There is no better time to become aware of the importance of Sun light to our lives. Now that the Winter Solstice has passed, we in the Northern Hemisphere are leaning more and more towards the Sun. This life-giving star of our Solar System gives us our light, gives us our warmth, and feeds all living beings. It’s no wonder that our ancestors carefully watched and worshiped the Sun! Science too shows us the importance of the Sun to maintain our health with Vitamin D.
Roles of Vitamin D
Our individual bodies can use the sun’s light to create Vitamin D. It’s now considered more of a steroid hormone in its actions within our metabolism than a vitamin. Vitamin D has multiple roles in the body, helping to:
- Maintain the health of bones and teeth
- Support the health of the immune system, brain and nervous system
- Regulate insulin levels and aid diabetes management
- Support lung function and cardiovascular health
- Influence the expression of genes involved in cancer development.
The Alchemy of Sun light into Vitamin D
Sunlight converts cholesterol on the skin into calciol (vitamin D3). The liver then converts Vitamin D3 into calcidiol. The kidneys then convert calcidiol into the active form of vitamin D, called calcitriol. As such, statins and other medications or supplements that inhibit cholesterol synthesis, liver function or kidney function may impair the synthesis of Vitamin D. Diseases of these organs also inhibit it.
Blocks to Vitamin D from the Sun
Scientists who study this process tell us that to absorb and convert into Vitamin D we need to allow sunlight to touch our skin. The cholesterol on our skin may be lacking if we just bathed.
Sunscreen may also inhibits this process. But as a practical matter, very few people put on enough sunscreen to block all UVB light, or they use sunscreen irregularly, so sunscreen’s effects on our Vitamin D levels might not be that important. An Australian study that’s often cited showed no difference in Vitamin D between adults randomly assigned to use sunscreen one summer and those assigned a placebo cream.
Unfortunately, studies have also shown that being obese is correlated with low vitamin D levels and that being overweight may affect the bioavailability of vitamin D. Since Vitamin D is so intertwined with health, this may be a contributing factor to the worse health outcomes related to excess weight.
Theoretically, age may be a factor. Older people have lower levels of the substance in the skin that UVB light converts into the vitamin D precursor, and there’s experimental evidence that older people are less efficient vitamin D producers than younger people. Yet the National Center for Health Statistics data on vitamin D levels don’t show a major drop-off in levels between middle-aged people and older folks.
Another factor is the latitude and season of the year. When our hemisphere is tipped away from the Sun, the rays are not as potent for creating Vitamin D. The further from the equator we are, the less the Sun will feed our Vitamin D in the winter season. In Boston, for example, little if any of the vitamin is produced in people’s skin tissue from November through February.
Interestingly, warm skin is a more efficient producer of vitamin D than cool skin. So, on a sunny, hot summer day, you’ll make more vitamin D than on a cool one.
Don’t worry if you live in a cloudy place – the UVB radiation, which can also cause sunburn, is still there to create Vitamin D3. However air pollution is a factor. Carbon particulates in the air from the burning of fossil fuels, wood, and other materials scatter and absorb UVB rays.
To maintain healthy blood levels, aim to get 10–30 minutes of midday sunlight, several times per week. This is if you’re wearing shorts and tank top with no sunscreen. People with darker skin may need a little more than this. Your exposure time should depend on how sensitive your skin is to sunlight. A fair skinned person in summer dress will get about 10,000 IU Vit D from 10 minutes exposure.
Maintain Your Vitamin D Level
Winter is another story. Studies consistently show that vitamin D status drops during the winter, with levels peaking in September and at their lowest in March. So for some people at least part of the year, it may be important to rely on dietary sources of vitamin D or supplements. Being covered and having cold skin, along with being tipped away from the sun all contribute.
Good digestion, as always is important when vitamin D that is consumed in food or as a supplement. It is absorbed in the part of the small intestine immediately downstream from the stomach. Stomach juices, pancreatic secretions, bile from the liver, the integrity of the wall of the intestine — they all have some influence on how much of the vitamin is absorbed. Therefore, conditions that affect the gut and digestion, like celiac disease, chronic pancreatitis, Crohn’s disease, and cystic fibrosis, can reduce vitamin D absorption.
Levels also drop if you are confined indoors. One study on Vitamin D levels of hospital patients showed that however high their Vitamin D was on entering the hospital, it was down to one half of that level within just 24-48 hours. This is concerning since immunity and healing are both greatly effected by Vitamin D.
Vitamin D is so important to our health, even helping protect us from serious COVID. Be sure you have healthy levels through lab tests in September to see your peak amount for the year. Inexpensive supplements are also highly effective, when needed to maintain healthy levels. A meta-analysis published in 2007 showed that vitamin D supplementation was associated with significantly reduced mortality.
Do embrace the Sun light – finding your healthy balance.