Welcome to Nutrition Bites. The no nonsense podcast where you get the truth about food so you can eat what you want and be healthy. I’m your host Maggie and welcome to the series! Summer is at our doorstep and everyone I know is so eager to finally bask in the sun. Apart from just generally feeling happier, sunshine also has a really important role to play in our health. On the menu today, Vitamin D.
I’m a summer person through and through. Call me Canadian, but there’s just something about walking outside without a jacket that gets me all giddy. And with the sun finally becoming a regular cast member in the daily show of our lives, I find myself trying to spend every spare moment outdoors. Saying hello to a friend? It better be outside. Business call? Let’s take that outside. Throwing out the garbage? Heck yes, let me step outside! Neighbors to the South may say it’s overkill, but I call it having PTSD from the death grip of winter. Now as excited as I am to soak up the sun this season, I also realize the damage caused by UV rays. For vanity-driven reasons, as well as for the fear of skin cancer, sunscreen is now part of my daily skincare routine. And while this helps to protect my skin from photodamage caused by the sun, it also happens to block the natural production of an important micronutrient - Vitamin D. It’s well known that Vitamin D is necessary to build and maintain strong bones, but over the past decade it’s also been given a reputation for being a panAcea of sorts - able to prevent cancer, fight depression and power our immune system. But is this cure-all hype actually deserved? And if so, what does that mean for those of us who are cooped up inside for half the year, and slathered in SPF the other half? Let’s dive in.
For starters, Vitamin D is not one single molecule - it’s actually a group of fat-soluble hormones. Its primary role in the body is to increase the absorption of calcium from the foods we eat. This in turn helps to mineralize our bones which improves their density and strength. But starting in the early 70s scientists began theorizing that Vitamin D could do more than just create a strong skeleton, in particular, it could help prevent colon cancer. This theory, which was based on observational studies, was further fueled by the discovery of the Vitamin D receptor - a protein that sits on the surface of a cell and connects with Vitamin D. More specifically, it lets Vitamin D enter a cell and interact with our DNA. Think of it like a lock and key scenario, where the lock opens a door that allows your genes to be worked on, in a good way that is. Research has found that Vitamin D turns specific genes on and off, in sort of a maintenance mode, to ensure that the things are running smoothly. And with Vitamin D receptor present on so many of our organs and tissues - from our brain, to heart, to pancreas, some doctors have nicknamed this micronutrient the “caretaker” of our body. And if you are deficient, or don’t have enough caretakers, some of this routine maintenance may be missed, and your health could be at risk.
Now considering the field of nutrition is all about how molecules in food affect our biology, it’s interesting that Vitamin D is not really common in our diet. The highest source is found in animal liver, especially from fish. Which is why parents from the 1800s up until the 1960s force fed their children spoonfuls of the infamously terrible cod liver oil. Other, less potent, dietary sources of Vitamin D include fatty fish, like salmon and mackerel, egg yolks, and mushrooms. But unless you regularly whip up a smoked salmon scramble for brekkie, most people don’t meet their Vitamin D quota through food. And this is one of the few cases in nutrition where it’s not a big deal because we actually make the vitamin on our own.
In the simplest of terms, we synthesize Vitamin D when our skin is exposed to sunshine. But in honour of our universal hero Bill Nye The Science Guy, let’s get a bit more detailed. Vitamin D synthesis is a really complex process involving multiple organs and a lot of difficult to pronounce molecules like 1,25-dihydroxycholecalciferol. So for the sake of my pronunciation skills, and your attention span, let’s park those fancy terms and instead talk about the journey taken to create Vitamin D. Always present in the layers of our skin is an inactive precursor molecule to Vitamin D - meaning it doesn’t do anything until it’s exposed to sunlight. Once it interacts with UVB rays in specific, it transforms into a substance called Vitamin D3. D3 then embarks on a lovely little journey to the liver where it gets transformed into a much-longer named molecule, even though Vitamin D4 was the obvious best choice. Anyways, this transformed molecule then makes its way to the kidneys where it is transformed again into the Vitamin D hormone. This is what we refer to as “active” Vitamin D - meaning it can bind to those Vitamin D receptors on our cells and do the maintenance work to keep our body healthy.
The primary source of these transformational UVB rays is the sun, but other artificial sources, like tanning beds, do exist. Although for the sake of our skin health I hope we’ve all graduated from the 2006 enthusiasm of a tanning salon. Exposure to sunlight seems like a pretty easy way to make Vitamin D, but in reality there are a lot of factors which impact the amount of sun we get. The most important one is where you live, specifically your latitude. The further you are positioned away from the Equator, the less sunlight that reaches you. Related to this is the weather and seasons. Cloudy skies can block UV rays, and Northern hemisphere winter and fall also equals less exposure. Time of day is another factor, with the UV rays being strongest between 10 am and 4 pm - when most people are at work indoor. And finally, air quality is an often forgotten element that also impacts sun exposure. The burning of fossil fuels release carbon particles in the air which can scatter and absorb UVB rays.
In addition to all those environmental factors there are also biological factors at play. The skin pigment melanin naturally protects skin by absorbing damaging UV rays, but this also means it absorbs the UVB rays necessary for Vitamin D synthesis. So people with higher concentrations of melanin need more exposure to sunlight in order to achieve their daily Vitamin D levels. Age is another factor to consider in the Vitamin D equation. The levels of the precursor molecule present in our skin decreases as we age, which means older adults may only make half as much Vitamin D compared to someone who is younger. The final contributor, or shall I say blocker, to Vitamin D synthesis is more of a lifestyle factor: sun protection. Whether you use sunscreen, which contains chemicals that absorb UV rays, or sunblock, which uses minerals to physically block exposure, or simply commit to a style of long sleeves and floppy hats - the result is still the same. Fewer UVB rays enter your skin.
Taken together, it’s easy to see that despite seeming like a simple process, the natural synthesis of Vitamin D can actually be quite difficult to achieve. In order to meet your daily Vitamin D quota, the general rule of thumb is that you need your entire back, or an equivalent surface area, exposed to the sun for 20 minutes under ideal conditions, 2-3 x per week. But for a lot of people this isn’t possible year-round, which is why we have a global deficiency. Some scientists estimate 1 billion people worldwide have insufficient levels of Vitamin D - including in hot and sunny climates like India and Australia. But it’s particularly bad in the Northern hemisphere where populations in Canada and Europe are thought to be up to 40% deficient.
Unfortunately, mild Vitamin D deficiencies can be really hard to spot. Symptoms are generic, like tiredness and hair loss. And If you just google reasons for fatigue, WebMD will tell you you have cancer, an iron deficiency, and should have actually passed away yesterday. Now historically, Vitamin D deficiency presented itself as rickets, a condition of weakened bones common in children. But this is a fairly rare condition today. Instead, lifelong Vitamin D deficiency now presents itself as skeletal issues in older adults, particularly, higher rates of osteoporosis and bone fractures. But this is old and boring news in the science world, with a direct cause and effect, and simple solution. And if you’ve seen any news articles with Vitamin D in the past few years, scientists aren’t hyped about bone health, but instead the association of Vitamin D with a bunch of other, more newsworthy, conditions.
Back in 2020 Vitamin D was making the rounds for its link with mental health, in particular how low levels allegedly trigger depression. And on a weekly basis, news articles are published that link Vitamin D deficiency with higher rates of various cancers. Of course you may also remember that during the midst of the COVID-19 pandemic headlines boldly stated that low levels of the micronutrient were also linked to severe outcomes of COVID infection. That last one really got people invested in Vitamin D. But unlike with most clickbaity nutrition news I cover, most of those Vitamin D claims do have some scientific support. Many of the associations are backed up by observational studies - a type of research where scientists simply observe individuals without any intervention. And when you think about how widespread Vitamin D receptors are in our body, it makes sense to think that this micronutrient, or lack thereof, could impact a wide variety of diseases and conditions.
The natural next step after an observational study is to conduct a clinical trial. You know, where scientists give sick people Vitamin D supplements and see what happens OR give healthy people supplements and see if they can avoid becoming sick. And this type of research is the Achilles heel of the Vitamin D hype train. From depression, to cancer, to COVID, no large-scale study has shown that supplementing people with Vitamin D prevents the disease or really improves outcomes once sick. Take for example, the largest ever clinical trial testing Vitamin D in cancer prevention, where researchers found zero protective effects of the supplement in over 25,000 people.
Now obviously this is pretty disappointing, but it also points to a greater issue we have in interpreting scientific studies. Observational research can only highlight associations, not prove cause and effect. Just because people hospitalized with severe COVID-19 also had a Vitamin D deficiency doesn’t mean that that deficiency caused their hospitalization. There are tons of other factors at play which may influence this correlation. For instance, people with a vitamin deficiency may have a less healthy diet overall, not visit the doctor for regular check-ups, or have a lower socioeconomic status. So while it’s important that we take note of these associations, we shouldn’t jump to conclusions about how one vitamin may cause, or cure, a complex condition. At the same time, when so many of us are deficient in Vitamin D, and we’re recommended to wear sunscreen to prevent skin cancer, it makes me wonder… should we be supplementing just in case?
In Episode 28 of the podcast, titled Eating for Immunity, I talked about how there isn’t much global consensus on daily Vitamin D supplementation. The FDA doesn’t have a recommendation, Health Canada only suggests it for older adults, and the UK only recommends it during the colder months. But some doctors strongly believe that a daily Vitamin D supplement, regardless of your age or the season, is a great way to keep your body in working order. It may not prevent COVID or decrease the likelihood of depression, but it will help to keep your immune system and brain healthy.
Now one issue with supplementing is in the choice of pill, drop or gummy to add to your daily routine. Both Vitamin D2 and D3 are common options at the pharmacy, but with a pretty significant difference. Vitamin D3 is sourced from animals, mainly fish, and is chemically similar to what we produce in our own bodies. The most common recommended adult dose I’ve seen is to take between 1000 and 3000 International Units (IUs) of D3 per day. Vitamin D2, on the other hand, is sourced from plants (which is perfect for vegetarians and vegans), but it’s also not treated the same in our body. D2 is shaped a little differently than what we’re used to, and because of that we need to take a higher dose - up to 10x the dosage of D3. Now what’s really important here is to not play Breaking Bad and mix these dosages up. Remember that Vitamin D is fat-soluble, which means that any excess not immediately used is stored in our fat. And If there is too much of a build up of Vitamin D in our fat, toxicity ensues and you can become pretty sick.
Alternatively if you really struggle with taking supplements, or remembering to take them every day, which is like, everyone, then another route to help increase your Vitamin D levels is through fortified foods and drinks. Wanting to tackle the wide-spread deficiency rates of Vitamin D, multiple countries, such as Canada, Finland and the US have national fortification policies that mandate adding the micronutrient to all milk products. And just this month, new legislation passed in Canada which allows additional Vitamin D fortification in plant-based beverages, like soy milk and oat milk. I got to say, it’s nice to see dusty food policy catering to the needs of the lactose-intolerant and plant-based crowds. Other countries, like Australia, Norway and Sweden, have similar, albeit less strict dairy fortification policies. And interestingly fortification remains a hot topic of debate in other Northern nations such as the UK and Denmark. So depending on where you live opting for fortified yogurt, margarine and oat milk may be a tasty strategy available to up your Vitamin D intake.
Whether you decide to consume fortified products, pop a daily D3 supplement, or soak up the sunshine - getting your daily dose of Vitamin D is important for overall health. It’s your body’s caretaker after all, and eerily similar to today’s workforce situation, without enough labour to keep things running smoothly, at lot of stuff can get messy. At the same time, I’d caution against viewing Vitamin D as a miracle micronutrient, and instead simply focus on ensuring you are not deficient in it to begin with. And while, I am not looking to obtain the reputation of Ms. Norbury in the Burn Book (that’s a Mean Girls deepcut), I’d personally recommend adding a Vitamin D supplement into your daily diet. It’s the easiest, safest, and sure-fire way to make sure you are meeting your needs. And huge plus, Vitamin D supplements often come in sugary gummy form, providing nostalgic excitement like the Flinstone’s vitamins of your youth. At least for me that is.
That’s been the bite for today. Stay hungry.