Spring is here, and with it comes some seemingly never-ending rain. So, on this rainy day I thought I would talk about the sunshine vitamin ☀, vitamin D! Let me first tell you a story about how my brain works (or doesn't work) in a sleep-deprived state. Don't worry, it's related to vitamin D and hopefully will help you to remember all of the exciting information to follow!
All throughout naturopathic medical school I was chronically sleep deprived. I regularly stayed awake well past midnight studying and was up to attend every 8am lecture, lab, or clinic shift of my 30+ credit-hour week. Now any parent who has stayed awake with sleepless children for months-years can tell you that sleep deprivation has real effects, and one of these effects is that it can cloud your thinking (among many other things, but that is a topic for another post.) So one day I found myself battling involuntary sleep during a nutrition lecture about vitamin D. Through the fog of half-sleep I heard the professor talking about the natural production of vitamin D in our skin from the sun's UVB rays. I heard her say that a fair skinned individual can make all the vitamin D that he or she needs in a day (about 10,000-20,000 IU of naturally produced vitamin D) in about 15 minutes if he or she exposes enough skin to direct sunlight of the proper strength. She offered a general rule - "If your shadow is longer than you are tall, you are not making enough vitamin D."
My head snapped up. What? I looked at her to see if she was joking, surely she did not expect us to believe that the length of your shadow could change based on your vitamin D status.... But she was continuing on straight-faced. Apparently she was serious. I glanced around the room at my peers - surely someone else was shocked that she was boldly making outrageous claims like this in class. But everyone else was diligently taking notes, on their phone, or sleeping. They were totally casual, as if what she said made absolute sense. I repeated her words in my head.... and finally the light dawned. Then I just had to use all my willpower to prevent laughing out loud at myself in class.
Of course what she meant was that our ability to produce vitamin D from the sun's rays is very efficient around noon in direct sunlight. And when the sun is high overhead, our shadow appears relatively short on the ground. However, earlier and later in the day as the sun is rising or setting the angle of the sun changes and the UVB rays become weaker. At this time our vitamin D production greatly declines...and our shadow also appears much longer. Therefore, if you are spending 15 minutes outside when your shadow is longer than you are tall, you are not making nearly as much vitamin D as you would around noon when your shadow is very short.
After that I was jolted awake enough to remember the rest of lecture with ease. And I think the shock of that outrageous claim has made the information about vitamin D stick in my clinical brain. I learned that vitamin D is so important in preventing so many illnesses and I have always remembered to consider vitamin D status in my patients.
You might be surprised to learn, as I was, that vitamin D isn't really a vitamin at all! In fact, it is a steroid hormone that is crucial to many biological processes. Vitamin D deficiency has been linked to:
- Heart disease - especially atherosclerosis and stroke risk
- Cancer risk - including breast, prostate, skin, and colon cancer
- Chronic pain
- Asthma and allergies
- Risk of infection
- Autoimmune diseases
- Diabetes mellitus
- Dementia and Alzheimer's Disease
If you are like me, perhaps you used to think that vitamin D was mainly important for bone health. The truth is, we have vitamin D receptors in nearly every tissue and cell type in our body! We have vitamin D receptors on our immune cells, like macrophages and T cells, on our heart cells, brain cells, and even fat cells. It plays a role in more vital processes than many of us realize. For example, vitamin D deficiency is more closely linked to developing diabetes than is obesity or BMI.
Given the pervasive role vitamin D plays in the functioning of our organs, tissues, and cells, the equally pervasive nature of vitamin D deficiency is somewhat alarming. A 2011 study found that over 40% of adults tested in the United States were deficient in Vitamin D!! A second study found that 61% of US children had deficient or insufficient Vitamin D levels! The following hopefully answers some questions you might have by now:
Vitamin D FAQs:
- Can I get enough Vitamin D from the sun and food? Based on the above studies, most likely you cannot get sufficient Vitamin D just from the sun and fortified foods! In order to make enough Vitamin D you need to spend 10-20 minutes in the mid-day sun with roughly 80% of your skin exposed (this is for lighter skinned individuals, for darker skin tones you need to spend longer, about half the amount of time it takes for your skin to burn. This could be a long time!) This may be possible some or most days of the week during the summer months, however for a large portion of the year this is not feasible!
- What form of Vitamin D is best to take? Cholecalciferol, or Vitamin D3 is the best form of Vitamin D for supplementation. Some foods and supplements are fortified with Vitamin D2, also known as ergocalciferol, which is not as effective for raising or maintaining Vitamin D levels as D3 is. Read all labels and choose options with cholecalciferol or Vitamin D3.
- What other factors affect my Vitamin D status? Vitamin D from sun, food, and supplements must undergo two conversions in the body - one by the liver and the second by the kidney. Therefore, if you have liver or kidney disease, or if these organs are not functioning optimally, it may effect your vitamin D status.
- Does this mean I should just start taking Vitamin D supplementation? Not necessarily!! It is possible to take too much Vitamin D - especially if you supplement for a long time. Overdoses can lead to heart palpitations, nausea, vomiting, confusion, and muscle weakness. Before beginning Vitamin D supplementation you should have your blood levels tested and you should repeat the testing every 8 weeks until you reach an optimal level (as determined by your physician) at which point you should establish a maintenance dose.
- Is Vitamin D supplementation appropriate for pregnant women? Yes! All women should have their Vitamin D levels tested, not only for themselves but also for the health of their fetus. A recent study found that as a woman's Vitamin D levels increased during pregnancy, the risk of her child being diagnosed with ADHD later in childhood decreased.
- Is Vitamin D supplementation appropriate for infants and young children? Yes, studies have shown that vitamin D supplementation in infants may help to prevent autoimmune diseases like Type 1 diabetes, and it decreases the likelihood of developing asthma and allergies. But ALWAYS consult your physician first before giving any supplements, vitamins, or medications to infants or young children.
- Is it enough to supplement with just Vitamin D if I am deficient? The answer is maybe. Your physician should thoroughly examine your diet and risk factors because most likely you will also need to balance your calcium, magnesium, and vitamin K levels as well.
Consider getting your vitamin D levels tests at your next appointment if you 1) haven't ever been tested 2) haven't had them tested since beginning supplementation with vitamin D or 3) haven't been tested in over a year. And get out and enjoy some sun, but remember the shadow rule! If your shadow is longer than you are tall, you aren't making enough vitamin D!