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Why you DONT need a vitamin D calculator

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Your shadow can tell you when you are getting vitamin D from the sun, you don't need a calculator.

What’s the cheapest way to get your full recommended dose of vitamin D?  Sunlight, of course!  It’s no secret that vitamin D deficiency peaks during the winter, while vitamin D levels are highest during the summer.

Since nearly half of all Americans are vitamin D deficient, there is a good chance that you are one of them.  So, you may want to think about taking advantage of that free, natural source of vitamin D: the sun. 

The right type of light

Unfortunately, simply being out and about in the sunshine doesn’t guarantee you’ll get the right amount of vitamin D. This is evident in the fact that a high percentage of people from sunny states like Hawaii, California, and Florida are still vitamin D deficient!

To maximize the vitamin D your skin cells produce, sunlight needs to be hitting you at just the right angle.

Your skin cells use energy from ultraviolet (UV) light from the sun to produce vitamin D.  Much of the UV light emitted from the sun is absorbed by the ozone layer.  Therefore, the amount of ozone that sunlight travels through affects how much UV light reaches us at the earth’s surface.  A longer path through the atmosphere means more UV is absorbed by the ozone, and less is available to us.

Maximizing sunlight exposure for vitamin D synthesis

The angle at which sunlight hits you is key to determining if you are receiving enough UV light to facilitate vitamin D synthesis. Angles lower than 45 degrees mean that the sunlight has to pass through too much ozone for any UV light to reach the ground. Angles greater than 45 degrees mean that enough UV light has made it through to help your body produce vitamin D.

Several institutions have developed online calculators or apps to help you determine if the sun angle is right for vitamin D synthesis.  Examples include the vitamin D calculator from the Norwegian Institute for Air Research and the Sunshine Calendar from GrassrootsHealth.  They take into account where exactly you are in the world and which month of the year it is.

However, you don’t need a complicated calculator to know if the sun angle is right or not!  Think about what else is directly related to the angle of the sun: your shadow

If sunlight is hitting you at an angle of 45°, your shadow will be exactly as long as you are tall.  Say you are 5’4” tall;  when the sun is exactly halfway up from the horizon, hitting you at a 45-degree angle, your shadow will be exactly 5 feet and 4 inches long.

At lower angles, insufficient for vitamin D production, your shadow will be longer than your height.  Conversely, at angles greater than 45 degrees, when the sun appears higher in the sky, your shadow will be shorter than you, indicating optimal conditions for vitamin D production. You can shine a lamp on a ruler stood on end and measure its shadow to visualize how this works.

In today’s complicated world, we all wish living a healthy lifestyle was easy.  Fortunately, getting enough vitamin D to meet your body’s needs is as simple as it gets.  Just take a walk outside and check out your shadow.  A shadow shorter than you means you are good to go for free, natural vitamin D!