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In this article, we are talking about Vitamin D – the Vitamin responsible for a strong immune and skeletal system.

Researched Based: This article is based on research. Number’s in Brackets are links to research papers and Scientific articles from well-established and authoritative websites (all links open in a new window).

What is Vitamin D

Vitamin D as well as two forms (D2 & D3) is a fat-soluble vitamin that is synthesized in the body mainly through the effect of ultraviolet radiation of the sun on our skin but is also taken up by consuming certain foods. Vitamin D’s main role is the proper development of our bones and the promotion of the health of our skeletal system.

In recent years, however, a number of scientific studies highlight the important role of vitamin D in the overall health of the body as it has been recorded that it helps in the better functioning of the immune system, in the control of blood sugar, and in the prevention of other serious diseases such as various forms of cancer, multiple sclerosis, psychiatric diseases, hypertension, and other diseases.

Vitamin D2 Vs D3

D2 (ergocalciferol) is found in plant products (such as mushrooms), while D3 (cholecalciferol) is found in animal products (such as eggs and fish). The two forms of vitamin D were previously thought to be equivalent because they are eventually converted in the kidneys into the molecule called 25(OH)D and circulate in the blood, acting as a hormone.

Of course, a British study published in the American Journal of Clinical Nutrition by researchers at the University of Surrey found that the D3 form has a much greater effect than the D2 form [1] [2].

It is therefore recommended that D3 is recommended, as cholecalciferol is the natural form and has the potential to raise total vitamin D levels more effectively.

Vitamin D Health Benefits

Here are some of the most important health benefits of Vitamin D.

Protection from diseases – Vitamin D plays an important role in boosting our immune system as well as protecting us from diseases such as:

  • Reducing the risk of multiple sclerosis [3]
  • Reducing the risk of heart disease [4]
  • reducing the risk of developing flu symptoms [5]

Osteoporosis – Vitamin D is traditionally considered the vitamin of bones, as its main action is to increase the absorption of calcium from the intestine. It is used to prevent and treat rickets in children, and to treat osteoporosis, bone pain (osteomalacia), bone loss in people with hyperparathyroidism.

Helps with Weight Loss – Vitamin D It is an ally in weight loss. In a study in the British Journal of Nutrition, people who took daily calcium and vitamin D supplement lost more weight than those who took a placebo supplement [6].

It improves our mood – Exposure to sunshine, which is essential for its synthesis, may play a role in this. In a study, in the Journal of Internal Medicine, people with depression who took a vitamin D supplement saw an improvement in their symptoms.

Fights acne – Vitamin D has the ability to activate certain blood cells that attack dead cells that cause acne! Also known as macrophages, these blood cells convert bad bacteria into nutrients for the body!

Specifically, macrophages differ from other skin defense mechanisms in dealing with acne. That’s because instead of causing redness and pus to defeat a bacteria (thus creating a pimple), they simply attack the bacteria directly, leaving the skin clean and healthy.

Vitamin D: Sources, Health Benefits, Deficiency, Side effects, RDA
.- Vitamin D can help fight acne.

Vitamin D Deficiency Symptoms

Vitamin D deficiency is very common. It is estimated that about 1 billion people worldwide have low levels of vitamin D in their blood.

Most people do not realize that they are vitamin D deficient, as the symptoms are generally subtle. You may not easily recognize them, even though they have a significant negative impact on your quality of life.

  1. Common Infections: One of its most important roles of Vitamind D is to maintain a strong immune system so that we are able to fight off viruses and bacteria that cause disease. If you get sick often, low vitamin D levels may be one of the culprits. Studies have shown a link between vitamin D deficiency and respiratory tract infections such as colds, bronchitis and pneumonia [7].
  1. Feeling tired: Feeling fatigue can have many causes and Vitamin D deficiency can be one of them. Unfortunately, it is often overlooked as a possible cause. Case studies have shown that very low blood levels can cause fatigue that has a serious negative impact on quality of life [8].
  1. Back pain: Vitamin D contributes to maintaining bone health in many ways. It improves calcium absorption [9]. Bone pain and lower back pain can be signs of insufficient vitamin D levels in the blood[6] [7].
  1. Hair loss (Alopecia): Hair loss is often attributed to stress, which is certainly a common cause. However, when hair loss is severe, it may be due to illness or nutrient deficiencies. Hair loss in women has been linked to low levels of vitamin D, although there is little research on this to date. [10]

Alopecia areata is a common form of autoimmune disease characterized by severe hair loss of the scalp and other parts of the body. Approximately one-third of cases affect people under the age of 18. Alopecia can occur during all childhood age groups and can potentially cause psychological stress to patients and parents alike. Vitamin D plays a significant role in immune regulation and maintenance of the hair cycle where low levels of Vitamin D are associated with alopecia and may be a risk factor for the development of the disease. [11]

  1. Depression: Depression is associated with low levels of vitamin D and some studies have found that supplements improve mood. More specifically a national study on Jordanian males aged 25 and above, showed a strong correlation between the two. [12]
  1. Inadequate wound healing: Inadequate vitamin D levels can lead to poor wound healing after surgery, injury or infection. More specifically the research by Dr.Joseph Andrew Molnar indicates that ”The most common micronutrient deficiencies among the elderly include vitamin D, zinc, and vitamin B12 (cobalamin), which may have a significant impact on wound healing”. [13]
  1. Loss of bone mass: A diagnosis of low bone density may be an indication of vitamin D deficiency. Getting enough vitamin D is important for maintaining bone mass as you age.
  1. Muscle pain: There is a correlation between chronic pain and low blood levels of vitamin D, which may be due to the interaction between the vitamin and the nerve cells that detect pain.

Which People Are Most at Risk of Vitamin D Deficiency?

People at increased risk of vitamin D deficiency are:

A) People with darker skin as melanin acts as a filter in absorbing UVB radiation (ultraviolet B radiation)

B) People with little or no sun exposure such as

  • Elderly people with multiple health problems who remain bedridden or confined to their residence
  • People who cover their skin completely with clothing due to religious or cultural beliefs (e.g. nuns)
  • People who deliberately avoid sun exposure due to aesthetic or health issues
  • People in occupations with little sun exposure (office workers, night watchmen)

C) People with medical conditions that predispose to vitamin D deficiency such as:

  • Obesity
  • Chronic kidney disease
  • Hepatic failure
  • Use of medications that increase vitamin D consumption (e.g. anticonvulsants)
  • Pathological conditions of the gastrointestinal system, either due to diseases (such as celiac disease, Crohn’s disease, cystic fibrosis) or due to surgery that removes or bypasses parts of the stomach or intestine (e.g. gastric bypass)

Vitamin D for Children

Vitamin D supplementation in the first year of life for children reduces the incidence of type 1 diabetes

Several studies suggest that boosting vitamin D intake in children reduces the risk of type 1 diabetes.

In a study of 10,366 children in Finland who were given 2,000iu of vitamin D3 daily during their first year of life, the risk of type 1 diabetes was reduced by about 80%, according to 30 years of data [14].

Vitamin D for Pregnancy

Proper intake of vitamin D is also important for pregnant women as it offers some unique properties that can’t be ignored.

Prevention of pre-eclampsia during pregnancy

During pregnancy, there is an increased risk of vitamin D deficiency, which increases the risk of pre-eclampsia and cesarean delivery. The daily intake of vitamin D in pregnancy should reach 1400iu and ideally 4000iu to effectively meet the needs of the mother and fetus during pregnancy [15].

Enhancing calcium absorption during lactation

During the period of breastfeeding, the mother needs to increase her calcium absorption to ensure adequate calcium content in her milk.

In the case of exclusive breastfeeding, the mother should bear in mind that breast milk contains very small amounts of vitamin D (about 20 IU per liter).

Therefore, in order to meet the infant’s vitamin D needs, the mother should take 4,000-6,000 IU of vitamin D daily to ensure that enough D is transferred to her milk [16].

Vitamin D dosage depends on many factors.

Some of them are age, the race we belong to, the latitude of the country we live in, the time of year, sun exposure, clothing, and more.

The American Institute of Medicine recommendations suggest that an average daily intake of 600 IU, or 10-20 micrograms, is sufficient for 97.5% of people [17].

Also, very importantly, they increased what they consider to be the maximum safe dose from 2000 IU to 4000 IU per day.

However, some studies have shown that the daily intake should be higher than this if you are not exposed to the sun.

couple walking in the beach
– A couple walking on the beach. Vitamin D is synthesized in the body when our skin is exposed to the sun.

Vitamin D Sources

The human body can meet its vitamin D needs through exposure to sunlight, diet, and supplementation.

The ultraviolet spectrum of solar radiation (UVB, 290-315 nm) penetrates the skin and converts 7-decrocholesterol into provitamin D3, which is directly converted into vitamin D3.

In addition to vitamins in pills and supplements, we can also boost our intake of vitamin D through food.

In particular, there are 10 foods that are rich in vitamin D that should not be missing from our daily diet this season.

Top 10 Foods High in Vitamin D

FoodServingVitamin DRDA*
Mackerel (raw)100 gr560 IU70%
Salmon (raw)100 gr440 IU55%
Canned tuna (in oil)100 gr268 IU34%
Canned sardines (in oil)100 gr192 IU24%
Caviar100 gr116 IU14%
Eggs (Whole)100 gr80 IU10%
Soy milk100 gr44 IU6%
Kefir100 gr40 IU5%
Almond milk100 gr40 IU5%
Shiitake mushrooms100 gr16 IU2%
* Based on an 800 IU RDA. Source: nutritionvalue.org

Vitamin D Side Effects

A higher intake of vitamin D than prescribed by your treating physician is not recommended, as high levels of calcium in the body can cause unwanted side effects such as:

  • heart arrhythmias,
  • decreased appetite,
  • frequent urination,
  • nausea,
  • tendency to vomit, or
  • disorientation.

Side effects are justified in the body’s attempt to eliminate high levels of calcium.

Vitamin D Toxicity

To reap the benefits of vitamin D, we need to maintain blood levels above 50 ng/mL throughout the year [18].

Doses of 5 -10,000iu per day, for adults, are the minimum to achieve a sufficient biological effect to achieve values above 50 ng/mL.

It is practically impossible for toxicity to occur by taking vitamin D in its natural form. The usual form of vitamin D administered for the purpose of supplementation is in its natural form -25(OH)D3– as produced in the human body by exposure to the sun.

This form is a pre-vitamin, is not active, and is activated by the body when and if needed.

The toxicity that has been recorded does not apply to the administration of vitamin D in its natural form. Rare cases of toxicity have been recorded following administration of pharmaceutical forms of D3: 1,25(OH)2 D3.

However, does an administration in increased doses cause toxicity? The answer is that theoretically, this can happen, but practically it is impossible.

Isolated cases are reported in the literature where huge amounts of vitamin D3, such as 2.400.000 or 1.680.000 units of vitamin D per day, were inadvertently taken [19].

Symptoms of vitamin D toxicity such as cramps, nausea, and dizziness were reported after taking these doses for 5 months. To receive this dose of vitamin D, one would have to consume more than 800 capsules of 2,000 units per day, which is practically impossible.

According to Robert Heany, professor of endocrinology and a pioneer in global vitamin D research, no toxicity has been reported in the literature up to a daily dose of 30,000 units of vitamin D and for blood levels of up to 200 ng/dl over long periods of time. [20]

Best Vitamin D Supplements

Below is a selection of the best Vitamin D productsavailable online.

Vitamin D absorption

What Helps Vitamin D Absorption

A new scientific study published in the Official Journal of the American Osteopathic Association (JAOA) shows that there is a synergy between the “sunshine vitamin” and valuable magnesium.

According to the new findings, if magnesium stores in the body are not sufficient, then vitamin D cannot be metabolized and remains inactive in the body.

“Many people take vitamin D supplements without knowing how this vitamin is metabolized in the body. Without enough magnesium, vitamin D is neither useful nor safe,” [21] says Mohammed S. Razzaque, professor of pathology at the Lake Erie College of Osteopathic Medicine in Lake Erie, Ohio, and one of the authors of the new study.


Vitamin D is essential if we want to have our immune system boosted and keep our teeth and bones strong.

If you don’t like fish, you don’t live in a sunny place, your job does not allow you to meet the sun or you are a vegan, then it is recommended to get Vitamin D from a supplement.

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