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Vitamin D: Is the Sun Ghosting You?

  • Writer: Emanuele Bortolotto
    Emanuele Bortolotto
  • Jul 16
  • 8 min read

Updated: Sep 8

Finnish winter is always challeanging. The sun, a distant and unreliable acquaintance at the best of time, clockes out of its shift at about 3:30 every afternoon and shows no intention of returning for the next seventeen hours. The sky is a thick, impenetrable blanket of what I can only describe as "damp grey." It’s a time of year that inspires profound, philosophical questions, such as "Do I exist if I can't see my own hands?" and "Is it possible to photosynthesize sadness?"


This seasonal gloom got me thinking about a nutrient that is intimately, and tragically, tied to the whims of our solar system. I’m talking, of course, about Vitamin D. It’s the forgotten vitamin, the one that doesn’t get the flashy headlines of Vitamin C or the controversial press of B12. It’s the quiet, moody goth kid of the nutritional world. 🦇

But in my investigations into the vegan lifestyle, I’ve found that this vitamin is the subject of a huge amount of confusion and anxiety. Is it a vitamin or a hormone? Can you get it from the sun, or is the sun just an elaborate celestial hoax? And do you really have to drink milk from a cow to get it? Today, I’m launching a full-scale investigation into the dark, mysterious, and surprisingly crucial world of Vitamin D.


The Great Deception: It's Not a Vitamin, Is It?


The first thing I discovered in my investigation is that Vitamin D is a liar. It’s not really a vitamin at all. A "vitamin" is, by definition, an essential nutrient that your body cannot produce on its own and must get from food. But Vitamin D is different. Your body can produce it. It’s technically a prohormone, which is a fancy way of saying it’s the raw material that your body uses to create a powerful steroid hormone called calcitriol.

This hormone is, in essence, the moody but indispensable maintenance guy for the entire castle that is your body. His job description is terrifyingly important.


  • Calcium Management: This is his most famous job. Vitamin D is in charge of calcium absorption in your gut. Without him, you could eat a mountain of calcium-rich kale, but your body wouldn't be able to unlock the door and let the calcium in. He is the bouncer for your bones.

  • Immune System Regulation: He has a profound effect on your immune cells, helping them to mature and fight off invaders. A deficiency is linked to a higher risk of infections and autoimmune diseases.

  • Mood & Brain Function: Your brain is full of Vitamin D receptors. He plays a key role in regulating mood, which is why his absence in the winter is strongly linked to Seasonal Affective Disorder (SAD), a condition that makes you feel like a deflated human puddle. 😥

  • Muscle Function: He’s also crucial for maintaining muscle strength.


So, this is not a minor player. This is a backstage superstar who is secretly running half the show.



The Two Brothers: D2 vs. D3


My investigation revealed that Vitamin D is not a monolith. It has two sons, two main forms that we get from the outside world. And they are not created equal.


D2 (Ergocalciferol): The Plant-Based, Less Impressive Brother


  • Who he is: Vitamin D2 is the form of the vitamin that is produced by plants and fungi when they are exposed to UV light.

  • Where you find him: The main natural source is mushrooms that have been intentionally zapped with UV light. 🍄 He’s also the form that is often used to fortify foods like orange juice and some plant milks.

  • The Verdict: D2 is absolutely vegan. And it does work. It can raise the Vitamin D levels in your blood. However, my research shows that most studies have found it to be significantly less effective than his more famous brother. Your body finds it harder to metabolize, and its effects don't last as long. He’s the reliable but slightly disappointing opening act.


D3 (Cholecalciferol): The Animal-Based (Usually) Superstar


  • Who he is: This is the same form of Vitamin D that your own skin produces when it’s exposed to sunlight. It’s also the form found in animals.

  • Where you find him: The main dietary sources are fatty fish (like salmon and mackerel), cod liver oil, and egg yolks. For many years, the only way to get a D3 supplement was from lanolin, a waxy substance extracted from sheep’s wool. You get lanolin by boiling the wool of a sheared sheep. So, traditional D3 supplements are essentially the boiled-down grease of a sheep. 🐑 This is, obviously, not vegan.

  • The Verdict: D3 is the undisputed champion. Study after study has shown that it is far more effective at raising and maintaining the levels of Vitamin D in your blood than D2. It is the rock star of the family.


Now, for years, this put vegans in a difficult position. They had to choose between the less effective but definitely vegan D2, or the more effective but definitely not vegan D3. But this is where the story takes a wonderful, mossy turn. In recent years, scientists have figured out how to extract a 100% vegan, bio-identical D3 from lichen, a strange and beautiful composite organism that is a symbiotic partnership between a fungus and an alga. This vegan D3 from lichen is just as effective as the animal-derived version. It is a true game changer.


The Great Sunlight Swindle: Why You're Probably Not Getting Enough Sun ☀️


"But I don't need a supplement," the hopeful person says, "I get all my Vitamin D from the sun!" This is a beautiful thought. It is also, for most people on Earth, a complete fantasy. My investigation into the science of sun exposure revealed a long and frankly quite depressing list of reasons why you are probably not getting enough.


  • The Geographical Prison: The single biggest factor is your latitude. The UVB rays that are needed to produce Vitamin D can only penetrate the Earth's atmosphere when the sun is at an angle greater than about 45 degrees. If you live anywhere north of the 37th parallel (a line that runs roughly through San Francisco, Athens, and Beijing), the sun is too low in the sky for the entire winter (roughly November to March) for you to produce any Vitamin D at all. None. Zero. It doesn't matter how sunny it is.

  • The Melanin Factor: Melanin, the pigment that gives skin its color, is a natural sunblock. People with darker skin tones require significantly more sun exposure—sometimes 3 to 5 times as much—to produce the same amount of Vitamin D as a person with fair skin.

  • The Sunscreen Shield: Sunscreen is a modern miracle that protects us from skin cancer. It is also, by design, incredibly effective at blocking the UVB rays that produce Vitamin D. An SPF of 30 can reduce Vitamin D synthesis in the skin by more than 95%.

  • The Indoor Prison: Most of us live our lives indoors. We work in offices, we exercise in gyms, we commute in cars and trains. We are a species of cave-dwellers who have forgotten we are solar-powered.

  • The Age Factor: As we age, our skin becomes less efficient at producing Vitamin D. An elderly person produces about four times less Vitamin D than a young person from the same amount of sun exposure.

So, unless you are a young, fair-skinned, nudist who lives in the tropics and has a deep philosophical objection to sunscreen, you are almost certainly not getting enough Vitamin D from the sun.


Questions from the Internet: "What are the actual symptoms of a Vitamin D deficiency?"


This is a great question, because a deficiency is the ninja of the nutrient world. 🥷 It’s very sneaky. The symptoms are often vague and can be easily blamed on other things, like "stress" or "not getting enough sleep" or "the general crushing weight of existence." My investigation shows the most common symptoms include:

  • Chronic Fatigue and Tiredness: This is the number one sign. A deep, persistent, bone-weary fatigue that sleep doesn't seem to fix.

  • Bone and Back Pain: A dull, aching pain in your bones, particularly your lower back, can be a sign that your body is struggling to maintain its calcium levels.

  • Depression or Low Mood: As we discussed, this is the classic symptom of Seasonal Affective Disorder.

  • Getting Sick All the Time: If you seem to catch every cold, flu, and plague that comes to town, it could be a sign that your immune system is compromised by low Vitamin D.

  • Slow Wound Healing:

  • Hair Loss

If this list reads like your personal biography for the last six months, it might be time to get your levels checked.


Questions from the Internet: "Okay, you've scared me. How much should I actually be taking?"


The official recommendations vary, but my research suggests a good, safe, and effective ballpark for most adults is between 1,000 to 2,000 IU (International Units) per day, especially during the autumn and winter months. The best way to know for sure is to ask your doctor for a blood test. They can tell you your exact level and recommend a specific dose to get you into the optimal range (which is generally considered to be between 30-50 ng/mL). It’s important to take your Vitamin D supplement with a meal that contains some fat, as it is a fat-soluble vitamin and is absorbed much better in the presence of fat.



The Conclusion: You Are a Houseplant with Complicated Emotions


So, after this deep dive into the shadowy world of our most elusive vitamin, what is my final verdict?

My investigation has led me to a simple and profound conclusion: as modern, indoor-dwelling humans, we are all basically houseplants. 🪴 We have removed ourselves from our natural, sun-drenched environment, and as a result, we are all wilting a little bit. Vitamin D deficiency is not a "vegan" problem. It is a global, modern human problem.

The fact that the few dietary sources happen to be animal-based is a quirk of biology, but it doesn't change the fundamental reality. The sun is ghosting us. And in the face of this solar neglect, the most logical, sensible, and scientific thing a person can do is take a supplement.

It is not a failure. It is not unnatural. It is a smart and necessary adaptation to the strange, indoor, sun-starved world we have built for ourselves. So go forth, embrace your inner houseplant, and give yourself the one nutrient you need to thrive, even when the sky is a blanket of relentless grey. ✅

Of course, a healthy body is nothing without a healthy mind. For a look at the complex relationship between diet and mental health, check out my investigation: [Did Going Vegan Give Me Anxiety? A Deep Dive into Diet and Dread].


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