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Vitamin D – Should You Take It?

By Jiří Kaloč

Vitamin D sounds almost too good to be true. A lot of research suggests that it can help prevent a variety of diseases and improve immune function and bone health. The question is, should you take vitamin D in the form of a supplement? Are there any risks? Let’s take a closer look.

What is vitamin D?

We use the name vitamin D to describe a fat-soluble vitamin that we can get from the sun, from certain foods, and from supplements. But vitamin D is not just one thing, it’s a group of compounds.

Vitamin D2 (ergocalciferol) is found in plants such as mushrooms and in yeasts.

Vitamin D3 (cholecalciferol) is found in animal products like fish, egg yolks, and cheese. It is also made on the surface of skin when it’s exposed to sunlight.

Calcifediol (25-hydroxyvitamin D) is the form of vitamin D that’s measured in blood tests. It is created in the liver from vitamin D3.

Calcitriol (1,25-dihydroxyvitamin D) is made in the kidney from calcifediol. It’s the most active form of vitamin D in the human body. It’s considered a hormone, no longer a vitamin.

Mushroom salad
Mushrooms are a good source of vitamin D2. © Profimedia

What does vitamin D do?

Vitamin D has wide-ranging effects on the human body. Our current understanding of vitamin D shows that it helps support the immune system, blood sugar regulation, bone health, calcium absorption and circulation, and normal blood pressure. It has also been shown to help prevent everything from osteoporosis to autoimmune disorders, cardiovascular disease, and cancer.

Should you take it?

Wouldn’t you want to take vitamin D after seeing such an extensive list of its beneficial effects? On top of that, statistics suggest that 20-40% of adults and children worldwide have insufficient levels of vitamin D. Do you want to know if you  also fall in that category?

Answer these questions first

If your answer to any of the following questions is “yes”, you are likely at an increased risk of vitamin deficiency.

  • Do you live far from the equator in a place where you experience winter? It’s nearly impossible to get enough vitamin D from the sun during the colder months there.
  • Do you have darker skin? Melanin, the pigment that makes skin dark, reduces your ability to produce vitamin D when exposed to sunlight.
  • Are you over 50 years old? Age decreases the body’s ability to synthesize vitamin D on the skin.
  • Are you obese or do you have a chronic illness or malabsorption issues? These conditions make it more likely to have issues absorbing and metabolizing vitamin D.
  • Do you always fully cover up with clothing or sunscreen when going outside? Sunscreen and clothing protect your skin from UVB and UVA rays, which blocks vitamin D synthesis.
  • Do you not spend time outside during daytime? If you’re not regularly outside when the sun is highest, you’re missing the window for optimal vitamin D synthesis.
  • Running
    How much time do you spend in the sun?

There are risks involved

Before you self-diagnose a need for vitamin D pills, you should consider the risks as well. It’s important to keep in mind that taking vitamin D when you’re not deficient will have little to no benefit. And research shows it may even cause harm in very high doses. Here are the four main concerns.

Toxicity – Mega doses of vitamin D can result in fatigue, forgetfulness, nausea, vomiting, or slurred speech. These symptoms occur when blood levels rise above 150 ng/ml (375 nmol/l). Thankfully, it isn’t common and happens only to people who take long-term, high-dose supplements without monitoring their blood levels.

Elevated blood calcium levels – Taking too much vitamin D may result in excessive absorption of calcium. Elevated calcium levels can lead to symptoms such as loss of appetite, nausea and vomiting, constipation, tiredness, weakness, muscle pain, confusion, and depression.

Bone loss – Mega doses of vitamin D can result in low vitamin K2 levels. This vitamin’s role is to keep calcium in the bones. With low K2 levels your bones won’t have enough calcium.

Overdosing with vitamin D can lead to low levels of calcium in the bones and subsequent bone loss.

Blood test is the only reliable way to decide

If you’re confused now whether you should go all out on vitamin D supplementation or avoid it altogether, that’s understandable. It’s a complex issue and any supplementation should be approached with care. Thankfully, there’s one way to reliably decide if you should supplement – getting a blood test.

In order to optimize bone health and minimize the risk of disease, you should aim for the blood level of vitamin D of around 75 nmol/L (30 ng/mL). Talk to your doctor if you’re considering supplementation and ask for a blood test.

How to make sure you keep optimal vitamin D levels without pills? What foods should you eat? And what type of supplements are the best? We will continue in the next article.

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