Vitamin D: What is it and why should you care?

​Vitamin D is a fat-soluble vitamin found in meat, fish, eggs, dairy products and legumes. Its role in the maintenance of bone health and regulation of blood calcium levels have been well understood for decades, however new research suggests that it also plays an important role in nervous system function. Studies have shown that adequate vitamin D during pregnancy is essential for proper brain development, and vitamin D deficiency show higher prevalence of mood and nervous system disorders such as schizophrenia and multiple sclerosis. 1 Furthermore the prevalence of vitamin D deficiency is on that rise in the US.2 The reason for this is still not clear, however several theories include decreased exposure to UV rays and decreased consumption of meat and dairy products. The good news is vitamin D is one of the only vitamins our bodies can synthesize all on its own, however this process requires exposure to UVB rays. While the exposure time needed to generate the reaction is fairly small, sedentary lifestyles as well as increased use of protective sunscreens has decreased the amount of vitamin D many of us are producing. Furthermore, the vitamin D that produced in our skin or obtained from our diet is not typically in its most active form. It needs to go through a conversion process in the liver and then the kidneys in order to be most useful to our body.2 As such, health issues that affect the liver and/or kidneys can also impact vitamin D levels. Finally individuals with increased levels of melanin in their skin (darker skin tones) are not able to absorb UVB rays as efficiently and therefore are less capable of producing vitamin D as their fairer-skinned counterparts. 

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How much do I need?

The Academy of Nutrition and Dietetics recommends adults obtain 600-800 IU (or 15-20 ug) per day. Between sun exposure and diet most adults are able to achieve this without issue. However several populations are at an increased risk of deficiency. These include post-menopausal women, elderly adults, and children growing up in poverty. Signs of vitamin D deficiency are joint/bone pain, gastrointestinal issues such as diarrhea and bloating, fatigue and muscle twitching. If you observe any of these see your primary care provider to discuss the possibility of a vitamin D deficiency. 

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Should I supplement?

Generally speaking most adults are able to obtain sufficient vitamin D from diet and incidental sun exposure. That said, a daily multivitamin acts as a good insurance policy to ensure adequate levels. That said, most over-the-counter supplements and even fortified foods contain vitamin D3  (also called calciferol or cholcalciferol), which is a lesser active form of the vitamin. The most active form of vitamin D (1,25 dehydroxycholcalciferol) is only available by prescription. Because the cause of vitamin D deficiency is often unknown, most healthcare practitioners recommend that patients presenting with a clinical vitamin D deficiency take the most active (prescription) supplement in order to ensure adequacy. This is because the root cause of the deficiency may be linked to an inability to convert the form of vitamin D obtained from sunlight and commonly found in food (vitamin D3) into the active form (1,25 dehydroxycholcalciferol). If you have a clinical deficiency, discuss the best treatment option with your doctor or healthcare provider.

References:
1. Wrzosek, M. et al. (2013). Vitamin D and the central nervous system. Pharmacological Reports, 65, 271-278.
 
2. Parva, N. et. a. (2018). Prevalence of vitamin d deficiency and associated risk factors in the US population. Cureus, 10(6), 2741.

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