the ultimate guide to vitamin d |


time to read 3 min

the ultimate guide to vitamin d |

Why do you need it?

In February we talked about Calcium- a vitamin critical for bone health- and how to get enough of it when dairy is off the table.  Today we are going to  hit on Vitamin D, another big player in bone health that we need to pay attention to.

The body makes Vitamin D when the sun hits the skin, but this is an inactive form.  This inactive form is then activated in the liver and kidneys.  Vitamin D improves calcium absorption in your gut and manages the calcium and phosphorus in your blood.  The vitamin is important in nerve function, disease prevention and, of course, bone health.  It was the Vitamin D in cod liver oil that proved to be the cure for the childhood disease rickets- a softening of the bones.

Just as with calcium, there are some people who have to pay special attention to Vitamin D.  You may be at risk of a deficiency if you are…

  • pregnant or breastfeeding
  • a person with darker skin
  • a person with little sun exposure (whether housebound or covered for cultural reasons)
  • obese OR
  • have an Inflammatory Bowel Disease

If you fall in any of these categories- ask your doctor if they think a Vitamin D check is appropriate.

Where should my levels be?

When you get tested, they will test your 25OHD- so when you see that, think Vitamin D.  A result of 50 nmol/L or more means you are in the clear.  They will likely treat you if …

  • your 25OHD is < 30 nmol/L or
  • your 25OHD is 30-50 nmol/L but you show symptoms of deficiency or are at risk of bone disease

Not surprisingly, a recent study has shown that there is a such thing as a too high Vitamin D.  A level of 100 nmol/L showed an increase risk of death due to stroke or coronary.  So, yeah, don’t go too crazy.

Where can you get it naturally?

There are very few natural food sources of Vitamin D.  Fatty fish like salmon (wild, not farmed), mackerel and sardines; mushrooms (chanterelle and shitake); and eggs (from hens that have been fed a diet rich in Vitamin D).

The sun.  UVB (Ultraviolet B) rays are responsible for activating the preVitamin D in the skin to be converted to Vitamin D.  Interestingly, a SPF of 10 will reduce Vitamin D synthesis by 90%, but it would be silly to not wear sunscreen considering Vitamin D can be corrected with a supplement, but melanoma can literally kill you.  The highlight of widespread Vitamin D deficiency in recent years and the suggestion that this coincides with recommendations to wear sunscreen drives dermatologists nuts- they only wish the public a) remembered to wear sunscreen in the first place and b) put it on well enough when they did remember to put it on.

So, what should I look for in a supplement?

I don’t always recommend supplements- I like to go for foods first and supplements only when absolutely needed.  The thing is, if you are on a dairy free diet, you are already at risk for low calcium- if you have low Vitamin D as well, that can have serious implications for your long-term bone health.

There are two types of Vitamin D- D2 (plant sourced) and D3 (animal sourced).  When looking for a supplement, I look for D3- there is some dispute that there is a difference between D2 and D3 in raising your levels, but D3 is more readily used by your body, more shelf stable, more potent, and costs the same as D2. Unless you are vegan there is no reason to choose D2 over D3, so that’s what I personally buy.  For regular maintenance, an average of 800-1000 IU per day will do.  If you are symptomatically or severely low, your doctor may put you on a regimen that gives you a very high dose once a week for several weeks. I will leave that discussion for you and your doctor.

Also, if you are on Prednisone or Dilantin, be sure to talk to your doctor before starting supplements.

Sources/Further Reading

Vitamin D and Bone Health: A Practical Clinical Guideline for Patient Management  by the National Osteoporosis Society

Vitamin D a Rapid Review

 A reverse J-shaped association between serum 25-hydroxyvitamin D and cardiovascular disease mortality – the CopD-study

Vitamin D – Linus Pauling Institute

Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline

Mayo Clinic Vitamin D Dosing


This article is only meant to provide information- NOT medical advice.  Talk to your healthcare provider before starting any supplements.

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