There are a couple of nuances of how we choose Vitamin D that I’d like to address.
The first is where to get the Vitamin D: sunlight or supplement?
The second is, if we use a supplement: Vitamin D3 or D2?
Before we get to those, let’s walk through the basics of vitamin D in our body.
Benefits of Vitamin D:
Bone health
Muscle health
Immune health (decreased risk of autoimmune disease)
Decreased risk of cancer (potentially, some observational studies have shown low vitamin D levels associated with cancers which does not necessarily mean that adequate vitamin D is protective)
Risks of Vitamin D really are risks of excessive Vitamin D, such as:
Irregular heartbeat
Kidney damage
Elevated calcium (building up in the blood vessels is dangerous)
The internet is a wildly confusing and overstimulating source of information (the word information is used loosely here). There is so much emphasis on protecting ourselves from sunlight, but also so much touting of vitamin D’s benefits for us especially as we age. So, how do we choose our source of this vitamin?
The answer is, of course, complex. The risks of sunlight exposure, especially during peak hours (11 am to 2 pm) are real. The risk of melanoma is higher in someone who is fair-skinned, light-eyed, freckled. Sunscreen does help, however in the U.S., sunscreen SPF is only regarding UVB protection and not UVA. UVA can be cancer-causing and can penetrate window glass. There are sunscreens that explicitly state they have UVB and UVA protection, be sure to look at the labeling. The risk of melanoma may be lower in a dark-skinned person, but their risk of vitamin D deficiency is higher.
I think the majority of experts are suggesting benefit of sunlight, but we have to choose our time of day (early morning), amount of exposure (30 minutes), and continue to use sunscreen. Early mornings and evenings are a great time to get outside!
I use sunscreen daily in my morning facial lotion, so it’s not an extra step I have to think about.
If we need or want to supplement, do we use D3 or D2? You may need to supplement if your vitamin D level is low (usually less than 30 ng/mL).
Animal sources provide D3, while plant sources provide D2. D3 has been shown to be better absorbed by our body, so this is generally favored over D2. If you’re looking to get D3 from diet before starting a supplement, foods like salmon, eggs, red meat, and liver are good sources. If you’re using a supplement, remember this is a fat-soluble vitamin, meaning it dissolves in fat, so is best taken with meals. Other fat-soluble vitamins are A, E, K.
The dose of daily D3 depends on age based on Institutes of Medicine (IOM) recommendations. Between ages 19-50, we should get 600 IU of vitamin D daily. This dose is also applicable to ages 51-70. Over age 70, the dose increases to 800 IU of vitamin D daily.
The Endocrine Society recommends a higher dose of 1500-2000 IU daily, citing the above IOM recommendations did not analyze data correctly. They offer that a higher dose is actually what is needed to maintain adequate blood levels of vitamin D and achieve the health benefits. This is what I commonly see prescribed to patients.
Supplements are not regulated by the FDA. The good thing about this is the choice is up to us, rather than the FDA choosing what can be sold. The downfall of this is the market is oversaturated with too many choices, which makes choosing harder. Another downfall is without regulation, there's no regular standard. Supplements are not tested clinically, but they can be manufactured well. To find something that is manufactured well, look for the USP (US Pharmacopeoia) or NSF (National Sanitation Foundation) endorsements.
Resources:
https://www.sciencedirect.com/science/article/abs/pii/B9780128099650000598
https://longevity.stanford.edu/lifestyle/2024/03/11/vitamin-d-benefits-sources-deficiency/
Menopause Practice, A Clinician’s Guide: 6th edition. The North American Menopause Society. (Now called The Menopause Society)
