Questions about Vitamin D and Sun Exposure

The sun often plays the role of villain among dermatologists. Too many patients come in with skin cancer, which is largely caused by excess sun exposure. What about vitamin D, the sun vitamin though? How do we balance adequate vitamin D intake and proper sun safety to prevent skin cancer and premature aging?

There has been some pushback from various organizations about the recommendations to limit sun exposure. One of the concerns with severely limiting sun exposure comes from the concern that extreme sun avoidance may lead to vitamin D deficiency. Perhaps with the help of some unexpected social media exposure, the issue of vitamin D deficiency is gaining more attention, and have raised some questions about finding the right balance of sun safety and adequate vitamin D intake. While the science is clear that UV rays are cancer-causing and contribute to premature aging, it is also true that the human body requires sufficient vitamin D to be healthy. The conundrum is that humans produce vitamin D in the skin when exposed to sunlight and it can be difficult to obtain sufficient vitamin D via diet alone. So what should we do?

What does vitamin D do, and why do we need it?

Vitamin D, like all vitamins is a vital nutrient to maintain good health. Vitamin D plays a hormone like role, helping to regulate calcium in the body. When vitamin D is deficient, bone related diseases like rickets and osteomalacia become a concern. Severe deficiencies in vitamin D can also impair brain function.

How do you get vitamin D?

Vitamin D can be obtained by food or via the skin when it is exposed to sunlight. Relatively few foods naturally contain significant amounts of vitamin D. Some recommended foods for obtaining vitamin D include fish, eggs, mushrooms, and liver. For many people’s diets, if they aren’t consciously taking in these foods, they will need to rely largely on some sun exposure to produce vitamin D.

As far as foods go, there is good news. Products like milk are now vitamin D fortified, as well as some cheese and yogurts. There are also supplements that can help provide vitamin D orally.

How much vitamin D do you need?

It’s true that vitamin D deficiency has been found to be more common than previously believed. Many factors can affect vitamin D levels including age, liver activity, diet, general exposure to UVB light. Health Canada and the US Institute of Medicine share similar guidelines on recommended daily allowance at 400 iu for infants, 600 from children until 70, and 800 iu after age 70. While the recommended guidelines for vitamin D intake are relatively consistent, in practical terms, most people aren’t clear about what they should eat or how much sun they should get.

The primary factors that affect vitamin D production are: Skin color, duration of exposure, and geographic location. This means that there is no uniform answer to how much sun exposure is necessary. Darker skin does not absorb as much UVB light and therefore requires longer sun exposure to produce vitamin D, and in the Northern Hemisphere, during the winter months, there is rarely enough sun to produce vitamin D. If you have dark skin and live in Alaska, for example, vitamin D deficiency is a concern that you should take more seriously than a light skin toned individual living in South America for example. In general however, very small amounts of sun exposure provide more than enough vitamin D production.

How much vitamin D does your skin produce?

In the summer, a lot. If you have fair skin, a few minutes with the skin exposed in the sun is more than sufficient. For people with darker skin, 10 to 15 minutes should be sufficient. This is an amount of sunlight that the overwhelming majority of people are incidentally exposed to in their daily lives.

Can I overdose on vitamin D if I sunbathe too long?

Vitamin D overdose is extremely rare, and overexposure to the sun cannot cause it. As vitamin D is produced in the skin, it quickly reaches an equilibrium where it is depleted as fast as it is produced once the body has produced sufficient vitamin D. We don’t recommend bathing in the sun too long however, as UV light is a major cause of skin cancer and premature aging.

Dogs don’t get skin cancer and all they do is bask in the sun. What gives?

Sadly, our best friends do in fact, get skin cancer just like humans, although it is not the leading cancer in dogs as their furs help protects their skin from direct sun exposure. As you might expect, skin cancer in dogs occur most commonly where their fur is short and sparse, like the nose, ears, or the belly as some dogs sunbathe belly up.

How do we balance vitamin D intake and proper sun safety to prevent skin cancer and premature aging?

The practical advice is to keep balance in mind. Most people will produce more than enough sunlight to produce adequate vitamin D through natural exposure. A few minutes a day of exposure is extremely common as most people do spend this much time outside with some part of their skin exposed. If you have several factors that predispose you to not receive adequate vitamin D, you may want to help supplement vitamin D intake via foods, supplements, and limited amounts of sun exposure without sunscreen. These factors include:

  • Living in the Northern Hemisphere (especially winter months)
  • Dark skin tone
  • Advanced age
  • Medical conditions that may limit vitamin D intake

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