Vitamin D: Why is it Important, Deficiency & Symptoms

3 June 2022 by admin0

Vitamin D is one of the most important micronutrients in the human body. It’s also one of the least absorbent ones, leaving the majority of the population deficient. Proper supplementation and smart sun exposure are key to bringing our numbers to satisfying levels. But, what’s the best way to go about it and why? Here’s what we know. 

What is Vitamin D? 

Is it a vitamin, a hormone, or a combination of both? Officially, this is a fat-soluble vitamin that’s prevalent in ultra-violet (UV) rays and our bodies mostly get it from sun exposure. It also exists in certain foods (naturally and added artificially through fortification) as well as dietary supplements. However, some experts like to refer to vitamin D as a hormone or a pre-hormone that stimulates the absorption of calcium by turning specific genes on and off. 

Vitamin D exists in two main forms:

  • Vitamin D2 (ergocalciferol) – mostly present in plants and yeast
  • Vitamin D3 (cholecalciferol) – comes from animal sources

Whether one is better than the other for human health is still unknown. According to the National Institute of Health’s Office of Dietary Supplements (NIH), both vitamin D2 and D3 are capable of increasing the levels of vitamin D in your blood. Some studies suggest that vitamin D3 is a bit more efficient in doing so, but researchers agree that more evidence is needed to make a final conclusion. 

Both forms are stored in the liver and they are metabolized by the liver and kidneys into their active form called calcitriol.

The Role of Vitamin D

Whether you’re on the vitamin or hormone side of vitamin D, its main role is the same: to help your body absorb and retain calcium it needs to maintain optimal bone health. It also helps absorb and retain phosphorus, aids in reducing inflammation and potential infections, and it may be a great ally in the fight against cancerous cells. 

Vitamin D plays a very important role in the human body that cannot be replaced or replicated by any other micronutrient. Unfortunately, most people in the world are this deficient and that’s why it’s crucial to keep its levels as optimal as possible, checking your numbers and acting accordingly. 

What Causes a Vitamin D Deficiency?

The global epidemic of vitamin D deficiency is caused by a myriad of different factors, some of which we can influence and others we can’t. Luckily, there are plenty of ways to elevate your vitamin D levels and ensure your body is absorbing as much calcium and phosphorus it needs to improve the health of your bones and cartilage. 

Generally, the causes of vitamin D deficiency include:

  • Limited sun exposure due to climate or living conditions
  • Having darker skin (because melanin acts as a shade)
  • Certain kidney and liver disorders
  • Autoimmune diseases such as cystic fibrosis, Crohn’s disease, and celiac disease
  • Rare hereditary disorders that don’t allow for vitamin D absorption
  • Specific medications such as antiseizure drugs, steroids, and rifampin.

When there’s not enough vitamin D in your blood, your body tries to raise calcium levels by producing more of the parathyroid hormone. This often causes hyperparathyroidism or excessive production of the parathyroid hormone which draws the calcium out of your bones and into the bloodstream. This does the opposite of what was intended, causing your bones to weaken. 

Symptoms of Deficiency

The symptoms usually present themselves in a very general manner, meaning they are rarely linked to vitamin D deficiency from the start. These symptoms include:

  • Fatigue and tiredness
  • Bone pain
  • Muscle weakness
  • Often mood swings

In the case of children, this deficiency can be quite serious since it causes rickets. This shows up as incorrect growth patterns, joint deformities, bone pain, and severe muscle weakness. Human breastmilk contains negligent levels of vitamin D so supplementation is crucial, especially during the first year of a child’s life. 

Tests for Vitamin D Deficiency

In order to get diagnosed with a this deficiency, it’s necessary to perform a blood test. There are two different tests that can be ordered by your doctor, but the most common one is the 25-hydroxy this test which detects the concentrations of this in your blood. Even though different labs use different numbers for references, NIH recommends the following range:

  • 50 nmol/L (20 ng/mL) or above – adequate for the majority of people
  • 30 nmol/L (12 ng/mL) and below – too low and 
  • Above 125 nmol/L (50 ng/mL) – too high and might cause health issues


For most people who have a diagnosis of a this deficiency, the usual recommendations would be to get at least 15-20 min of sun exposure a day, add more vitamin D-rich foods into their diet, and add a dietary supplement. 

When it comes to sun exposure, it’s important to be smart about it as overexposure, especially when paired with no sunscreen use can cause sunburn, which is known to increase the risk of developing skin cancer.

In terms of vitamin D-rich foods, there aren’t many. And even in the ones that contain vitamin D, it isn’t very bioavailable, meaning your body won’t absorb even nearly enough for your levels to become adequate.  

That’s why your best option would be a dietary supplement. The recommended dietary allowance (RDA) is variable depending on your age:

  • Infants and babes up to 12 months – 10 micrograms (mcg) or 400 International Units (IU)
  • Up to 70 years  – 15 mcg or 600 IU
  • 70 and above – 20 mcg or 800 IU

That being said, there are some people who need more than that because they live in countries with very little sunlight throughout the year or because their bodies simply cannot absorb enough this even with adequate sun exposure. 

Side Effects of Too Much Vitamin D

Since most people are this deficient, having too much vitamin D in your blood is really rare. However, vitamin D toxicity can occur, usually in people with certain medical conditions such as granulomatous disorders, congenital disorders, specific lymphomas, and dysregulated vitamin D metabolism. 

Vitamin D toxicity can also occur in cases where you severely exceed your RDA due to misuse of your supplements or a prescription error. Still, this has to be happening for a prolonged period of time for your body to actually start accumulating large doses of this. Whatever the case may be, the side effects are the same as they cause elevated calcium levels in your blood. This causes

  • Fatigue, confusion, hallucinations, and dizziness
  • Digestive distress, constipation, diarrhea, and lack of appetite
  • Nausea, vomiting, 
  • kidney stones and even kidney failure in worst cases
  • High blood pressure and heart problems
  • Dehydration

Avoid buying and taking vitamin D dietary supplements on your own and always consult with your healthcare provider about the necessary dose for you and your health needs. 

Vitamin D and Cancer

Recent research suggests that vitamin D may be an incredible ally in the prevention and fight against cancer. The evidence on vitamin D and breast cancer took the world by storm, showcasing that up to 50% of breast cancer could potentially be prevented with vitamin D supplementation. And it seems like vitamin D helps prevent and increase survival rate with other cancers too, especially prostate cancer, ovarian cancer, and colon cancer

Final Thoughts

Vitamin D is extremely important and yet, almost every single one of us is vitamin D deficient. Check your levels on a yearly basis and make sure to do the necessary steps if your levels are too low. Your health depends on it. 

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