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The XALI Vitamin D Handbook

In our article on how to find skin and reef friendly sunscreen, we briefly mentioned how it's necessary for vitamin D production that UVB rays graze your skin directly and aren't being blocked by a mineral or chemical barrier.

But I have to put on sunscreen every day to protect my skin from burning, skin cancer and wrinkles!

Well, yes, it's recommended to protect yourself if you're going to spend long chunks of time outdoors. But it's actually also medically recommended to catch some minutes of sunshine daily while unprotected, so your body can get going with vitamin D synthesis.

But many of us aren't getting enough of that unprotected sunshine time and are vitamin D deficient. Numbers go from about 20% of the population in India, Tunisia, Pakistan, and Afghanistan to Australia with 23%, while roughly 40% of Europeans don't get enough of it. The same is suggested for the United States with a little over 40%, but it's been found that in Hispanic adults the number of vitamin D deficient people rises up to 69%, in African American adults even up to 82%!

Why do we need vitamin D?

Vitamin D mainly helps the body absorb and retain calcium and phosphorus. Both are important for building bones and keeping them healthy. Because many of the body's organs and tissues have receptors for vitamin D, research is continually investigating other possible functions and benefits.

So far it's been suggested that there are many protective benefits of having sufficient vitamin D, such as decreased risk of developing:

  • cancer

  • heart disease

  • hypertension

  • type 2 diabetes

  • depression

  • cognitive impairment related to ageing

  • Parkinson's disease

  • osteopenia and osteoporosis

  • and age related macular regeneration (this article explains the mechanisms behind all of these)

It may also protect from falling ill with influenza and generally contribute to controlling infections and reducing inflammation. Vitamin D deficiency causes a decrease in the absorption of dietary calcium and phosphorus and will eventually result in a mineralization defect in the skeleton, osteopenia and osteoporosis (bones become weak and brittle).

Photo by Jernej Graj on Unsplash.

Okay, got it. Why aren't we getting enough?

  • Indoor lifestyle: many of us spend the biggest chunks of our time at home, in an office, plan leisurely activities in bars, restaurants, movie theaters, concert venues, etc.

  • Sunblock: most of us will apply sun screen or cover our skin with clothing when we do get outside, preventing us from generating vitamin D.

  • Skin color: Because the pigment melanin acts similar to a sunscreen, the darker your skin, the lower its ability to produce vitamin D.

  • Location: depending on where you live, there are only enough UVB rays triggering vitamin D production between 9am and 3pm in mid summer. The farther away from the equator you move, the shorter the time frame for vitamin D production. The farther away you move from mid summer, the shorter the time frame for vitamin D production. Depending on where you live, there are 3-6 full months per year where you can't naturally synthesize vitamin D, but vitamin D deposits in the body usually only last for 3 months (if they were properly stored during summer). For example, if you live in central Europe, from September until end of March you can't obtain vitamin D naturally. If your deposit is full, it would still make sense to supplement from mid-December until end of March. Speak to your GP about this so they can recommend a dose and supplement specifically for your needs.

  • Rare in foods: Absorbing vitamin D from foods is difficult as well, because only few contain it and the doses aren't very high. Main sources are cod liver oil, salmon, swordfish, tuna fish, orange juice fortified with vitamin D, dairy and plant milks fortified with vitamin D, sardines, beef liver, egg yolk and fortified cereals.

  • Medical problems: because vitamin D is fat soluble, patients with fat malabsorption syndrome are often unable to absorb it. Patients on a wide variety of medications are at risk of vitamin D deficiency as well. People who are obese typically need to supplement vitamin D and need higher doses to achieve the levels comparable to those within a normal weight range, because greater amounts of subcutaneous fat captivate more of the vitamin and alter its release into the circulation.

Photo by Leohoho Unsplash.
  • Ageing: In older individuals, 7-dehydrocholesterol levels are decreased (this is the "pre-vitamin D" that reacts with the UVB rays to synthesize vitamin D). They're also more likely to spend a lot of time indoors.

  • Raising a child vegan: one of the first studies how raising children on a vegan diet affects metabolism found that the vegan children's vitamin D levels were significantly lower compared to children without a special diet. The vegan children in the study received regular, medically informed vitamin D supplementation, but their levels were lower despite of that. Because this is a first and very recent finding however, more research needs to be done. We just wanted to include it because it may be of big interest.

  • Unhealthy gut microbiome: a very recent study suggests that people who have an unhealthy gut microbiome may not be able to metabolize the inactive precursor of vitamin D that's stored in the body into active vitamin D. So they may be missing out on the important protective benefits of vitamin D, despite having a full storage. Chronic use of medication can alter gut microbiome. A diet of highly processed foods containing additives and high in unhealthy fats is associated with disturbing your gut microbiome as well. Not only does an unhealthy gut microbiome affect your ability to metabolize vitamin D, there's also a link between unhealthy gut microbiome and developing depression:

The human microbiome consists of trillions of microorganisms, many of which reside in the intestinal tract. These microbiota are essential for normal physiological functioning. However, research has suggested that alterations in the microbiome may underlie the host's susceptibility to illness, including neuropsychiatric impairment.

There are many reasons for trying to eat more unprocessed or barely processed, fresh foods. Helping keep your gut microbiome healthy or restore it's health is one of them.

Wow, mind blown! So how can I make sure I get enough natural vitamin D in a safe way?

The first thing you can do is search the web to figure out which months of the year you can be exposed to enough UVB rays to trigger vitamin D production. If that's possible all year long, then you may be able to get enough vitamin D from natural sources. If vitamin D synthesis from sunlight isn't possible for 3 months or longer, talk you your GP about supplementing.

Around noon there's more occurrence of UVB rays, so try to catch your daily dose of sunshine then. A relaxing post lunch stroll or finding a nice bench in the park can help you do that. Pro-tip: if you're self employed or working from home, you can also do some work that requires less focus outside in the park.

The more skin you expose, the more vitamin D you can produce. You may want to protect your face with a hat, but make sure your arms are fully exposed and if possible, your legs as well. Even better, sport your XALI swim and lie down with a nice book. Because the angle with which the sun hits your skin matters as well! We can produce more vitamin D lying down than sitting and standing.

Thanks to @theamberage and @cherri_polcat for this beautiful photo!

If your skin isn't used to unprotected time in the sunshine, start with very short exposure and gradually increase it in baby steps day after day until you hit your recommended time. To find out how long you can stay in the sun unprotected, talk to your GP. As a rule of thumb: 5-10min of daily exposure are enough, if:

  • you have very light skin

  • are young

  • aren't obese

  • it's summer

  • it's in the middle of the day

  • you have lots of skin exposed to the sun

  • are lying down

  • aren't wearing sunscreen

  • have a healthy liver

  • there aren't any clouds or air pollution

  • and have a very good response to sunshine

After you've reached you recommended daily time of unprotected sun exposure, make sure you use sunscreen or cover up if you plan to stay outside longer.

Want more articles like that?

We hope this little XALI vitamin D Handbook can help you understand the importance of sun exposure better and helps you catching those rays in a safe way. We were really blown away by some of the information we figured out during the research process. We'd love to know if you're interested in reading more health related articles, please let us know! This helps us make our blog as informative and helpful as possible.

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