Vitamin D: How much do you really need?

Vitamin D is an essential vitamin that we primarily absorb from the sun. Living in Canada, we’re amongst the most deficient countries in the world when it comes to vitamin D. In this article we’ll explore the debate about adequate versus beneficial amounts of vitamin D in the body, and how to make sure you’re getting enough of this important nutrient.

Why do we need Vitamin D?

  • Bone health – vitamin D allows us to absorb calcium and promote bone growth. Low vitamin D contributes to low bone density, known as osteoporosis, which leads to increased risk of fractures.
  • Powerful cancer prevention – vitamin D deficiency is linked to increased risk of breast cancer, colon cancer and prostate cancer.
  • Important for mood – Seasonal Affective Disorder (SAD) is caused by low vitamin D levels, and primarily affects people during the winter.
  • Helpful in treating (and possibly preventing, although not all research studies agree) autoimmune disease, autism, chronic pain, diabetes and heart disease.
  • Required for immune system function, helping to fight infection and prevent illness.

Where do we get vitamin D from?

Most of our vitamin D is produced from exposure to the sun. We need about 15 minutes of our arms and legs exposed to the sun daily, during peak sunshine hours, without sunscreen, to produce adequate vitamin D levels.

People with darker skin tones don’t absorb vitamin D as well as those with lighter skin tones due to higher melanin content in their skin.

It is possible to get small amounts of vitamin D from fortified sources, including milk. However, Health Canada statistics still show that even people who consume the most amount of dairy (toddlers and seniors), are still not reaching adequate blood levels of vitamin D.

What should we be looking for on lab testing?

There is a lot of debate between Health Canada versus scientific research about how much vitamin D is “adequate”. When Health Canada runs its statistics about how many Canadians are deficient in vitamin D, they use the number 50 nmol/L as the cut off. Lab test reference ranges and Canadian MDs use 75 nmol/L as the cut off. However, most scientific literature showing significant benefit to human health promotes 100 nmol/L as the appropriate cut off for being vitamin D sufficient.

Research estimates we would see significant reductions of diagnoses of cancer, heart disease, dementia, diabetes, multiple sclerosis, hip fractures due to osteoporosis, and respiratory infection. A study published in 2016 found that by increasing the standard to 100 nmol/L, Canadians would save about $12.5 billion annually on healthcare costs, and prevent 23,000 premature deaths per year.

As you can imagine, the low cutoff used by Health Canada skews the numbers to show that only 60-66% of Canadians are deficient (still a huge number!). When we use the research-supported cut off of 100 nmol/L, we find that about 93% of Canadians are falling short.

Is vitamin D testing covered by OHIP?

Despite this research vitamin D testing is not covered by OHIP. If I’m running labs with my patients, I always discuss the benefit of testing vitamin D ($33). If a patient is getting labs done through their family doctor, I always recommend they ask to pay out of pocket to be tested.

It sounds like the solution is to take lots of Vitamin D orally?

It’s very important to note that taking too much vitamin D orally is toxic, and this amount can vary from person to person. Since vitamin D is a fat-soluble vitamin, the body cannot simply get rid of any excess. Research also shows us that damage due to toxicity can occur in the body before we notice anything overtly in terms of symptoms – meaning we could be doing damage by taking too much before we notice anything is wrong.

The bottom line:

  1. Have your vitamin D levels tested at least once per year.
  2. Most of us need to supplement with oral vitamin D, at least during the winter.
  3. Vitamin D can be toxic, so it’s important to know how much you need to take daily, and use lab testing monitor that you’re staying within a healthy blood-level.

 

References:

Alshahrani, F., & Aljohani, N. (2013). Vitamin D: deficiency, sufficiency and toxicity. Nutrients5(9), 3605-16. doi:10.3390/nu5093605

GrassrootsHealth – Scientists’ Call to D*action. http://www.grassrootshealth.net/epidemic

Greene-Finestone, L. S., et al. CaMos Research Group (2010). 25-Hydroxyvitamin D in Canadian adults: biological, environmental, and behavioral correlates. Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA22(5), 1389-99.

Janz T, Pearson C. Vitamin D blood levels of Canadians. January 2013. Statistics Canada Catalogue no. 82-624-X http://www.statcan.gc.ca/pub/82-624-x/2013001/article/11727-eng.pdf

William B. Grant, Susan J. Whiting, Gerry K. Schwalfenberg, Stephen J. Genuis & Samantha M. Kimball. 2016. Estimated economic benefit of increasing 25-hydroxyvitamin D conzcentrations of Canadians to or above 100 nmol/L,Dermato Endocrinology, 8:1, DOI: 10.1080/19381980.2016.1248324

Vitamin D Society Press Release. 2013. Stats Canada Data: Canadians’ Vitamin D Levels Declining. http://www.prweb.com/releases/2013/2/prweb10380382.htm

 

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s