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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Does sun exposure lower folate status?

Folate is a form of vitamin B and is an essential nutrient for our health. Folate is naturally found in green leafy vegetables such as broccoli and spinach, asparagus, mushrooms and some organ meats. For supplementation, the synthetic form of folate is known as folic acid.

Folate is possibly best known for its importance for pregnant women and women of childbearing age. Maintaining healthy folate levels is important in preventing a birth defect known as neural tube defects. Neural tube defects occur in the brain, spine or spinal cord of the fetus and can happen in the beginning of pregnancy, sometimes before the woman is aware she is pregnant. A common neural tube defect is spina bifida, a condition where the fetal spinal column doesn’t close all the way, which can lead to paralysis in the legs.

Past research has suggested that sun exposure may degrade concentrations of folate in the body. One theory why we evolved to have dark skin in equatorial Africa is to protect our folate status. The theory is that our skin evolved to strike a perfect balance between getting enough vitamin D and protecting folate status. However, there have only been a few studies looking at the relationship between folate and sun exposure, some finding significant associations and others coming up short on an association.

Of these studies, none have looked at the effects sun exposure might play on folic acid supplementation in women of childbearing age. So, recently, researchers set out to answer this question.

The research team, based out of Australia, recruited 45 women all between the ages of 18 and 47 years old. For two weeks, they supplemented with 500μg of folic acid to reflect the National Health and Medical Research Council recommendations for women of childbearing age. The National Health and Medical Research Council is a public health organization of the Australian government.

After two weeks of supplementation, the women ceased their folic acid intake and underwent one week of self-monitoring their personal sun exposure, physical activity, sunscreen use, and clothing worn in a diary.

After the three weeks of the study, the researchers analyzed changes in folate levels over just the last week. Here is what they found:

  • Self-reported sun exposure was significantly associated with a decrease in serum folate levels (p=0.015).
  • Those with moderate and high sun exposure experienced a larger decrease in folate levels compared to those with the lowest sun exposure.
  • Those with moderate to heavy physical activity had higher folate depletion than those with light daily physical activity (p=0.019).

The researchers concluded:

“In our study investigating the effects of natural solar UV radiation on serum folate status, we observed that significantly greater depletion of serum folate status occurred in participants with higher sun exposures compared to those with lower exposures (p=0.015).”

Additionally, the researchers noted:

“A dose-dependent effect was observed with regard to sun exposure and serum folate depletion, with participants who reported the highest sun exposures experiencing increased depletion compared to those with intermediate exposures and the lowest exposures.”

The researchers added that the observational design of the study means that they cannot know for sure if sun exposure is the direct cause of the decreased folate status in those with the highest sun exposure. Also, the fact that supplementation was completely stopped during measurements of sun exposure means that we cannot know if supplementation would maintain levels throughout sun exposure.

Larger randomized controlled trials need to be conducted to further understand this relationship. Further study will also be important to understand the clinical meaning to this. While they found that reduced folate levels correlated with increased sun exposure, they didn’t look at any clinical outcomes, so it’s not clear if the amount of reduced folate levels is clinically significant.

It is unlikely that sun exposure’s effect on folate levels is harmful, even if it decreases levels. If it were, we’d likely see that higher vitamin D levels (which would correlate with lower folate levels, in theory) correlate with worse pregnancy outcomes. However, we see the exact opposite. Higher vitamin D levels correlate with better pregnancy outcomes.

Regardless, this relationship between sun exposure and folate status is a reminder that sun exposure and health is a complicated subject. Sun exposure carries both risks and benefits. We need to evaluate both. The Vitamin D Council maintains that sensible moderate sun exposure carries more health benefits than risks.

Source

Borradale, D. Exposure to solar ultraviolet radiation is associated with a decreased folate status in women of childbearing age. Journal of Photochemistry and Photobiology, 2014.

  About: Jeff Nicklas

Jeff Nicklas was a staff member for the Vitamin D Council from October 2013 to January 2015. He is now pursuing his passion for public health through graduate studies.

7 Responses to Does sun exposure lower folate status?

  1. Rita and Misty says:

    I wonder if the study results would have been the same if folate had been used rather than folic acid?

    In other words: if “5-methyltetrahydrofolate” or “5-MTHF” had been used…

    Also, I think it would be interesting to devise a study where participants were on healthy “green” diets for folate–where they actually consumed substantial amounts of leafy greens 5X per week (for example). I wonder what any test results would then yield?

    Our hunter/gatherer ancestors received much more sun and consumed much more greens than we do today–I think…

    By the way: Folic acid supplementation has been linked to increase cancer, masking of B12 deficiency and cognitive decline.

  2. Ian says:

    Rita: “By the way: Folic acid supplementation has been linked to increase cancer,”

    I thought this had been de-bunked.
    Folic acid supplementation and cancer risk: a meta-analysis of randomized controlled trials.
    Qin X, Cui Y, Shen L, Sun N, Zhang Y, Li J, Xu X, Wang B, Xu X, Huo Y, Wang X.
    Int J Cancer. 2013 Sep 1;133(5):1033-41.

  3. Ian says:

    Also the meta-analysis by Qin et al showed folate supplementation reduces risk of melanoma.

    Could this relate to the study by Borrodale, UVB/A drives down folate increasing risk of melanoma and supplementation corrects that. So that increasing both vitamin D and folate status by supplementation may jointly reduce risk of melanoma. Of course reducing intermittent sun exposure may reduce risk as well.

  4. Rita and Misty says:

    Ian–thanks for the link to that study. I haven’t read it yet so perhaps it is unfair for me to make this next comment. But, I will make it anyway: does one study prove or disprove anything?

    Since it is possible to supplement with folate, wouldn’t that be a wiser choice?

    Wiser yet–a diet high in healthy, organic greens?

    I wish for sunshine and kale 😉

  5. Rita and Misty says:

    Well I am embarrassed (maybe not)…I just realized you linked a meta-analysis, and a good-sized one at that. So, I would say it is okay to supplement with folic acid, as this review was certainly of more than one study.

    Sorry for jumping the gun.

    Here is an excerpt:

    “19 studies contributed data to our meta-analyses, including 12 randomised controlled trials (RCTs). Meta-analysis of the 10 RCTs reporting overall cancer incidence (N=38 233) gave an RR of developing cancer in patients randomised to folic acid supplements of 1.07 (95% CI 1.00 to 1.14) compared to controls. Overall cancer incidence was not reported in the seven observational studies. Meta-analyses of six RCTs reporting prostate cancer incidence showed an RR of prostate cancer of 1.24 (95% CI 1.03 to 1.49) for the men receiving folic acid compared to controls. No significant difference in cancer incidence was shown between groups receiving folic acid and placebo/control group, for any other cancer type. Total cancer mortality was reported in six RCTs, and a meta-analysis of these did not show any significant difference in cancer mortality in folic acid supplemented groups compared to controls (RR 1.09, 95% CI 0.90 to 1.30). None of the observational studies addressed mortality.”

  6. Rita and Misty says:

    <3

    At least you know that I do (finally) read what you post, and I admit when I'm mistaken.

    P.S. I still prefer folate.

  7. Ian says:

    Yes MTHF supplementation would be better than folic acid supplementation. Most people would not know if they have one of the many SNPs in folate metabolism. If you don’t have SNPs then folic acid would be just as good. Just like cholecalcifrol is just as good if not better than 1,25-dihydoxyvitaminD. However for some people and some pathologies 1,25-dihydoxyvitaminD would be necessary.