Skip to content

Our bodies are designed to get vitamin D through sun exposure

In this week's Ask the Nutritionist column, Nonie De Long explains the health benefits of vitamin D and nitric oxide
Stock photo

Dear Readers, this week’s question comes from a client who is in Canada from Africa for study purposes. He approached me because he suspects the difference in his exposure to sunlight here is impacting his mood and energy levels. 

As we all know, the sun is much less intense this far north of the equator and sunlight is our primary source of vitamin D. But did you know that supplementing does not do for us what natural sunlight does? This could be because sunlight is not only important for the vitamin D it stimulates. Red and near-infrared light are also parts of natural sunlight and they are equally valuable for optimal health. 

What is red and near infrared light and why is it important?

Red and near infrared light refer to a specific spectrum of light from 600nm to 700nm (red) and 700nm to 1,100nm (near-infrared). The 600 to 700nm spectrum is visible to our eyes as red light. The 700nm and up spectrum is not visible to our eyes but has a special ability to penetrate our body more deeply than other spectrums of light. Some wavelengths of this light have been more studied than others, especially the 630 to 680nm and 800 to 880nm for their therapeutic benefits.

There have been thousands of studies on red and near-infrared light therapy (photomodulation) over the past 20 years. The studies show benefit for many health issues from aging to athletic performance to injury recovery to immunity. More specifically, there has been significant benefit shown for Hashimoto's disease, Alzheimer’s disease, and Parkinson’s disease. You can read more about the benefits of red and near-infrared light here.

We also know exposure to sunlight, including red and near infrared light, increases the release of nitric oxide (NO) which is extremely beneficial for health. To better understand the role of NO, go here

What about melanoma?

It’s a myth that regular, judicious exposure to sunlight increases the risk of melanoma. 

“There's a bunch of studies comparing outdoor workers to indoor workers, showing that outdoor workers have lower rates of melanoma despite three to nine times more sun exposure." Ari Whitten, author of The Ultimate Guide to Red Light Therapy.

Whitten goes on to explain that how often we’re exposed to sunlight mitigates - or increases - our risks of developing skin cancers from it. When we’re exposed occasionally, we get higher risk than when we are exposed routinely. This is because of melanin in the skin that helps the skin adapt to protect from DNA damage with UV light exposure. 

He suggests we view light as a nutrient because it’s actually necessary for normal cellular function. Our bodies are programmed to have evolved with regular exposure to natural sunlight function properly. 

Blue light and sleep

There are a variety of wavelengths in sunlight. Blue and green wavelengths are also important. They enter through our retinas and travel through our nerves to signal our brains that it is daylight and time to wake. This in turn regulates our sleep/ wake cycles. When we are exposed to blue light disproportionately at night, when we should be exposed to red, our internal clock (circadian rhythm) gets disrupted. This has a lot to do with sleep disorders and lack of energy during the day. Almost all our electronic devices and interior lights emit blue lights into our eyes during the time of day when our eyes actually need dimmer, red spectrum light to signal that it’s time to sleep. 

And this, in turn, has profound impacts on all the hormones in our bodies. 

What about vitamin D?

Well, for starters, it’s technically not even a vitamin. And it’s not singular. It’s a group of hormone precursors, very similar in structure to steroid molecules. As many readers may already know, the most important players in this group (as we currently understand it) are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).

Vitamin D3 is so essential for our health that we have a built in mechanism to ensure we get enough, irrespective of dietary intake. It’s actually manufactured by our bodies when our skin is exposed to UVB rays from the sun. This synthesis requires our own cholesterol and activation by our liver and kidneys. It’s unique among vitamins, not only because we generate it from the sun, but also because almost every cell in our bodies has a vitamin D receptor, which has the ability to impact the expression of our genes. This is science we are just starting to understand, but it indicates this little secosteroid is essential in a way no other nutrient is. 

Animal foods are the best source of vitamin D3, but dietary consumption alone is not enough to reach optimal levels. It’s present in certain fish, fish oils, liver, and quality egg yolks, quality butter, and - dare I speak it - raw, whole fat milk from gras- fed cattle. I mention this because raw milk contains every known fat and water soluble vitamin, all 18 fatty acids, and multiple enzymes and probiotics to aid digestion - all of which are almost completely destroyed by pasteurization. But selling raw milk is illegal in Canada, so let’s do forget I said that and keep moving along. 

We can get vitamin D2 from mushrooms that have been exposed to UV rays, fortified foods, and lower quality supplements. But it’s not the desired form of this hormone group for therapeutic value. You can check the label of your dairy and baby formula products to see which form of vitamin D they contain, and then take that with a grain of salt. According to this study published in the New England Journal of Medicine, we don’t really know how much vitamin D - or which form - is being added to our fortified products. Note that most of the infant formula tested contained 200x or more vitamin D than was on the label. With fortified foods it’s hard to know what exactly you’re getting.

What does vitamin D do?

Vitamin D is best known for its role in bone and dental health. Without adequate vitamin D children can develop rickets, and adults are at risk of premature bone ageing and resulting fractures, as adequate vitamin D is needed for calcium, phosphate, and magnesium absorption and regulation. These play a direct role in bone growth and density, as well as neuromuscular function, immunity, and inflammation. Additionally, vitamin D helps regulate hormones and has a positive impact on mood, concentration, learning, and memory

Vitamin D also helps keep abnormal cells from multiplying in breast and colon tissues. Isn’t it interesting how these cancers have proliferated since the campaign to push sunscreen? Vitamin D synthesis can’t happen in the presence of sunscreens with SPF 15 or higher. There is additional data to support that vitamin D deficiency increases our overall risk of cancer and our risk of melanoma, the deadliest type of skin cancer. Low vitamin D levels are associated with a number of serious diseases:

“A growing number of studies point to vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease (PAD), strokes, and the conditions associated with cardiovascular disease, such as high blood pressure and diabetes,” according to John Hopkins Heart and Vascular Institute

How much do we need?

The Canadian government Dietary Reference Intake for vitamin D is between 600-800IU on the low end to 4000IU on the high end for adults. But serum 25-hydroxy-vitamin-D testing is still the best way to know your vitamin D status. The upper end of the optimal range is 50nmol/L. <30nmol/L means you’re suboptimal and between those two you may need to supplement accordingly. To give you an idea of safety, levels >125nmol/L are considered a possible reason for concern. 

Certain populations are known to be more likely to be deficient in vitamin D and should be supplementing with the guidance of a professional and annual testing to determine blood levels. At risk populations include:

  • those over 65 - older skin often doesn’t produce as much vitamin D as it used to
  • those with darker skin tones - it takes more sun to synthesize the same amount of vitamin D in darker skin
  • those who work indoors, wear sunscreen all the time, or cover much of their skin when outside
  • those who live in places where the sun’s rays are weaker and/or they don’t get as much exposure to the sun for good parts of the year
  • those who have a gastrointestinal condition like Crohn’s disease or celiac disease or who have bile issues (both important for vitamin D synthesis and uptake)
  • those who are vegetarian or vegan (animal products are the best sources of the active form of vitamin D if they don’t get enough sun exposure or supplement)
  • those who have severe kidney disease (the kidneys have to convert it to the active form)
  • those who have to avoid the sunlight for other medical reasons
  • those who do shift work

It’s estimated that in the U.S. up to 90 per cent of those with darker skin tones and 75 per cent of those with lighter skin are deficient in this key hormone, so in Canada we are likely to be even more deficient, due to our latitude and cold winters.

Are there any safety concerns?

Yes. Fat soluble supplements are stored in the tissues so they build up over time. As such, toxicity can develop and it’s best to stay below the safe upper limit and have your physician test your levels annually as part of your check up. 

How do I best get it? 

It’s almost always best to get vitamin D from sunlight - as we were designed to. Research on supplementing with vitamin D has not demonstrated the same protective benefits as we theorize that it should. It may be possible that supplementing does not do what sunlight does for us, especially if the other wavelengths are necessary for activating or working synergistically with vitamin D. There could be unrecognized cofactors we need for optimal conversion and utilization. In addition sunlight has many other benefits for our health, as the research on red and near-infrared light shows. 

My preference when I do advise clients to supplement is to use quality, sustainable cod liver oil (CLO) as this is a whole food supplement with vitamins A and D in the proper ratios (4-8x the A to D), as well as EPA and DHA omega 3s for maximal benefit. It’s theorized that this A:D ratio helps protect against vitamin D toxicity. Add a daily dose of vitamin K2 in the form of Emu oil or natto and you have done more to protect your bones and hormones than anything else you can do. 

I also recommend time outdoors as much as possible, with unfiltered year-round exposure to natural sunlight, including at sunset and sunrise, when the red spectrum is strongest.

As always, if readers have a health or nutrition-related question, I welcome you to write to me at [email protected]. And if you’re looking for more specific health information check out my website at, where you can contact me directly. I provide 1:1 health coaching, family health plans, and a variety of webinars online to help people better manage their health holistically. Happy Thanksgiving!

Nonie Nutritionista