Vitamin D: Why Is It Needed And Why To Take It?

Updated on  February 25, 2023
William Toro

Published By:  William Toro

Fact Checked by: Bridget MacDonald, RDN

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Vitamin D is one of the most discussed substances in dietetics and medicine. It helps to strengthen the immune system and the absorption of calcium. It is impossible to replace it with synthetic additives and tablet analogues offered by the modern market.

This substance is necessary for a person even before birth, because in the case of a deficiency of vitamin D in the body of the expectant mother, the newborn may have health problems. It makes bones and teeth stronger and increases their resistance to aggressive influences. It is also known for its role in regulating the heartbeat process and normalizing the work of the blood clotting system.

What Causes Vitamin D Deficiency?

Vitamin D deficiency can be triggered by the following factors:


Reduced daylight hours in the winter season. [1]


The smoky atmosphere of megacities. [2]


A decrease in the producing ability to form a substance, characteristic of persons over 60 years of age. [3]


Insufficient amount of fat in the daily diet. [4]

The danger threatens those who adhere to restrictive or strict diets, as well as bedridden patients who do not have the opportunity to regularly visit the fresh air. This substance is necessary for a person throughout his life, while women in the menopausal period and people in the elderly have a special need. If there is a lack of it in the body, the bone tissue is irritated, which increases the risk of fractures.

Functions and Properties

The functionality of vitamin D is due to the fact that it not only acts as a useful substance, but also is a hormone. When it enters the digestive tract, it reacts to the effects of bile and is absorbed in the small intestine. Its functions also include preventing the softening of bone tissue by regulating calcium deposits, which prevents the likelihood of injuries to the musculoskeletal system.

In addition to ensuring normal calcium metabolism, vitamin D has a direct effect on the immune responses of the body. The consumption of this substance in sufficient quantities significantly reduces the risk of dermatological problems. It is recommended to include it in the diet for the prevention of atherosclerosis,and pathologies of the cardiovascular system associated with a regular increase in blood pressure and a violation of the heart rhythm.

Is Excess Vitamin D Dangerous?

Despite the numerous useful properties, large amounts of vitamin D can cause serious damage to the body. [5] An increase in the level of calcium in the blood is fraught with damage to the heart and kidneys. The initial stages of hypervitaminosis are accompanied by the following symptoms:

Lethargy, apathy, lack of appetite.

Persistent headache and dizziness.

Muscle spasms and the appearance of painful sensations in the joints.

Intoxication can be supplemented by convulsions, sudden pressure surges, bradycardia and fever. However, an excessively high content of the substance in the blood is a rare phenomenon. As a rule, it occurs with prolonged use of synthetic additives. People who regularly sunbathe and consume products enriched with calciferol may not be afraid to face hypervitaminosis.

Sources of Vitamin D

Most foods contain ergocalciferol, the share of which in providing the body with vitamin D is about 10% of the total daily requirement. This value is negligible compared to the recommended consumption rates of this substance. However, it is still not worth completely excluding fortified food from the daily diet, since it can become a tangible support in addition to natural sources. [6]

Let's take a closer look at the list of products that you should first pay attention to:


Shiitake mushrooms.

In its raw form, these mushrooms are rarely seen on the shelves of stores. Most major supermarkets sell dried shiitake. They are perfectly combined with dishes of European and Asian cuisine. 50 g of the product contains 163 mg of vitamin D.


Red caviar

This delicacy, which is especially popular during the New Year holidays, is rich in omega-3 and is able to effectively fight some diseases, including depression. However, only high-quality caviar has useful properties. One tablespoon of the product contains 0.020 mg of vitamin D.



Eggs are the cheapest and most affordable source of calciferol. They can be eaten for breakfast, added to soups and salads. The highest concentration of vitamin is in the yolk. However, it is not worth starting the day with scrambled eggs or omelet every day, since this product is known for its high cholesterol content.



One serving of tuna (about 100 g) contains half of the recommended daily value of calciferol. It is equally useful both in fresh and canned form. When choosing canned food, you should carefully read the composition, while the preferred option is preservation in its own juice.


Vegetable oils

Vitamin D can be obtained from sunflower, olive, corn or wheat oil. When using them, you should not abuse the heat treatment, since many useful components disintegrate during the frying process. It is best to use this product as a salad dressing.



Vitamin D is found in large quantities in parsley and other greens. It can be used to give dishes a spicy taste. Seasonings and spices containing herbs are perfectly combined with soups, salads, meat and various side dishes.



100 g of salmon contains 75% of the recommended daily value of vitamin D. It is necessary to include this red fish in the daily diet not only for this reason. It improves brain function and helps reduce the risk of degenerative diseases, such as Alzheimer's disease. This is due to the presence of omega-3 fatty acids in the composition.

In order for vitamin D to bring only benefits to the body, it is necessary to control its dosage. A comprehensive approach, including compliance with the principles of proper nutrition and a healthy lifestyle, will help you feel cheerful for many years.

William Toro

William Toro ‧ CPT & Nutritionist

William is a certified personal trainer from NASM, he has also been a rehab physiologist for sports persons. He has more than 15 years of experience training people. And has featured in multiple publications like FoxNews, CNBC, Bustle, and other. 


1. Matthias Wacker, Michael F. Holick, Sunlight and Vitamin D, retrieved from
2. Sayed Esmaeil Mousavi, Heresh Amini, Pouria Heydarpour, Fatemeh Amini Chermahini, Lode Godderis, Air pollution, environmental chemicals, and smoking may trigger vitamin D deficiency: Evidence and potential mechanisms, retrieved from
3. J. Christopher Gallagher, MD, MRCP, Vitamin D and Aging, retrieved from
4, 6. Harvard T.H. Chan School of Public Health, Vitamin D, retrieved from
5. Katherine Zeratsky, R.D., L.D., What is vitamin D toxicity? Should I be worried about taking supplements?, retrieved from

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