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Vitamin D What we need to know

Vitamin D helps to regulate the amount of calcium and phosphate in the body. These nutrients are needed to maintain healthy bones, teeth and muscles.
Vitamin D deficiency can cause bone deformities such as rickets in children and bone pain caused by osteomalacia in adults.
Vitamin D is both a nutrient we eat and a hormone our body makes. In addition, laboratory studies show that vitamin D reduces the growth of cancer cells, helps control infections and reduces inflammatory processes. Many organs and tissues in the body have receptors for vitamin D, indicating its important role beyond bone health.

For most people, the best way to get vitamin D is through a supplement, since it's difficult to get enough vitamin D from food.
Vitamin D supplements are available in two forms: vitamin D2 ("ergocalciferol" or previtamin D) and vitamin D3 ("cholecalciferol"). Both are also naturally occurring forms produced by the sun's ultraviolet B (UVB) rays, hence its nickname the "sunshine vitamin," but D2 is produced in plants and fungi, while D3 is produced in animals, including humans.

People with darker skin have lower levels of vitamin D in their blood because the pigment (melanin) reduces vitamin D production (and also reduces the harmful effects of sunlight on the skin, including skin cancer). Low levels of vitamin D in the blood are also common in people who live in cold countries where sunlight is rare or who spend most of their time indoors or in transport.

Food sources

Several foods are naturally rich in vitamin D3. The best sources are fatty fish and fish liver oil. Smaller amounts are found in products: egg yolk, cheese and beef liver. Some mushrooms contain vitamin D2; Foods and supplements such as dairy products and grains are also rich in vitamin D.
Other foods that are rich in vitamin D include:

  • liver oil;
  • fatty fish (tuna, salmon, mackerel, tuna);
  • Orange juice;
  • milk and vegetable milk;
  • yogurt;
  • shrimps;
  • sardine
  • beef liver;
  • egg yolk
  • wheat/cereal.

Is there a difference between vitamin D3 and vitamin D2 supplements?

If you buy vitamin D supplements, you may see two different forms: vitamin D2 and vitamin D3. Vitamin D2 is made from plants and is found in fortified foods and some supplements. Vitamin D3 occurs naturally in the human body and is found in animal products.
Is vitamin D3 "cholecalciferol" better than vitamin D2 "ergocalciferol" in increasing blood levels of the vitamin. A meta-analysis of randomized controlled trials comparing the effects of vitamin D2 and D3 supplements on blood levels found that D3 supplements increased blood levels of the vitamin more and maintained these levels longer than D2.

Ultraviolet radiation

Vitamin D3 can be produced when a chemical reaction occurs in human skin when the steroid 7-dehydrocholesterol is broken down by UVB sunlight. The following are conditions that reduce exposure to UV rays and therefore reduce vitamin D absorption:

  • use of sun protection products; Proper use of sunscreen can reduce vitamin D absorption by more than 90%.
  • Wearing clothing that covers all skin.
  • Spending limited time outdoors.
  • In old age, when the level of 7-dehydrocholesterol decreases and there are changes in the skin.
  • A population that is likely to spend more time indoors.
  • Signs of deficiency and toxicity.


Vitamin D deficiency can be caused by dietary deficiency, poor absorption, or high metabolic demand. If a person does not consume enough vitamin D and does not get enough UV radiation for a long time, they can become vitamin D deficient. People who cannot tolerate or do not eat milk, eggs and fish, such as those who are lactose intolerant or follow a vegan diet, are at a higher risk of deficiency. Other groups of people at high risk of vitamin D deficiency include:
Inflammatory bowel disease (ulcerative colitis, Crohn's disease)

  • muscle weakness and pain;
  • weakening of the immune system;
  • hypertension;
  • Depression;
  • Excessive sweating;
  • Heart conditions.

Problems caused by long-term vitamin D deficiency

  • Rickets: A condition of soft bones and skeletal deformities in infants and children caused by hardening of the bone tissue.
  • Osteomalacia: A condition in adults with weak and softened bones that can be corrected with nutritional supplements. This is different from osteoporosis, in which the bones become porous and brittle, and the condition is irreversible.


Vitamin D toxicity most commonly occurs with dietary supplements. It is unlikely that even small amounts of a dietary vitamin will reach toxic levels. Prolonged exposure to the sun does not cause toxicity because excess heat on the skin inhibits D3 production. It is recommended that you do not take daily vitamin D supplements without a doctor's supervision.
Symptoms of toxicity:

  • Anorexia;
  • Weight loss;
  • Irregular heartbeat;
  • Hardening of blood vessels and tissues due to increased calcium levels in the blood, which can cause heart and kidney damage.

What happens if I take too much vitamin D?

Taking large amounts of vitamin D over a long period of time can lead to the accumulation of excess calcium in the body (hypercalcemia). It can weaken bones and damage the kidneys and heart.

It's impossible to overdose on vitamin D from sun exposure, but always remember to cover up or protect your skin if you're in the sun for long periods of time to reduce your risk of skin damage and skin cancer.




Vitamin D


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