The Importance of “Vitamin” D

What is Vitamin D

You may all be wondering why the comas on the word Vitamin. So, why comas? Because “Vitamin” D is in fact a pro-hormone produced by the body as a response to sun exposure. Contrary to true Vitamins, that you fully get through food, and your body is not able to produce them by itself, Vit D is synthesized when you expose your skin to sunlight,a small percentage from food, and from supplementation.

When you are exposed to the sun, through your skin, vitamin D (cholecalciferol or Vitamin D3) is produced and sent to your liver, where, by an enzymatic process called hydroxilation , it is transformed into calcidiol, the storage form of Vit D. Then when required, your body, again by hydroxilation transforms it into calcitriol, the active form of Vitamin D, also known as activated Vit D. When taking supplements or via ingestion of food that has Vit D, it is also sent to the liver and follows the same process (there are differences in the metabolites produces from D2 or D3, but lets not get too much into the biochemistry).

In normal conditions, up to 80% of vitamin D is produced naturally through sun exposure and the remainder, a small percentage  comes from animal food sources such as egg yolks, fatty fish (salmon, sardines, king mackerel) and beef liver.

Why do we need Vitamin D?

Vit D in its active form is extremely important for Calcium and Phosphorus metabolism, promoting absorption in the gut. Even if you have adequate intake levels of  these minerals through your diet, if you are deficient in Vit. D you will not be able to absorb them. But it does not stop there. Researchers and scientists are finding an increasing number of benefits from Vit D, and conditions associated with its deficiency.

  • Vit D boosts the immune system fighting infections, and reducing the risk of flu
  • Chronic pain
  • Osteoporosis
  • Diabetes – Several studies pointed to low levels of Vit D being associated with negative effects in insulin secretion and glucose tolerance
  • Studies show influence of Vit D deficiency in aggravating allergic and atopic diseases
  • Fibromyalgia
  • Promotes a healthy heart, and blood pressure
  • Vit D deficiency may be associated with a greater risk of pre-eclampsia in pregnant women
  • Prevention of cancer
  • Low levels of Vit D were associated with symptoms of depression
  • Low levels of Vit D have been associated with higher risk of Alzheimer, rheumatoid arthritis among others

Current research indicates vitamin D deficiency plays a role in causing seventeen varieties of different cancers as well as heart disease, stroke, autoimmune diseases, birth defects, and periodontal disease – Calvo MS, Whiting SJ, Barton CN. Vitamin D intake, A global perspective of current status. J Nutr. 2007;135:310–7.

When and why did we become deficient?

It is estimated that a large part of the world’s population, over 1 billion people,  even in tropical countries (in fact darker skinned people have more difficulties in synthesizing Vit D), is deficient in Vit D. (check this study – It is also known that a large portion of the population is deficient in magnesium,  needed to utilize vitamin D.

  • Decreased exposure to sunlight

Sun “phobia” associated with anti skin cancer campaigns (I know, it is polemic, I know many will not agree). The media campaigns to avoid the sun like a plague to to use sunscreen/sun blockers as a solution for skin cancer prevention (in fact not quite correct, as it depends on the type of skin cancer), created almost a phobia in people and caused a decrease in exposure to sun. As sun is needed for the synthesis of Vit D, because we cannot get all our requirements from food, and Vit D is often underrated by professionals and not even included in blood panels, we are creating a population deficient in Vit D (I am fair skinned, I live in the Tropics, and I still need to supplement, of course according to the results I get from my blood analysis).

Research shows that the ability to synthesize Vit D decreases alarmingly with the sun protection factor you use. A SPF higher than 30 (which is recommended as the best practice to prevent skin cancer) reduces it up to 99 percent. As we do not spend time outdoors as we used to (even children) it puts us at a higher risk of lacking Vit D.

On the other side, cultural and religious influences (the use of clothes that cover the body, common in some religions), the impact of the beauty industry (the idea that fair skinned is more beautiful than a tanned face, adopted in fashion campaigns, adopted by women that go to the extreme of “hating the sun”), living in countries where sunlight is limited like northern latitudes all contribute for a sharp decline in sun exposure.

  • Dark skin

“Ironically” and contrary to what most people think, melanin (the pigment responsible for skin tone) reduces the ability of the skin to synthesize Vit D. The more melanin you have the darker your skin color is, but NOT the higher your Vit D, as the lighter your skin is, the easier it will synthesize Vit D.

  • Medical or metabolic conditions that affect the synthesis/absorption of Vit D

Conditions such as IBS, Leaky Gut, Chron’s, Celiac disease affect the ability of the gut to absorb Vit D from food. That, paired with the decrease in the exposure to sun, can lead to Vit D deficiency.

Kidney and or/liver conditions that affect the ability to convert Vit D into activated Vit D (associated with age or a disease) will also contribute for a deficiency in Vit D

Obesity – fat cells absorb Vit D from teh blood current and affect circulating vit D i.e. affect the availability of circulating Vit D in the body
  • Dietary restrictions

Strict vegans with no supplementation or no sun exposure are at a higher risk of Vit D deficiency  as food sources are mainly of an animal based origin.

An interesting source of dietary Vit D for vegetarians and vegans are mushrooms, that contain plant sterols. Plant sterols convert  Ultraviolet light to vitamin D. However, unfortunately most mushrooms are grown indoors, so people do not benefit from their Vit D potential .

How to diagnose, prevent, solve?

  • Diagnose

The ONLY way to know if you are deficient (as symptoms are easily confused with other conditions, and supplementation is s serious issue) is to have it tested. The most accurate is by testing “25-hydroxy vitamin D” in the blood. Nutritional guidelines vary from country to country and I will not indicate what the optimum level is. That should be tested, interpreted and advised by your doctor.

  • Prevent and solve

a. Increase exposure to sunlight (consult your doctor first to see if there is any contra indication and for advise on how to do it).

Usually, 15 minutes of sun exposure per day, with no sun screen work well for fair to medium skin toned people.

Darker toned people should spend considerably more time in the sun, and 40 minutes would be a good time.

In winter, or if living in northern latitudes this time might need to be increased to guarantee enough vitamin D production

The sun exposure should occur during the time the sun is high in the sky (peak times) and thus able to boost Vit D synthesis by your body.

b. Take a vitamin D supplement: although they are readily available never supplement without consulting with your doctor. Toxicity is as dangerous as deficiency. Being soluble in fat, Vit D is better absorbed by the body when consumed with fat containing foods (avocado, seed or nut butters, coconut oil, e.g.).

Note. your body can convert some D2 active Vit D to be used by the body, but it is much more effective in using D3, being that the reason why supplementing with D3 is a better option. Vit D3 converts at a much faster rate and its approximately 4 times more effective than Vitamin D2.

Make sure you discuss this with your doctor to clarify any doubts you have on your supplementation and understand his reasons.

  • Boost your dietary intake of vitamin D:

Beef liver, mushrooms (confirm if they were exposed to sunlight), fatty fish (salmon, cod fish, tuna, mackerel, sardines), fish liver oil, cheese and egg yolks are possible sources of Vit D.






Passionate about the ketogenic and lowcarb lifestyle, solo traveler, passionate about helping people achieve their dreams. Amateur photographer, recipe developer, creator of the famous keto perfect bread.


  1. Diane

    Excellent article -very informative . Thank you.


  2. motoguzzimomma

    So many facts I didn’t know about relating to ‘Vit ‘D, Dalila.

    I never thought about sunscreen, ‘Research shows that the ability to synthesize Vit D decreases alarmingly with the sun protection factor you use. A SPF higher than 30 (which is recommended as the best practice to prevent skin cancer) reduces it up to 99 percent’.

    I too am fair skinned and spend a lot of time in very sunny places.

    Thank you for such an informative post <3


    1. heelsandspices

      And thank you again for always contributing with kind comments


  3. Barb Trevitt

    There are so many chemicals in sunscreen that are bad for your skin. Thanks for easing my mind that covering up before burning is a good way to go. I kinda like a tan… lol


  4. kathleen paul

    I live in Eugene/Springfield OR we get a lot of rain, not so much sun and a lot of people don’t have enough Vit. D and don’t even realize it!


    1. heelsandspices

      True Kat


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