Everything You Need to Know About Vitamin D

Vitamin D revealed

Vitamin D is actually a vitamin and a hormone because it can be manufactured in the body. This vitamin/hormone is produced from cholesterol when our skin comes into direct contact with electromagnetic radiation, transmitted from the sun. Sunlight interacts with cholesterol to form cholecalciferol which is then transformed into 25-hydroxycholecalciferol in the liver, another form of vitamin D. The liver then sends this form of vitamin D to the kidneys for conversion into its most active state, 125-dihydroxycholecalciferol, commonly referred to as vitamin D3. 

Many people think of vitamin D as the bone and immune health vitamin however, it is responsible for many more functions in the body which we will discuss today.

Vitamin D receptors can be found in nearly every type of human cell in the body, confirming its importance for whole-body health. 

Optimal vitamin D levels

Deficiency in vitamin D has been linked with numerous diseases which is why establishing optimal levels is so important to ensure you stay well. Vitamin D status may be a more significant determinant of disease risk than we think.

But before you decide to start supplementing, it is recommended to test your levels in order to establish whether deficiency is an issue for you or not and to determine your dosage.

The National Institute of Health, adequate levels fall around 20 ng/ml, though optimal ranges aim for much higher from 50 to 70 ng/ml (1).

Vitamin D levels can be tested via bloodwork blood by asking your medical provider for a 25-Hydroxy Vitamin D test

Symptoms of low vitamin D

A deficiency in vitamin D can show up quite commonly, especially in countries that are far away from the equator. A  Canadian 2013 study showed Inadequate levels of vitamin D affected about 32% of Canadians while10% were deficient (2)Up to one-third of Canadians are said to reach below the recommended levels of vitamin D.

Vitamin D requirements usually increase during the winter months when sunlight exposure is limited.

Signs and symptoms associated with low vitamin D status include:

  • mood imbalances such as anxiety and depression
  • fatigue
  • bone pain and bone loss
  • muscle weakness and cramps
  • compromised immunity and falling sick often
  • slow wound healing
  • hair loss

Research also suggests that vitamin D therapy could also help to prevent and treat certain conditions such as diabetes, cardiovascular disease, glucose intolerance, and autoimmune conditions. 

Causes of low vitamin D 

  • Low dietary intake
  • Impaired digestive absorption such as fat malabsorption or gastric bypass surgery
  • Excessive alcohol consumption
  • Tobacco smoking 
  • Limited access to direct sunlight 
  • Decrease in cutaneous vitamin D synthesis
  • Impaired conversion from the kidneys 

Additional factors that can be linked to low vitamin D include obesity, impaired absorption in cases such as celiac and Crohn's disease, darker colored skin tones,  and kidney and liver diseases. 

Due to the importance of vitamin D for bone health, a deficiency is particularly problematic in elderly populations and can increase the risk of bone loss and osteoporosis. 

How much vitamin D should I supplement?

Though we always suggest testing to verify your personal levels, requirements will vary with age as well. These are the recommendations from the National Istntitue of Health

  • 0-6 months: 1000 IU
  • 7-12 months: 1,500 IU
  • 1-3 years: 2,500 IU
  • 4-8 years: 3,000 IU
  • 9-18 years: 4,000 IU
  • 19+ years: 4,000 IU


When should I take vitamin D?  

As a fat-soluble vitamin, it is recommended to take vitamin D along with a meal that contains fat in order to improve the absorption rate

Morning is most likely the best time to take vitamin D as it could potentially affect sleep if taken later at night. This also helps to support our natural circadian rhythm. 

Supplementing with vitamin D has the potential to interact with various medications so be sure to verify with your health care practitioner to avoid any potential interactions. 

Supplementing with vitamin D

Vitamin D supplementation is available in various forms such as capsule, powder, liquid, and intravenously

The 2 primary forms of vitamin D are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Vitamin D2 is found in plant sources whilst vitamin D3 can be found in animal products, the same type produced by our skin with exposure to sunlight.

Evidence favors vitamin D3 as being the more bioavailable and bioactive form as experts believe it to be the more potent form of the vitamin (3).

This is why we recommend choosing vitamin D3 when you are looking for a supplement. Cod liver oil is another food supplement source of vitamin D, shown to be the richest source of vitamin D found in foods. 

What helps the absorption of vitamin D?

It is not enough to simply take a vitamin D supplement, you must be absorbing it! Improving the absorption of vitamin D and its beneficial effects in the body will be determined by various factors.

As mentioned before, vitamin D is a fat-soluble vitamin therefore either taking the vitamin alongside dietary fat or choosing a supplement that already provides a fat such as coconut or olive oil will help to improve the absorption. It is usually recommended to take your vitamins with food to improve the assimilation of the nutrients. 

The effectiveness and benefits of vitamin D are also linked to adequate intake of other nutrients such as magnesium as this mineral helps to activate vitamin D in the body (3)

Vitamin K2 is also recommended alongside vitamin D as vitamin K2 helps to enhance the effects of vitamin D and ensure it goes exactly where it is needed in the body instead of coagulating in the arteries.

In order to ensure healthy bones, vitamin D works best with adequate calcium, phosphorus, magnesium, and vitamin K2 intake. This is why most bone supporting formulas include these vitamins and minerals together as they work more effectively synergistically than isolated. 

Restoring vitamin D levels

Your personal vitamin D status will determine your course of action to restore your vitamin D levels. If you do find out you are deficient, you will require higher levels of vitamin D for a certain period of time, usually several weeks. We recommend working with your health care provider to ensure you are doing this properly and to avoid any side effects.

Vitamin D rich foods

Vitamin D is found in relatively low quantities in just a few foods, most of them being animal-based which is why vegans and vegetarians are recommended to supplement. 

Animal sources of vitamin D include egg yolks, dairy, butter, liver, and oily fish such as mackerel, sardines, and wild salmon. 

Many foods are also enriched in vitamin D such as plant-based milks, orange juice, and cereal.

Vitamin D foods for vegetarians

  • mushrooms
  • dairy milk
  • fortified vegan milks
  • eggs
  • cheese

    Our favorite vitamin D supplements

      Side effects of vitamin D supplementation

      Though fairly rare, vitamin D toxicity is also possible. This is mainly caused by excess intake in the form of supplementation, especially over longer periods of time.

      Less severe symptoms of vitamin D toxicity include excessive thirst, diarrhea, nausea, weakness, nausea, vomiting, stomach pain, weight loss, constipation, and headaches. 

      More serious signs and symptoms of vitamin D toxicity may include:

      • polyuria (increased urinary frequency)
      • heart arrhythmias
      • hypercalcemia (calcium buildup in the blood)
      • kidney failure 
      • bone loss 

      You may also notice increased blood and urine levels of calcium and phosphorus, as well as the calcification of soft tissues. 

      We recommend working closely with your health care practitioner if you are supplementing with a high dose of vitamin D and to verify your levels regularly.


      Can you receive the benefits of vitamin D through a window?

      Humans can manufacture vitamin D through exposure to direct sunlight but does this work through a window? Ultraviolet rays, needed for vitamin D production, are blocked by glass windows therefore you would need to actually get outside to receive the benefits of vitamin D (4)

      Can you receive the benefits of vitamin D from a tanning bed?

      Tanning beds may provide an effective source of vitamin D, and this would be especially useful during the winter months. Tanning beds have been shown to increase serum vitamin D levels D without burning, especially useful for those with compromised digestive absorption (5). However, tanning beds still represent a risk for health as they are linked with skin cancer, therefore supplementation is generally preferred.

      Can you get vitamin D from the sun?

      Yes, sunshine is the most effective way to obtain vitamin D naturally.

      However, there are many factors that can alter the synthesis of vitamin D from sunlight which include season, time of day, location, cloud coverage, and skin pigmentation. Your ability to create vitamin D from the sun may also be inhibited by smog, clouds, clothing, glass windows, sunscreens, and darker skin tones.

      Sun exposure for about 15-20 minutes three times a week between the Spring and Fall months is usually sufficient to reach adequate levels however the effects will vary from person to person.

      Benefits of vitamin D

      • Does vitamin D help hair growth?
        Vitamin D is an important mineral for hair health as it helps to stimulate hair growth. Deficiency can lead to hair loss and is linked with alopecia areata, an autoimmune condition that triggers hair to fall out in patches. If you are dealing with hair loss it may be worthwhile to verify your vitamin D levels.
      • Does vitamin D improve immune function?
        Commonly recommended to support the immune system during the cold and flu season, vitamin D can help to regulate the innate and adaptive immune responses and improve the clearance of foreign agents that put the body out of balance (6). In addition, vitamin D can help to stimulate certain proteins that are naturally antimicrobial and can attack pathogens. Research has linked low vitamin D levels with an increased vulnerability to illness and disease such as infections and autoimmunity (7)
        • Does vitamin D help with depression?
          Vitamin D can significantly impact mood and mental health as low levels have been linked to depression and seasonal affective disorder (8)(9). Vitamin D receptors have been found in various areas of the brain and lowered levels of this hormone can affect neurotransmitter production such as serotonin, our feel-good hormone. Sufficient vitamin D levels help to protect brain cells and reduce inflammation (10). Though depression is more complex than just a vitamin D deficiency it is a natural treatment that can help to improve symptoms of low mood.
        • Vitamin D and sleep
          Inadequate blood levels of vitamin D have been linked to poor quality sleep and sleep disorders in humans (11)(12). A study found that participants suffering from insomnia who were supplementing with vitamin D were able to improve sleep quality and increase sleep duration (13).
          Vitamin D does play a role in the production of serotonin, a hormone needed for optimal melatonin synthesis, which promotes sleep. 
          Supplementing in the morning may be a good idea because vitamin D is inversely related to melatonin, meaning if you take it at night it could keep you up! This also makes sense from an evolutionary standpoint as we get vitamin D from the sun which rises in the morning. 
        • Does vitamin D help with anxiety?
          Vitamin D affects the brain in various ways such as reducing inflammatory markers which can help to reduce anxiety and improve mental health disorders (14). Vitamin D is an important nutrient for brain health and needed for proper neuroendocrine functioning.
          Low levels of serum vitamin D have been associated with neurological conditions such as Parkinson's disease, Multiple Sclerosis, Alzheimer's disease, and Autism (15). The rates of anxiety are actually increased in those experiencing low vitamin D which is why regular screening and supplementation may be a worthwhile treatment (16)



        About Author

        Laurence Annez

        Laurence AnnezLaurence Annez is a Certified Nutritional Practitioner and Health Coach, specializing in PCOS and women's hormones. She also holds a degree in Creative Writing and has extensive experience writing on health and wellness topics. Laurence's mission is to inspire and motivate individuals to take control of their own health and reach their ultimate health goals.

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