Do I Need to Take Vitamin D?

If you are wondering if you need to take a Vitamin D supplement or if you need to have your level checked on your annual lab tests you are not alone.  

The data on Vitamin D and health in the medical literature is ever changing which is why the advice from your doctor may vary from from year to year.   Adding more confusion to the mix, patients of different ages and demographics have different Vitamin D requirements.

Image: Mathew Schwartz

What DO we know about Vitamin D? 

Vitamin D is crucial for bone health.  Deficiency in Vitamin D is associated with osteoporosis, increased risk of falls in the elderly and may be linked to fractures. Vitamin D is part of a tightly regulated system within the body which determines the amount of calcium and phosphorus we absorb from our gut, filter in our kidneys, and then in turn how much is available in our blood for bone building.  

Vitamin D is found naturally in very few foods.  

These include fatty fish such as salmon, mackerel, tuna, and sardines as well as in shiitake mushrooms and a small amount in eggs.  This is why many foods are fortified with Vitamin D such as cereal, dairy and orange juice. 

Image: Engin Akyurt

Sunlight is important in Vitamin D production.

Interestingly, human skin contains a cholesterol called 7-dehydrocholesterol (7-DHC), which is a pre-curser to Vitamin D, and sunlight (ultraviolet B) is required to convert 7-DHC into the active form of Vitamin D, Vitamin D3.  Therefore, if most of your time is spent indoors, you may have an increased risk of Vitamin D deficiency so there may be some benefit to spending around 10-15 minutes in the midday sun to help increase active Vitamin D3 levels.  However, this must be weighed against your risk for skin cancer, so please discuss this further with your doctor (

Image: Greg Kantra

So, should all patients have a Vitamin D level checked?  

No, currently a routine Vitamin D level check is not routinely recommended for every patient.  However, you still should consider if you are getting enough Vitamin D.  If you spend most of your day inside or live in the northern latitudes where there is less sun exposure, and calculate inadequate intake through dietary sources (as most people will), a Vitamin D3 supplement is recommended.  For adults under age 50 years old the dose for Vitamin D is 400-800 international units (IU) daily, and for those age 50 years and older it is 800-1000 IU daily ( 

A Vitamin D blood test is recommended for people at risk of Vitamin D deficiency.  

Deficiency is considered to be less than 20 ng/mL with sufficient levels being greater than 30 ng/mL.  Patients considered at risk for deficiency include those with certain medical conditions resulting in malabsorption or on certain medications, the elderly, people who are overweight, people with darker skin tones, and those with decreased bone mineral density (  For patients found to have deficiency once supplementation is started a repeat level will be checked approximately 3 months later.  

There may also be other health benefits to Vitamin D including cancer, infection, and chronic disease prevention and treatment, a role in mental health, treatment of asthma, an impact on female fertility, and more ( 

These additional health benefits are currently under investigation and require more studies for a definitive association but are exciting none-the-less!  Stay tuned for updates on Vitamin D as the research and medical literature continues to grow and evolve.

Leave a Reply