By Joel Exebio, PhD Candidate, dietetic intern, MBRS Fellow, vitamin D expert

The incidence of diabetes has increased dramatically over the last 30 years. It is widely known that Scandinavian countries such as Finland and Sweden have the highest rate of type 1 diabetes in the world due to the limited amount of sunlight they receive over the year. Similarly, data suggest that sun exposure can play an important role in the onset type 2 diabetes as suggested by the peaks of blood glucose seem during the winter months. Spending some time under the sun may be the cheapest and easiest way to prevent diabetes¹.

Vitamin D plays a vital role in the production of insulin (the hormone that regulates blood sugar levels). Several studies have shown a positive association between insulin resistance and vitamin D deficiency². In lay language, the lower your levels of vitamin D, the more prone you are to develop type 2 diabetes.

Many studies supplementing vitamin D to subjects at risk of diabetes have shown significant improvements in fasting glucose levels, insulin production, insulin resistance, and A1c control (a marker of long term blood glucose levels). Therefore, expending more time under the sun or taking vitamin D supplements may delay the onset of type 2 diabetes².

How much time do you need under the sun? Sun sensitivity varies from person to person, skin color, the latitude of your location, and the time of the day. Most experts agree that, for those at risk of diabetes, 30 minutes of daily sun is adequate and safe. The exposure is to your arms, face, and hands. However, if you live in a northern area with limited sunlight you must consider taking a daily vitamin D supplement and adding some vitamin D rich foods to your diet such as fatty fish, sardines, shrimp, fortified milk, cheese, and yogurt.

In addition, skin color plays a role. The higher the melanin (the pigment that provides the color to our skin) content, the darker the skin color is. Melanin provides a barrier against ultraviolet radiation. In fact, vitamin D deficiency is more prevalent among individuals with darker skin color like African Americans and Hispanics. That may be the reason why both groups are more prone to develop type 2 diabetes compare to Caucasians³. The take home message is, the darker your skin color the more time you need to spend under the sun or the higher the dose of vitamin D supplementation you need in order to avoid vitamin D deficiency. Eating vitamin D can be delicious!

Try this recipe recommended by Larkin Hospital dietetic interns.  

¹Exebio JC, Zarini G, Ajabshir S, Antwi J, Huffman FG. Validation of a Sun Exposure Quiestionnaire among Subjects with Type 2 Diabetes Residing in South Florida. Journal of immigrant and Minority Health. 2015. DOI 10.1007/s10903-015-0163-7. ²Scragg R, Sowers M, Bell C. Serum 25-hydroxyvitamin D, diabetes, and ethnicity in the Third National Health and Nutrition Examination Survey. Diabetes Care. 2004. 27(12):2813-8. ³Center for Disease Control and Prevention. Vitamin D status: United States, 2001-2006. http://www.cdc.gov/nchs/data/databriefs/db59.pdf.