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You Probably Don’t Need As Much Vitamin D As You Think

Understanding Vitamin D 

When reading up on Vitamin D, the typical “WebMD” response is to first emphasize foods that contain vitamin D, and then promote supplements. As a third and last resort, it includes sunshine. These suggestions are structured in such a way because excessive sun exposure is a carcinogen. The other two suggestions, eating foods like salmon or fortified milk and buying a supplement require a purchase to obtain vitamin D safely. Almost every article written for a consumer audience on the subject suggested fortified milk and breakfast cereals to obtain adequate Vitamin D levels. According to a Yale doctor, the general population does not have a Vitamin D deficiency. 

The messaging is that Vitamin D is essential, but many aren’t getting enough of it because our lifestyles don’t put us outside or because sunshine can be a skin-cancer risk. The safe ways to get Vitamin D both by ingesting it, instead of absorbing UVB. 

Metabolizing Vitamin D through food or a supplement is not the same as synthesizing it through UVB Rays. When obtaining Vitamin D through food or supplementation, a different conversion process takes place in the liver and kidneys. When Vitamin D goes through the metabolic process, it gets converted into a hormone called calcitriol before entering the bloodstream. Keep in mind, many supplements have low absorbability meaning the kidneys often put most of it into the urine stream. 

When Vitamin D is synthesized through the skin, a precursor molecule in the skin is released. This helps a “pre-vitamin D” converts “vitamin D” into cholecalciferol which enters the bloodstream, bypassing the kidney and livers. It’s also a slightly different compound. Both are essential, but different. 

How much sun is needed for healthy Vitamin D? 

According to JSTOR Daily, the body will continue to synthesize Vitamin D for about three days after exposure ends. Moderate sun exposure is sufficient. We also know that 10 minutes of sun exposure can produce Vitamin D that is stored in fat cells for weeks to months. What is moderate exposure? 

The NIH is reluctant to suggest that any amount of sunlight is safe, but it does state, “Some expert bodies and vitamin D researchers suggest, for example, that approximately 5–30 minutes of sun exposure, particularly between 10 a.m. and 4 p.m., either daily or at least twice a week to the face, arms, hands, and legs without sunscreen usually leads to sufficient vitamin D synthesis.” 

Translation: 35 minutes up to 3.5 hours per week of sun exposure for synthesis. 

Considering these metrics, most people are likely getting more than enough Vitamin D from sunlight in amounts that are probably not carcinogenic. However, considering a long list of variables from genetics to the smog index to altitude, no one seems to know. 

All in all, any narrative that created a choice between Vitamin D deficiencies vs Skin Cancer drove up sales for supplements and fortified foods. The good news, it is possible to stay safe from Skin Cancer as the amount of sunlight needed for Vitamin D production is pretty minimal for the general population.