Vitamin D3 is normally made by the body when sunlight, particularly UVB, triggers the conversion of cholesterol into the more active form of the vitamin. There are actually several forms, but it is generally agreed on that D3 (cholecaliferol) is the most biologically relevant. Most of the research that is done on this vitamin focuses on increasing levels of D3 circulating in the bloodstream and on increasing levels of parathyroid hormone (PTH). Both of these are involved in bone density and calcium use by the body, but vitamin D3 plays important roles in immunity and other biological processes, too.
Its role in the appearance, texture, and general condition of the skin, however, is much less clear. I found two particularly good studies that looked at what is observed with vitamin D supplementation, but it should be noted that these studies used very large doses of 50,000 IU per week as “loading doses” to correct pre-existing deficiencies (blood levels < 35 ng/mL). In the first, they looked at whether there was a biological difference between the vitamin D that your skin makes versus oral supplements of vitamin D. This study demonstrated that vitamin D levels in the blood increased faster with the supplement, but stabilized at about the same concentration. They found no significant differences between the skin-made vs oral groups with regard to PTH, total cholesterol, HDL, LDL, or CRP levels. Interestingly, the triglycerides (free fat in the bloodstream) decreased in the supplement group, but not in the skin-made group. That part of the study has nothing to do with the skin, but it’s good to know what’s going on under-the-hood a little bit. The biggest differences were in two immune-related signaling molecules (called cytokines), IFN-α and IFN-γ. Both of these are involved in immune system responses. IFN-α is mostly considered an antiviral cytokine and is usually made by fibroblasts (skin cells) and some types of white blood cells when a virus is detected. IFN-γ is made in response to a wider variety of immune triggers and helps direct your T cell responses. Both cytokines were decreased in the supplement group, but not in the skin-made group. It’s unclear what this might do to the immune system responses, but it suggests that there may be lower levels of inflammation (that’s my personal speculation based on my experience with both cytokines). Perhaps most important, they found this consistently in the supplement group’s blood and skin samples . This study used n=58 people, so it was small, and the doses of vitamin D were not given in the same manner as in the Halo Beauty supplement.
The second study was much smaller and was a pilot study . This means it’s small (only n=25 people), with preliminary results. They actually looked at the possible bioactivity of vitamin D in the skin after either oral supplement or UVB exposure. As with the previous study, though, they used 50,000 IU weekly, so the dose isn’t directly comparable to the Halo Beauty product. During this pilot, they looked at areas of skin that were sun-damaged already (forearm) and protected areas of skin (probably butt cheek). They found that after supplementation, levels of the vitamin D receptor increased in undamaged skin, which means that the skin would be more responsive to any vitamin D available. They also looked at expression of CYP24, which a gene for an enzyme that degrades vitamin D. They found that supplementation increased expression of CYP24 in protected skin, unprotected skin, and even in normal moles (it’s cool that they looked at those). This study is one of few that showed pictures of skin biopsies with and without vitamin supplementation. Their biopsies were stained specifically to look for two things: loricrin and caspase 14. There wasn’t an observable difference in loricrin (which is important for the skin’s absolutely outermost layer, the stratum corneum). Caspase 14 is involved in cell death via apoptosis, which helps the body get rid of damaged cells. This study showed some increase in caspase 14 production in the damaged skin areas only, which overall should help get rid of very sun-damaged cells.
The next study that I found particularly interesting and maybe relevant used a mouse model. Again, mice aren’t tiny humans, but they were using this to test whether giving vitamin D before treating skin cancer might help get rid of the skin cancer faster/better . They gave the vitamin D to mice either orally or via injection before using photodynamic therapy (PDT) as a treatment for squamous cell skin cancer. They had very clear evidence that pre-treatment helped kill more cancer cells via apoptosis with this treatment, which is interesting. I wonder if that’s related to some of the changes that the other articles saw, like increased vitamin D receptors and increased caspase 14.
One study I looked at with definite interest didn’t actually have anything to do with skin at all, but did look at whether we receive enough vitamin D. Since we seem to be finding more people who are vitamin D deficient (myself included), this might be interesting or relevant to some. They actually looked at Arabic women who were veiled, and compared blood levels of vitamin D with Danish women (Moslem-assumed veiled and non-Moslem). Before anyone jumps me for my terms, those are the terms used in the article . They essentially found that there was seasonal variation, but that Danish Moslem women got more vitamin D than Arabic women (either veiled or non), but Danish women who were not Moslem got most of their vitamin D from supplements. Regardless of source or origin, veiled women (Arabic veiled or Danish Moslem) had very low levels of vitamin D3 in the bloodstream. Essentially, the recommended daily intake for vitamin D based on current guidelines was not sufficient if there was reduced sun exposure (due to veiling or time of year based on this study, but it may be more broadly applicable).
I did look at one other source—a conference abstract . I can’t speak to the results because I haven’t seen the data, but they were looking for genetic differences that might have to do with melanoma and how that might relate to vitamin D supplementation. The study design described is good, and their reported results appear reasonable based on what they have done so far and the other research that I’ve seen. If you’re curious, ask me questions in the comments (or go check out the abstract).
In summary for Vitamin D, I think it’s even less clear what effect this has on skin, but the most consistent things that stand out to me from these studies is that having acceptable levels of vitamin D is important for immune system function—including in the skin. A very rough description of that might be that low levels of vitamin D may be associated with increased inflammation in the skin, and decreased sensitivity and response to sun damage. Thus, supplementation with vitamin D may be beneficial to the skin’s overall health and potentially its appearance as well.
Next up: Vitamin B1!
- Ponda, M.P., et al., A randomized clinical trial in vitamin D-deficient adults comparing replenishment with oral vitamin D3 with narrow-band UV type B light: effects on cholesterol and the transcriptional profiles of skin and blood. Am J Clin Nutr, 2017. 105(5): p. 1230-1238.
- Curiel-Lewandrowski, C., et al., Pilot study on the bioactivity of vitamin d in the skin after oral supplementation. Cancer Prev Res (Phila), 2015. 8(6): p. 563-9.
- Anand, S., et al., Combination of oral vitamin D3 with photodynamic therapy enhances tumor cell death in a murine model of cutaneous squamous cell carcinoma. Photochem Photobiol, 2014. 90(5): p. 1126-35.
- Glerup, H., et al., Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. Journal of Internal Medicine, 2000. 247(2): p. 260-268.
- Anderson, E., et al., 265 Pilot trial to evaluate the effect of vitamin D on melanocyte biomarkers. Journal of Investigative Dermatology. 136(5): p. S47.