muscle strength, as it reduced the participants amount of falls by 19% (4).  This, combined with vitamin D’s bone strengthening abilities could help to decrease a person risk for bone fractures as they age.

Vitamin D also may help to increase cognition and immune health while also helping to prevent against some diseases, like heart disease and diabetes (1).  Some suggest also suggest that vitamin D could have an effect on your risk for some types of cancer.  Research has shown that vitamin D could help in the prevention of colon, prostate, and breast cancers.  The strongest research is for colon cancer, and more research needs to be done to see if a lack of vitamin D has more effect than having optimal levels (2).

Final Thoughts

If you live in an area that is far from the equator or you do not spend much time in the sun, you would most likely benefit from supplementing with vitamin D.  Science has shown that it can help to strengthen your bones and maybe even your muscles.  As more research comes out, even more benefits of vitamin D supplementation could be confirmed.  Although, like with any vitamin, too much could cause health concern, so try to stay below the upper limit of 4,000 IU a day and you should be okay.



Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

(1) Gill, Herman. “Vitamin D – Scientific Review…” Independent Analysis on Supplements & Nutrition. 1, n.d. Web. 28 July 2016.

(2) Office of Dietary Supplements. “Vitamin D.” Vitamin D — Health Professional Fact Sheet. National Institute of Health, 11 Feb. 2016. Web. 28 July 2016.

(3) U.S. Centers for Disease Control and Prevention. Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population 2012. Atlanta (GA): National Center for Environmental Health; April 2012.

(4) “Vitamin D and Health.” The Nutrition Source. Harvard School of Public Health, n.d. Web. 28 July 2016.



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