I live in Canada. I work inside. And I wear sunscreen diligently as part of my evidence-based skin care routine. So, every winter, I take 1000 IU of vitamin D every day.
But do I really need it?
In this little blog post, I’m going to answer some questions about taking vitamin D supplements.
What is Vitamin D?
According to Harvard’s School of Public Health:
Vitamin D is both a nutrient we eat and a hormone our bodies make. It is a fat-soluble vitamin that has long been known to help the body absorb and retain calcium and phosphorus; both are critical for building bone. Also, laboratory studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation. Many of the body’s organs and tissues have receptors for vitamin D, which suggest important roles beyond bone health, and scientists are actively investigating other possible functions.
Many of the foods we eat in North America have vitamin D, like fish, red meat, eggs, cheese, and other dairy products. Prepared foods like cereals, plant-based milks, and juices are often fortified with vitamin D.
Our skin also makes this hormone/vitamin. About fifteen minutes of sun exposure to the face and hands is enough for your body to make enough vitamin D for the day.
If our bodies make vitamin D, and it’s in our food, do we need a supplement?
The short answer is, probably not.
A Cochrane post from 2023 outlined three groups of people where there’s enough evidence to support supplementing with vitamin D:
Infants and children in order to reduce the risk of rickets (a bone disease)
Older adults with either a) osteoporosis, to possibly reduce the risk of fracture and/or b) who live in care facilities to potentially reduce the risk of falls
Pregnant people to reduce the risk of pre-eclampsia, diabetes, and low birthweight
(There are caveats to taking vitamin D in the above groups, so it’s always important to talk to your primary care provider about whether it’s recommended for you.)
Otherwise, for healthy adults, there isn’t enough evidence to recommend taking a vitamin D supplement.
But what about testing for deficiency?
I don’t routinely test for vitamin D deficiency. Choosing Wisely recommends against measuring vitamin D levels in the blood as a screening test. It just doesn’t change the treatment plan.
Some people in Northern climates are probably low in vitamin D, but very few people are seriously deficient. For my patients concerned about their vitamin D levels, I ask them what they eat and how much sun they get. If they want to take a supplement, they can!
Is there harm in taking vitamin D supplements?
There are possible harms from taking vitamin D, although the risk is low. For instance, too much vitamin D supplementation can be harmful to the kidneys. Some supplements have much more vitamin D than the label states, and some have much less. If you want to supplement with vitamin D, try to buy a brand that says it’s third-party tested for quality control.
Plus, supplements cost money. Since there’s little evidence to support taking them regularly (outside of the groups we discussed above), then the financial cost may outweigh the potential benefit.
I hope this post was helpful. I’ll probably keep taking my vitamin D supplement at 2 cents a pill in the winter.
Let me know what you want to hear about in the next post!
Stay well friends,
Dr. Kuhnow
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