Both vitamin D3 and provitamin D3 are found in microalgae, which shows that vitamin D3 is present in the plant kingdom. Many people will be surprised to learn that vitamin D3 is also found in a number of plant species. Specifically, some types of algae, such as certain species of red (e.g. Corallina and Lithothamnion) and brown algae, have the ability to synthesize vitamin D3 when exposed to ultraviolet (UV) light. The name “vitamin D” also refers to vitamin D2, which is created in fungi and yeasts after provitamin D2 is exposed to UVB rays.

The vitamin D3 produced by algae is in the form of ergocalciferol, which is converted into the active form of vitamin D3 by humans and animals. However, it is important to note that not all algae produce vitamin D3, and the amount and availability of vitamin D3 in algae can vary depending on the species, growing conditions, and processing methods.

In recent years, there has been growing interest in using algae as a vegan-friendly source of vitamin D3, particularly for those who follow plant-based diets or have limited sun exposure.