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"Is Summer Sun Exposure Enough for Vitamin D Levels, or Do You Need to Supplement?"

Updated: May 7


Not only is the sun energetically pleasing; summertime is a season of adventure, fun vacations, body goals and a natural mood elevator. The winter months may require optimal vitamin D ranges through supplementation, but sunlight is a sure way to naturally increase the amount of vitamin D and reap the protective benefits of vitamin D; the “sunshine vitamin.”



How does the sun contribute to vitamin D synthesis?

Vitamin D is a fat-soluble vitamin that is made through the sun’s UVB rays. In the skin, UVB rays actively transform 7-dehydrocholesterol to pre-vitamin D leading to its circulation in the blood stream and transforming into 25- dihydroxyvitamin D in liver. Eventually, pre-vitamin D activates further in the kidneys to form 1,25-dihydroxyvitamin D [1,25(OH)2D]. Many sources agree that 5 to 30 minutes every day without sunscreen is enough to generate an adequate amount of vitamin D. However, the amount of cutaneous vitamin D created depends on several factors:


-The amount of UVB reaching the earth’s surface 

-UVB disperses unevenly throughout the earth’s surface because of air pollutants and cloud matter

-Individuals who live above the equator and those who reside in higher latitude areas have less exposure to the sun

-individuals with increased melanin compete with 7-dehydrocholesterol for UVB photons; findings show that African American women are 20 times more likely to have low vitamin D levels (<25nmol/l)

-age also decreases the amount of 7 dehydroxycholesterol in the epidermis

Since vitamin D is absorbed through the GI tract, conditions that may disrupt proper absorption may lead to deficiency. For example, the following conditions are known to affect vitamin D absorption:


-Obesity, a higher amount of vitamin D deposits in adipose cells

-Crohn’s, intestinal inflammation leading to impaired absorption

-Cystic Fibrosis, impaired absorption

-Celiac Disease, intestinal malabsorption

-Kidney disease, decreases vitamin D hydroxylation

-Liver disease, decreases vitamin D hydroxylation


What are the optimal ranges for vitamin D?

About 80% of vitamin D is produced with UBV sunlight, the rest is found in food sources. The Food and Nutrition Board expert committee determined the following lab values for deficiency, insufficiency, and adequacy:

  • <30 nmol/L or (<12 ng/mL) Vitamin D deficiency

  • 30-50 nmol/L or (12-20 ng/mL) generally considered inadequate for bone and overall health in healthy individuals

  • ≥50 nmol/L or (≥20 ng/mL) is considered adequate for bone and overall health in healthy individuals

  • >125 or (>50 ng/mL) over the optimal amount, may cause potential problems

  • Serum concentrations of vitamin D Is reported in nmols and ng/ml. One nmol/L = 0.4 ng/mL, and 1 ng/mL = 2.5 nmol/L. According to the NIH the daily value of vitamin D is 800IU or 20mcg for those ages 4 years and older.


What does vitamin D do in the body?

Vitamin D is involved in several physiological processes. It helps absorb calcium supports and maintains bone structure and strength, especially in older adults; vitamin D at 700-900 IU was found to decrease falls by 19%.  Vitamin D is essential for tooth strength, its deficiency can leave our teeth susceptible to decay. The VITAL trail measured the effects of a 2,000 IU vitamin D supplement compared to a placebo and found that vitamin D was not effective in the primary prevention of cancer after a 5 year follow up but vitamin D’s efficacy is thought to be in the decreased progression of cancer and possible prognostic improvement, instead of the incident prevention of cancer. Severe vitamin D deficiency is strongly associated with stroke, cardiovascular events, and death.

Vitamin D is further recognized for its immunoprotective mechanisms. The BMJ discovered through a primary prevention trial of 25,871 participants that included men ≥50 years old and women ≥55 years old who were randomized into groups receiving fish oil or a 2,000 IU daily vitamin D supplement were found to have a 22% statistically significant reduction in autoimmune diseases (HR = 0.78; 95% CI, 0.61-1) after five years.


What are the mental health benefits of vitamin D?

Vitamin D receptors are present throughout the brain. Research has found these receptors specifically in areas of the brain that are linked to depression; the prefrontal cortex, hippocampus, thalamus, hypothalamus, cingulate gyrus and substantia nigra. Vitamin D is also associated with serotonin synthesis in the brain, a neurotransmitter implicated in depression, and has neuroprotective effects on regions that are responsible for the synthesis for other neurotransmitters such as epinephrine. A study conducted of 4,000 adults ages 50 and older over four years showed that those who had a higher incidence of depression were 75% more likely to be vitamin D deficient. Some studies have found statistically insignificant results regarding the benefit of vitamin D for depressive symptoms, while others are finding an overall improvement in mood but a lack of evidence supporting its use as a standalone therapy for depression.



Foods high in vitamin D

According to NIH the foods with the highest values of vitamin D include:

  • 1 tablespoon of cod liver oil-1 tablespoon contains 170% of the daily value of vitamin D

  • Trout-3 ounces contain 81% of the daily value of vitamin D

  • Salmon-3 ounces are 71% of the daily value of vitamin D

  • Mushrooms ½ cup of raw mushrooms are 46% of the daily value of vitamin D

  • Milk; vitamin D fortified, 2% milkfat 1 cup is 15% of the daily value of vitamin D

 

So get outside; get toned and have fun while your body heals in the most natural way possible!

 

References:


Akpınar, Ş. and Karadağ, M.G. (2022). Is Vitamin D Important in Anxiety or Depression? What Is the Truth? Current Nutrition Reports, 11(4). doi:https://doi.org/10.1007/s13668-022-00441-0.


American College of Cardiology. (n.d.). Vitamin D and Omega-3 Trial. [online] Available at: https://www.acc.org/latest-in-cardiology/clinical-trials/2018/11/08/22/42/vital#:~:text=The%20VITAL%20trial%20showed%20that.


Briggs, R., McCarroll, K., O’Halloran, A., Healy, M., Kenny, R.A. and Laird, E. (2019). Vitamin D Deficiency Is Associated With an Increased Likelihood of Incident Depression in Community-Dwelling Older Adults. Journal of the American Medical Directors Association, 20(5), pp.517–523. doi:https://doi.org/10.1016/j.jamda.2018.10.006.

National Institutes of Health (2023). Vitamin D. [online] Nih.gov. Available at: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.


Tsiaras, W.G. and Weinstock, M.A. (2011). Factors influencing vitamin D status. Acta dermato-venereologica, [online] 91(2), pp.115–24. doi:https://doi.org/10.2340/00015555-0980.


Xie, F., Huang, T., Lou, D., Fu, R., Ni, C., Hong, J. and Ruan, L. (2022). Effect of vitamin D supplementation on the incidence and prognosis of depression: An updated meta-analysis based on randomized controlled trials. Frontiers in Public Health, 10. doi:https://doi.org/10.3389/fpubh.2022.903547.

 

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