Vitamin D, also known as “calciferol,” is a fat-soluble vitamin. It is also called sunshine vitamin as the human body can produce it when exposed to ultraviolet rays. However, its deficiency is common even in tropical regions, as people cannot spend much time in direct sunlight.
Once inside the body, it converts to more active forms like calcidiol in the liver and calcitriol in the kidneys.
Vitamin D has hundreds of functions, and science is still discovering its role in good health. It is essential for bone mineralization. It plays an important role in calcium metabolism. Thus, its deficiency may result in weaker bones.
However, now science realizes that it is also vital for the production of hormones, reducing inflammation, cell growth, immune function, and even glucose metabolism. It also plays an important role in gene regulation.
Vitamin D requirement and dietary sources
Vitamin D is now among the well-studied vitamins. Recommended dietary allowance for the vitamin is 20 mcg or 800 IU daily for adults.
There is a reason why the human body can produce vitamin D. First and foremost, it underlines its importance for optimal health and its role in various body functions. Secondly, it is present only in very few foods. Finally, it means that fulfilling its requirement through diet is quite challenging.
Some foods rich in vitamin D are cod liver oil, trout, salmon, mushrooms, milk, soy, egg, cheese, and some fortified food products.
Here it is vital to notice that vitamin D is relatively uncommon in plant-based foods. It is more commonly found in animal products. Animal products contain not only vitamin D but also its highly active form 25(OH)D or calcidiol.
It means that there are relatively very few sources of vegan vitamin D (vegan vd). Hence, vegetarians and vegans may also struggle to get a sufficient amount of the vd.
Different forms of vitamin D
Unlike the common belief, vitamins are not one substance and are often the name of chemically related substances. It means that there are many sub-types of vitamin D. The two main types of vitamin D present in food are D2 (ergocalciferol) and D3 (cholecalciferol).
The human body mainly absorbs vitamin D through the small intestines. Its absorption is better in the presence of dietary fats.
When it comes to vitamin D2, it is a vegan vd that is mainly present in plant-based foods, especially in mushrooms, yeast, and fungi. Vitamin D is almost absent in other vegan foods.
Vitamin D3 is mainly present in animal-based foods like oily fish, liver, eggs, and more. Since it is mixed in fats, it is a highly bioavailable form. Additionally, animal foods may also contain a biologically active form of vitamin D called calcidiol.
What is the difference between D2 and D3, and which is better?
As already said that though both D2 and D3 are forms of vitamin D, but they have different origins. Vitamin D2 is vegan vd and is of plant origin. In contrast, D3 is of animal origin.
The body equally absorb both vitamin D2 and D3. However, here their similarities end. Vitamin D2 and D3 are metabolized quite differently in the body. Studies show that vitamin D2 fails to help much as it does not result in a prolonged increase in vitamin D levels in the blood.
Thus, now researchers say that it is wrong to think of vegan vd or D2 as something similar to D3. It appears that in those living with vitamin D deficiency, only D3 helps adequately. Vegan vd can only cause a short-term increase in vitamin D levels. However, it fails to help in the long run.
It also means that not all vitamin D supplements are the same. For example, vegan vd is not suitable for those living with low vitamin D. Hence, one should prefer vitamin D3 supplements over the D2.
There is strong evidence from clinical studies that vitamin D3 is much better than D2. Studies show that vegan vd does not help much. Meta-analysis of studies shows that vitamin D3 is more efficacious at raising vitamin D serum levels.
Thus, vitamin D3 supplements are especially good for bone health, preventing osteoporosis in older adults, type 2 diabetes, boosting heart health, improving muscle function, and even lowering the risk of certain types of cancers.
Vitamin D is one of the most important vitamins. However, it is not present in many foods. It is almost absent in plant-based foods, with only small amounts in mushrooms and fungi. It means that vegans are particularly at risk of vitamin D deficiency.
Fortunately, vitamin D deficiency is readily managed through supplements. But it is worth knowing that not all supplements are equally good. For example, vitamin D2 is not good for managing vd deficiency. Hence, one should prefer vitamin D3 supplements.
When using vitamin D supplements, one should not abuse them, as vitamin D can be toxic at higher dosages. In addition, it considerably increases calcium absorption and can cause hypercalcemia. Furthermore, high vitamin D levels may cause side effects like nausea, vomiting, muscle weakness, and even neurological issues.