All About Vitamin D

“How serious is vitamin D deficiency (especially in the winter months)?  Should I be concerned, and what can I do to overcome it?”

Be concerned. Vitamin D deficiency is serious.

Here are some of vitamin D’s functions, and risks of being deficient.  I will also describe ways to overcome deficiency (it is possible!)

Functions of Vitamin D 

Vitamin D has been shown to be responsible for many different functions in the body.  Nowadays, we never hear about calcium without its friend, vitamin D.  This is because bones require both in order to be healthy and strong.  Specifically, vitamin D promotes calcium to be absorbed in the GI tract, and subsequent reabsorption in the kidneys.  By absorbing more calcium, vitamin D works to help stimulate bone remodeling.  Without D, calcium wouldn’t be able to strengthen bones all alone.

When exposed to sunlight or UV radiation, the skin can produce vitamin D (known as vitamin D3).  Since vitamin D is synthesized in the body, it acts like a hormone and sends chemical messages in the bloodstream from one organ to the next.  The Institute of Medicine (IOM) has now assessed 1000+ studies to look at how vitamin D may be beneficial beyond bone health.  These data suggest that vitamin D might have protective effects against diabetes, internal cancers, multiple sclerosis, hypertension and immunity.



How to Get Vitamin D Naturally

The Beatles say, “here come’s the sun,” and Marissa agrees, “it’s all right,” since being in direct sunlight without sunscreen for just 10-15 minutes can produce up to 10,000 IU per day of vitamin D. (1)  When skin is not exposed in the winter months, there are a few natural ways to consume D through food, most of which are high in fat.  These include fatty fish and eggs, predominantly. Some foods are fortified with vitamin D, such as cow’s milk, orange juice, some soy and rice milk and breakfast cereals.  In supplemental-form, vitamin D can be obtained from multivitamins, as a calcium combination with D or as a separate vitamin D supplement.

Below are the IOM recommendations per life stage on how many International Units (IU’s) to consume.


In children, vitamin D deficiency causes rickets.  In adults, a deficiency can cause osteomalacia (bone cancer), osteopenia (bone mineral density that is lower than normal) and eventually, osteoporosis (the most common bone disease, aka, “the disease of brittle bones”).  Osteoporosis is characterized by a severe loss of bone mass, strength and susceptibility to fracture.

Vitamin D deficiency has been defined by the Institute of Medicine and an Endocrine Society practice guideline as a level of serum 25-0H vitamin D less than 20 ng/mL (2, 3).  The Endocrine Society went on to further define vitamin D insufficiency as a level between 21 and 29 ng/mL (3).


There are a few ways to prevent and reverse a vitamin D deficiency.

#1 Blood test at your doctor’s office.  Ask for a vitamin D test to find out if your blood levels are within normal range.  A normal vitamin D level will show a blood range between 30-100 ng/mL.

#2 Look at your current sunlight exposure.  In the summer it is usually not a problem.  In the winter, it might be time to get some from your diet and/or supplements.

#3 Diet and supplements.  From the diet, vitamin D comes in the form of fatty fish, milk, eggs and in supplemental form, through D alone, a multi or a combination of calcium with D (sometimes will also include magnesium).  Supplements are great ways to get in enough vitamin D.  Look at the IOM’s guidelines above for how much you need to consume per day.  Although the IOM states a minimum of 600 IU’s per day, many supplements will offer upwards of 2,000 IU’s per day.  I take this amount and have been able to reverse a Bone DEXA diagnosis of osteopenia to normal.  So long as you are not exceeding the 4,000 IU’s per day Upper Level Intake, ranges in 2,000 IU’s per day seem to be effective.

#4 Exercise.  If you have yet to read a previous post of mine on Exercise’s role in building bone, now is the time.  Weight-bearing activity puts lots of (good) stress on the bones, which in turn produces more bone cells to strengthen the bone!  If you are not currently weight training at least 1-2x per week, fit it into your schedule to help solidify strong bones.



(2) IOM (Institute of Medicine). 2011. Dietary reference intakes for calcium and D. Washington DC: The National Academies Press.

(3) Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. JCEM. 2011 Jul; 96(7):1911-30.


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