Your Sunshine Index

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By Mark Lundegren

Does the topic of the sun seem an unexpected one, or right just now?

As I write this, it is September and the autumnal equinox is fast approaching in the northern hemisphere.  The days are growing shorter and seasonal talk about sun exposure is waning with the cooling weather.  In some ways, this is exactly the reverse of what should happen.

Perhaps you live in a mid or higher latitude and when you read this, the days are shortening for you as well.  Or perhaps you were attracted to my title because the days are lengthening where you are, and both opportunities for life in the sun and sun exposure warnings are on the rise.  In either case, I would encourage you to seize your opportunities for sunlit life and to take your place in the sun-drenched natural world.  As I will explain, I advocate and our best science suggests a healthy respect for, but not a fear of, the ancient sun we evolved under.

On the other hand, instead of living amidst this rising and falling of the day, you may live in the tropics, in a lower latitude, where there is always strong sunlight.  You may live where it is almost always easy to be outdoors and to have a high “sunshine index,” as I will call our personal relationship to optimal sun exposure.  In the lower latitudes, as elsewhere, it of course easy to get too much sun and increase our sunshine exposure above its optimum.

Wherever we live and whatever the time of the year, especially since we are all now so accustomed to fear the sun, it is never ill-timed to have a discussion of sunlight and to consider what the optimal amount of sunlight might be more us and our health.  The truth is that all of us need to ensure we get enough sunlight to optimize our health, and that we spend enough time outdoors and especially in nature to optimize our well-being and quality of life in general.

Do we really need sunlight?  Our natural intuition, and the preponderance of our science, clearly tells us “yes.”  In fact, we need sunlight every day if we are to be healthy as humans, and we need more sun if we are in upper latitudes or if we have a darker skin color.  Is this statement contrary to popular thinking and media messaging?  Like so many aspects of our natural health and the many missed opportunities for more natural and satisfying life, it unfortunately is.

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Humans, and our pre-human ancestors, naturally evolved in and lived under the sun for millions of years.  This is settled science – we simply were not placed under the sun in a sudden way.  It is true that pre-human species lived in and around tropical forests, and no doubt had considerable natural sun protection from this way of life.  But as our lineage became more fully human, our life was increasingly in the open and under the sun, and our skin color became dark in an adaptation to a life of moving across hot tropical plains and coastal areas. 

As true modern human populations migrated out of Africa and across the world in the last 100,000 years, our skin color often changed (or rather, was selected) to optimize our health in higher latitudes – as some of our ancestors lived with less light and less strong light, and used clothing and shelters to protect us from the cold, further limiting our light exposure.  Lighter skin is more sensitive to the sun, in a good way (promoting healthy metabolism in less light) and a bad way (more quickly burning and susceptible to skin cancers in strong light).

Given our long history of life in the sun and our physical relationship to available sunlight, why is it that warnings about sun exposure strike us as sensible?  And why do recommendations to seek out the sun seem risky and controversial.  Do you equate the sun with pain and burning, or with luxuriant light?  Certainly, our ancestors sought shade, but against the backdrop of life generally in sunlight of various strengths.  By comparison, modern people often get much less sunlight than people in the past, even people in our settled past, potentially with great negative consequences for their health.

Though it might seem so based on popular thinking, it is no secret to scientists that sunlight is essential for a number of important physiological mechanisms in our bodies.  These range from the regulation of our hormones to the breakdown of metabolic wastes.  It is also no secret that we simply feel better when we get an optimal amount of sunlight, and such opportunities for feeling better are an essential part of being better and mastering the challenges and stresses of life on Earth.

While all this points to the critical nature of sunlight in our lives, I’ve actually even held back the newest and perhaps most important piece of science on sunlight: Vitamin D production.  Vitamin D is somewhat misnamed, since it is really a pre-hormone, one that is essential to a number of metabolic and immunological processes.  You probably know that strong sunlight causes our bodies to produce this vitamin, often in fairly prodigious quantities if we are light-skinned (about 10,000 units in 20 minutes for fair-skinned people, but much less than this amount if our skin color is darker). 

What you may not know is the new science surrounding Vitamin D.  It turns out that this vitamin is much more critical to our health and longevity than previously thought, perhaps most notably in our body’s defense against cancers and in the maintenance of a healthy skeleton.  You may also not be aware of the newer finding that we cannot get enough Vitamin D to be optimally healthy, except through adequate exposure to sunlight.  Forget about fortified milk and other foods, or pills and supplements.  These dietary sources provide only small amounts of Vitamin D, far less than is provided by natural sunlight exposure, and dietary Vitamin D ingestion in amounts greater than this can be toxic to us.

In other words, if you want to optimally healthy, you need to be thinking about the sun and your sunshine index in particular.  But how much sun is the optimal amount for you, for your latitude and skin type?  This is a very important question, especially since we are all now much longer lived than our natural ancestors, and both the benefits and risk of sunlight exposure are magnified by our longer lives. 

A simple but reliable answer to the question of optimal sunlight is “just enough and no more.”  Excessive sun can have negative effects (skin cancers, accelerated aging of the skin and eyes) for people of all skin colors, so we should get what we need for our health and then seek shade, put on protective clothing, or apply sunscreen.  In practice, optimal sun exposure ranges from 15-20 minutes of strong sunlight each day for very light-skinned people and 2-3 hours or more a day if we have dark skin.

The following points provide a quick summary to help you optimize your own sun exposure, adapted from “Revisiting The Sun,” an article in the HumanaNatura library providing more background the evolving science of sun exposure: 

  • The sun can cause skin cancer, including deadly melanomas, particularly in very light-skinned people who allow themselves to burn frequently over the course of their lives.  It is worth noting that non-melanomic skin cancers are usually treatable and unlikely to be fatal in developed countries.  Mortality from skin cancer in light-skinned people appears to be especially linked to frequent sunburns when we are young.
  • Modest sun exposure can dramatically increase circulating vitamin D in light-skinned, non-obese people, though more sunlight required to have the same impact in darker-skinned people.  Other sources of vitamin D (both foods and supplements) provide much lower levels of circulating vitamin D, when taken at non-toxic levels.  Without regular sun exposure, maintenance of high and optimal levels of circulating vitamin D appears impossible. 
  • People with high levels of circulating vitamin D appear significantly less likely to die of cancers of all forms than people with low levels of circulating vitamin D, on the order of 30 deaths prevented through sun exposure for each death from skin cancer linked to the sun.  This is a new scientific finding and really a remarkable ratio if it stands up to additional analysis over time.
  • Consensus is building that lighter-skinned people, who have evolved to produce Vitamin D more rapidly in sunlight, should be getting at least 15-20 minutes of direct sun (without sunscreen) on at least their face and arms several times a week.  This sunlight should be at midday during winter in upper latitudes and within a few hours of midday in the summer.  If we are at risk of burning with this amount of sun exposure, the consensus is that we should work up to this amount of sun gradually, taking care never to burn.
  • People with even medium-colored and especially darker skin types need progressively more sun to promote equivalent Vitamin D production and healthy metabolism, up to several hours of strong sunlight a day if our natural skin color is quite dark (with sunglasses or a hat for a majority of this time to prevent excessive sunlight to our eyes).
  • Because those of us with darker skin color are adapted to live in the tropics and lower latitudes, it is unclear at this point how darker-skinned people can reliably maintain adequate circulating vitamin D during the winter months in upper latitudes and this a reduced cancer risk throughout their lives.  While this may be difficult news, it is already well-established that African-Americans have higher cancer mortality than European-Americans in the northern United States, just as native Europeans have more cancer mortality in light-starved regions like Scandinavia than in the temperate parts of Europe. 
  • Vitamin “D3” supplementation may be a minimal, if imperfect, substitute for regular time under the tropical or subtropical sun for medium and darker complexioned people.  It is certainly worth a conversation with your physician if you have darker skin and live in an upper latitude.

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Are these conclusions surprising to you?  I suspect that some are, given widespread traditional thinking about the sun.  In the least, they a well-timed reminder of the importance of healthy sun exposure throughout the year – and the health standard of just enough sun and no more (or no less).

For now, I’ll leave you to consider your own optimal sunlight exposure.  To help you in this, it might be useful thinking of a scale ranging from 0 to 10, where 5 is your optimal sunlight exposure.  As we have discussed, your personal optimum will depend on your location and skin type, with more daily sun advisable the higher your latitude, the cloudier your location, and the darker your natural skin color.  Always, though, as we drive our sunshine index to an optimal score of five, we should take care never to burn our skin.

In whatever month, place, and phase the year you find yourself, I would encourage you to think about your own life in the sun and how it contributes to your short and long-term health.  For many people, this will mean more time outdoors, which I count as a good thing, as it will perhaps mean a simultaneous and more deliberate step into our natural health and a more natural life.

Mark Lundegren is the founder of HumanaNatura.

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