What Is Water-Soluble Vitamin D？ Does It Really Exist?

What is water-soluble vitamin D? Before we explain this concept, we should first understand what water-soluble vitamins actually are. Please continue reading for more information.

What are water-soluble vitamins and fat-soluble vitamins?

Water-soluble vitamins and fat-soluble vitamins are two different types of essential micronutrients that our bodies need to ensure normal physiological functioning. Vitamins have a crucial role in controlling human growth, metabolism, and development. Normally, humans need only tiny amounts of vitamins each day, with quantities often measured in milligrams or micrograms. However, if there is a lack of certain vitamins, it could impact the body severely and even become potentially hazardous for some diseases.

Typically, we classify vitamins into two categories: water-soluble ones and fat-soluble ones. Out of the 42 indispensable nutrients needed by our bodies, 14 are vitamins—4 are fats soluble (namely A, D, E, K) while 10 are water-soluble (B1, B2, B3, B5 B6 B7 B9 B12 choline C).

Most water-soluble vitamins get involved in the body's metabolic processes together with substances and energy as coenzymes. They have no pure storage form inside their bodies; every type has its own distinctive way of getting metabolized and stored location.

When the body has enough water-soluble vitamins, any excess ones are disposed of through urine. Conversely, when tissues lack these vitamins, a significant number of consumed vitamins will be soaked up and utilized by the tissues instead of being excreted in urine.

Water-soluble vitamins are generally classified as safe and non-hazardous. Nonetheless, excessive intake could result in poisoning. For example, when vitamin C or B intake exceeds 15 to 100 times our body's normal demand, poisoning risks amplification.

On the other hand, fat-soluble vitamins mostly dissolve in fats or organic solvents and often exist alongside fats in food. Upon overconsumption, they get stored within the liver which may cause toxic accumulation.

What is water-soluble vitamin D? 

From the classification of water-soluble and fat-soluble vitamins mentioned earlier, it's an obvious fact that there is no such substance as water-soluble vitamin D. Vitamin D only exists as a fat-soluble vitamin. So, why does the term "water-soluble vitamin D" appear? It is actually a concept promoted by some manufacturers. They claim to enhance the absorption of regular vitamin D using patented water-soluble technology, asserting that it is not only safe but also meets daily human requirements.

They mention that the absorption rate of regular vitamin D is around 60%, whereas water-soluble vitamin D achieves nearly 100% absorption. Under safe dosage conditions, it can ensure that the body receives an adequate amount of absorbed vitamin D. However, due to the technical challenges involved, production costs are higher, and correspondingly higher price.

What are the functions of vitamin D?

The main function of vitamin D is to regulate calcium and phosphorus metabolism, promote the absorption of calcium and phosphorus in the intestine, and facilitate bone mineralization, maintaining the balance of blood calcium and blood phosphorus levels. Active vitamin D acts on the cell nucleus of the intestinal mucosal cells, promoting the biosynthesis of calcium-binding proteins. These calcium-binding proteins form soluble complexes with calcium, thereby accelerating calcium absorption.

In Canada, adults are recommended to take 15 micrograms of vitamin D, often achieved through consuming vitamin D-fortified milk or soy milk twice a day. Canadian law requires regular milk and margarine to be fortified with vitamin D. In the United States, adults are also recommended to consume 15 micrograms of vitamin D, which can be obtained through products such as milk, breakfast cereals, margarine, yogurt, and orange juice products.

The main ways for the human body to obtain vitamin D are through exposure to sunlight and dietary intake. Therefore, two ways are recommended here to get more vitamin D.

1. Keep plenty of sunlight. Sunlight is irritating to the body. When exposed to ultraviolet rays, cholesterol in the body will be converted into vitamin D. However, because overexposure to UV rays can increase the risk of skin cancer, experts recommend adequate sun protection. Ideally, approximately 20-25 minutes in the sun is recommended.

2. Eat more fatty fish. Fish such as salmon, trout, mackerel, tuna, and eel are excellent sources of vitamin D. Eating a variety of deep-sea fish can help supplement vitamin D.