Vitamin D – Importance and Sources

By Nettali Ben Yosef, Dietician at the Nutrition & Diet Unit, Reuth Rehabilitation Center

The most important function of vitamin D is maintaining the right balance of calcium in our body, essential for the health of our bones.

In addition, vitamin D also protects the heart the brain and the respiratory system.

Vitamin D and exposure to sunlight

The main source of vitamin D is exposure to sunlight. UVB rays hit cholesterol compounds in the skin, causing a biochemical chain reaction in the cells, passing through the liver and kidneys, and ultimately producing active vitamin D.

Our modern lifestyle constantly diminishes our sunlight exposure, causing a significant lack of vitamin D in some parts of the population. To address this problem experts have recommended controlled exposure of limited skin areas for about 15 minutes per day, depending on the amount of radiation.  Yet it must be noted that sunlight exposure is a risk factor for developing skin cancers.

 Nutritional sources of vitamin D

The main nutritional sources of vitamin D are animal products including fatty fish, egg yolks, butter and liver. Today vitamin D is also added to milk and other dairy products, as well as cereals. Some vegetable groups also contain a very small amount of vitamin D. Relatively higher concentrations are found in mushrooms and green-leaf vegetables.

For people who do not eat animal foods and are rarely exposed to sunlight dietary supplements can be important. You must consult with a dietician before taking a supplement, to make sure it is the right one for you.  Notice that There is a thin line between deficiency and excess which can lead to toxicity: too much calcium and phosphorus carried in the blood, and deposited in soft tissues, can cause headaches, nausea, over-calcification of bones and kidney stones.


The information presented in this article is general. It does not constitute medical advice or replace consultation with a physician. It should not be regarded as a recommendation or an alternative for medical treatment.

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