What is vitamin D?

Vitamin D (also known by the names: vitamin D3, calciferol and cholecalciferol) is an essential vitamin that is mostly produced in the human body, is found in a small number of foods and is marketed as nutritional supplements. It is a fat-soluble vitamin that, along with calcium, is one of the most essential components for bone health.

Research done in recent years on this vitamin shows that it has other vital roles such as protecting the respiratory system, the heart and the brain. Additional studies are being done to examine the ability of vitamin D to prevent a long series of diseases including diabetes, cancer, mental illness, heart disease, stroke (both for prevention and treatment), multiple sclerosis and inflammatory bowel diseases such as Crohn's and ulcerative colitis.

What are the ways in which the body receives vitamin D?

1. Self-production of vitamin D in the human body. Exposure of the skin to the sun's rays causes it to produce vitamin D. An inactive derivative of vitamin D is produced in the skin, and this undergoes action in both the liver and the kidneys to create the substance calcitriol, which is the active form of vitamin D.

2. Vitamin D in food. Vitamin D is also present in a small number of foods, including certain fish (such as salmon, mackerel and sardines), fish oil, fish liver oil and egg yolk.

3. Vitamin D in nutritional supplements: Vitamin D is also marketed in nutritional supplements - in drops or tablets - which can be purchased in pharmacies and health food stores. Sometimes the nutritional supplement includes only vitamin D and sometimes it includes vitamin D along with other vitamins and minerals. An accepted combination is vitamin D and calcium.

What is the role of vitamin D in the human body?

Vitamin D is essential for bone health. It encourages absorption of calcium from the digestive system, maintains normal levels of calcium and phosphorus in the blood and bones, encourages bone building and reduces bone breakdown. Without normal levels of vitamin D in the blood, rickets may develop. Rickets is a condition where the bones become soft and brittle and may break. In the medical language, rickets in children is called rickets, while rickets in adults is called osteomalacia. In old age, vitamin D can prevent osteopenia and osteoporosis (bone thinning), if it is taken together with calcium.

In addition, vitamin D deficiency may cause muscle weakness, worsening of muscle diseases such as fibromyalgia and joint diseases. Thus, for example, it became clear that many of those who suffered a hip fracture had a significant vitamin D deficiency.

Why do many in the population suffer from vitamin D deficiency?

Even in sunny areas, there is a lack of vitamin D among the general population. People of all ages tend to suffer from this deficiency: children, teenagers and adults. The main reason for vitamin D deficiency is little exposure to the sun - mainly because of the deep-rooted fear of skin cancer following exposure to the sun. Moreover, when people leave their homes or offices, many of them make sure to use sunscreens that block the sun's radiation.

Staying in homes also characterizes children and teenagers. Today they prefer to be in front of various screens and not play outside as before. In addition to this, it should be remembered that as you get older - and especially from the age of 70 onwards - the rate of production of vitamin D in the skin decreases and is not as effective as it is in young people.

Which populations may especially suffer from vitamin D deficiency?

1. Elderly people. As mentioned, as you get older, the natural production of vitamin D in the skin decreases when exposed to the sun. On top of that, many of the adults often stay at home and rarely go outside and be exposed to the sun.
2. People who for various reasons are rarely exposed to the sun, such as people who work from home, people who work all day in an office or immobile patients who are hospitalized in medical institutions.
3. People who wear long clothes all day and wear a hat because of faith, religion or the need to work in such conditions.
4. People who for medical reasons can be exposed to the sun only after they have protected themselves well with sunscreens.
5. Medicinal reasons: People who take medicines that increase the skin's sensitivity to sunlight and need to use sunscreens. Many medications increase the skin's sensitivity to the sun, so those taking medications should find out - from their doctor or the pharmacist or a consumer leaflet - if they increase the skin's sensitivity to sunlight. There are also drugs that cause an increased breakdown of vitamin D or increase the risk of osteoporosis, such as steroids and certain drugs for the treatment of epilepsy.
6. People who suffer from inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. An inflamed colon absorbs less vitamin D from food compared to a normal colon.
7. People who suffer from diseases that reduce the absorption of fatty food. These are diseases such as cystic fibrosis, celiac disease and certain liver diseases.
8. People who suffer from obesity and people after gastric bypass surgery (bariatric surgery).
9. People suffering from advanced kidney failure and dialysis patients, since in such situations the kidneys do not activate the vitamin created in the skin.
10. People who suffer from bone depletion (osteoporosis or osteopenia).
11. Babies from birth to one year old.

What amount of vitamin D is recommended to consume daily?

Vitamin D is measured in international units (IU). Vitamin D can also be measured in micrograms, but this method is less accepted (1 IU of vitamin D is equivalent to 0.025 micrograms of vitamin D).

The daily amount of vitamin D that is recommended to consume varies according to age:

• Babies from birth to one year old: 400 IU per day. In Israel, infants up to one year of age are given a vitamin D supplement at a dose of 400 IU per day.
• From the age of one year and older: 600 IHB. There are no guidelines from the Ministry of Health for the administration of a vitamin D supplement to those aged one year and older. You must consult with the attending physician.
• Pregnant or lactating women: 600 IU per day.
• Adults up to the age of 70 years: 600 to 800 IU per day.
• 70 years of age and older: 800 IU per day.

The Association for Osteoporosis and Bone Diseases recommends that men and women 50 years of age and older take a vitamin D supplement at a dose of 800 to 1,000 IU per day. This is a safe dose that does not require monitoring of vitamin D in the blood.


People who suffer from vitamin D deficiency receive higher doses - according to the doctor's recommendations.

What do you do in case of vitamin D deficiency?

In case of lack of vitamin D, the doctor is expected to give a supplement that contains this vitamin. There are many preparations on the market that contain vitamin D, including vitamin D in drops, vitamin D in capsules, vitamin D in tablets and vitamin D in chewable tablets.

The doctor determines the dose according to the severity of the vitamin D deficiency. In many cases, the doctor is expected to recommend a fixed dose of 1,000 to 2,000 IU per day - until the deficiency disappears.

For patients who suffer from a decrease in bone density or bone depletion (osteoporosis and osteopenia), the doctor is expected to recommend higher doses at the beginning of treatment. He is also expected to recommend a supplement that contains calcium.

Should we be afraid of a high dose of vitamin D?
Toxicity from excess vitamin D is rare. Its symptoms are, among others, weight loss, lack of appetite, increased urination and heart rhythm disorders. Patients who have too high blood levels of vitamin D may also suffer from calcium build-up in the arteries of the heart or kidneys and increase the risk of heart attacks or kidney stones, especially if they also take a calcium supplement. Therefore, elderly patients who use a dietary supplement containing vitamin D should adhere to the dose of vitamin D as determined by the attending physician and not exceed it.

So what should you do?

1. The recommendations for the general population include exposure of the limbs to the sun for 20 minutes a day. It is advisable to do this in the morning or evening, when the sun's radiation is not at its peak, and even then exposure should be limited to no more than 20 minutes a day, since increased exposure to the sun increases the risk of skin cancer.
2. Take a vitamin D supplement
3. Babies from birth to one year old receive a nutritional supplement containing vitamin D at a dose of 400 IU per day.
4. Even elderly people in most cases need a nutritional supplement containing vitamin D, especially if they suffer from bone loss (osteoporosis or osteopenia). They also need a supplement containing calcium.
5. Blood tests to detect vitamin D deficiency are usually done only for people at risk of such a deficiency and not for the entire population. Vitamin D supplementation is not always necessary for the general population. It is recommended to consult the attending physician.
6. Those who are included in the risk group for vitamin D deficiency are expected to be sent - on the orders of their attending physician - to take a blood test to assess the levels of vitamin D in their blood. If a deficiency is indeed detected, the doctor is expected to prescribe a nutritional supplement containing vitamin D.

* The information in the guide is for general information only and does not replace consultation with a doctor!